NIMP| Andrei KUNCSER, Author at NIMP

Projects

1. New frontiers for hyperthermia-based therapies

Project Type: TE, Start Date: 2022-10-05 End Date: 2024-09-05

Publications

1. Understanding the Photocatalytic Activity of Sodium Hexatitanate Nanoparticles for Pollutants Degradation: A Spectroscopic Insight

Authors: Teixeira, ARFA; de Oliveira, ALM; Neatu, F; Kuncser, AC; Galca, AC; Rostas, AM; dos Santos, IMG

Published: MAR 2023, ACS APPLIED NANO MATERIALS, DOI: 10.1021/acsanm.2c05577

Sodium hexatitanate (Na2Ti6O13) nanoparticles have been synthesized by the hydrothermal method with microwave and conven-tional heating, after which their photocatalytic properties toward an azo dye pollutant degradation have been investigated. Insights into the dynamics and reactivity of the species involved in the photocatalytic mechanism of the (Na2Ti6O13) samples were precisely investigated, for the first time, by X-band electron paramagnetic resonance (EPR) spectroscopy under different experimental conditions. X-ray diffraction structural analysis revealed that all samples crystallized in a monoclinic C2/m structure, with different short-range structural order according to the employed heating, as indicated by Raman. Field-emission scanning electron microscopy and transmission electron microscopy results revealed the formation of rod-and fiber-like nanoparticles with different diameters and lengths. EPR measurements indicated the presence of different Ti3+ point defects and F centers in the samples. X-ray photoelectron spectroscopy analysis proved the presence of oxygen-related defects, but no Ti3+ was detected on the surface. Spin trapping experiments monitored the generation of hydroxyl (OH center dot) radicals over UV-irradiation time. Various parameters contribute to the photocatalytic activity of the samples; however, the type of defect and particle morphology appeared as key factors for enhanced efficiency. Our study provides significant information about paramagnetic defects in Na2Ti6O13 materials and their role in photocatalysis to design other Ti-based photocatalysts.

2. Understanding the Photocatalytic Activity of Sodium Hexatitanate Nanoparticles for Pollutants Degradation: A Spectroscopic Insight

Authors: Teixeira, ARFA; de Oliveira, ALM; Neatu, F; Kuncser, AC; Galca, AC; Rostas, AM; dos Santos, IMG

Published: MAR 24 2023, ACS APPLIED NANO MATERIALS, 6, DOI: 10.1021/acsanm.2c05577

3. Antimicrobial Properties of TiO2 Microparticles Coated with Ca- and Cu-Based Composite Layers

Authors: Bucuresteanu, R; Ionita, M; Chihaia, V; Ficai, A; Trusca, RD; Ilie, CI; Kuncser, A; Holban, AM; Mihaescu, G; Petcu, G; Nicolaev, A; Costescu, RM; Husch, M; Parvulescu, V; Ditu, LM

Published: JUL 2022, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 23, 6888, DOI: 10.3390/ijms23136888

The ability of TiO2 to generate reactive oxygen species under UV radiation makes it an efficient candidate in antimicrobial studies. In this context, the preparation of TiO2 microparticles coated with Ca- and Cu-based composite layers over which Cu(II), Cu(I), and Cu(0) species were identified is presented here. The obtained materials were characterized by a wide range of analytical methods, such as X-ray diffraction, electron microscopy (TEM, SEM), X-ray photoelectron (XPS), and UV-VIS spectroscopy. The antimicrobial efficiency was evaluated using qualitative and quantitative standard methods and standard clinical microbial strains. A significant aspect of this composite is that the antimicrobial properties were evidenced both in the presence and absence of the light, as result of competition between photo and electrical effects. However, the antibacterial effect was similar in darkness and light for all samples. Because no photocatalytic properties were found in the absence of copper, the results sustain the antibacterial effect of the electric field (generated by the electrostatic potential of the composite layer) both under the dark and in light conditions. In this way, the composite layers supported on the TiO2 microparticles' surface can offer continuous antibacterial protection and do not require the presence of a permanent light source for activation. However, the antimicrobial effect in the dark is more significant and is considered to be the result of the electric field effect generated on the composite layer.

4. A curcumin-loaded silica carrier with NH3 sensitivity and antimicrobial properties

Authors: Todan, L; Voicescu, M; Culita, DC; Lincu, D; Ion, RM; Calin, M; Raut, I; Kuncser, AC

Published: JAN 2022, CHEMICAL PAPERS, DOI: 10.1007/s11696-022-02090-7

In this study curcumin was immobilized in a silica matrix to overcome its poor aqueous solubility and rapid degradation profile. Two kinds of sol-gel powders based on colloidal silica were synthesized and characterized, one prepared with an ethanolic solution of curcumin and the other using cethyltrimethylammonium bromide (CTAB) to solubilize the dye. The successful integration of curcumin in the matrix as well as the interaction with the components of the composite powders was validated by different analysis methods (DSC, FTIR). The samples morphology was evaluated by SEM. UV-Vis and fluorescence studies showed that curcumin was stable, in its enol configuration in both matrices. The sensitivity to ammonia was proved by exposing the powders to NH3 vapors in a sealed vessel. Color changes were measured with a colorimeter. UV-Vis spectra showed that the enol form of the dye in EtOH/CTAB based SiO2 matrices was energetically stable under NH3 atmosphere, even after being kept a few days at low temperature. A fluorescence quenching of both samples was noticed due to interaction curcumin-ammonia. Both samples have antimicrobial properties, the CTAB containing one being more efficient. The EtOH/CTAB based SiO2 powders may represent a novel signaling and antimicrobial system, useful for food or pharmaceutical applications. [GRAPHICS] .

5. Self-connected CuO-ZnO radial core-shell heterojunction nanowire arrays grown on interdigitated electrodes for visible-light photodetectors

Authors: Costas, A; Florica, C; Preda, N; Besleaga, C; Kuncser, A; Enculescu, I

Published: APR 27 2022, SCIENTIFIC REPORTS, 12, 6834, DOI: 10.1038/s41598-022-10879-5

An original photodetector system based on self-connected CuO-ZnO radial core-shell heterojunction nanowire arrays grown on metallic interdigitated electrodes, operating as visible-light photodetector was developed by combining simple preparation approaches. Metallic interdigitated electrodes were fabricated on Si/SiO2 substrates using a conventional photolithography process. Subsequently, a Cu layer was electrodeposited on top of the metallic interdigitated electrodes. The CuO nanowire arrays (core) were obtained by thermal oxidation in air of the Cu layer. Afterwards, a ZnO thin film (shell) was deposited by RF magnetron sputtering covering the surface of the CuO nanowires. The morphological, structural, compositional, optical, electrical and photoelectrical properties of the CuO nanowire arrays and CuO-ZnO core-shell nanowire arrays grown on metallic interdigitated electrodes were investigated. The performances of the devices were evaluated by assessing the figures of merit of the photodetectors based on self-connected CuO-ZnO core-shell heterojunction nanowire arrays grown on the metallic interdigitated electrodes. The radial p-n heterojunction formed between CuO and ZnO generates a type II band alignment that favors an efficient charge separation of photogenerated electron-hole pairs at the CuO-ZnO interface, suppressing their recombination and consequently enhancing the photoresponse and the photoresponsivity of the photodetectors. The electrical connections in the fabricated photodetector devices are made without any additional complex and time-consuming lithographic step through a self-connecting approach for CuO-ZnO core-shell heterojunction nanowire arrays grown directly onto the Ti/Pt metallic interdigitated electrodes. Therefore, the present study provides an accessible path for employing low dimensional complex structures in functional optoelectronic devices such as photodetectors.

6. Tuning the acidity by addition of transition metal to Mn modified hollow silica spheres and their catalytic activity in ethanol dehydration to ethylene

Authors: Florea, M; Bocirnea, A; Neatu, S; Kuncser, AM; Trandafir, MM; Neatu, F

Published: SEP 25 2022, APPLIED CATALYSIS A-GENERAL, 646, 118860, DOI: 10.1016/j.apcata.2022.118860

Due to the currently worldwide petrochemical feedstock shortage, the ethylene synthesis from renewable non-oil sources becomes of high interest. The catalysts were prepared in two steps: (i) formation of spheres containing the carbon-coated Mn core by hydrothermal method, (ii) formation of the Si-Zr oxide shell by sol-gel method. The prepared catalysts were characterized by N2 physisorption, SEM-EDX, XRD, XPS, and NH3-TPD. The catalytic results have shown that Fe, Zn or Ni modified Mn core exhibited superior activity compared to the catalysts containing only Mn in the core. With 75% yield and 98% ethanol conversion at 350 degrees C and WHSV of 1.4 h-1, MnNi@SiZr was the best catalyst. These results are due to an increased number of acid sites compared to the other materials and an optimal ratio of weak/medium acid sites. Our findings suggest new lines for developing active and stable catalysts for ethylene synthesis from ethanol.

7. Relationship between the Formation of Magnetic Clusters and Hexagonal Phase of Gold Matrix in AuxFe1-x Nanophase Thin Films

Authors: Locovei, C; Radu, C; Kuncser, A; Iacob, N; Schinteie, G; Stanciu, A; Iftimie, S; Kuncser, V

Published: APR 2022, NANOMATERIALS, 12, 1176, DOI: 10.3390/nano12071176

AuxFe1-x nanophase thin films of different compositions and thicknesses were prepared by co-deposition magnetron sputtering. Complex morpho-structural and magnetic investigations of the films were performed by X-ray Diffraction, cross-section Transmission Electron Microscopy, Selected Area Electron Diffraction, Magneto Optical Kerr Effect, Superconducting Quantum Interference Device magnetometry and Conversion Electron Mossbauer Spectroscopy. It was proven that depending on the preparation conditions, different configurations of defect alpha-Fe magnetic clusters, i.e., randomly distributed or auto-assembled in lamellar or filiform configurations, can be formed in the Au matrix. A close relationship between the Fe clustering process and the type of the crystalline structure of the Au matrix was underlined, with the stabilization of a hexagonal phase at a composition close to 70 at. % of Au and at optimal thickness. Due to different types of inter-cluster magnetic interactions and spin anisotropies, different types of magnetic order from 2D Ising type to 3D Heisenberg type, as well as superparamagnetic behavior of non-interacting Fe clusters of similar average size, were evidenced.

8. New superdielectric materials: (1-x) SrFe12O19 - x BNT-BT nanocomposites

Authors: Greculeasa, SG; Comanescu, C; Iacob, N; Kuncser, A; Smaranda, I; Amarande, L; Cioangher, M; Burdusel, M; Teodorescu, V

Published: OCT 1 2022, PHYSICA B-CONDENSED MATTER, 642, 414139, DOI: 10.1016/j.physb.2022.414139

Novel (1-x) SrFe12O19 - x BNT-BT0.08 (x = 0; 0.5; 0.8; 1) nanocomposites were explored in this study. The samples were produced by sol-gel method and compacted by conventional sintering. The composition, morphology, local structure, dielectric and magnetic properties were investigated by X-ray diffraction, Transmission Electron Microscopy, Impedance Analysis, Mossbauer spectroscopy, and SQUID magnetometry. The desired composition and the presence of the magnetoplumbite SrFe12O19 and perovskite BNT-BT structures were verified by X-ray diffraction. Irregular morphology and large size distributions are evidenced in the electron microscopy micrographs. The reported room temperature dielectric constants in this study are the highest values obtained in multiferroic composites at room temperature: giant dielectric constants (similar to 1.3 x 10(6)) were obtained, relative to 0.13 x 10(4) in BNT-BT. The hyperfine parameters allowed the identification of the Wyckoff positions of the Fe ions corresponding closely to the theoretical case. The hard magnetic character of the SrFe12O19 phase is evidenced from the magnetic measurements. For the first time in multifermic composites, superdielectric characteristics are evidenced at room temperature.

9. Enhanced magnetocaloric properties of La0.8K0.2-xPbxMnO3 nanoparticles by optimizing Pb doping concentrations

Authors: Bouzid, SA; Essoumhi, A; Rostas, AM; Kuncser, AC; Negrila, CC; Iacob, N; Galatanu, A; Popescu, B; Sajieddine, M; Galca, AC; Kuncser, V

Published: JUN 15 2022, CERAMICS INTERNATIONAL, 48, DOI: 10.1016/j.ceramint.2022.02.239

Polycrystalline La(0.8)K(0.2-x)Pb(x)MnO3 (x = 0.05, 0.10, 0.15, 0.20) ceramics were successfully prepared by flash combustion route and their structural, morphological, magnetic and magnetocaloric properties were investi-gated. Structural analyses using X-ray diffraction reveal that all samples are crystallized in the rhombohedral structure and belong to R <(3) over bar > c space group. The increase of Pb doping does not modify the crystalline structure but changes the grain size and lattice parameters. X-ray photoelectron spectroscopy (XPS) fitting results of Mn 2p peaks confirmed the coexistence of Mn3+ and Mn4+ ions which contribute to the double exchange interactions improving the ferromagnetic order in the samples. The magnetization's temperature and magnetic field de-pendences indicate a second-order ferromagnetic-paramagnetic transition of the ceramics. A significant mag-netic entropy change near room temperature was observed for La0.8K0.1Pb0.1MnO3, showing considerable magnetocaloric properties. Furthermore, electron paramagnetic resonance spectroscopy (EPR) was also used to examine the ferromagnetic-paramagnetic transition.

10. Full Length Article Towards high degree of c-axis orientation in MgB2 bulks

Authors: Grigoroscuta, MA; Aldica, GV; Burdusel, M; Sandu, V; Kuncser, A; Pasuk, I; Ionescu, AM; Suzuki, TS; Vasylkiv, O; Badica, P

Published: AUG 2022, JOURNAL OF MAGNESIUM AND ALLOYS, 10, DOI: 10.1016/j.jma.2021.10.013

The paper presents fabrication and characterization of spark plasma sintered textured (001) MgB2 with a record degree of orientation of about 40% and 16% by high-energy ultra-sonication and slip casting in high magnetic field (12 T) and 0 T magnetic field, respectively. Structural characterization was performed by X-ray diffraction, and electron microscopy. The analysis revealed unexpected preferred orientation also in the MgO secondary phase due to the epitaxial growth of (111) MgO on (001) MgB2. The influence of oriented microstructure on the superconducting characteristics expressed by critical current density (Jc), irreversibility field ( H irr), and on the pinning properties were assessed. High anisotropy versus sample orientation in applied magnetic field, H , was observed for Jc, Hirr, pinning activation energy ( U *) extracted from relaxation measurements. The zero-field critical current, Jc0 and Fp,maxare weakly or not dependent on the direction of H , while the other indicated parameters are significantly influenced. Results enable control of superconducting parameters by further optimization of microstructure through MgB2 texturing as a novel and viable strategy for development of bulk MgB2 with enhanced properties when taking advantage of its anisotropy.(c) 2021 Chongqing University. Publishing services provided by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ) Peer review under responsibility of Chongqing University

11. A new method for obtaining the magnetic shape anisotropy directly from electron tomography images

Authors: Radu, C; Vlaicu, ID; Kuncser, AC

Published: JUL 5 2022, BEILSTEIN JOURNAL OF NANOTECHNOLOGY, 13, DOI: 10.3762/bjnano.13.51

A new methodology to obtain magnetic information on magnetic nanoparticle (MNP) systems via electron tomography techniques is reported in this work. The new methodology is implemented in an under-development software package called Magn3t, written in Python and C++. A novel image-filtering technique that reduces the highly undesired diffraction effects in the tomography tiltseries has been also developed in order to increase the reliability of the correlations between morphology and magnetism. Using the Magn3t software, the magnetic shape anisotropy magnitude and direction of magnetite nanoparticles has been extracted for the first time directly from transmission electron tomography.

12. EXCHANGE COUPLED NANOCOMPOSITES: MAGNETOPLUMBITE Sr FERRITE AND MAGNETITE

Authors: Greculeasa, SG; Comanescu, C; Iacob, N; Kuncser, A

Published: 2022, ROMANIAN JOURNAL OF PHYSICS, 67, 606, DOI:

Exchange coupling in a SrFe12O19 - Fe3O4 nanocomposite magnet was explored in this study. The composition, microstructure, local structure and magnetic properties were investigated by XRD, SEM, Mossbauer spectroscopy, and SQUID magnetometry. The magnetoplumbite SrFe12O19 and spinel Fe3O4 structures were verified by X-ray diffraction. The morphology of the composite reveals the characteristics of the two components. The hyperfine parameters allowed the identification of the Wyckoff positions of the iron ions corresponding to the involved phases. The magnetic measurements of the composite, showing a single-phase-like magnetic hysteresis loop, confirmed the exchange coupling between the hard and soft magnetic phases.

13. Magnetic Properties of Nanosized Fe and FeCo Systems on Trenched Mo Templates

Authors: Stanciu, AE; Schinteie, G; Kuncser, AC; Locovei, C; Trupina, L; Iacob, N; Leca, A; Borca, B; Kuncser, V

Published: SEP 2022, COATINGS, 12, 1366, DOI: 10.3390/coatings12091366

The manipulation of magnetic anisotropy represents the fundamental prerequisite for the application of magnetic materials. Here we present the vectorial magnetic properties of nanostructured systems and thin films of Fe and FeCo prepared on linearly trenched Mo templates with thermally controlled periodicity. The magnetic properties of the nanosystems are engineered by tuning the shape, size, thickness, and composition parameters of the thin films. Thus, we control coercivity, magnetization, orientation of the easy axis of magnetization, and the long-range magnetic order of the system in the function of the temperature. We distinguish magnetic components that emerge from the complex morpho-structural features of the undulating Fe or FeCo nanostructured films on trenched Mo templates: (i) assembly of magnetic nanowires and (ii) assembly of magnetic islands/clusters. Uniaxial anisotropy at room temperature was proven, characterized, and explained in the case of all systems. Our work contributes to the understanding of magnetic properties necessary for possible further applications of linear systems and undulated thin films.

