NIMP| Arpad ROSTAS, Author at NIMP

Publications

1. Effect of transition metal ions on the dielectric properties of chromium potassium phosphates

Authors: Mighri, Z; Patru, RE; Leonat, LN; El Khouja, O; Nasri, H; Rostas, AM; Galca, AC

Published: DEC 25 2024, JOURNAL OF ALLOYS AND COMPOUNDS, 1009, 176870, DOI: 10.1016/j.jallcom.2024.176870

Potassium ions are important for developing electrode materials because they have similar properties to lithium and sodium ions. Mixed chromium phosphates (KMIICr(PO4)2) II Cr (PO 4 ) 2 ) with substituted M II sites using divalent elements (M = Ni, Co, Cu) were synthesized using a solid-state reaction method. The samples were analyzed using various techniques such as powder X-ray diffraction, Fourier transform infrared, Raman, and electron paramagnetic resonance spectroscopy. The proposed phosphates had a monoclinic phase structure with a P21/n 1 /n space group, and they contained large tunnels occupied by K+ + cations. The dielectric properties showed that the Ni-based phosphates had slower dielectric relaxation, while the Co and Cu-based phosphates had quicker polarization and depolarization processes. Additionally, the resistance of the grains decreased from Ni to Co to Cu-based phosphates, indicating easier charge movement in each material, consistent with the increase in conductive losses and a.c. conductivity when changing the M II ions.

2. Interaction of Low-Density Polyethylene Nanofragments with Autotrophic and Chemotrophic Bacteria

Authors: Ciorita, A; Suciu, M; Rostas, AM; Tarta, A; Popovici, G; Bocaneala, M; Nekvapil, F; Macavei, SG; Potara, M; Marica, I; Kacso, I; Moldovan, CS; Stiufiuc, RI; Tuta, CS; Cinta-Panzaru, S; Barbu-Tudoran, L

Published: JUL 11 2024, ACS SUSTAINABLE CHEMISTRY & ENGINEERING, 12, DOI: 10.1021/acssuschemeng.4c02440

Plastics are omnipresent in the environment and degrade into smaller fragments in time. This study shows how plastics could reach nanometer sizes under specific conditions and the interaction of the nanofragments with prokaryotic cells. Imaging and spectroscopy techniques were employed to determine the modifications induced in artificially aged low-density polyethylene (LDPE). Scanning electron microscopy indicated that nanometer-scale LDPE could be obtained after ultraviolet-C (UVC) exposure for 10 days. Raman and Fourier-transformed infrared spectroscopy confirmed the chemical changes within the UVC-exposed LDPE are consistent with the increase of crystallinity. Moreover, the interaction between the degraded LDPE and chemo- and photosynthetic organisms was observed through fluorescence, confocal, electron microscopy techniques, and electron paramagnetic resonance spectroscopy. The results showed how micro/nano-LDPE could influence the development of Escherichia coli and Arthrospira platensis after only 72 h of interaction. This fundamental study indicates the environmental presence and effects of nanometer-sized LDPE resulting from light exposure.

3. Nitrogen-Doped WO₃ Nanoparticles as Electrode Materials in All-in-One Supercapacitor Devices

Authors: Ammar, AU; Popa, A; Toloman, D; Macavei, S; Ciorita, A; Bocirnea, AE; Stan, M; Erdem, E; Rostas, AM

Published: JAN 10 2024, ACS APPLIED ENGINEERING MATERIALS, 2, DOI: 10.1021/acsaenm.3c00654

The effect of the annealing temperature on 1% nitrogen-doped WO3 materials was studied, which were then used as electrode materials for high-performance supercapacitor (SC) devices. The supercapacitive performance of the proposed materials was strongly influenced by the doping element and the annealing temperature by directly changing the defect structure of the host material. The 1% N-doped WO3 materials annealed at different temperatures were thoroughly characterized through various characterization techniques, including electron paramagnetic resonance and photoluminescence spectroscopy, giving insight into the effect of N-doping on the defect structure and optical properties of WO3. When the WO3:N materials were used as electrode material in symmetric SCs, the doping element and the annealing temperature improved the electrochemical performance. No booster materials (such as carbon black) were used in the symmetric SC designs, showing increased specific capacitance (102 F/g) and energy density (14.6 W h/kg) values.

4. Adsorption-catalysis synergy in the visible-light-driven removal of 17 β-estradiol by (Au)TiO 2 nanotubes-graphene composites

Authors: Cosma, DV; Rosu, MC; Socaci, C; Rostas, AM; Urda, A; Radu, T; Turza, A; Dan, MNC; Costescu, R; Gustavsen, KR; Dobroliubov, O; Wang, KY

Published: JUN 2024, JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING, 12, 112885, DOI: 10.1016/j.jece.2024.112885

Visible light-mediated photodegradation offers a sustainable and environmentally friendly solution for removing emerging contaminants from water sources. Herein, we report on the synergy effect between adsorption and visible-light-driven photo-degradation of 17 fl - estradiol using (Au)TiO 2 nanotubes-graphene composites. The graphene structures (graphene oxide - GO or thermally reduced graphene oxide - trGO) provide a platform for strong adsorption of 17 fl -estradiol molecules and facilitate the charge transfer between plasmonic Au nanoparticles and TiO 2 , leading to an improvement of the overall degradation process. To better understand the effect of Au nanoparticles and TiO 2 separately, three different concentrations of Au (1 %, 2.5 %, and 5 %) were prepared and characterized. The estrogenic molecules preferred GO over trGO, suggesting that hydrogen bonds govern the interaction between GO and 17 fl -estradiol. Consequently, a higher photocatalytic efficiency of GOcontaining composites was observed when removing estrogenic molecules. The role of adsorption proved crucial for capturing and retaining more contaminant molecules on the composite surface, thus increasing the odds of surface reactions with the photogenerated carriers. A total removal of 17 fl -estradiol has been obtained for Au (1 %, 2.5 %, and 5 %) TiO 2 nanotubes-GO. The mechanism behind the adsorption and photo-degradation processes has been discussed.

5. Hybrid supercapacitors based on X-site Ba(II) ions substituted by Sr(II) in Langbeinite-type phosphates

Authors: Mighri, Z; Yildirim, ID; Leonat, LN; El Khouja, O; Erdem, E; Nasri, H; Galca, AC; Rostas, AM

Published: AUG 2024, MATERIALIA, 36, 102147, DOI: 10.1016/j.mtla.2024.102147

The compounds KBa 1-x Sr x Cr 2 (PO 4 ) 3 (with x = 0.00; 0.25; 0.50; 0.75; 1.00) were synthesized by a solid-state reaction, and they were thoroughly characterized by different spectroscopic and microscopic techniques. Their structures were indexed in a cubic system with a P2 1 3 space group forming a 3D framework built on CrO 6 octahedra and PO 4 tetrahedra sharing vertices leading to identical Cr 2 P 3 O 18 (U) units. The interconnection between the tetrahedral and octahedral groups leads to the formation of two large closed cavities (K, M II )(1) and (K, M II )(2), statistically occupied by K + and M 2+ (M = Ba, Sr) atoms. Electron paramagnetic resonance spectroscopy confirmed the presence of paramagnetic Cr 3+ ions, showing the effects of substituting the Ba 2+ ions with smaller Sr 2+ ions on the dipolar coupling between the Cr 3+ centers. The obtained materials and active carbon were used as electrode materials in hybrid SC devices. At the same time, their electrochemical properties were assessed by potentiostatic electrochemical impedance spectroscopy, cyclic voltammetry, and galvanostatic charge-discharge measurements, showing promising results with a maximal specific capacitance (3.86 F/g), energy density (343 mWh/kg), and power density (30.9 kW/kg) in the case of KBa 0.5 Sr 0.5 Cr 2 (PO 4 ) 3 , proving them as good candidates for positive and/or negative electrode materials for energy storage applications.