14. Layered SnSe nanoflakes with anharmonic phonon properties and memristive characteristics

Authors: Buruiana, AT; Bocirnea, AE; Kuncser, AC; Tite, T; Matei, E; Mihai, C; Zawadzka, N; Olkowska-Pucko, K; Kipczak, L; Babinski, A; Molas, MR; Velea, A; Galca, AC

Published: OCT 15 2022, APPLIED SURFACE SCIENCE, 599, 153983, DOI: 10.1016/j.apsusc.2022.153983

Understanding the phonon anharmonicity and temperature-dependent behavior of phonons that affect the thermal transport properties in 2D materials is crucial for developing efficient thermoelectric and memristor devices. SnSe has attracted significant interest because of its potential applications for developing such novel devices. Here, orthorhombic SnSe nanoflakes with a thickness of less than 100 nm and oriented along the [100] crystal axis were obtained using physical vapor transport at atmospheric pressure. Polarization-resolved Raman spectroscopy of SnSe nanoflakes was performed at a temperature of 5 K. Temperature-dependent frequencies and linewidths of Raman modes in tin selenide were fitted according to the anharmonic phonon coupling theory. The results indicate that both two and three order processes are responsible for the phonon decay in tin selenide. The memristive property was confirmed by electrical measurements of SnSe devices. SnSe memristors have an operating current of 10-4 A, similar to other transition-metal dichalcogenide memristors, but are more energy efficient than memristors based on defect migration, with a threshold voltage of 3 V.

15. Fracture peculiarities and high-temperature strength of bulk polycrystalline boron

Authors: Demirskyi, D; Badica, P; Kuncser, A; Vasylkiv, O

Published: MAR 2022, MATERIALIA, 21, 101346, DOI: 10.1016/j.mtla.2022.101346

We report the mechanical behavior of a bulk boron ceramic prepared by spark plasma sintering of commercially available beta-boron powder. In order to fabricate polycrystalline boron ceramic, we used a protective tantalum foil reacted with carbon from the graphite die or graphite foil forming a thin layer of TaB2 and TaC covering the boron specimen. This is the first study to show the high-temperature flexural strength, toughness, and Young's moduli of boron up to 1400 degrees C. At 1600 degrees C and above, boron will react with testing environment forming an outer shell. The flexural strength and fracture toughness at room temperature reached an average of 340 MPa and 4.1 MPa m (1/2) , respectively. Despite showing clear signs of plastic deformation on the strain-stress curves, the yield strength of the monolithic boron ceramic exceed 1 GPa at 1200 degrees C. It was determined that fracture at elevated temperatures follows a quasi-transgranular mechanism, where the sub-grains of the boron fracture as plate-like structures. An interpretation for the observed fracture behavior was proposed.

16. Electrocatalytic Properties of Mixed-Oxide-Containing Composite-Supported Platinum for Polymer Electrolyte Membrane (PEM) Fuel Cells

Authors: Ayyubov, I; Talas, E; Salmanzade, K; Kuncser, A; Paszti, Z; Neatu, S; Mirea, AG; Florea, M; Tompos, A; Borbath, I

Published: MAY 2022, MATERIALS, 15, 3671, DOI: 10.3390/ma15103671

TiO2-based mixed oxide-carbon composite supports have been suggested to provide enhanced stability for platinum (Pt) electrocatalysts in polymer electrolyte membrane (PEM) fuel cells. The addition of molybdenum (Mo) to the mixed oxide is known to increase the CO tolerance of the electrocatalyst. In this work Pt catalysts, supported on Ti1-xMoxO2-C composites with a 25/75 oxide/carbon mass ratio and prepared from different carbon materials (C: Vulcan XC-72, unmodified and functionalized Black Pearls 2000), were compared in the hydrogen oxidation reaction (HOR) and in the oxygen reduction reaction (ORR) with a commercial Pt/C reference catalyst in order to assess the influence of the support on the electrocatalytic behavior. Our aim was to perform electrochemical studies in preparation for fuel cell tests. The ORR kinetic parameters from the Koutecky-Levich plot suggested a four-electron transfer per oxygen molecule, resulting in H2O. The similarity between the Tafel slopes suggested the same reaction mechanism for electrocatalysts supported by these composites. The HOR activity of the composite-supported electrocatalysts was independent of the type of carbonaceous material. A noticeable difference in the stability of the catalysts appeared only after 5000 polarization cycles; the Black Pearl-containing sample showed the highest stability.

17. Synthesis and Characterization of Hematite-Based Nanocomposites as Promising Catalysts for Indigo Carmine Oxidation

Authors: Kuncser, AC; Rostas, AM; Zavoianu, R; Pavel, OD; Vlaicu, ID; Badea, M; Culita, DC; Tirsoaga, A; Olar, R

Published: JUL 2022, NANOMATERIALS, 12, 2511, DOI: 10.3390/nano12142511

The hematite-based nanomaterials are involved in several catalytic organic and inorganic processes, including water decontamination from organic pollutants. In order to develop such species, a series of bimetallic hematite-based nanocomposites were obtained by some goethite composites-controlled calcination. Their composition consists of various phases such as alpha-FeOOH, alpha-Fe2O3 or gamma-Fe2O3 combined with amorphous (Mn2O3, Co3O4, NiO, ZnO) or crystalline (CuO) oxides of the second transition ion from the structure. The component dimensions, either in the 10-30 or in the 100-200 nm range, together with the quasi-spherical or nanorod-like shapes, were provided by Mossbauer spectroscopy and powder X-ray diffraction as well as transmission electron microscopy data. The textural characterization showed a decrease in the specific area of the hematite-based nanocomposites compared with corresponding goethites, with the pore volume ranging between 0.219 and 0.278 cm(3)g(-1). The best catalytic activity concerning indigo carmine removal from water in hydrogen peroxide presence was exhibited by a copper-containing hematite-based nanocomposite sample that reached a dye removal extent of over 99%, which correlates with both the base/acid site ratio and pore size. Moreover, Cu-hbnc preserves its catalytic activity even after four recyclings, when it still reached a dye removal extent higher than 90%.

18. A curcumin-loaded silica carrier with NH3 sensitivity and antimicrobial properties

Authors: Todan, L; Voicescu, M; Culita, DC; Lincu, D; Ion, RM; Calin, M; Raut, I; Kuncser, AC

Published: MAY 2022, CHEMICAL PAPERS, 76, DOI: 10.1007/s11696-022-02090-7

19. Novel Magnetic Nanocomposites Based on Carboxyl-Functionalized SBA-15 Silica for Effective Dye Adsorption from Aqueous Solutions

Authors: Simonescu, CM; Culita, DC; Tatarus, A; Mocanu, T; Marinescu, G; Mitran, RA; Atkinson, I; Kuncser, A; Stanica, N

Published: JUL 2022, NANOMATERIALS, 12, 2247, DOI: 10.3390/nano12132247

In this study, three novel magnetic nanocomposites based on carboxyl-functionalized SBA-15 silica and magnetite nanoparticles were prepared through an effective and simple procedure and applied for methylene blue (MB) and malachite green G (MG) adsorption from single and binary solutions. Structure, composition, morphology, magnetic, and textural properties of the composites were thoroughly investigated. The influence of the amount of carboxyl functional groups on the physicochemical and adsorptive properties of the final materials was investigated. The capacity of the synthesized composites to adsorb MB and MG from single and binary solutions and the factors affecting the adsorption process, such as contact time, solution pH, and dye concentration, were assessed. Kinetic modelling showed that the dye adsorption mechanism followed the pseudo-second-order kinetic model, indicating that adsorption was a chemically controlled multilayer process. The adsorption rate was simultaneously controlled by external film diffusion and intraparticle diffusion. It was evidenced that the molecular geometry of the dye molecule plays a major role in the adsorption process, with the planar geometry of the MB molecule favoring adsorption. The analysis of equilibrium data revealed the best description of MB adsorption behavior by the Langmuir isotherm model, whereas the Freundlich model described better the MG adsorption.

20. Sintered and 3D-Printed Bulks of MgB2-Based Materials with Antimicrobial Properties

Authors: Badica, P; Batalu, ND; Chifiriuc, MC; Burdusel, M; Grigoroscuta, MA; Aldica, GV; Pasuk, I; Kuncser, A; Popa, M; Agostino, A; Operti, L; Padhi, SK; Bonino, V; Truccato, M

Published: OCT 2021, MOLECULES, 26, DOI: 10.3390/molecules26196045

Pristine high-density bulk disks of MgB2 with added hexagonal BN (10 wt.%) were prepared using spark plasma sintering. The BN-added samples are machinable by chipping them into desired geometries. Complex shapes of different sizes can also be obtained by the 3D printing of polylactic acid filaments embedded with MgB2 powder particles (10 wt.%). Our present work aims to assess antimicrobial activity quantified as viable cells (CFU/mL) vs. time of sintered and 3D-printed materials. In vitro antimicrobial tests were performed against the bacterial strains Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923, Enterococcus faecium DSM 13590, and Enterococcus faecalis ATCC 29212; and the yeast strain Candida parapsilosis ATCC 22019. The antimicrobial effects were found to depend on the tested samples and microbes, with E. faecium being the most resistant and E. coli the most susceptible.</p>

21. A novel composite based on pyrene thiazole grafted on graphene oxide: physico-chemical characterization and electrochemical investigations

Authors: Tudose, M; Baratoiu-Carpen, RD; Anghel, EM; Voicescu, M; Somacescu, S; Culita, DC; Hanganu, A; Kuncser, A; Radoi, A

Published: APR 1 2021, MATERIALS CHEMISTRY AND PHYSICS, 262, DOI: 10.1016/j.matchemphys.2021.124315

We report the obtaining of a new composite starting from pyrene thiazole, a compound certified by nuclear magnetic resonance and its covalent grafting on the surface of graphene oxide. Novel material was synthesized in two stages: the first involving transformation of carboxyl groups of graphene oxide into acid chlorides and the second the amide reaction between acid chloride and amine group of pyrene thiazole (PTC). Numerous characterization methods have been used to certify this material, such as: Raman spectroscopy, fluorescence, infrared spectroscopy and X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. Their results show the successful covalent functionalization of graphene oxide with pyrene thiazole through the formation of amide bonds. The electrochemical investigation consisted of evaluating the redox behavior of the carbon screen printed electrodes modified with the new composite (GO-PTC) using caffeic acid, as analyte. From analytical point of view, it is relevant to be able to quantify the presence of caffeic acid and for such reason we used as analytical method the square wave voltammetry. The results showed that the GO-PTC modified carbon screen printed electrodes were able to detect the caffeic acid over more than one order of magnitude (linear working range: 0.005-0.1 mM) and GO-PTC modified electrodes can be considered promising for other analytical investigations.

22. MgB2 powders and bioevaluation of their interaction with planktonic microbes, biofilms, and tumor cells

Authors: Badica, P; Batalu, ND; Chifiriuc, MC; Burdusel, M; Grigoroscuta, MA; Aldica, G; Pasuk, I; Kuncser, A; Enculescu, M; Popa, M; Marutescu, LG; Gheorghe, I; Thamer, O; Bleotu, C; Pircalabioru, GG; Operti, L; Bonino, V; Agostino, A; Truccato, M

Published: MAY-JUN 2021, JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T, 12, 2184, DOI: 10.1016/j.jmrt.2021.04.003

Commercial nanopowders of MgB2 were characterized from the viewpoint of granulometric distribution, structure, microstructure, and pH behavior in water. The powders are very different: a higher amount of the MgB2 phase with a lower tendency for agglomeration determines a higher rate of pH-increase. A higher rate of pH-increase usually produces a stronger antimicrobial activity against Staphylococcus aureus, Enterococcus faecium, Escherichia coli, Pseudomonas aeruginosa, Candida albicans, and Candida parapsilosis reference strains. The variation of the pH-increase rate suggests the possibility of temporo-spatial control of MgB2 bioactivity, although the contribution of other factors should not be neglected. Remarkably, the efficiency of the MgB2 powders is higher against biofilms than on microbes in the planktonic state. Further, our experiments confirm the antimicrobial efficiency of MgB2 in the in vitro tests against 29 methicillin resistant clinical S. aureus isolates and 33 vancomycin resistant E. faecium/faecalis strains, but in this case the biofilms are more resistant than planktonic cells. The MgB2 treatment of infected mice led to a significant decrease of E. coli colonization in liver, spleen and peritoneal liquid and it also caused changes in the intestinal microbiota. The activity of powders on HeLa and HT-29 tumor cell lines was assessed by inverted microscopy, flow cytometry, and evaluation of the cellular cycle. MgB2 inhibits tumor cell growth influencing DNA synthesis (S-phase). The obtained results indicate that the tested powders could provide promising solutions for the development of large-spectrum multifunctional antimicrobial and anti-biofilm agents, and/or for anti-cancer therapies. (C) 2021 The Authors. Published by Elsevier B.V.

23. Sensing Properties of NiO Loaded SnO2 Nanoparticles-Specific Selectivity to H2S

Authors: Stanoiu, A; Kuncser, AC; Ghica, D; Florea, OG; Somacescu, S; Simion, CE

Published: JUN 2021, CHEMOSENSORS, 9, DOI: 10.3390/chemosensors9060125

NiO-loaded SnO2 powders were prepared involving two chemical procedures. The mesoporous SnO2 support was synthesized by a hydrothermal route using Brij 35 non-ionic surfactant as a template. The nickel loadings of 1 and 10 wt.%. NiO were deposited by the wet impregnation method. The H2S sensing properties of xNiO-(1-x)SnO2 (x = 0, 1, 10%) thick layers deposited onto commercial substrates have been investigated with respect to different potential interfering gases (NO2, CO, CO2, CH4, NH3 and SO2) over a wide range of operating temperatures and relative humidity specific for in-field conditions. Following the correlation of the sensing results with the morphological ones, 1wt.% NiO/SnO2 was selected for simultaneous electrical resistance and work function investigations. The purpose was to depict the sensing mechanism by splitting between specific changes over the electron affinity induced by the surface coverage with hydroxyl dipoles and over the band bending induced by the variable surface charge under H2S exposure. Thus, it was found that different gas-interaction partners are dependent upon the amount of H2S, mirrored through the threshold value of 5 ppm H2S, which from an applicative point of view, represents the lower limit of health effects, an eight-hour TWA.

24. Physicochemical Characterization and Drug Release Properties of Methyl-Substituted Silica Xerogels Made Using Sol-Gel Process

Authors: Len, A; Paladini, G; Romanszki, L; Putz, AM; Almasy, L; Laszlo, K; Balint, S; Krajnc, A; Kriechbaum, M; Kuncser, A; Kalmar, J; Dudas, Z

Published: SEP 2021, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 22, DOI: 10.3390/ijms22179197

In this work, a multi-analytical approach involving nitrogen porosimetry, small angle neutron and X-ray scattering, Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies, X-ray diffraction, thermal analysis and electron microscopy was applied to organically modified silica-based xerogels obtained through the sol-gel process. Starting from a tetraethoxysilane (TEOS) precursor, methyltriethoxysilane (MTES) was added to the reaction mixture at two different pH values (2.0 and 4.5) producing hybrid xerogels with different TEOS/MTES molar ratios. Significant differences in the structure were revealed in terms of the chemical composition of the silica network, hydrophilic/hydrophobic profile, particle dimension, pore shape/size and surface characteristics. The combined use of structural characterization methods allowed us to reveal a relation between the cavity dimensions, the synthesis pH value and the grade of methyl substitution. The effect of the structural properties on the controlled Captopril release efficiency has also been tested. This knowledge facilitates tailoring the pore network for specific usage in biological/medical applications. Knowledge on structural aspects, as reported in this work, represents a key starting point for the production of high-performance silica-based hybrid materials showing enhanced efficacy compared to bare silica prepared using only TEOS.

25. Ecological formulation for improving resveratrol stability and release in aqueous environment

Authors: Todan, L; Voicescu, M; Culita, DC; Pandele-Cusu, J; Albu, C; Kuncser, AC

Published: MAY 2021, CHEMICAL PAPERS, 75, 2041, DOI: 10.1007/s11696-020-01409-6

Resveratrol (RES) is a naturally occurring product with numerous biological activities. Despite its potential benefits, its use is limited due to its low aqueous stability and solubility in its native form. The porous sol-gel silica materials which are able to entrap different organic molecules represent new studied release carriers. The aim of this work was to generate a solid matrix to encapsulate RES ensuring protection, increased solubility and release in solutions. A non-toxic ingredient, namely beta-cyclodextrin (beta-CD), able to form inclusion complexes (ICs) with RES has been used. Ecological formulations have been processed by entrapping the RES containing ICs in silica matrices obtained from a silica colloidal sol by the aqueous route of the sol-gel method. Characterization methods (DSC, FTIR, UV-Vis, fluorescence studies, SEM) have evidenced the presence of RES-beta-CD inclusion complex in the silica powder, RES stability in the matrix and its release in aqueous and organic solutions, and the morphology of the carrier. An evaluation of the antioxidant activity of RES in the present formulation was performed by the chemiluminescence assay and RES release profile in aqueous solutions was obtained by HPLC-MS. The resulted materials can find applications in different domains. Graphic abstract

26. Kaolin clay pottery discovered in the Roman city of Romula (Olt County, Romania)

Authors: Badica, P; Alexandru-Dinu, A; Grigoroscuta, M; Locovei, C; Kuncser, A; Bartha, C; Aldica, G; Negru, M; Batalu, D; Cruceru, N; Savulescu, I

Published: APR 2021, JOURNAL OF ARCHAEOLOGICAL SCIENCE-REPORTS, 36, DOI: 10.1016/j.jasrep.2021.102899

Pottery vessels made of kaolin clay from the Roman Period (2nd, 3rd centuries CE) found in Romula (Re?ca village, Olt County, Romania) from Dacia Inferior (Malvensis) were investigated by petrographic, X-ray diffraction, X-ray fluorescence, thermal analysis, electron microscopy, and mechanical tests. Our results are compared with available data on kaolin clays and pottery vessels from other sites located along the lower course of Danube river and near the Black Sea, namely in Moesia Superior, Moesia Inferior, and Thracia. Archeological and geographical contexts are addressed. Results of our analysis suggest a local production of ceramics in Romula, by using raw materials from the north of Lower Danube, in opposition to the idea that kaolin ware was imported from the provinces south of the Danube.

27. Chemical Degradation of Methylene Blue Dye Using TiO2/Au Nanoparticles

Authors: Jinga, LI; Popescu-Pelin, G; Socol, G; Mocanu, S; Tudose, M; Culita, DC; Kuncser, A; Ionita, P

Published: JUN 2021, NANOMATERIALS, 11, DOI: 10.3390/nano11061605

Gold nanoparticles (similar to 10 nm) were deposited on titanium dioxide nanoparticles (similar to 21 nm) and the material obtained was characterized using IR, UV-Vis, N-2 adsorption-desorption isotherm, DLS, EDS (EDX), TEM, XPS, and XRD techniques. It was found that the methylene blue dye is degraded in the presence of this material when using hydrogen peroxide as the oxidant. Tests were performed at 2, 4, 6, and 24 h, with hydrogen peroxide contents varying from 1 to 5 mg/mL. Longer exposure time and a higher content of oxidant led to the degradation of methylene blue dye at up to 90%. The material can be reused several times with no loss of activity.

28. Partially-oriented MgB2 superconducting bulks with addition of B4C and cubic BN obtained by slip casting under high magnetic field and spark plasma sintering

Authors: Grigoroscuta, MA; Aldica, G; Pasuk, I; Burdusel, M; Sandu, V; Kuncser, A; Suzuki, TS; Vasylkiv, O; Badica, P

Published: FEB 2021, MATERIALS RESEARCH BULLETIN, 134, DOI: 10.1016/j.materresbull.2020.111103

Partially-oriented MgB2 bulk discs (13 and 9 %) with the starting compositions of (MgB2)(0.99)(B4C)(0.01) and (MgB2)(0.99)(c-BN)om were fabricated by slip casting under an H-0 = 12 T magnetic field (perpendicular to the disc surface) and subsequent spark plasma sintering. The maximum critical current density and irreversibility field are for H//H-0 (H=applied field). These values are higher or similar to the randomly-oriented samples with the same composition. The maximum volume pinning force (F-p) is lower in the partially-oriented ones than in the randomly-oriented samples. The pinning-force-related parameters depend on the additive and orientation. Assessment of the major pinning mechanism within the scaling and percolation models considering these parameters shows significant limitations. A method to scale F-p is proposed; for the randomly and partially-oriented samples (that show an extra peak in F-p), the single and double Gaussian functions fit well. The results suggest an anisotropic influence of carbon substituting for boron in the MgB2.

29. EPR spectroscopy and structural investigations, of Eu2+-doped chloroborate glass-ceramic

Authors: Secu, M; Kuncser, A; Negrila, C; Rostas, AM

Published: DEC 15 2021, CERAMICS INTERNATIONAL, 47, 35095, DOI: 10.1016/j.ceramint.2021.09.051

Europium doped (0.1% and 1%) chlomborate BaO-B2O3-BaCl2 glass and glass-ceramic with embedded BaCl2 nanocrystals have been synthesised, investigated, and compared with the corresponding nanocrystalline powder. The structural analysis of the glass evidenced ionic bonds characteristic to the glass host structure and compositional changes during the melting. X-ray diffraction and transmission electron microscopy revealed the formation of orthorhombic BaCl2 nanocrystals of about tens on nm in size and a smaller amount of BaB2O4 nanocrystals. Structural analysis of the Eu2+-doped BaCl2 nanocrystals has shown a distortion of the crystalline cell assigned to the growth process, affected by defects and ionic impurities. Photoluminescence spectra of the glass-ceramic revealed Eu3+ and Eu2+ luminescent ion species, but only Eu2+ is incorporated within the BaCl2 nanocrystalline phase. Electron paramagnetic resonance measurements in X-band sustain the presence of Eu2+ ions. The EPR parameters (g values and hyperfine constants) resulting from the Q-band EPR spectra simulations recorded on glass-ceramic are similar to those in Eu2+-doped BaCl2 and confirmed the partial incorporation of Eu2+ ions within the BaCl2:Eu2+ nanocrystals in the glass-ceramics.

30. Facile Synthesis of Cobalt Ferrite (CoFe2O4) Nanoparticles in the Presence of Sodium Bis (2-ethyl-hexyl) Sulfosuccinate and Their Application in Dyes Removal from Single and Binary Aqueous Solutions

Authors: Simonescu, CM; Tatarus, A; Culita, DC; Stanica, N; Butoi, B; Kuncser, A

Published: NOV 2021, NANOMATERIALS, 11, DOI: 10.3390/nano11113128

A research study was conducted to establish the effect of the presence of sodium bis-2-ethyl-hexyl-sulfosuccinate (DOSS) surfactant on the size, shape, and magnetic properties of cobalt ferrite nanoparticles, and also on their ability to remove anionic dyes from synthetic aqueous solutions. The effect of the molar ratio cobalt ferrite to surfactant (1:0.1; 1:0.25 and 1:0.5) on the physicochemical properties of the prepared cobalt ferrite particles was evaluated using different characterization techniques, such as FT-IR spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N-2 adsorption-desorption analysis, and magnetic measurements. The results revealed that the surfactant has a significant impact on the textural and magnetic properties of CoFe2O4. The capacity of the synthesized CoFe2O4 samples to remove two anionic dyes, Congo Red (CR) and Methyl Orange (MO), by adsorption from aqueous solutions and the factors affecting the adsorption process, such as contact time, concentration of dyes in the initial solution, pH of the media, and the presence of a competing agent were investigated in batch experiments. Desorption experiments were performed to demonstrate the reusability of the adsorbents.

31. Soft synthesis and characterization of goethite-based nanocomposites as promising cyclooctene oxidation catalysts

Authors: Kuncser, AC; Vlaicu, ID; Pavel, OD; Zavoianu, R; Badea, M; Radu, D; Culita, DC; Rostas, AM; Olar, R

Published: AUG 24 2021, RSC ADVANCES, 11, 27602, DOI: 10.1039/d1ra04211d

Goethite based nanocomposites with a different composition such as 6FeO(OH)center dot MnO(OH)center dot 0.5H(2)O (Mn-composite), xFeO(OH)center dot M(OH)(2)center dot yH(2)O (Co-composite (M: Co, x = 12, y = 3), Ni-composite (M: Ni, x = 7, y = 2)) and xFeO(OH)center dot MO center dot yH(2)O (Cu-composite (M: Cu, x = 5.5, y = 3), Zn-composite (M: Zn, x = 6, y = 1.5)) have been prepared by a soft chemical synthesis consisting in acetate hydrolysis. The data provided by Fourier transform infrared (FTIR), ultraviolet-visible-near infrared (UV-Vis-NIR), electron paramagnetic resonance (EPR) and Mossbauer spectra account for a slight modification of all composites' physicochemical properties compared to the starting material. Powder X-ray diffraction and transmission electron microscopy (TEM) investigations revealed the secondary phase nature and presence along with that of goethite. The TEM data are also consistent with a nano rod-like morphology with a 5-10 nm width and an average length of 40 nm. The catalytic oxidation of cyclooctene with O-2 using isobutyraldehyde as reductant and acetonitrile as a solvent was performed in batch conditions for 5 h at room temperature. The selectivity for the epoxide was higher than 99% for all tested solids. The conversion of cyclooctene decreased from 55% to 4% following the same order of variance as the base/acid sites ratio: Mn-composite > Fe-composite > Co-composite > Ni-composite > Zn-composite > Cu-composite. The 6FeO(OH)center dot MnO(OH)center dot 0.5H(2)O (Mn-composite) exhibited the most promising catalytic activity in cyclooctene oxidation, which can be correlated with the redox ability of Mn(iii) combined with the increased base character of this solid. The catalytic activity of this sample decreases by 10% after several successive reaction cycles.

32. Influence of Thickness on the Magnetic and Magnetotransport Properties of Epitaxial La0.7Sr0.3MnO3 Films Deposited on STO (001)

Authors: Greculeasa, SG; Stanciu, AE; Leca, A; Kuncser, A; Hrib, L; Chirila, C; Pasuk, I; Kuncser, V

Published: DEC 2021, NANOMATERIALS, 11, DOI: 10.3390/nano11123389

Epitaxial La0.7Sr0.3MnO3 films with different thicknesses (9-90 nm) were deposited on SrTiO3 (0 0 1) substrates by pulsed laser deposition. The films have been investigated with respect to morpho-structural, magnetic, and magneto-transport properties, which have been proven to be thickness dependent. Magnetic contributions with different switching mechanisms were evidenced, depending on the perovskite film thickness. The Curie temperature increases with the film thickness. In addition, colossal magnetoresistance effects of up to 29% above room temperature were evidenced and discussed in respect to the magnetic behavior and film thickness.

33. Bistability of the BiOi complex and its implications on evaluating the "acceptor removal"process in p-type silicon

Authors: Besleaga, C; Kuncser, A; Nitescu, A; Kramberger, G; Moll, M; Pintilie, I

Published: NOV 21 2021, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 1017, DOI: 10.1016/j.nima.2021.165809

The dependencies of the BiOi defect concentration on doping, irradiation fluence and particle type in p-type silicon diodes have been investigated. We evidenced that large data scattering occurs for fluences above 10(12) 1 MeV neutrons/cm(2), becoming significant larger for higher fluences. We show that the BiOi defect is metastable, with two configurations A and B, of which only A is detected by Deep Level Transient Spectroscopy and Thermally Stimulated Currents techniques. The defect' electrical activity is influenced by the inherent variations in ambient and procedural experimental conditions, resulting not only in a large scattering of the results coming from the same type of measurement but making correlation between different types of experiments difficult. It is evidenced that the variations in [BiOiA] are triggered by subjecting the samples to an excess of carriers, by either heating or an inherent short exposure to ambient light when manipulating the samples prior to experiments. For the samples investigated in this work both, the [BiOiA] as determined from electrical spectroscopic measurements and the full depletion voltage as measured from Current-Voltage characteristics reach a steady state in similar to 7h. Any electrical measurement performed before will give a different result. The bi-stable behavior of the BiOi defect fully accounts for these variations.

34. Benzofurazan derivatives modified graphene oxide nanocomposite: Physico-chemical characterization and interaction with bacterial and tumoral cells

Authors: Tudose, M; Anghel, EM; Hristea, EN; Voicescu, M; Somacescu, S; Culita, DC; Musuc, AM; Dumitrascu, F; Hanganu, A; Kuncser, A; Zorila, FL; Alexandru, M; Acasandrei, MA; Savu, DI

Published: APR 2021, MATERIALS SCIENCE & ENGINEERING C-MATERIALS FOR BIOLOGICAL APPLICATIONS, 123, DOI: 10.1016/j.msec.2021.112028

Two novel graphene oxide-benzofuran derivatives composites were obtained through the covalent immobilization of [4-hydrazinyl-7nitrobenz-[2,1,3-d]-oxadiazole (NBDH) and respectively, N1-(7-nitrobenzo[c][1,2,5] oxadiazol-4-yl)benzene-1,2-diamine (NBD-PD), on graphene oxide. This covalent functionalization was achieved by activating the carboxylic groups on the surface of graphene oxide by the reaction with thionyl chloride followed by coupling with the amino group of benzofurazane derivatives to obtain the NBD derivatives grafted on graphene oxide. The formation of new materials was check by Raman spectroscopy, fluorescence, infrared spectroscopy and X-ray photoelectron spectroscopy, thermal analysis, scanning electron microscopy, and elemental mapping. The antimicrobial effect of the new composites was evaluated on Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa, both on planktonic and adherent biofilm populations. The cytotoxic effects of the materials on human colon cancer HCT-116 cell line and the normal human fibroblast BJ cell line were evaluated by investigating cell viability and membrane integrity. Apoptosis and colony forming ability of tumor cells were also investigated following exposure to new materials. The biological results of this study have shown that the new materials have potential in combating biofilm formation and also, the tested materials induced cytotoxicity in human colon cancer HCT-116 cell line with limited effects on normal BJ fibroblasts, suggesting their antitumor potential.

35. Tuning structural and magnetic properties of Fe oxide nanoparticles by specific hydrogenation treatments

Authors: Greculeasa, SG; Palade, P; Schinteie, G; Leca, A; Dumitrache, F; Lungu, I; Prodan, G; Kuncser, A; Kuncser, V

Published: OCT 14 2020, SCIENTIFIC REPORTS, 10, DOI: 10.1038/s41598-020-74188-5

Structural and magnetic properties of Fe oxide nanoparticles prepared by laser pyrolysis and annealed in high pressure hydrogen atmosphere were investigated. The annealing treatments were performed at 200 degrees C (sample A200C) and 300 degrees C (sample A300C). The as prepared sample, A, consists of nanoparticles with similar to 4 nm mean particle size and contains C (similar to 11 at.%), Fe and O. The Fe/O ratio is between gamma-Fe2O3 and Fe3O4 stoichiometric ratios. A change in the oxidation state, crystallinity and particle size is evidenced for the nanoparticles in sample A200C. The Fe oxide nanoparticles are completely reduced in sample A300C to alpha-Fe single phase. The blocking temperature increases from 106 K in A to 110 K in A200C and above room temperature in A300C, where strong inter-particle interactions are evidenced. Magnetic parameters, of interest for applications, have been considerably varied by the specific hydrogenation treatments, in direct connection to the induced specific changes of particle size, crystallinity and phase composition. For the A and A200C samples, a field cooling dependent unidirectional anisotropy was observed especially at low temperatures, supporting the presence of nanoparticles with core-shell-like structures. Surprisingly high M-S values, almost 50% higher than for bulk metallic Fe, were evidenced in sample A300C.

36. Photodetecting properties of single CuO-ZnO core-shell nanowires with p-n radial heterojunction

Authors: Costas, A; Florica, C; Preda, N; Kuncser, A; Enculescu, I

Published: OCT 29 2020, SCIENTIFIC REPORTS, 10, DOI: 10.1038/s41598-020-74963-4

CuO-ZnO core-shell radial heterojunction nanowire arrays were obtained by a simple route which implies two cost-effective methods: thermal oxidation in air for preparing CuO nanowire arrays, acting as a p-type core and RF magnetron sputtering for coating the surface of the CuO nanowires with a ZnO thin film, acting as a n-type shell. The morphological, structural, optical and compositional properties of the CuO-ZnO core-shell nanowire arrays were investigated. In order to analyse the electrical and photoelectrical properties of the metal oxide nanowires, single CuO and CuO-ZnO core-shell nanowires were contacted by employing electron beam lithography (EBL) and focused ion beam induced deposition (FIBID). The photoelectrical properties emphasize that the p-n radial heterojunction diodes based on single CuO-ZnO core-shell nanowires behave as photodetectors, evidencing a time-depending photoresponse under illumination at 520 nm and 405 nm wavelengths. The performance of the photodetector device was evaluated by assessing its key parameters: responsivity, external quantum efficiency and detectivity. The results highlighted that the obtained CuO-ZnO core-shell nanowires are emerging as potential building blocks for a next generation of photodetector devices.

37. Unexpected magneto-functionalities of amorphous Fe-Gd thin films crossing the magnetization compensation point

Authors: Stanciu, AE; Schinteie, G; Kuncser, A; Iacob, N; Trupina, L; Ionita, I; Crisan, O; Kuncser, V

Published: MAR 15 2020, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 498, DOI: 10.1016/j.jmmm.2019.166173

A complex investigation of the morpho-structural, magnetic, magneto-optical and magneto-transport properties of amorphous Fe-Gd thin films crossing the magnetization compensation point is reported and the unexpected observed magneto-functionalities are discussed. A tendency of magnetic domain formation with increasing the Fe content over the compensation concentration is observed. The switch from a reversed Magneto-optical Kerr Effect loop to a direct loop when increasing the Fe content over the compensation point is explained via the specific contribution to the rotation of the polarization vector from each magnetic sublattice, belonging to Fe and Gd, respectively. Local atomic configurations and magnetic interactions ascertained the amorphous character and revealed an out-ofplane orientation of the magnetic moment of Fe above the compensation point. The thermomagnetic curves prove a concentration dependent behavior, explained by weakly coupled magnetization relaxation processes of the two magnetic sub-lattices. On the other hand, the magnetic hysteresis loops gave evidence of two exchange coupled magnetic phases with different coercive fields. According to structural and Fe-57 Mossbauer Spectroscopy results, the two phases correspond to definite nanosized volumes of two different average concentrations (one of them closer to the compensation point) which are randomly distributed in the film. The unexpected single step-like behavior of the magneto-resistivity curves was explained by dissimilar switching of the spins in these two magnetic phases distributed in nano-sized volumes.

38. Low temperature CO sensing under infield conditions with in doped Pd/SnO2

Authors: Stanoiu, A; Ghica, C; Somacescu, S; Kuncser, AC; Vlaicu, AM; Mercioniu, IF; Florea, OG; Simion, CE

Published: APR 1 2020, SENSORS AND ACTUATORS B-CHEMICAL, 308, DOI: 10.1016/j.snb.2020.127717

A one-step method assisted by hydrothermal treatment was approached to obtain nanocrystalline 1 and 10 mol. % In doped 2 mol.% Pd-SnO2 powders using a non-ionic surfactant Brij52 and Polyethylene glycol 6000 (PEG) as templates. Depending on In content, the samples were labeled as Pd1InSn and Pd10InSn. The obtained materials consist of nanosized crystallites packed into micrometric grains with a high porosity, as revealed by the morphological and structural investigations (SEM, TEM). A dependence of the grain size with respect to the In content has been revealed i.e. the sample Pd1InSn was showing an average grain size of around 10 nm, whilst for the sample Pd10InSn the average grain size was found to be around 5 nm. The XPS investigations highlighted the differences occurred in the surface chemistry in terms of surface hydroxylation as well as the chemical states of Pd. The sensing properties towards different CO concentrations have been examined under infield background conditions, at low operating temperature of 50 degrees C. The sensing mechanism model for CO was discussed in detail according to the possible interplay between oxygen and water related species based on the experimentally results acquired through simultaneous electrical resistance and work function measurements.