6. α-MoO₃ Micro- and Nanoparticles as Catalysts for Biofuel Production

Authors: de Medeiros, SASL; de Oliveira, ALM; Duarte, TM; Kennedy, BJ; Rostas, AM; Negrila, CC; Galca, AC; Maia, AD; Sambrano, JR; Dantas, MC; Farias, AF; dos Santos, IMG

Published: 2024 MAY 21 2024, ACS APPLIED NANO MATERIALS, DOI: 10.1021/acsanm.4c01239

Herein, alpha-MoO3 micro- and nanoparticles were synthesized by a modified Pechini method, and the impact of the crystal structure and crystal growth orientation on the formation of ionic defects and, consequently, on the catalytic performance of the materials in the ethylic transesterification reaction for biodiesel production was investigated. Structural refinements from X-ray diffraction data and Raman spectra revealed the formation of alpha-MoO3 in a Pbnm orthorhombic phase, with nanoplate-like morphology at 500 degrees C (thickness between 100 and 260 nm) or ribbon-like morphology at 700 degrees C (thickness between 400 and 900 nm). An anisotropic crystal orientation along the [010] direction was observed with an increase of the calcination temperature. We emphasize the dependence of the orientation change with the elimination of ionic-type defects (oxygen vacancies and reduced Mo5+ centers) by the temperature using complementary techniques such as X-ray photoelectron and electron paramagnetic resonance spectroscopies. The catalytic activity of the samples depends on the orientation process and the presence of defects that act as acid-active sites on the catalyst surface and therefore play an important role in biodiesel production. This effect was confirmed by surface stability and reactivity simulated by density functional theory calculations, suggesting that the Mo and O surface terminals greatly impacted the interface catalytic reaction. The highest catalytic performance toward the biodiesel conversion (89% of conversion at 150 degrees C for 2 h) was achieved for the polycrystalline catalyst calcined at 500 degrees C, which was correlated with random crystal orientation and the presence of reduced Mo5+ and oxygen vacancy centers on the different facets exposed on the surface. The biodiesel production was confirmed by H-1 and C-13 NMR spectroscopy and gas chromatography analysis.

7. Antiferromagnet-mediated interlayer exchange: Hybridization versus proximity effect

Authors: Polishchuk, DM; Tykhonenko-Polishchuk, YO; Lytvynenko, YM; Rostas, AM; Kuncser, V; Kravets, AF; Tovstolytkin, AI; Gomonay, OV; Korenivski, V

Published: JUN 28 2023, PHYSICAL REVIEW B, 107, 224432, DOI: 10.1103/PhysRevB.107.224432

We investigate the interlayer coupling between two thin ferromagnetic (F) films mediated by an antiferromagnetic (AF) spacer in F*/AF/F trilayers and show how it transitions between different regimes on changing the AF thickness. Employing layer-selective Kerr magnetometry and ferromagnetic-resonance techniques in a complementary manner enables us to distinguish between three functionally distinct regimes of such ferromagnetic interlayer coupling. The F layers are found to be individually and independently exchange-biased for thick FeMn spacers-the first regime of no interlayer F-F* coupling. F-F* coupling appears on decreasing the FeMn thickness below 9 nm. In this second regime found in structures with 6.0-9.0-nm-thick FeMn spacers, the interlayer coupling exists only in a finite temperature interval just below the effective Neel temperature of the spacer, which is due to magnon-mediated exchange through the thermally softened antiferromagnetic spacer, vanishing at lower temperatures. The third regime, with FeMn thinner than 4 nm, is characterized by a much stronger interlayer coupling in the entire temperature interval, which is attributed to a magnetic-proximity induced ferromagnetic exchange. These experimental results, spanning the key geometrical parameters and thermal regimes of the F*/AF/F nanostructure, complemented by a comprehensive theoretical analysis, should broaden the understanding of the interlayer exchange in magnetic multilayers and potentially be useful for applications in spin thermionics.

8. Characterization of defect structures in nanoscaled W-doped TiO2 tested as supercapacitor electrode materials

Authors: Ammar, AU; Stefan. M; Macavei, SG; Tripon, S; Pana, O; Leostean, C; Vlaicu, ID; Rostas, AM; Erdem, E

Published: JAN 2023, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 34, 8, DOI: 10.1007/s10854-022-09540-8