39. Influence of surfactant-tailored Mn-doped ZnO nanoparticles on ROS production and DNA damage induced in murine fibroblast cells

Authors: Popescu, T; Matei, CO; Vlaicu, ID; Tivig, I; Kuncser, AC; Stefan, M; Ghica, D; Miclea, LC; Savopol, T; Culita, DC; Moisescu, MG

Published: OCT 22 2020, SCIENTIFIC REPORTS, 10, DOI: 10.1038/s41598-020-74816-0

The present study concerns the in vitro oxidative stress responses of non-malignant murine cells exposed to surfactant-tailored ZnO nanoparticles (NPs) with distinct morphologies and different levels of manganese doping. Two series of Mn-doped ZnO NPs were obtained by coprecipitation synthesis method, in the presence of either polyvinylpyrrolidone (PVP) or sodium hexametaphosphate (SHMTP). The samples were investigated by powder X-ray Diffraction, Transmission Electron Microscopy, Fourier-Transform Infrared and Electron Paramagnetic Resonance spectroscopic methods, and N-2 adsorption-desorption analysis. The observed surfactant-dependent effects concerned: i) particle size and morphology; ii) Mn-doping level; iii) specific surface area and porosity. The relationship between the surfactant dependent characteristics of the Mn-doped ZnO NPs and their in vitro toxicity was assessed by studying the cell viability, intracellular reactive oxygen species (ROS) generation, and DNA fragmentation in NIH3T3 fibroblast cells. The results indicated a positive correlation between the specific surface area and the magnitude of the induced toxicological effects and suggested that Mn-doping exerted a protective effect on cells by diminishing the pro-oxidative action associated with the increase in the specific BET area. The obtained results support the possibility to modulate the in vitro toxicity of ZnO nanomaterials by surfactant-controlled Mn-doping.

40. Optimization of magnetic fluid hyperthermia with respect to nanoparticle shape-related parameters: case of magnetite ellipsoidal nanoparticles

Authors: Iacob, N; Kuncser, A; Comanescu, C; Palade, P; Kuncser, V

Published: MAY 22 2020, JOURNAL OF NANOPARTICLE RESEARCH, 22, DOI: 10.1007/s11051-020-04842-6

Issues related to the optimization of heat transfer mechanisms dominated by superparamagnetic relaxation are considered in the case of AC (alternating current) magnetic field hyperthermia procedures. The key role in the conversion of electromagnetic energy to the thermal one via the superparamagnetic relaxation mechanism is played by the magnetic anisotropy of nanoparticles, easily to be controlled via the shape anisotropy component. The optimization process has been discussed in the case of magnetite (Fe3O4) ellipsoidal nanoparticles with dominant shape anisotropy dispersed in different media. Nanoparticles of different sizes and aspect ratios have been considered in correlation with those specific parameters of the actuating AC magnetic field which respect an established biological safely criterion. It has been proven that the dissipated power can be maximized for a given set of biological compatible RF (radiofrequency) field parameters (frequency and field amplitude at the sample space) only for specific pairs of particle sizes and aspect ratios. For instance, it has been shown that ellipsoidal magnetite nanoparticles with 10 nm equatorial size and aspect ratio of 2 are optimal for a maximum transferred power under radiofrequency excitations of 250 kHz and field amplitude of 20 kA/m, if high viscosity dispersion media are used. The methodology for deriving the optimal shape (geometrical) parameters of a specific type of nanoparticles in conditions of using available radiofrequency excitations, or vice versa, for deriving the optimal radiofrequency working parameters in the case of ferrofluids with specific nanoparticles (type and geometry) is described and discussed in detail.

41. Electron paramagnetic resonance and microstructural insights into the thermal behavior of simonkolleite nanoplatelets

Authors: Rostas, AM; Kuncser, AC; Ghica, D; Palici, A; Maraloiu, VA; Vlaicu, ID

Published: MAY 7 2020, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 22, 9512, DOI: 10.1039/d0cp00641f

The aim of this paper is the study of the thermal behavior of the simonkolleite Zn-5(OH)(8)Cl-2 center dot H2O (ZHC) by electron paramagnetic resonance (EPR) spectroscopy, in particular. It is well known that during heating ZHC undergoes a complex transformation which involves several overlapping stages. However, with reference to the data reported on this subject, it can be concluded that there is still an ongoing debate regarding the intermediate stages of this process. The data presented in this study support a simple decomposition process of the ZHC prepared using the precipitation method. The EPR data correlated to the data obtained by other experimental techniques, such as XRD, TEM, SEM and EDX, indicate that during the thermal treatment the ZHC suffers a partial decomposition to ZnO with no intermediate products. After annealing at 500 degrees C for 1 h, a recombination process of ZHC is observed. Moreover, the kinetics associated to these decomposition steps were determined and the evolution of the paramagnetic centers was also followed and studied. This study offers new information related to the thermal behavior of ZHC, especially regarding the EPR data which is reported for the first time on this subject and material.

42. Functionalization of eggshell membranes with CuO-ZnO based p-n junctions for visible light induced antibacterial activity against Escherichia coli

Authors: Preda, N; Costas, A; Beregoi, M; Apostol, N; Kuncser, A; Curutiu, C; Iordache, F; Enculescu, I

Published: DEC 1 2020, SCIENTIFIC REPORTS, 10, DOI: 10.1038/s41598-020-78005-x

Biopolymers provide versatile platforms for designing naturally-derived wound care dressings through eco-friendly pathways. Eggshell membrane (ESM), a widely available, biocompatible biopolymer based structure features a unique 3D porous interwoven fibrous protein network. The ESM was functionalized with inorganic compounds (Ag, ZnO, CuO used either separately or combined) using a straightforward deposition technique namely radio frequency magnetron sputtering. The functionalized ESMs were characterized from morphological, structural, compositional, surface chemistry, optical, cytotoxicity and antibacterial point of view. It was emphasized that functionalization with a combination of metal oxides and exposure to visible light results in a highly efficient antibacterial activity against Escherichia coli when compared to the activity of individual metal oxide components. It is assumed that this is possible due to the fact that an axial p-n junction is created by joining the two metal oxides. This structure separates into components the charge carrier pairs promoted by visible light irradiation that further can influence the generation of reactive oxygen species which ultimately are responsible for the bactericide effect. This study proves that, by employing inexpensive and environmentally friendly materials (ESM and metal oxides) and fabrication techniques (radio frequency magnetron sputtering), affordable antibacterial materials can be developed for potential applications in chronic wound healing device area.

43. Unidirectional Magnetic Anisotropy in Dense Vertically-Standing Arrays of Passivated Nickel Nanotubes

Authors: Locovei, C; Filipoiu, N; Kuncser, A; Stanciu, AE; Antohe, S; Florica, CF; Costas, A; Enculescu, I; Piraux, L; Kuncser, V; Antohe, VA

Published: DEC 2020, NANOMATERIALS, 10, DOI: 10.3390/nano10122444

We report the facile and low-cost preparation as well as detailed characterization of dense arrays of passivated ferromagnetic nickel (Ni) nanotubes (NTs) vertically-supported onto solid Au-coated Si substrates. The proposed fabrication method relies on electrochemical synthesis within the nanopores of a supported anodic aluminum oxide (AAO) template and allows for fine tuning of the NTs ferromagnetic walls just by changing the cathodic reduction potential during the nanostructures' electrochemical growth. Subsequently, the experimental platform allowed further passivation of the Ni NTs with the formation of ultra-thin antiferromagnetic layers of nickel oxide (NiO). Using adequately adapted magnetic measurements, we afterwards demonstrated that the thickness of the NT walls and of the thin antiferromagneticNiO layer, strongly influences the magnetic behavior of the dense array of exchange-coupled Ni/NiO NTs. The specific magnetic properties of these hybrid ferromagnetic/antiferromagnetic nanosystems were then correlated with the morpho-structural and geometrical parameters of the NTs, as well as ultimately strengthened by additionally-implemented micromagnetic simulations. The effect of the unidirectional anisotropy strongly amplified by the cylindrical geometry of the ferromagnetic/antiferromagnetic interfaces has been investigated with the magnetic field applied both parallel and perpendicular to the NTs axis.

44. Enhanced critical current density at high magnetic fields in MgB2 with Ga/In acetylacetonate processed by spark plasma sintering

Authors: Batalu, D; Aldica, G; Burdusel, M; Grigoroscuta, M; Pasuk, I; Kuncser, A; Ionescu, AM; Badica, P

Published: MAY-JUN 2020, JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T, 9, 3733, DOI: 10.1016/j.jmrt.2020.01.109

Dense samples (94-96%) with starting composition (MgB2)(0.99)(X-acac)(0.01) (X-acac denotes Ga or In acetylacetonate) were obtained by spark plasma sintering. The resulting material is a superconducting composite, where carbon substitutes for boron in the crystal structure of MgB2. Added samples show enhanced critical current density at high magnetic fields and this is reflected in high values of irreversibility field (H-irr) at temperatures below 25 K when compared to a pristine sample. More efficient is In-acac addition and it promotes a H-irr of similar to 12.4T (100 A/cm(2) criterion) at 5 K. Carbon substitution for boron in the crystal structure of MgB2 has a strong influence on the pinning force and its related parameters and promotes in the added samples a grain boundary pinning mechanism as the dominant one, whereas the pristine sample with a low amount of carbon shows a major mechanism of point pinning type. However, our analysis indicates on the synergetic effects of the carbon substituting for boron and of the microstructural details on pinning and critical current density. The result strongly emphasizes the significantly different behavior of the additive during processing of the MgB2 samples, although thermal analysis experiments on both additives show very similar decomposition patterns. (C) 2020 The Authors. Published by Elsevier B.V.

45. Coagulating and flocculating ferrihydrite: application of zinc acetate salt

Authors: Islam, S; Das, S; Mishra, G; Das, B; Malakar, A; Carlomagno, I; Meneghini, C; De Giudici, G; Goncalves, LPL; Sousa, JPS; Kolen'ko, YV; Kuncser, AC; Ray, S

Published: AUG 1 2020, ENVIRONMENTAL SCIENCE-WATER RESEARCH & TECHNOLOGY, 6, 2064, DOI: 10.1039/d0ew00357c

This paper outlines a method of extraction of iron from water in the form of iron oxyhydroxide natural nanoclusters at comparatively low concentrations and varied ranges of pH using zinc acetate salt. The zinc acetate salt dissociates into Zn(2+)and acetate ions in water where Zn(2+)interacts with iron clusters present in a solution of a given iron concentration and pH, while the acetate ion helps in charge-neutralization based coagulation and consequent precipitation of such nanoclusters. The Zn(2+)ions may also lead to the growth of layered zinc hydroxide (LZH) nanosurfaces at pH >= 6 at sufficient loading. The advantage of this method is the active chemical interaction of Zn(2+)with Fe clusters, followed by growth, which ensures that only some added Zn ions remain in the water while the rest precipitate out along with the residual iron oxyhydroxide, especially at higher pH. The solid that precipitated under various different conditions was successfully evaluated by XRD (formation of ferrihydrite-like nanoclusters (n-Fh)), FTIR (the presence of acetate in the solid n-Fh), TEM (the presence of zinc at higher pH), and EXAFS (local structural characterization). ICP analysis of the obtained solid and the corresponding filtrate revealed the removal efficiency of iron and zinc from the solution at various initial concentrations and pH values. This method of extracting soluble Fh-like nanoclusters by charge neutralization appears to be a suitable promising tool for water purification, because ferrihydrite is capable of isolating other adsorbed contaminants from water, along with itself.

46. Hierarchical composites of B4C-TiB2 eutectic particles reinforced with Ti

Authors: Solodkyi, I; Bogomol, I; Bolbut, V; Loboda, P; Kuncser, A; Vasylkiv, O; Badica, P

Published: DEC 15 2020, CERAMICS INTERNATIONAL, 46, 28144, DOI: 10.1016/j.ceramint.2020.07.312

Eutectic particles of B4C-TiB2 were reinforced with Ti by spark plasma sintering (SPS) or infiltration. The SPSed samples with 20, 30 and 40 wt. % Ti consisted of ceramic phases, and had a bicontinuous macrostructure formed by the Ti-rich region and the eutectic particles region, while the infiltrated sample was a complex composite comprised of a 3D Ti-rich continuous network, composite in nature, that contained Ti-metal and in which are embedded isolated ceramic (eutectic) particles. The SPSed samples are brittle with the maximum bending strength of 300 MPa for the 30 wt. % Ti, higher than for a reference sample produced by SPS from directionally solidified eutectic particles. A higher amount of added Ti results in a higher displacement in the bending test suggesting a higher fracture toughness. Simultaneous strengthening and toughening of the composite was realized. The infiltrated sample was ductile, while its bending strength (220 MPa) was comparable to the values measured for the brittle as-introduced reference sample and the sample with 20 wt. % Ti, both produced by SPS. In the SPSed and infiltrated samples at the interface between the Ti-rich region and B4C-TiB2 eutectic particles, a local 'pull-out' intergranular fracturing mechanism mainly involving Ti-B 1D-grains was observed. This local micromechanism together with a 'pull out' macromechanism of the eutectic grains from the Ti-rich component are considered important for the bridging/anchoring behavior responsible for the strengthening and toughening processes in our novel hierarchical composites.

47. Highly Efficient Ultralow Pd Loading Supported on MAX Phases for Chemoselective Hydrogenation

Authors: Trandafir, MM; Neatu, F; Chirica, IM; Neatu, S; Kuncser, AC; Cucolea, EI; Natu, V; Barsoum, MW; Florea, M

Published: MAY 15 2020, ACS CATALYSIS, 10, 5908, DOI: 10.1021/acscatal.0c00082

Palladium is one of the most efficient metals for the hydrogenation of organic compounds. However, when molecules, such as nitroaromatics, with several reducible functionalities, are hydrogenated, Pd, like any other very active metal, such as nickel or platinum, often behaves unselectively. One strategy to render Pd more selective is to choose the proper support. Herein, we show that MAX phase powders of Ti3SiC2, Ti2AlC, or Ti3AlC2 can chemoselectively hydrogenate 4-nitrostyrene to 4-aminostyrene, with 100% selectivity, at around 3-4% conversion. To boost the latter, we loaded Ti3SiC2 with 0.0005 wt % Pd and increased the conversion to 100% while maintaining the 4-AS selectivity at >90%. By optimizing the Pd loading, we were also able to increase the turnover frequency 100-fold relative to previous literature results. The identification of this highly efficient and chemoselective system has broad implications for the design of cost-effective, earth-abundant, nontoxic, metal catalysts, with ultralow noble metal loadings.

48. Mesoporous Cobalt Ferrite Nanosystems Obtained by Surfactant-Assisted Hydrothermal Method: Tuning Morpho-structural and Magnetic Properties via pH-Variation

Authors: Palade, P; Comanescu, C; Kuncser, A; Berger, D; Matei, C; Iacob, N; Kuncser, V

Published: MAR 2020, NANOMATERIALS, 10, DOI: 10.3390/nano10030476

A facile and cheap surfactant-assisted hydrothermal method was used to prepare mesoporous cobalt ferrite nanosystems with BET surface area up to 151 m(2)/g. These mesostructures with high BET surface areas and pore sizes are made from assemblies of nanoparticles (NPs) with average sizes between 7.8 and 9.6 nm depending on the initial pH conditions. The pH proved to be the key factor for controlling not only NP size, but also the phase purity and the porosity properties of the mesostructures. At pH values lower than 7, a parasite hematite phase begins to form. The sample obtained at pH = 7.3 has magnetization at saturation M-s = 38 emu/g at 300 K (54.3 emu/g at 10 K) and BET surface area S-BET = 151 m(2)/g, whereas the one obtained at pH = 8.3 has M-s = 68 emu/g at 300 K (83.6 emu/g at 10 K) and S-BET = 101 m(2)/g. The magnetic coercive field values at 10 K are high at up to 12,780 Oe, with a maximum coercive field reached for the sample obtained at pH = 8.3. Decreased magnetic performances are obtained at pH values higher than 9. The iron occupancies of the tetrahedral and octahedral sites belonging to the cobalt ferrite spinel structure were extracted through decomposition of the Mossbauer patterns in spectral components. The magnetic anisotropy constants of the investigated NPs were estimated from the temperature dependence of the hyperfine magnetic field. Taking into consideration the high values of BET surface area and the magnetic anisotropy constants as well as the significant magnetizations for saturation at ambient temperature, and the fact that all parameters can be adjusted through the initial pH conditions, these materials are very promising as recyclable anti-polluting agents, magnetically separable catalysts, and targeted drug delivery vehicles.

49. High-temperature strength of boron carbide with Pt grain-boundary framework in situ synthesized during spark plasma sintering

Authors: Vasylkiv, O; Demirskyi, D; Borodianska, H; Kuncser, A; Badica, P

Published: MAY 2020, CERAMICS INTERNATIONAL, 46, 9144, DOI: 10.1016/j.ceramint.2019.12.163

Grain boundaries, twins, and defects are considered to influence the thermomechanical behavior of any covalent ceramic, as a result, monolithic B4C samples show different curve shapes of bending strength vs temperature and the present theoretical models fail to fit them over the entire temperature range. To overcome these issues, we fabricated a novel high-density boron carbide and evaluated its high-temperature bending strength. The as-obtained ceramic is composed of boron carbide grains and a fine grain-boundary metal Pt framework. The material shows a decreased strength, which is due to a non-linear increase in the volume expansion coefficient of the B4C. Recovery in strength above 1000 degrees C is due to the presence of twins, their growth and rearrangements. We consider twins rearrangements are the pieces of evidence for a novel 'micro' mechanism of high-temperature stress accommodation for the boron carbide bulks.

50. Complex exchange coupling mechanisms in SRO/BFO/Fe heterostructures

Authors: Greculeasa, SG; Schinteie, G; Hrib, LM; Stancu, V; Pasuk, I; Kuncser, A; Kuncser, V

Published: JAN 30 2019, JOURNAL OF ALLOYS AND COMPOUNDS, 773, 345, DOI: 10.1016/j.jallcom.2018.09.208

Temperature dependent interfacial coupling mechanisms in SRO/BFO/Fe layered structures were investigated. The BFO/Fe heterostructures were prepared by PLD and sputtering, respectively, on the STO(0 0 1) substrate with a 20 nm SRO buffer layer. An annealing treatment in external magnetic field was further applied. Complex characterizations with X-ray diffraction, atomic force microscopy, Transmission Electron Microscopy, Mossbauer spectroscopy, magneto-optic Kerr effect and SQUID magnetometry were performed. Before annealing, the films show good crystallization and epitaxy of the SRO and BFO layers with smooth interfaces. Two coupling mechanisms of the ferromagnetic layers (top Fe and bottom SRO, respectively) to the epitaxial BFO film with mainly antiferromagnetic structure were evidenced in the as deposited samples at low temperatures. Negative exchange bias fields of up to 67(10) Oe and 37(5) Oe at low temperatures were observed for the two ferromagnetic components, respectively, depending on the thickness of the Fe layer. The field annealing treatments induce a specific morphology and magnetic spin structure at both interfaces of the BFO spacer layer, giving rise to a long range magnetostatic coupling between the two ferromagnetic films, in addition to the interfacial couplings. Moreover, the experimentally evidenced Fe clusters penetrating the BFO/Fe interface toward the BFO layer give support for this interaction. As an additional consequence, a considerable enhancement of both uniaxial and unidirectional anisotropies as well as an increased blocking temperature of exchange bias were obtained. The involved exchange coupling mechanisms were discussed in detail. (C) 2018 Elsevier B.V. All rights reserved.

51. Direct Immobilization of Biomolecules through Magnetic Forces on Ni Electrodes via Ni Nanoparticles: Applications in Electrochemical Biosensors

Authors: Barsan, MM; Enache, TA; Preda, N; Stan, G; Apostol, NG; Matei, E; Kuncser, A; Diculescu, VC

Published: JUN 5 2019, ACS APPLIED MATERIALS & INTERFACES, 11, 19877, DOI: 10.1021/acsami.9b04990

The present work describes a new simple procedure for the direct immobilization of biomolecules on Ni electrodes using magnetic Ni nanoparticles (NiNPs) as biomolecule carriers. Ni electrodes were fabricated by electroplating, and NiNPs were chemically synthesized. The chemical composition, crystallinity, and granular size of Ni electrodes, NiNP, and NiNP-modified Ni electrodes (NiNP/Ni) were determined by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy (XPS). The electrochemical characterization of Ni electrodes by cyclic voltammetry and electrochemical impedance spectroscopy confirmed the existence of nickel oxides, hydroxides, and oxohydroxide films at the surface of Ni. Magnetic characterization and micromagnetic simulations were performed in order to prove that the magnetic force is responsible for the immobilization process. Further, Ni electrodes were employed as amperometric sensors for the detection of hydrogen peroxide because it is an important performance indicator for a material to be applied in biosensing. The working principle for magnetic immobilization of the enzyme-functionalized NiNP, without the use of external magnetic sources, was demonstrated for glucose oxidase (GOx) as a model enzyme. XPS results enabled to identify the presence of GOx attached to the NiNP (GOx-NiNP) on Ni electrodes. Finally, glucose detection and quantification were evaluated with the newly developed GOx-NiNP/Ni biosensor by amperometry at different potentials, and control experiments at different electrode materials in the presence and absence of NiNP demonstrated their importance in the biosensor architecture.

52. Nanoclustered Pd decorated nanocrystalline Zn doped SnO2 for ppb NO2 detection at low temperature

Authors: Somacescu, S; Ghica, C; Simion, CE; Kuncser, AC; Vlaicu, AM; Stefan, M; Ghica, D; Florea, OG; Mercioniu, IF; Stanoiu, A

Published: SEP 1 2019, SENSORS AND ACTUATORS B-CHEMICAL, 294, 156, DOI: 10.1016/j.snb.2019.05.033

Nanoclustered Pd (2 mol%) was used to decorate Zn doped SnO2 (10 mol% Zn) in order to increase its sensing performances. Zn doped SnO2 built from nanoparticles was prepared by a hydrothermal method using a nonionic surfactant -Brij52 and Tripropylamine (TPA) as co-templates. The presence of well-dispersed Zn2+ ions in the SnO2 matrix leads to a nonstoichiometric surface. Pd was deposited by subsequent wet impregnation using hydrazine as reducing agent. The as obtained powders were deposited as thick layers onto commercial substrates, in order to obtain the sensitive structures. The coexistence of a mixture of valence states (Pd-0, Pd2+ and Pd4+) was highlighted on the surface of the as prepared layers. Several aspects have been followed regarding the Zn and Pd dispersion into the SnO2 matrix: the large scale and low scale morphology (SEM and TEM/HRTEM) in relation with the synthesis route, the obtained crystallographic phases (XRD, SAED) and the way in which the Zn2+ ions are inserted into the SnO2 structure (XRD, XPS, EPR), the spatial distribution of the added chemical elements, Zn and Pd (SEM, STEM, EDS). All these morphological and structural aspects, as well as the Pd surface chemistry, have been correlated with the sensing properties of the nanostructured materials under controlled gas atmosphere. Through this study, we could harvest the specific role of the aforementioned loadings towards selective detection of low NO2 concentrations, between 350 ppb to 5 ppm, at low operating temperature of 100 degrees C, for infield conditions.

53. Core-shell nanowire arrays based on ZnO and CuxO for water stable photocatalysts

Authors: Florica, C; Costas, A; Preda, N; Beregoi, M; Kuncser, A; Apostol, N; Popa, C; Socol, G; Diculescu, V; Enculescu, I

Published: NOV 21 2019, SCIENTIFIC REPORTS, 9, DOI: 10.1038/s41598-019-53873-0

Staggered gap radial heterojunctions based on ZnO-CuxO core-shell nanowires are used as water stable photocatalysts to harvest solar energy for pollutants removal. ZnO nanowires with a wurtzite crystalline structure and a band gap of approximately 3.3 eV are obtained by thermal oxidation in air. These are covered with an amorphous CuxO layer having a band gap of 1.74 eV and subsequently form core-shell heterojunctions. The electrical characterization of the ZnO pristine and ZnO-CuxO core-shell nanowires emphasizes the charge transfer phenomena at the junction and at the interface between the nanowires and water based solutions. The methylene blue degradation mechanism is discussed taking into consideration the dissolution of ZnO in water based solutions for ZnO nanowires and ZnO-CuxO core-shell nanowires with different shell thicknesses. An optimum thickness of the CuxO layer is used to obtain water stable photocatalysts, where the ZnO-CuxO radial heterojunction enhances the separation and transport of the photogenerated charge carriers when irradiating with UV-light, leading to swift pollutant degradation.

54. Fluorescent coumarin-modified mesoporous SBA-15 nanocomposite: Physico-chemical characterization and interaction with prokaryotic and eukaryotic cells

Authors: Tudose, M; Culita, DC; Voicescu, M; Musuc, AM; Kuncser, AC; Bleotu, C; Popa, M; Marutescu, L; Chifiriuc, MC; Nicolescu, M; Deleanu, C

Published: NOV 1 2019, MICROPOROUS AND MESOPOROUS MATERIALS, 288, DOI: 10.1016/j.micromeso.2019.109583

Three novel fluorescent mesoporous silica composites were obtained through the covalent immobilization of 7-amino-4-(trifluoromethyl)coumarin, 6-amino-chromen-2-one and 7-amino-4-methyl-3-coumarinylacetic acid, respectively, inside the channels of mesoporous silica SBA-15. Presence of fluorescent moieties was assessed by elemental analysis, thermal analysis, infrared, UV-Vis, Si-29- and C-13-CP/MAS NMR, and fluorescence spectroscopy. Reduction of specific surface area of the composites by 50-60% and also the average pore size diameter by 0.5-0.55 nm compared to unfunctionalized SBA-15 was evidenced by N-2 adsorption desorption analysis. Their antioxidant, antimicrobial activity and cytotoxicity on HeLa-2 cells were evaluated in order to formulate some potential applications of the obtained compounds. The obtained results recommend the obtained fluorescent mesoporous nanocomposites as potential candidates for the development of novel probes for the in situ tracking of oxidative stress, as well as for antimicrobial applications.

55. Radial heterojunction based on single ZnO-CuxO core-shell nanowire for photodetector applications

Authors: Costas, A; Florica, C; Preda, N; Apostol, N; Kuncser, A; Nitescu, A; Enculescu, I

Published: APR 3 2019, SCIENTIFIC REPORTS, 9, DOI: 10.1038/s41598-019-42060-w

ZnO-CuxO core-shell radial heterojunction nanowire arrays were fabricated by a straightforward approach which combine two simple, cost effective and large-scale preparation methods: (i) thermal oxidation in air of a zinc foil for obtaining ZnO nanowire arrays and (ii) radio frequency magnetron sputtering for covering the surface of the ZnO nanowires with a CuxO thin film. The structural, compositional, morphological and optical properties of the high aspect ratio ZnO-CuxO core-shell nanowire arrays were investigated. Individual ZnO-CuxO core-shell nanowires were contacted with Pt electrodes by means of electron beam lithography technique, diode behaviour being demonstrated. Further it was found that these n-p radial heterojunction diodes based on single ZnO-CuxO nanowires exhibit a change in the current under UV light illumination and therefore behaving as photodetectors.

56. Formation peculiarities and optical properties of highly-doped (Y(0.86)La(0.09)Vb(0.05))(2)O-3 transparent ceramics

Authors: Kryzhanovska, OS; Baumer, VN; Parkhomenko, SV; Doroshenko, AG; Yavetskiy, RP; Balabanov, AE; Tolmachev, AV; Skorik, SN; Li, J; Kuncser, A

Published: SEP 2019, CERAMICS INTERNATIONAL, 45, 16007, DOI: 10.1016/j.ceramint.2019.05.111

Formation peculiarities of highly-doped (Y(0.86)La(0.09)Vb(0.05))(2)O-3 transparent ceramics have been studied by X-ray diffraction and electron microscopy methods. The phase composition evolution of 1.81Y(2)O(3).0.18La(2)O(3)0.01Yb(2)O(3) powder mixtures annealed at the temperatures of 1100, 1200, 1300, and 1400 degrees C has been studied by XRD. It has been shown that Yb2O3 phase dissolves in Y2O3 matrix in the calcination temperature range of 1300-1400 degrees C. Complete dissolution of La2O3 in Y2O3 matrix occurs at temperatures above 1400 degrees C. La3+ ions enter in Y2O3 and Yb2O3 crystal structures simultaneously in the 1200-1300 degrees C range, which leads to a remarkable increase in the volume of the corresponding crystal lattices. The possible reasons for suppressing the crystalline growth of Y2O3 and Yb2O3 cubic phases have been discussed. Finally, (Y(0.86)La(0.09)Vb(0.05))(2)O-3 transparent ceramics have been obtained by solid-state vacuum sintering at 1650-1750 degrees C. Ceramics synthesized at a temperature of 1750 degrees C have been characterized by an in-line optical transmittance of 60% and a homogeneous distribution of constituent components within the volume and along the grain boundaries.

57. Bulks of Al-B-C obtained by reactively spark plasma sintering and impact properties by Split Hopkinson Pressure Bar

Authors: Vasylkiv, O; Borodianska, H; Demirskyi, D; Li, P; Suzuki, TS; Grigoroscuta, MA; Pasuk, I; Kuncser, A; Badica, P

Published: DEC 20 2019, SCIENTIFIC REPORTS, 9, DOI: 10.1038/s41598-019-55888-z

Mixtures of B4C, alpha-AlB12 and B powders were reactively spark plasma sintered at 1800 degrees C. Crystalline and amorphous boron powders were used. Samples were tested for their impact behavior by the Split Hopkinson Pressure Bar method. When the ratio R = B4C/alpha-AlB12 >= 1.3 for a constant B-amount, the major phase in the samples was the orthorhombic AlB24C4, and when R < 1 the amount of AlB24C4 significantly decreased. Predictions that AlB24C4 has the best mechanical impact properties since it is the most compact and close to the ideal cubic packing among the Al-B-C phases containing B-12-type icosahedra were partially confirmed. Namely, the highest values of the Vickers hardness (32.4 GPa), dynamic strength (1323 MPa), strain and toughness were determined for the samples with R = 1.3, i.e., for the samples with a high amount of AlB24C4. However, the existence of a maximum, detectable especially in the dynamic strength vs. R, indicated the additional influence of the phases and the composite's microstructure in the samples. The type of boron does not influence the dependencies of the indicated mechanical parameters with R, but the curves are shifted to slightly higher values for the samples in which amorphous boron was used.

58. Growth of SrTiO3 Single Crystals with a Diameter of about 30 mm by the Verneuil Method

Authors: Tateno, Y; Endo, K; Arisawa, S; Vlaicu, AM; Nedelcu, L; Preda, N; Secu, M; Iordanescu, R; Kuncser, AC; Badica, P

Published: FEB 2019, CRYSTAL GROWTH & DESIGN, 19, 612, DOI: 10.1021/acs.cgd.8b01004

The work demonstrates growth by the Verneuil method of SrTiO3 single crystals of 30 mm in diameter. Experiments are performed under an industrial environment. Growth was for 4.75 h, i.e., within one production shift. The optimum growth conditions for which the length of the region with bubbles D is zero and the effective length EL (i.e., the crystal length of commercial value) is maximized are for the amount of SrCO3 additive of similar to 3 wt % and for H-2 outer flow rate of similar to 35 L/min. These two parameters show the strongest influence on the bubble-free growth, but other growth parameters (H-2 inner flow rate, O-2 flow rate increase, rotation speed) were also optimized. Selected crystals are characterized from the structural, microstructural, optical, and THz spectroscopy viewpoints, and they are compared with a commercial substrate and with crystals reported in the literature. This work opens the possibility for the industrial growth of large SrTiO3 single crystals and commercialization of large area substrates.

59. Superconducting MgB2 textured bulk obtained by ex situ spark plasma sintering from green compacts processed by slip casting under a 12T magnetic field

Authors: Grigoroscuta, MA; Sandu, V; Kuncser, A; Pasuk, I; Aldica, G; Suzuki, TS; Vasylkiv, O; Badica, P

Published: DEC 2019, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 32, DOI: 10.1088/1361-6668/ab4620

MgB2 green bodies were prepared by magnetic field slip casting in ethyl alcohol with added polyethyleneimine dispersing agent under a high magnetic field, mu H-0(0) = 12 T. Samples were further processed by spark plasma sintering (SPS) and characterized for superconducting properties. Slip casting provides texturing of MgB2 (the degree of c-axis orientation is approximately 3.5%), which is further increased significantly (to about 21%) in the SPSed sample. The critical current density (J(c)) displays anisotropy relative to the orientation of the measuring magnetic field. Specific features of J(c)(H, T) and of the pinning force extracted from magnetic measurements with the field parallel and perpendicular to H-0 are discussed.

60. On the relaxation time of interacting superparamagnetic nanoparticles and implications for magnetic fluid hyperthermia

Authors: Kuncser, A; Iacob, N; Kuncser, VE

Published: JUN 24 2019, BEILSTEIN JOURNAL OF NANOTECHNOLOGY, 10, 1289, DOI: 10.3762/bjnano.10.127

A critical discussion on the presently available models for the relaxation time of magnetic nanoparticles approaching the superparamagnetic regime in the presence of interparticle dipolar interactions is considered. The direct implications of such interactions for magnetic fluid hyperthermia therapy through susceptibility loss mechanisms give rise to an indirect method for their study via specific absorption rate measurements performed on ferrofluids of different volume fractions. The theoretical support for the specific evolution of the relaxation time constant and the anisotropy energy barrier versus the interparticle interactions in a perturbation approach of the simple Neel expression for the relaxation time is provided via static and time-dependent micromagnetic simulations.

61. Zinc incorporation in marine bivalve shells grown in mine-polluted seabed sediments: a case study in the Malfidano mining area (SW Sardinia, Italy)

Authors: Medas, D; Carlomagno, I; Meneghini, C; Aquilanti, G; Araki, T; Bedolla, DE; Buosi, C; Casu, MA; Gianoncelli, A; Kuncser, AC; Maraloiu, VA; De Giudici, G

Published: DEC 2018, ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH, 25, 36660, DOI: 10.1007/s11356-018-3504-y

Zinc incorporation into marine bivalve shells belonging to different genera (Donax, Glycymeris, Lentidium, and Chamelea) grown in mine-polluted seabed sediments (Zn up to 1% w/w) was investigated using x-ray diffraction (XRD), chemical analysis, soft x-ray microscopy combined with low-energy x-ray fluorescence (XRF) mapping, x-ray absorption spectroscopy (XAS), and transmission electron microscopy (TEM). These bivalves grew their shells, producing aragonite as the main biomineral and they were able to incorporate up to 2.0-80mg/kg of Zn, 5.4-60mg/kg of Fe and 0.5-4.5mg/kg of Mn. X-ray absorption near edge structure (XANES) analysis revealed that for all the investigated genera, Zn occurred as independent Zn mineral phases, i.e., it was not incorporated or adsorbed into the aragonitic lattice. Overall, our results indicated that Zn coordination environment depends on the amount of incorporated Zn. Zn phosphate was the most abundant species in Donax and Lentidium genera, whereas, Chamelea shells, characterized by the highest Zn concentrations, showed the prevalence of Zn-cysteine species (up to 56% of total speciation). Other Zn coordination species found in the investigated samples were Zn hydrate carbonate (hydrozincite) and Zn phosphate. On the basis of the coordination environments, it was deduced that bivalves have developed different biogeochemical mechanisms to regulate Zn content and its chemical speciation and that cysteine plays an important role as an active part of detoxification mechanism. This work represents a step forward for understanding bivalve biomineralization and its significance for environmental monitoring and paleoreconstruction.