In this work, Tungsten(W)-doped TiO2 nanoparticles were synthesized using the sol-gel method and were used as electrode materials in supercapacitor applications. The structural and morphological properties of the prepared samples were analyzed by means of XRD, STEM, TEM, and XPS. The analysis of the defect centers was carried out using EPR spectroscopy. The electrochemical analysis of the assembled supercapacitor was done using cyclic voltammetry, galvanostatic cycling with potential limitation technique, potentiostatic electrochemical impedance spectroscopy, and voltage-holding experiments. All the presented samples showed paramagnetic defects in the EPR analysis, while 0.5% W-doped TiO2 showed a maximum signal intensity. The supercapacitor performance from the synthesized electrode material showed highly encouraging results. The equivalent series resistance (R-s) value for all the designs showed values under "1 omega,' which reflects high conductivity. As the maximum EPR intensity comes from TiO2 doped with 0.5% W, the supercapacitor performance of this sample was tested with a newly designed five-electrode system. This design showed superior performance compared to any other used designs with a specific capacitance of 25.5 F g(-1), with an energy density of 14.16 Wh kg (-1 )at 302 kW kg (-1).

9. Structural and Electrical Properties of Novel Cr/Fe Mixed Transition-Metal Phosphates

Authors: Mighri, Z; Souiwa, K; Rostas, AM; Patru, RE; Bocirnea, AE; Iacob, N; Kuncser, V; El Khouja, O; Leonat, LN; Hidouri, M; Nasri, H; Galca, AC

Published: 2023 MAY 24 2023, INORGANIC CHEMISTRY, DOI: 10.1021/acs.inorgchem.2c04389

The phosphate KCoCr-(PO4)(2) and iron-substitutedvariants KCoCr1-x Fe x (PO4)(2) (x =0.25, 0.5, and 0.75) were synthesized by a solid-state reaction route,while a high substitution level of Fe was achieved. Their structureswere refined using powder X-ray diffraction and indexed in a monoclinicsystem with a P2(1)/n spacegroup. A 3D framework with six-sided tunnels parallel to the [101]direction was formed in which the K atoms are located. Mo''ssbauerspectroscopy confirms the exclusive presence of octahedral paramagneticFe(3+) ions, with isomer shifts increasing slightly with x substitution. Electron paramagnetic resonance spectroscopyconfirmed the presence of paramagnetic Cr3+ ions. The activationenergy, determined by dielectric measurements, shows that the iron-containingsamples present higher ionic activity. Relative to the electrochemicalactivity of K, these materials could be good candidates for positiveand/or negative electrode materials for energy storage applications. The synthesized phosphate KCoCr-(PO4)(2) and Fe-substituted variants KCoCr1-x Fe x (PO4)(2) (x = 0.25, 0.5, and 0.75) present a 3D frameworkwith six-sided tunnels in which the K atoms are located. The activationenergy, determined by dielectric measurements, shows that the iron-containingsamples present improved ionic activity, making these materials goodcandidates for positive and/or negative electrode materials for energystorage applications.

10. Multi-analytical characterization of the white inlaid decoration on the prehistoric pottery from southern Romania

Authors: Secu, M; Matei, E; Secu, C; Bartha, C; Buruiana, T; Rostas, AM; Popescu, AD; Boroneant, A; Bajenaru, R

Published: JUN 2023, SOLID STATE SCIENCES, 140, 107193, DOI: 10.1016/j.solidstatesciences.2023.107193

Complex physico-chemical investigations have been performed on white inlaid substance used in the orna-mentation of prehistoric clay artefacts from southern Romania ceramics from the Early Chalcolithic, up to the Middle/Late Bronze Age. Structural and morphological investigations of the white pigments have showed hundreds of nm up to microns size particles with calcite and hydroxyapatite (ash bone) as dominant components. The calcite was found on Early Chalcolithic pigment vessels while those where hydroxyapatite was dominant from the Middle/Late Bronze Age. FTIR spectra revealed the biogenic source of the hydroxyapatite (i.e. cremated animal bone) and the crystallinity degree values agrees with the expected temperatures of firing of the ancient furnaces; the calcite-based pigments were supposed to be filled post firing. The EPR was not able to able to provide a clear assignment of the cremated animal bones but thermoluminescence showed various sources of calcite.

11. 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.