62. Ferroelectric photovoltaic characteristics of pulsed laser deposited 0.5Ba (Zr0.2Ti0.8)O-3-0.5(Ba0.7Ca0.3)TiO3/ZnO heterostructures

Authors: Silva, JPB; Sekhar, KC; Cortes-Juan, F; Negrea, RF; Kuncser, AC; Connolly, JP; Ghica, C; Moreira, JA

Published: JUN 2018, SOLAR ENERGY, 167, 23, DOI: 10.1016/j.solener.2018.03.072

In this work, we investigate the photovoltaic response of Pt/0.5Ba(Zr0.2Ti0.8)O-3-0.5(Ba0.7Ca0.3)TiO3(0.5BZT-0.5BCT)/ITO structures through the insertion of a semiconductor ZnO layer at different positions. The values of short-circuit photocurrent density (J(sc)) of the Pt/ZnO/0.5BZT-0.5BCT/ITO, Pt/0.5BZT-0.5BCT/ZnO/ITO and Pt/ZnO/0.5BZT-0.5BCT/ZnO/ITO capacitors are around 5.31, 0.0034 and 0.052 mA/cm(2), respectively. The enhanced photovoltaic (PV) effect is observed when ZnO layer is inserted between Pt and the 0.5BZT-0.5BCT layer. The built-in field developed at the ZnO/ferroelectric interface in the same direction of the depolarizing field, provides a favorable electric potential for the efficient separation and transportation of photo generated e-h pairs. Furthermore, the polarization-dependent interfacial coupling effect enhances PV effect, which is confirmed by investigating the role of polarization flipping on switchable photo response. This work provides an efficient pathway in tuning the PV response in ferroelectric-based solar cells.

63. Ex Situ Spark Plasma Sintering of Short Powder-in-Tube MgB2 Tapes with Open and Closed Ends

Authors: Aldica, G; Burdusel, M; Popa, S; Pasuk, I; Ionescu, AM; Kuncser, A; Badica, P

Published: NOV 2018, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 31, 3432, DOI: 10.1007/s10948-018-4616-9

Short powder-in-tube tapes of MgB2 in the Fe sheath were fabricated by ex situ route from a commercial powder containing some free Mg and MgO impurity phases. The final heat treatment was performed by spark plasma sintering (SPS). Tapes were with open (OT) or closed (CT) endings. Closed endings were made by folding and pressing. The MgB2 core of the OT sample has shown a higher low-field critical current density, a higher maximum pinning force, a slightly higher disorder, smaller average MgB2 crystallite size, a weak contact between Fe and MgB2 core, and more macro-flux jumps. The upper and irreversibility fields were similar for OT and CT samples. In the center of the MgB2 cores, the detected impurity phase is MgO, while at the interface with Fe, MgB4 also occurs. Impurity phases found at interface, MgO and MgB4, are present in the center of the bulk SPSed samples. Reactions and pinning-force-related parameters are discussed with respect to Mg behavior influenced by condition of endings. It is inferred that the presence of free Mg in the raw MgB2 powder has an important contribution to observed differences, and its removal or control is recommended.

64. Improved Optical and Morphological Properties of Vinyl-Substituted Hybrid Silica Materials Incorporating a Zn-Metalloporphyrin

Authors: Dudas, Z; Fagadar-Cosma, E; Len, A; Romanszki, L; Almasy, L; Vlad-Oros, B; Dascalu, D; Krajnc, A; Kriechbaum, M; Kuncser, A

Published: APR 2018, MATERIALS, 11, DOI: 10.3390/ma11040565

This work is focused on a novel class of hybrid materials exhibiting enhanced optical properties and high surface areas that combine the morphology offered by the vinyl substituted silica host, and the excellent absorption and emission properties of 5,10,15,20-tetrakis(N-methyl-4-pyridyl) porphyrin-Zn(II) tetrachloride as a water soluble guest molecule. In order to optimize the synthesis procedure and the performance of the immobilized porphyrin, silica precursor mixtures of different compositions were used. To achieve the requirements regarding the hydrophobicity and the porous structure of the gels for the successful incorporation of porphyrin, the content of vinyltriacetoxysilane was systematically changed and thoroughly investigated. Substitution of the silica gels with organic groups is a viable way to provide new properties to the support. An exhaustive characterization of the synthesized silica samples was realised by complementary physicochemical methods, such as infrared spectroscopy (FT-IR), absorption spectroscopy (UV-Vis) and photoluminescence, nuclear magnetic resonance spectroscopy (Si-29-MAS-NMR) transmission and scanning electron microscopy (TEM and SEM), nitrogen absorption (BET), contact angle (CA), small angle X ray and neutron scattering (SAXS and SANS). All hybrids showed an increase in emission intensity in the wide region from 575 to 725 nm (Q bands) in comparison with bare porphyrin. By simply tuning the vinyltriacetoxysilane content, the hydrophilic/hydrophobic profile of the hybrid materials was changed, while maintaining a high surface area. Good control of hydrophobicity is important to enhance properties such as dispersion, stability behaviour, and resistance to water, in order to achieve highly dispersible systems in water for biomedical applications.

65. Magnetism and magnetoresistance of single Ni-Cu alloy nanowires

Authors: Costas, A; Florica, C; Matei, E; Toimil-Molares, ME; Stavarache, I; Kuncser, A; Kuncser, V; Enculescu, I

Published: AUG 30 2018, BEILSTEIN JOURNAL OF NANOTECHNOLOGY, 9, 2355, DOI: 10.3762/bjnano.9.219

Arrays of magnetic Ni-Cu alloy nanowires with different compositions were prepared by a template-replication technique using electrochemical deposition into polycarbonate nanoporous membranes. Photolithography was employed for obtaining interdigitated metallic electrode systems of Ti/Au onto SiO2/Si substrates and subsequent electron beam lithography was used for contacting single nanowires in order to investigate their galvano-magnetic properties. The results of the magnetoresistance measurements made on single Ni-Cu alloy nanowires of different compositions have been reported and discussed in detail. A direct methodology for transforming the magnetoresistance data into the corresponding magnetic hysteresis loops was proposed, opening new possibilities for an easy magnetic investigation of single magnetic nanowires in the peculiar cases of Stoner-Wohlfarth-like magnetization reversal mechanisms. The magnetic parameters of single Ni-Cu nanowires of different Ni content have been estimated and discussed by the interpretation of the as derived magnetic hysteresis loops via micromagnetic modeling. It has been theoretically proven that the proposed methodology can be applied over a large range of nanowire diameters if the measurement geometry is suitably chosen.

66. Coordination environment of Zn in foraminifera Elphidium aculeatum and Quinqueloculina seminula shells from a polluted site

Authors: de Giudici, G; Meneghini, C; Medas, D; Buosi, C; Zuddas, P; Iadecola, A; Mathon, O; Cherchi, A; Kuncser, AC

Published: JAN 20 2018, CHEMICAL GEOLOGY, 477, 111, DOI: 10.1016/j.chemgeo.2017.12.009

Foraminifera, unicellular organisms that are widespread throughout marine ecosystems, build Ca-carbonate shells that may incorporate trace metals present in the ocean waters because of natural or anthropogenic supply. In this study, we focussed on the trace element Zn, which is abundant in both contaminated and clean waters. We used X-ray and electron spectromicroscopy to investigate the Zn coordinative environment in individual shells of two species of benthic foraminifera, Elphidium aculeatum and Quinqueloculina seminula, that were sampled from a heavy-metal polluted area of Sardinia, Italy. These species synthesise the Ca-carbonate in extracellular and intracellular spaces, respectively, which implies some diversity in their physiologies and cation transport processes, and they can adapt and survive in metal-polluted environments. Our analyses of X-ray micro-fluorescence (mu-XRF) maps and Zn-K mu-X-ray absorption near-edge spectroscopy (XANES) reveal that although 50% of Zn occurs as a Ca substitute in calcite or as a tetracoordinate oxygen-adsorbed ion, detectable amounts can also be found in other Zn-independent mineral phases, particularly hydrozincite, whose formation is due to foraminiferal cellular processes. Other Zn phases, sphalerite (attributed to early diagenetic process) and Zn-phosphate, were recognised. Moreover, we found distinct differences in the Zn concentration, distribution and chemical speciation at the micro- and nano-metric scales of the investigated E. aculeatum and Q. seminula species. In the calcite needles of Q. seminula, Zn is uniformly distributed and recognised in a disordered local environment, which suggests that it is incorporated in the calcite phase during the intracellular calcification process. These findings offer insight into Zn incorporation in foraminifera and its potential application in biomonitoring and environmental studies.

67. Local configurations and atomic intermixing in as-quenched and annealed Fe1-xCrx and Fe1-xMox ribbons

Authors: Stanciu, AE; Greculeasa, SG; Bartha, C; Schinteie, G; Palade, P; Kuncser, A; Leca, A; Filoti, G; Birsan, A; Crisan, O; Kuncser, V

Published: 2018, PHILOSOPHICAL MAGAZINE, 98, 1067, DOI: 10.1080/14786435.2018.1425556

Local atomic configuration, phase composition and atomic intermixing in Fe-rich Fe1-xCrx and Fe1-xMox ribbons (x = 0.05, 0.10, 0.15), of potential interest for high-temperature applications and nuclear devices, are investigated in this study in relation to specific processing and annealing routes. The Fe-based thin ribbons have been prepared by induction melting, followed by melt spinning and further annealed in He at temperatures up to 1250 degrees C. The complex structural, compositional and atomic configuration characterisation has been performed by means of X-ray diffraction (XRD), transmission Mossbauer spectroscopy and differential scanning calorimetry (TG-DSC). The XRD analysis indicates the formation of the desired solid solutions with body-centred cubic (bcc) structure in the as-quenched state. The Mossbauer spectroscopy results have been analysed in terms of the two-shell model. The distribution of Cr/Mo atoms in the first two coordination spheres is not homogeneous, especially after annealing, as supported by the short-range order parameters. In addition, high-temperature annealing treatments give rise to oxidation of Fe (to haematite, maghemite and magnetite) at the surface of the ribbons. Fe1-xCrx alloys are structurally more stable than the Mo counterpart under annealing at 700 degrees C. Annealing at 1250 degrees C in He enhances drastically the Cr clustering around Fe nuclei.

68. Limits and Particularities of the Synthesis of Ba1-xCaxTiO3 for Piezoelectric Applications, by Topochemical Conversion from Molten Salt Solutions

Authors: Vlaicu, ID; Maraloiu, AV; Ghica, D; Mercioniu, IF; Stefan, M; Vlaicu, AM; Negrea, RF; Kuncser, AC; Bulat, S; Krzmanc, MM; Ciobanu, R; Plopa, O

Published: 2018, 2018 INTERNATIONAL CONFERENCE AND EXPOSITION ON ELECTRICAL AND POWER ENGINEERING (EPE), 1050, DOI:

Because of the unique properties of the ferroelectric perovskite particles with a well-defined anisotropic form like shape-and size dependent at low dimensions they have all the attention of the scientific world. Extensive morphostructural techniques will be used to characterize the piezoelectric material.

69. Electrochemically shape-controlled transformation of magnetron sputtered platinum films into platinum nanostructures enclosed by high-index facets

Authors: Khalakhan, I; Lavkova, J; Matolinova, I; Vorokhta, M; Potin, V; Kus, P; Vaclavu, M; Maraloiu, VA; Kuncser, AC; Matolin, V

Published: JAN 15 2017, SURFACE & COATINGS TECHNOLOGY, 309, 11, DOI: 10.1016/j.surfcoat.2016.11.017

A new method based on transformation of magnetron sputtered platinum thin films into platinum nanostructures enclosed by high-index facets, using electrochemical potential cycling in a twin working electrode system is reported. The controllable formation of various Pt nanostructures, described in this paper, indicates that this method can be used to control a selective growth of high purity Pt nanostructures with specific shapes (facets or edges). The method opens up new possibilities for electrochemical preparation of nanostructured Pt catalysts at high yield. (C) 2016 Elsevier B.V. All rights reserved.

70. Magnetite-based glass-ceramics prepared by controlled crystallization of borosilicate glasses: Effect of nucleating agents on magnetic properties and relaxation

Authors: Sandu, V; Cimpoiasu, E; Greculeasa, S; Kuncser, A; Nicolescu, MS; Kuncser, V

Published: FEB 15 2017, CERAMICS INTERNATIONAL, 43, 3413, DOI: 10.1016/j.ceramint.2016.11.188

The specific magnetic structure and magnetic relaxation phenomena in magnetite nanoentities grown in a glassy matrix by controlled crystallization of Fe-containing borosilicate and boroaluminosilicate glasses in the presence of two types of nucleating agents, Cr2O3 and P2O5, were investigated. The structure, morphology and magnetic properties are strongly influenced by the nucleating agents. Cr2O3 generates magnetite-based glass ceramics with magnetite configurations showing an upward relaxation of magnetization at low and high temperatures but downward at intermediate temperatures. The magnetite grown with P2O5 displays only downward relaxation but with different signs of the temperature derivative of the relaxation rate S in different temperature ranges. The observed effects are discussed with respect to the following factors: i) the existence of a multimodal size distribution of the magnetite (nano)particles as revealed by high resolution electron microscopy; ii) the degree of occupation of different sublattices of the magnetite structure with Fe3+ and Fe2+ ions; and the interplay between the relaxation mechanisms in different temperature ranges.

71. Significant change of local atomic configurations at surface of reduced activation Eurofer steels induced by hydrogenation treatments

Authors: Greculeasa, SG; Palade, P; Schinteie, G; Kuncser, A; Stanciu, A; Lungu, GA; Porosnicu, C; Lungu, CP; Kuncser, V

Published: APR 30 2017, APPLIED SURFACE SCIENCE, 402, DOI: 10.1016/j.apsusc.2017.01.056

Reduced-activation steels such as Eurofer alloys are candidates for supporting plasma facing components into kamak-like nuclear fusion reactors. In order to investigate the impact of hydrogen/deuterium insertion in their crystalline lattice, annealing treatments in hydrogen atmosphere have been applied on Eurofer slabs. The resulting samples have been analyzed with respect to local structure and atomic configuration both before and after successive annealing treatments, by X-ray diffractometry (XRD), scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS) and conversion electron Mossbauer spectroscopy (CEMS). The corroborated data point out for a bcc type structure of the non-hydrogenated alloy, with an average alloy composition approaching Fe0.9Cr0.1 along a depth of about 100 nm. EDS elemental maps do not indicate surface inhomogeneities in concentration whereas the Mossbauer spectra prove significant deviations from a homogeneous alloying. The hydrogenation increases the expulsion of the Cr atoms toward the surface layer and decreases their oxidation, with considerable influence on the surface properties of the steel. The hydrogenation treatment is therefore proposed as a potential alternative for a convenient engineering of the surface of different Fe-Cr based alloys.(C) 2017 Elsevier B.V. All rights reserved.

72. A general perspective on the magnetization reversal in cylindrical soft magnetic nanowires with dominant shape anisotropy

Authors: Kuncser, A; Antohe, S; Kuncser, V

Published: FEB 1 2017, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 423, 38, DOI: 10.1016/j.jmmm.2016.09.066

Peculiarities of the magnetization reversal process in cylindrical Ni-Cu soft magnetic nanowires with dominant shape anisotropy are analyzed via both static and time dependent micromagnetic simulations. A reversible process involving acoherent-like spin rotation is always observed for magnetic fields applied perpendicularly to the easy axis whereas nucleation of domain walls is introduced for fields applied along the easy axis. Simple criteria for making distinction between a Stoner-Wohlfarth type rotation and a nucleation mechanism in systems with uniaxial magnetic anisotropy are discussed. Superposed reversal mechanisms can be in action for magnetic fields applied at arbitrary angles with respect to the easy axis within the condition of an enough strong axial component required by the nucleation. The dynamics of the domain wall, involving two different stages (nucleation and propagation), is discussed with respect to initial computing conditions and orientations of the magnetic field. A nucleation time of about 3 ns and corkscrew domain walls propagating with a constant velocity of about 150 m/s are obtained in case of Ni-Cu alloy (Ni rich side) NWs with diameters of 40 nm and high aspect ratio.

73. Tuning magneto-transport properties of Fe-Au granular thin films by cluster organization

Authors: Stanciu, AE; Kuncser, A; Schinteie, G; Palade, P; Leca, A; Greculeasa, SG; Catrina, A; Kuncser, V

Published: JUL 12 2017, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 50, DOI: 10.1088/1361-6463/aa7405

A comparative study of morpho-structural, magnetic and magneto-transport properties of two Fe-Au granular films with different concentrations of Fe nanoclusters of almost similar size is reported. Different organizations of the Fe clusters, i.e. in lamellar-like or random-like configuration, were obtained by varying the amount of Fe in the Fe-Au films. The specific magnetic behaviour was investigated with respect to local structure and morpho-structural aspects by combining magneto-optic Kerr effect and superconducting quantum interference device magnetometry, Fe-57 conversion electron Mossbauer spectroscopy and a wide range of electron microscopy techniques. A strong in-plane magnetic texture with uniaxial anisotropy was observed in the case of the lamellar-like organization of the clusters (specific to the Fe-Au film with higher Fe concentration) whereas a superparamagnetic behaviour was evidenced in the case of random distribution of the clusters (specific to the Fe-Au film with lower Fe concentration), despite the similar average size of the clusters in the two samples. Specific magnetoresistance effects were investigated with respect to both the involved magnetic configurations and magnetic interactions of the Fe clusters.

74. Magnetic properties of glass-ceramics obtained by crystallization of iron-rich borosilicate glasses

Authors: Sandu, V; Cimpoiasu, E; Kuncser, A; Nicolescu, MS

Published: SEP 2017, JOURNAL OF ADVANCED CERAMICS, 6, 261, DOI: 10.1007/s40145-017-0236-2

The specific dynamic magnetic response and magnetic relaxation phenomena in magnetite-based glass-ceramics by controlled crystallization of Fe-rich borosilicate glasses with 25 wt% Fe2O3, in the presence of two types of nucleating agents, Cr2O3 and P2O5, were investigated. The magnetic response is complex and shows contributions arising from two subsystems: a system with collective characteristics, superspin-glass like, and another one with single particle characteristics (superparamagnetic) with dipolar interaction. The nucleating agents have strong influence on the characteristic temperatures and anisotropy energy.

75. Comparative physical, chemical and biological assessment of simple and titanium-doped ovine dentine-derived hydroxyapatite coatings fabricated by pulsed laser deposition

Authors: Duta, L; Mihailescu, N; Popescu, AC; Luculescu, CR; Mihailescu, IN; Cetin, G; Gunduz, O; Oktar, FN; Popa, AC; Kuncser, A; Besleaga, C; Stan, GE

Published: AUG 15 2017, APPLIED SURFACE SCIENCE, 413, 139, DOI: 10.1016/j.apsusc.2017.04.025

We report on the synthesis by Pulsed Laser Deposition of simple and Ti doped hydroxyapatite thin films of biological (ovine dentine) origin. Detailed physical, chemical, mechanical and biological investigations were performed. Morphological examination of films showed a surface composed of spheroidal particulates, of micronic size. Compositional analyses pointed to the presence of typical natural doping elements of bone, along with a slight non-stoichiometry of the deposited films. Structural investigations proved the monophasic hydroxyapatite nature of both simple and Ti doped films. Ti doping of biological hydroxyapatite induced an overall downgrade of the films crystallinity together with an increase of the films roughness. It is to be emphasized that bonding strength values measured at film. Ti substrate interface were superior to the minimum value imposed by International Standards regulating the load-bearing implant coatings. In vitro tests on Ti doped structures, compared to simple ones, revealed excellent biocompatibility in human mesenchymal stem cell cultures, a higher proliferation rate and a good cytocompatibility. The obtained results aim to elucidate the overall positive role of Ti doping on the hydroxyapatite films performance, and demonstrate the possibility to use this novel type of coatings as feasible materials for future implantology applications. (C) 2017 Elsevier B.V. All rights reserved.

76. Effect of Cr2O3 on the magnetic properties of magnetite-based glass-ceramics obtained by controlled crystallization of Fe-containing aluminoborosilicate glass

Authors: Sandu, V; Greculeasa, S; Kuncser, A; Nicolescu, MS; Kuncser, V

Published: AUG 2017, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 37, 3099, DOI: 10.1016/j.jeurceramsoc.2017.03.055

The phase structure and magnetic properties of magnetite-based glass-ceramics obtained by crystallization of Fe-containing boroaluminosilicate glass melts are presented. The use of Cr2O3 as nucleating agent generated magnetite configurations showing a complex temperature dependence of the relaxation of the remanent magnetization. Specifically, the expected decrease in time of the remanent magnetization occurs only in a limited temperature range, whereas it increases at low and high temperatures (upward relaxation). We tentatively attribute these effects to the complex spin structure of the tiny magnetite nanoparticles, their complex size distribution and the interplay between the relaxation mechanisms in different temperature ranges. (C) 2017 Elsevier Ltd. All rights reserved.

77. Structure, transition temperature, and magnetoresistance of titanium-doped lanthanum barium manganite epilayers onto STO 001 substrates

Authors: Galca, AC; Oumezzine, M; Leca, A; Chirila, CF; Kuncser, V; Kuncser, A; Ghica, C; Pasuk, I; Oumezzine, M

Published: OCT 30 2017, APPLIED PHYSICS LETTERS, 111, DOI: 10.1063/1.4998011

We have developed a thin film structure with a maximum magnetoresistance effect (MRE) at room temperature, which is one of the operating requirements for many applications. It is shown that La0.67Ba0.33Ti0.02Mn0.98O3 epilayers obtained by pulsed laser deposition onto (001) SrTiO3 single crystal substrates exhibit the highest MRE, Delta R/R(H) approximate to 150% or Delta R/R(0) approximate to 60% under 5 T, at 300 K, a temperature near to the corresponding Curie temperature (T-C). Both doping with a tiny amount of titanium and induced stress due to lattice mismatch between the thin film and the substrate contribute to a decrease in T-C as compared to the pristine compound and therefore to the decrease in the temperature where the highest MRE is recorded. Published by AIP Publishing.

78. Physical Mechanisms of Exchange Coupling Effects in Nanoparticulate Diluted Magnetic Oxides Obtained by Laser Pyrolysis

Authors: Kuncser, VE; Schinteie, GA; Kuncser, AC; Leca, A; Scarisoreanu, M; Morjan, I; Filoti, G

Published: APR 27 2017, JOURNAL OF PHYSICAL CHEMISTRY C, 121, 9069, DOI: 10.1021/acs.jpcc.7b01500

TiO2 nanoparticles, undoped and doped with Fe, have been prepared by laser pyrolysis and further investigated with respect to morphological, structural and magnetic aspects by transmission electron microscopy, diffractometry, Mossbauer spectroscopy, and magnetometry. The obtained nanoparticles, consisting of mainly anatase phase, agglomerate in clusters of tenths of units and present a large size distribution in the range from 5 to 40 nm. The anatase to rutile weight ratio (about 9) and the morphology of particles is similar in all analyzed samples (doped by up to 12 0,0 at. % Fe). Only Fe3+ ions in high spin-configuration were observed mainly at the, surface of TiO2 nanoparticles, either distributed or forming fine clusters of Fe oxide.;:Both a paramagnetic phase and a superparamagnetic one with blocking temperature lower than 50 K are superposed over a long-range ferromagnetic phase specific to diluted magnetic oxide systems. The influence of doping Fe ions on the magnetic behavior of each phase is discussed in detail. Evidences for interface exchange couplings (with unidirectional anisotropy in specific conditions) between the long-range ferromagnetic phase and the fine clusters (antiferromagnetic in nature), which become frozen below temperature of 50, K, are provided. The specificity of the processing route and the physical mechanisms responsible observed relevant magnetic features, which can be tailored for suitable applications, are discussed.

79. Structural, magnetic and magnetocaloric effects in epitaxial La0.67Ba0.33Ti0.02Mn0.98O3 ferromagnetic thin films grown on 001-oriented SrTiO3 substrates

Authors: Oumezzine, M; Galca, AC; Pasuk, I; Chirila, CF; Leca, A; Kuncser, V; Tanase, LC; Kuncser, A; Ghica, C; Oumezzine, M

Published: 2016, DALTON TRANSACTIONS, 45, 15040, DOI: 10.1039/c6dt01914e

Epitaxial La0.67Ba0.33Ti0.02Mn0.98O3 (denoted as LBTMO hereafter) thin films of approximately 95 nm thickness were deposited by a pulsed laser deposition technique onto SrTiO3 (STO) (001) substrates. High-resolution X-ray diffraction (HRXRD) and transmission electron microscopy (TEM) investigations revealed that the films are epilayers with a four-fold symmetry around the [001] direction. Cross-sectional TEM and the presence of Pendellosung fringes in the XRD profiles demonstrate smooth interfaces. The STO substrate induces an in-plane compressive strain, which leads to a slight tetragonality of the film structure. The epilayers exhibit paramagnetic-to-ferromagnetic phase transitions at the Curie temperature T-C (286 K), close to room temperature. The magnetization easy axis lies in the film plane along the [100] direction of the (001) substrate. The magnetic entropy change (Delta S-M) associated with the second-order magnetic phase transition was determined via magnetization measurements in the temperature range between 210 and 350 K under different magnetic fields. The relative cooling power (RCP) of this film is about 220 J kg(-1), somewhat lower than that of bulk Gd (410 J kg(-1)) for a 50 kOe field change, making the LBTMO ferromagnetic thin films a promising candidate for micro/nanomagnetic refrigeration around room temperature. The proposed universal curve provides a simple method for extrapolating Delta S-M in a wide range of fields and temperatures, thus confirming the order of the magnetic transition in this system. The magnetic entropy (Delta S-M)(max) around T-C is proportional to (mu H-0/T-C)(2/3) in agreement with the mean-field theory, indicating the existence of long-range ferromagnetic interactions in epitaxial LBTMO thin films.

80. Effect of P2O5 on the Structural and Magnetic Properties of Magnetite-Based Glass-Ceramics

Authors: Sandu, V; Greculeasa, S; Kuncser, A; Kuncser, V

Published: DEC 2016, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 99, 4021, DOI: 10.1111/jace.14457

The specific morphology and magnetic properties of magnetite-based glass-ceramics obtained by crystallization of Fe-containing borosilicate glassmelts in the presence of P2O5 as nucleating agent are investigated. We found that the distribution of the tiny nanoparticles of magnetite determines the low temperature response to magnetic field. The observed effects are discussed with respect to the following factors: (1) the existence of a multimodal size distribution of the tiny grains as revealed by Mossbauer spectroscopy, magnetometry, and high-resolution electron microscopy; (2) the existence of a disordered layer at the grain surface which is driven by field in a magnetically ordered state; and (3) the interplay between the relaxation mechanisms in different temperature ranges.

81. High performance FETs based on ZnO nanowires synthesized by low cost methods

Authors: Florica, C; Costas, A; Kuncser, A; Preda, N; Enculescu, I

Published: NOV 25 2016, NANOTECHNOLOGY, 27, DOI: 10.1088/0957-4484/27/47/475303

Single ZnO nanowires prepared by wet and dry methods are used as channels in high performance back-gated field effect transistors working in low power operation mode, with on-off ratios up to 10(5) and mobilities up to 167 cm(2) V-1 s(-1). The nanowires' properties, generated by the growth techniques, influence the parameters of the transistors, therefore a throughout comparison is made.

82. Superconductivity in MgB2 irradiated with energetic protons

Authors: Sandu, V; Craciun, L; Ionescu, AM; Aldica, G; Miu, L; Kuncser, A

Published: SEP 15 2016, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 528, 34, DOI: 10.1016/j.physc.2016.07.006

A series of MgB2 samples were irradiated with protons of 11.3 and 13.2 MeV. Magnetization data shows an insignificant reduction of the critical temperatures but a continuous decrease of the Meissner fraction with increasing fluence or energy. All samples show a consistent improvement of the critical current density compared to the virgin sample and an increase of the pinning energy at high fields as resulted from relaxation data. (C) 2016 Elsevier B.V. All rights reserved.

83. Fast atomic diffusion in amorphous films induced by laser pulse annealing

Authors: Teodorescu, VS; Ghica, C; Maraloiu, AV; Kuncser, A; Lepadatu, AM; Stavarache, I; Ciurea, ML; Scarisoreanu, ND; Andrei, A; Dinescu, M

Published: 2016, 2016 39TH INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), 158, DOI:

Fast atomic diffusion was evidenced in the surface layer of amorphous thin films of oxides and semiconductors irradiated with low fluence UV pulse laser. This process takes place in a surface layer with a thickness related to the laser radiation absorption depth in the target material and was revealed by the cross section transmission electron microscopy studies. These high values of diffusivity can be explained by supposing the glass transition transformation in the amorphous structure, triggered by the action of the laser pulse field. This effect can have application for controlling structural modifications at nanoscale of the thin films surface and also for inducing structural modification of interfaces between the film and substrate.

84. Reactive spark plasma sintering of MgB2 in nitrogen atmosphere for the enhancement of the high-field critical current density

Authors: Badica, P; Burdusel, M; Popa, S; Pasuk, I; Ivan, I; Borodianska, H; Vasylkiv, O; Kuncser, A; Ionescu, AM; Miu, L; Aldica, G

Published: OCT 2016, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 29, DOI: 10.1088/0953-2048/29/10/105020

High density bulks (97%-99%) of MgB2 were prepared by spark plasma sintering (SPS) in nitrogen (N-2) atmosphere for different heating rates (10, 20 and 100 degrees C min(-1)) and compared with reference samples processed in vacuum and Ar. N-2 reacts with MgB2 and forms MgB9N along the MgB2 grain boundaries. The high-field critical current density is enhanced for the sample processed in N-2 with a heating rate of 100 degrees C min(-1). At 2-35 K, this sample shows the strongest contribution of the grain boundary pinning (GBP). All samples are in the point pinning (PP) limit and by increasing temperature the GBP contribution decreases.

85. Spark plasma sintered MgB2 co-added with c-BN and C-60

Authors: Ionescu, AM; Aldica, G; Popa, S; Enculescu, M; Sandu, V; Pasuk, I; Kuncser, A; Miu, L; Badica, P

Published: FEB 15 2016, MATERIALS CHEMISTRY AND PHYSICS, 170, 209, DOI: 10.1016/j.matchemphys.2015.12.040

High density (above 92%) superconducting bulks of MgB2 co-added with cubic BN (c-BN) and fullerenes (C-60) were obtained by the ex-situ spark plasma sintering (SPS). Compositions were (MgB2)((1-x))(C)(x)(c-BN)(0.01), x = 0.0125, 0.025, 0.05, 0.075. The co-added sample (MgB2)(0.975)(C)(0.025)(c-BN)(0.01) shows a marginally higher critical current density J(c) at intermediate magnetic fields and below 15 K than for optimum samples added with c-BN or C-60. For this sample, pinning is in the point pinning limit and the delta T-c mechanism is dominant. At high magnetic fields co-added samples are inferior to samples added with one additive, but are superior to pristine sample. Co-addition of c-BN and C-60 is not effective for vortex pinning when compared with individual addition. The result is discussed based on phase formation aspects, microstructural details and residual strain. It was found that in the presence of C-60, c-BN consumption with formation of MgNB9 is intensified with implications on different elements that influence pinning. (C) 2015 Elsevier B.V. All rights reserved.

86. Nanostructuring of GeTiO amorphous films by pulsed laser irradiation

Authors: Teodorescu, VS; Ghica, C; Maraloiu, AV; Vlaicu, M; Kuncser, A; Ciurea, ML; Stavarache, I; Lepadatu, AM; Scarisoreanu, ND; Andrei, A; Ion, V; Dinescu, M

Published: APR 7 2015, BEILSTEIN JOURNAL OF NANOTECHNOLOGY, 6, 900, DOI: 10.3762/bjnano.6.92

Laser pulse processing of surfaces and thin films is a useful tool for amorphous thin films crystallization, surface nanostructuring, phase transformation and modification of physical properties of thin films. Here we show the effects of nanostructuring produced at the surface and under the surface of amorphous GeTiO films through laser pulses using fluences of 10-30 mJ/cm(2). The GeTiO films were obtained by RF magnetron sputtering with 50:50 initial atomic ratio of Ge:TiO2. Laser irradiation was performed by using the fourth harmonic (266 nm) of a Nd:YAG laser. The laser-induced nanostructuring results in two effects, the first one is the appearance of a wave-like topography at the film surface, with a periodicity of 200 nm and the second one is the structure modification of a layer under the film surface, at a depth that is related to the absorption length of the laser radiation. The periodicity of the wave-like relief is smaller than the laser wavelength. In the modified layer, the Ge atoms are segregated in spherical amorphous nanoparticles as a result of the fast diffusion of Ge atoms in the amorphous GeTiO matrix. The temperature estimation of the film surface during the laser pulses shows a maximum of about 500 degrees C, which is much lower than the melting temperature of the GeTiO matrix. GeO gas is formed at laser fluences higher than 20 mJ/cm(2) and produces nanovoids in the laser-modified layer at the film surface. A glass transition at low temperatures could happen in the amorphous GeTiO film, which explains the formation of the wave-like topography. The very high Ge diffusivity during the laser pulse action, which is characteristic for liquids, cannot be reached in a viscous matrix. Our experiments show that the diffusivity of atomic and molecular species such as Ge and GeO is very much enhanced in the presence of the laser pulse field. Consequently, the fast diffusion drives the formation of amorphous Ge nanoparticles through the segregation of Ge atoms in the GeTiO matrix. The nanostructuring effects induced by the laser irradiation can be used in functionalizing the surface of the films.

87. B4C in ex-situ spark plasma sintered MgB2

Authors: Burdusel, M; Aldica, G; Popa, S; Enculescu, M; Mihalache, V; Kuncser, A; Pasuk, I; Badica, P

Published: OCT 2015, CURRENT APPLIED PHYSICS, 15, 1270, DOI: 10.1016/j.cap.2015.07.017

Powder mixtures of MgB2 and B4C with composition ((MgB2) + (B4C) x, x = 0.005, 0.01, 0.03) were consolidated by Spark Plasma Sintering at 1150 degrees C for 3 min. The average particle size of B4C raw powder was relatively high of 4 mm. Despite this, it is shown that processing processes are fast and, as in the case of the in-situ routes, for our ex-situ method carbon substitutes for the boron in the crystal lattice of MgB2. Specifics of microstructure are discussed based on electron microscopy observations. Carbon substitution and microstructure contribute to enhancement of the critical current density J(c) at high magnetic fields and of the irreversibility field H-irr. Samples are shown to be in the point pinning limit with some tendency toward the grain boundary pinning depending on B4C doping amount and temperature. An optimum composition is found for x = 0.01: for this sample, at 20 K, a J(c) of 100 A/cm(2) is obtained at 5.35 T. This value is higher than for the pristine MgB2 sample and for an optimum ex-situ nano-SiC-doped sample obtained for the same SPS processing conditions. (C) 2015 Elsevier B.V. All rights reserved.

88. Magnetization reversal via a Stoner-Wohlfarth model with bi-dimensional angular distribution of easy axis

Authors: Kuncser, A; Kuncser, V

Published: DEC 1 2015, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 395, 40, DOI: 10.1016/j.jmmm.2015.07.035

A numerical extension of the simple Stoner-Wohlfarth model to the case of bi-dimensional angular distributions of easy axis is provided. The results are particularized in case of step-like, Gaussian-like and user defined distributions. In spite of its simplicity, the model can be applied to magnetically textured thin films and multilayers with in-plane magnetic anisotropy, independently on the texture source. Exemplifications are provided for a simple ferromagnetic textured FeCo film as well as for a FeMn/FeCoi CufFeCo spin valve structure. (C) 2015 Elsevier B.V. All rights reserved.