12. 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

13. Characterization of defect structures in nanoscaled W-doped TiO₂ tested as supercapacitor electrode materials

Authors: Ammar, AU; Stefan, M; Macavei, SG; Tripon, S; Pana, O; Leostean, C; Vlaicu, ID; Rostas, AM; Erdem, E

Published: JAN 2023, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 34, 8, DOI: 10.1007/s10854-022-09540-8

14. Structural and Electrical Properties of Novel Cr/Fe Mixed Transition-Metal Phosphates

Authors: Mighri, Z; Souiwa, K; Rostas, AM; Patru, RE; Bocirnea, AE; Iacob, N; Kuncser, V; El Khouja, O; Leonat, LN; Hidouri, M; Nasri, H; Galca, AC

Published: MAY 24 2023, INORGANIC CHEMISTRY, 62, DOI: 10.1021/acs.inorgchem.2c04389

15. Photo-stable, 1D-nanofilaments TiO2-based lepidocrocite for photocatalytic hydrogen production in water-methanol mixtures

Authors: Badr, HO; Natu, V; Neatu, S; Neatu, F; Kuncser, A; Rostas, AM; Racey, M; Barsoum, MW; Florea, M

Published: SEP 6 2023, MATTER, 6, DOI: 10.1016/j.matt.2023.05.026

Water and sunlight are the cleanest, most renewable, and abundant resources on Earth. Developing inexpensive, scalable photocatalysts that are highly stable for hydrogen (H-2) production has long been a cherished dream of humanity. Herein, we report on one-dimensional lepidocrocite-based sub-nanofilaments (NFs), approximate to 5 x 7 & Aring;(2) in cross-section, that generate H-2 from 80:20 v/v water/methanol mixtures when illuminated by simulated sunlight. The NFs were stable in the mixtures for times >4,300 h, 300 h of which were under irradiation. Apparent quantum yields as high as 11.7% were obtained. Based on deuterated water results, we conclude that water is the H-2 source. Further, no carbon dioxide (CO2) due to photocatalytic degradation of methanol was detected. Therefore, the NFs have strong green credentials and lucrative economic prospects for large scale up. We expect these NFs will lead to new lines for developing cheap and ultra-stable materials to produce H-2 photochemically for a long time.

16. TiO₂ Phase Ratio's Contribution to the Photocatalytic Activity

Authors: Stepanova, A; Tite, T; Ivanenko, I; Enculescu, M; Radu, C; Culita, DC; Rostas, AM; Galca, AC

Published: OCT 25 2023, ACS OMEGA, 8, DOI: 10.1021/acsomega.3c05890

Photocatalysis is one of the approaches for solving environmental issues derived from extremely harmful pollution caused by industrial dyes, medicine, and heavy metals. Titanium dioxide is among the most promising photocatalytic semiconductors; thus, in this work, TiO2 powders were prepared by a hydrothermal synthesis using titanium tetrachloride TiCl4 as a Ti source. The effect of the hydrochloric acid (HCl) concentration on TiO2 formation was analyzed, in which a thorough morpho-structural analysis was performed employing different analysis methods like XRD, Raman spectroscopy, SEM/TEM, and N-2 physisorption. EPR spectroscopy was employed to characterize the paramagnetic defect centers and the photogeneration of reactive oxygen species. Photocatalytic properties were tested by photocatalytic degradation of the rhodamine B (RhB) dye under UV light irradiation and using a solar simulator. The pH value directly influenced the formation of the TiO2 phases; for less acidic conditions, the anatase phase of TiO2 crystallized, with a crystallite size of approximate to 9 nm. Promising results were observed for TiO2, which contained 76% rutile, showing a 96% degradation of RhB under the solar simulator and 91% under UV light after 90 min irradiation, and the best result showed that the sample with 67% of the anatase phase after 60 min irradiation under the solar simulator had a 99% degradation efficiency.

17. Analysis and characterization of magneto-structural transformations and critical exponent analysis of La_0.8Ca_0.2-xPb_xMnO₃

Authors: Bouzid, SA; Sajieddine, M; Hlil, E; Boubekri, AE; Rostas, AM; Essoumhi, A

Published: NOV 2023, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 34, 2166, DOI: 10.1007/s10854-023-11475-7