89. Applicability of the Stoner-Wohlfarth Model for Ni-Fe Graded Thin Films

Authors: Kuncser, A; Schinteie, G; Ghica, C; Antohe, S; Kuncser, V

Published: MAR 2015, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 28, 969, DOI: 10.1007/s10948-014-2684-z

Fe-Ni graded films have been prepared by co-sputtering permalloy and Fe targets at different time-power sequences. Morpho-structural and magnetic investigations have been performed by transmission electron microscopy, Xray reflectometry, conversion electron Mossbauer spectroscopy and magneto-optic Kerr effect vector magnetometry, proving the thickness dependence of the properties. A magnetization reversal involving the displacement of Bloch-type walls is characteristic for a 115 nm thick Fe-Ni graded film whereas an in-plane coherent rotation of the spins, according to a Stoner-Wohlfarth mechanism was evidence for a 23 nm thick Fe-Ni graded film.

90. GeO2-added MgB2 superconductor obtained by Spark Plasma Sintering

Authors: Batalu, D; Aldica, G; Popa, S; Kuncser, A; Mihalache, V; Badica, P

Published: OCT 2015, SOLID STATE SCIENCES, 48, 30, DOI: 10.1016/j.solidstatesciences.2015.06.013

Dense samples (relative density > 93%) of bulk MgB2 with GeO2 additions were obtained by Spark Plasma Sintering. The critical current density J(c) of the added samples is improved at high magnetic fields when compared to the pristine sample. The optimum composition is for MgB2(GeO2)(0.005). For this sample, a J(c)(20 K) = 10(2) A/cm(2) is obtained at 5.1 T versus 3.9 T for the pristine sample. Ge substitution in the crystal lattice of MgB2 can be considered negligible, and T-c,T-onset and T-c,T-midpoint from magnetization measurements scatter within 0.2 and 0.6 K, respectively. TEM investigations show some specific details at nano scale: the tendency to form secondary phases (25-100 nm) with sphere-like or irregular shapes is observed and discussed. Samples are composites and the residual strain of MgB2 is constant for pristine and GeO2-added samples. Therefore, pinning enhancement leading to improvement of Jc for the GeO2 added samples is purely a 'microstructure' effect due to the presence of secondary phases. The point pinning is determined to be the predominant mechanism. Addition of a higher amount of GeO2 is shifting the pinning mechanism toward a grain boundary pinning. (C) 2015 Elsevier Masson SAS. All rights reserved.

91. Engineering Magnetic Properties of Nanostructures via Size Effects and Interphase Interactions

Authors: Kuncser, V; Palade, P; Kuncser, A; Greculeasa, S; Schinteie, G

Published: 2014, SIZE EFFECTS IN NANOSTRUCTURES: BASICS AND APPLICATIONS, 205, 237, DOI: 10.1007/978-3-662-44479-5_7

Finite size effects and interfacial interactions as well as their influence on the magnetic properties of nanosized systems are discussed by starting from very basic principles of magnetism. Some preparation and subsequent processing tools for a proper engineering of the properties of such magnetic nanosized systems are introduced together with specific characterization tools. A summary of the most important technological applications related to size effects and interfacial interactions, with exemplifications starting from bio-medical applications of magnetic fluids to magnetoresitive multilayers for sensor applications are also provided.

92. Focusing geometry-induced size tailoring of silver nanoparticles obtained by laser ablation in water

Authors: Stasic, J; Joksic, G; Zivkovic, L; Mihailescu, IN; Ghica, C; Kuncser, A; Trtica, M

Published: OCT 2014, LASER PHYSICS, 24, DOI: 10.1088/1054-660X/24/10/106005

Silver nanoparticles were obtained by picosecond laser ablation in water at 1064 nm, using focusing geometry to design the particles' size. The position of the target surface with respect to the focal point strongly influences the NPs' size: above and in the focus it is up to 20 nm and below focus <= 150 nm. Generated particles have a spherical shape. The solutions were further employed on human cells and the tests showed a deteriorating effect on DNA.

93. Experimental configuration for the simultaneous study of magnetization reversal and giant magnetoresitance effects in exchange coupled spin valve structures

Authors: Schinteie, G; Kuncser, C; Kuncser, A; Iofciu, F; Jepu, I; Antohe, S

Published: SEP-OCT 2011, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 13, 1094, DOI:

A designed experimental configuration for the simultaneous study of magnetization reversal and giant magnetoresistance effects in layered systems is reported. The suitability of the device, designed mainly for didactical purposes, to prove giant magneto-resistance effects is exemplified in case of exchange coupled spin valve structures. The multilayer structures were prepared by theromo-ionic vacuum arc methods and initially characterized by X-ray diffractometry and energy dispersive Xray spectroscopy. According to the performed experiments, it has been clearly proven the presence of magnetoresistance maxima ever ranges of applied fields inducing antiparallel magnetizations of the two ferromagnetic layers interfacing a thin conductive layer.

94. Synthesis and Characterization of Graphite Oxide Derived TiO2-Carbon Composites as Potential Electrocatalyst Supports

Authors: Ayyubov, I; Borbath, I; Paszti, Z; Sebestyen, Z; Mihaly, J; Szabo, T; Illes, E; Domjan, A; Florea, M; Radu, D; Kuncser, A; Tompos, A; Talas, E

Published: OCT 2021 , TOPICS IN CATALYSIS, DOI: 10.1007/s11244-021-01513-1

TiO2-C (carbon) hybrid materials are promising electrocatalyst supports because the presence of TiO2 results in enhanced stability. Use of new types of carbonaceous materials such as reduced graphene oxide instead of traditional active carbon provides certain benefits. Although the rutile polymorph of TiO2 seems to have the most beneficial properties in these hybrid materials, the anatase type is more frequent in TiO2-rGO composites, especially in graphite oxide (GO) derived ones, as GO has several properties which may interfere with rutile formation. To explore and evaluate these peculiarities and their influence on the composite formation, we compared TiO2-C systems formulated with GO and Black Pearls (BP) carbon. Various physicochemical methods, such as attenuated total reflection infrared (ATR-IR)-, solid state NMR-, Raman- and X-ray photoelectron spectroscopy, X-ray powder diffraction (XRD), electron microscopy, etc. were used to characterize the samples from the different stages of our multistep sol-gel synthesis. Our experiments demonstrated that utilization of GO is indeed feasible for composite preparation, although its sodium contamination has to be removed during the synthesis. On the other hand, high temperature treatment and/or solvothermal treatment during composite synthesis resulted in decomposition of the functional groups of the GO and the functional properties of the final product were similar in case of both composites. However, Pt/TiO2-GO derived sample showed higher oxygen reduction reaction activity than Pt/TiO2-BP derived one. Based on the decrease of electrochemical surface area, the stability order was the following: Pt/C (commercial) < Pt/TiO2-BP derived C < Pt/TiO2-GO derived C.

95. Ecological formulation for improving resveratrol stability and release in aqueous environment

Authors: Todan, L; Voicescu, M; Culita, DC; Pandele-Cusu, J; Albu, C; Kuncser, AC

Published: , CHEMICAL PAPERS, DOI: 10.1007/s11696-020-01409-6

96. Synthesis and Characterization of Graphite Oxide Derived TiO2-Carbon Composites as Potential Electrocatalyst Supports

Authors: Ayyubov, I; Borbath, I; Paszti, Z; Sebestyen, Z; Mihaly, J; Szabo, T; Illes, E; Domjan, A; Florea, M; Radu, D; Kuncser, A; Tompos, A; Talas, E

Published: , TOPICS IN CATALYSIS, DOI:

97. Effects of the Severe Plastic Deformation on the Magnetic Properties of Zr13Co87 Ribbons

Authors: Popescu, B; Palade, P; Sofronie, M; Kuncser, A; Gurau, C; Gurau, G; Tolea, F

Published: , METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, DOI: 10.1007/s11661-021-06507-y

The influence of the severe plastic deformation via high-speed high-pressure torsion (HSHPT) on the structural and magnetic properties of the Zr13Co87 alloys is investigated. Moderate applied deformation promotes the growth of the rhombohedral hard magnetic phase leading to the increase of the sample's hardness and magnetic coercivity. A higher degree of deformation affects the samples morphology leading to a critical value of the grain size under which the exchange coupling of the soft phase is less effective. Additionally, it produces a random alignment of the anisotropy axes, which are both detrimental to the hard magnetic properties.

98. EXCHANGE COUPLED NANOCOMPOSITES: MAGNETOPLUMBITE Sr FERRITE AND MAGNETITE

Authors: Greculeasa, SG; Comanescu, C; Iacob, N; Kuncser, A

Published: , ROMANIAN JOURNAL OF PHYSICS, 2022, DOI: 606

Dr. Andrei KUNCSER

Scientific Researcher III

Projects

1. New frontiers for hyperthermia-based therapies

Publications

1. Understanding the Photocatalytic Activity of Sodium Hexatitanate Nanoparticles for Pollutants Degradation: A Spectroscopic Insight

2. Understanding the Photocatalytic Activity of Sodium Hexatitanate Nanoparticles for Pollutants Degradation: A Spectroscopic Insight

3. Antimicrobial Properties of TiO2 Microparticles Coated with Ca- and Cu-Based Composite Layers

4. A curcumin-loaded silica carrier with NH3 sensitivity and antimicrobial properties

5. Self-connected CuO-ZnO radial core-shell heterojunction nanowire arrays grown on interdigitated electrodes for visible-light photodetectors

6. Tuning the acidity by addition of transition metal to Mn modified hollow silica spheres and their catalytic activity in ethanol dehydration to ethylene

7. Relationship between the Formation of Magnetic Clusters and Hexagonal Phase of Gold Matrix in AuxFe1-x Nanophase Thin Films

8. New superdielectric materials: (1-x) SrFe12O19 - x BNT-BT nanocomposites

9. Enhanced magnetocaloric properties of La0.8K0.2-xPbxMnO3 nanoparticles by optimizing Pb doping concentrations

10. Full Length Article Towards high degree of c-axis orientation in MgB2 bulks

11. A new method for obtaining the magnetic shape anisotropy directly from electron tomography images

12. EXCHANGE COUPLED NANOCOMPOSITES: MAGNETOPLUMBITE Sr FERRITE AND MAGNETITE

13. Magnetic Properties of Nanosized Fe and FeCo Systems on Trenched Mo Templates

14. Layered SnSe nanoflakes with anharmonic phonon properties and memristive characteristics

15. Fracture peculiarities and high-temperature strength of bulk polycrystalline boron

16. Electrocatalytic Properties of Mixed-Oxide-Containing Composite-Supported Platinum for Polymer Electrolyte Membrane (PEM) Fuel Cells

17. Synthesis and Characterization of Hematite-Based Nanocomposites as Promising Catalysts for Indigo Carmine Oxidation

18. A curcumin-loaded silica carrier with NH3 sensitivity and antimicrobial properties

19. Novel Magnetic Nanocomposites Based on Carboxyl-Functionalized SBA-15 Silica for Effective Dye Adsorption from Aqueous Solutions

20. Sintered and 3D-Printed Bulks of MgB2-Based Materials with Antimicrobial Properties

21. A novel composite based on pyrene thiazole grafted on graphene oxide: physico-chemical characterization and electrochemical investigations

22. MgB2 powders and bioevaluation of their interaction with planktonic microbes, biofilms, and tumor cells

23. Sensing Properties of NiO Loaded SnO2 Nanoparticles-Specific Selectivity to H2S

24. Physicochemical Characterization and Drug Release Properties of Methyl-Substituted Silica Xerogels Made Using Sol-Gel Process

25. Ecological formulation for improving resveratrol stability and release in aqueous environment

26. Kaolin clay pottery discovered in the Roman city of Romula (Olt County, Romania)

27. Chemical Degradation of Methylene Blue Dye Using TiO2/Au Nanoparticles

28. Partially-oriented MgB2 superconducting bulks with addition of B4C and cubic BN obtained by slip casting under high magnetic field and spark plasma sintering

29. EPR spectroscopy and structural investigations, of Eu2+-doped chloroborate glass-ceramic

30. Facile Synthesis of Cobalt Ferrite (CoFe2O4) Nanoparticles in the Presence of Sodium Bis (2-ethyl-hexyl) Sulfosuccinate and Their Application in Dyes Removal from Single and Binary Aqueous Solutions

31. Soft synthesis and characterization of goethite-based nanocomposites as promising cyclooctene oxidation catalysts

32. Influence of Thickness on the Magnetic and Magnetotransport Properties of Epitaxial La0.7Sr0.3MnO3 Films Deposited on STO (001)

33. Bistability of the BiOi complex and its implications on evaluating the "acceptor removal"process in p-type silicon

34. Benzofurazan derivatives modified graphene oxide nanocomposite: Physico-chemical characterization and interaction with bacterial and tumoral cells

35. Tuning structural and magnetic properties of Fe oxide nanoparticles by specific hydrogenation treatments

36. Photodetecting properties of single CuO-ZnO core-shell nanowires with p-n radial heterojunction

37. Unexpected magneto-functionalities of amorphous Fe-Gd thin films crossing the magnetization compensation point

38. Low temperature CO sensing under infield conditions with in doped Pd/SnO2

39. Influence of surfactant-tailored Mn-doped ZnO nanoparticles on ROS production and DNA damage induced in murine fibroblast cells

40. Optimization of magnetic fluid hyperthermia with respect to nanoparticle shape-related parameters: case of magnetite ellipsoidal nanoparticles

41. Electron paramagnetic resonance and microstructural insights into the thermal behavior of simonkolleite nanoplatelets

42. Functionalization of eggshell membranes with CuO-ZnO based p-n junctions for visible light induced antibacterial activity against Escherichia coli

43. Unidirectional Magnetic Anisotropy in Dense Vertically-Standing Arrays of Passivated Nickel Nanotubes

44. Enhanced critical current density at high magnetic fields in MgB2 with Ga/In acetylacetonate processed by spark plasma sintering

45. Coagulating and flocculating ferrihydrite: application of zinc acetate salt

46. Hierarchical composites of B4C-TiB2 eutectic particles reinforced with Ti

47. Highly Efficient Ultralow Pd Loading Supported on MAX Phases for Chemoselective Hydrogenation

48. Mesoporous Cobalt Ferrite Nanosystems Obtained by Surfactant-Assisted Hydrothermal Method: Tuning Morpho-structural and Magnetic Properties via pH-Variation

49. High-temperature strength of boron carbide with Pt grain-boundary framework in situ synthesized during spark plasma sintering

50. Complex exchange coupling mechanisms in SRO/BFO/Fe heterostructures

51. Direct Immobilization of Biomolecules through Magnetic Forces on Ni Electrodes via Ni Nanoparticles: Applications in Electrochemical Biosensors

52. Nanoclustered Pd decorated nanocrystalline Zn doped SnO2 for ppb NO2 detection at low temperature

53. Core-shell nanowire arrays based on ZnO and CuxO for water stable photocatalysts

54. Fluorescent coumarin-modified mesoporous SBA-15 nanocomposite: Physico-chemical characterization and interaction with prokaryotic and eukaryotic cells

55. Radial heterojunction based on single ZnO-CuxO core-shell nanowire for photodetector applications

56. Formation peculiarities and optical properties of highly-doped (Y(0.86)La(0.09)Vb(0.05))(2)O-3 transparent ceramics

57. Bulks of Al-B-C obtained by reactively spark plasma sintering and impact properties by Split Hopkinson Pressure Bar

58. Growth of SrTiO3 Single Crystals with a Diameter of about 30 mm by the Verneuil Method

59. Superconducting MgB2 textured bulk obtained by ex situ spark plasma sintering from green compacts processed by slip casting under a 12T magnetic field

60. On the relaxation time of interacting superparamagnetic nanoparticles and implications for magnetic fluid hyperthermia

61. Zinc incorporation in marine bivalve shells grown in mine-polluted seabed sediments: a case study in the Malfidano mining area (SW Sardinia, Italy)

62. Ferroelectric photovoltaic characteristics of pulsed laser deposited 0.5Ba (Zr0.2Ti0.8)O-3-0.5(Ba0.7Ca0.3)TiO3/ZnO heterostructures

63. Ex Situ Spark Plasma Sintering of Short Powder-in-Tube MgB2 Tapes with Open and Closed Ends

64. Improved Optical and Morphological Properties of Vinyl-Substituted Hybrid Silica Materials Incorporating a Zn-Metalloporphyrin

65. Magnetism and magnetoresistance of single Ni-Cu alloy nanowires

66. Coordination environment of Zn in foraminifera Elphidium aculeatum and Quinqueloculina seminula shells from a polluted site

67. Local configurations and atomic intermixing in as-quenched and annealed Fe1-xCrx and Fe1-xMox ribbons

68. Limits and Particularities of the Synthesis of Ba1-xCaxTiO3 for Piezoelectric Applications, by Topochemical Conversion from Molten Salt Solutions

69. Electrochemically shape-controlled transformation of magnetron sputtered platinum films into platinum nanostructures enclosed by high-index facets

70. Magnetite-based glass-ceramics prepared by controlled crystallization of borosilicate glasses: Effect of nucleating agents on magnetic properties and relaxation

71. Significant change of local atomic configurations at surface of reduced activation Eurofer steels induced by hydrogenation treatments

72. A general perspective on the magnetization reversal in cylindrical soft magnetic nanowires with dominant shape anisotropy

73. Tuning magneto-transport properties of Fe-Au granular thin films by cluster organization

74. Magnetic properties of glass-ceramics obtained by crystallization of iron-rich borosilicate glasses

75. Comparative physical, chemical and biological assessment of simple and titanium-doped ovine dentine-derived hydroxyapatite coatings fabricated by pulsed laser deposition