Because of their significant magnetocaloric properties, Ca and Pb-doped LaMnO3 can be employed in magnetic refrigeration systems. The partial substitution effect of Ca2+ by Pb2+ cations on the structural, magnetocaloric properties, and critical behavior of mixed valence perovskites La0.8Ca0.2-xPbxMnO3 (0 <= x <= 0.15), synthesized by the flash combustion route, was studied in this work. The presence of structural transformations of the prepared ceramics from an orthorhombic structure (Pbnm space group) for samples with x <= 0.05 to a rhombohedral system (R (3) over barc space group) for x >= 0.1 was detected by X-ray diffraction analysis, which is related to the A-site disorder. The field-cooled (FC) magnetization indicated a second-order ferromagnetic-paramagnetic transition for the investigated samples when the temperature was increased. Due to the change in the Mn3+/Mn4+ ratio, substituting Ca2+ with larger Pb2+ ions increases the Curie temperature (T-C) by increasing Pb doping content from 90 K for x = 0 to 205 K for x = 0.15. The magnetization isotherms of all samples showing a second-order phase transition were studied, where an applied magnetic field of 5 T, the value of maximum magnetic entropy variation /Delta S-M(max)/ for the sample with x = 0.15 was estimated to be 2.73 Jkg(-1) K-1. In addition, it has a significant relative cooling power of about 276 Jkg(-1) under the same applied magnetic field strength. The critical behavior of the samples was investigated close to T-C. The exponent values were identical to the mean-field method, indicating a large disorder of spin magnetic moments in the perovskite compounds.

18. 'Put variety in White': Multi-analytical investigation of the white pigments inlaid on Early Chalcolithic pottery from Southern Romania

Authors: Opris, V; Velea, A; Secu, M; Rostas, AM; Buruiana, AT; Simion, CA; Mirea, DA; Matei, E; Bartha, C; Dimache, M; Lazar, C

Published: APR 2022, JOURNAL OF ARCHAEOLOGICAL SCIENCE-REPORTS, 42, 103402, DOI: 10.1016/j.jasrep.2022.103402

The current study aims to present and discuss the results obtained by complementary archaeometric methods applied for the first time on white pigments inlaid on excised pottery of the Boian-Vidra tradition (Early Chalcolithic, c. 4900-4600 BCE). The samples came from three settlements located in Southern Romania (Sultana-Ghetarie, Vidra, and Vladiceasca). They were selected considering that the pottery was produced in approximately contemporary sites, located relatively close to each other in the same geographical region, namely the Romanian Plain. The experimental part included the analysis of local samples of carbonate concretions and prehistoric animal bone ash as reference materials. Archaeometric investigations consisted in applying "in-air" PIXE and EDX methods for the chemical composition, XRD and FTIR for mineralogical data, SEM for microstructure observation, and EPR for the characterisation of the paramagnetic centres. Calcite, bone ash, and silica rich sediments were identified as the primary decorating pigments. The mixtures of calcite and bone-ash observed in 13 samples were specific to the sites at Vidra and Vladiceasca. Silica-rich sediments from distant sources were the main whitening materials in two samples from Vladiceasca, while for the samples from Sultana-Ghetarie, calcite was the only whitening mineral. The results show with a high degree of confidence the use of both local (i.e., carbonate neo-formations and bone ash) and exotic (silica-rich sediments) raw materials to obtain the white pigment applied to Boian-Vidra pottery. Thus, the current data show the adaptability of the potters with respect to the surrounding resources and also provide new evidence for a vast trade network of raw materials and/or finished products in the Lower Danube area during the Early Chalcolithic. The deliberate mixing of two whitening materials from different sources could be a technological choice and may highlight complex symbolic behaviours.

19. Insights into Structure and Biological Activity of Copper(II) and Zinc(II) Complexes with Triazolopyrimidine Ligands

Authors: Argaseala, A; Maxim, C; Badea, M; Ionita, L; Chifiriuc, MC; Rostas, AM; Bacalum, M; Raileanu, M; Ruta, LL; Farcasanu, IC; Iorgulescu, EE; Olar, R

Published: FEB 2022, MOLECULES, 27, 765, DOI: 10.3390/molecules27030765

In an attempt to increase the biological activity of the 1,2,4-triazolo[1,5-a]pyrimidine scaffold through complexation with essential metal ions, the complexes trans-[Cu(mptp)(2)Cl-2] (1), [Zn(mptp)Cl-2(DMSO)] (2) (mptp: 5-methyl-7-phenyl-1,2,4-triazolo[1,5-a]pyrimidine), [Cu-2(dmtp)(4)Cl-4]center dot 2H(2)O (3) and [Zn(dmtp)(2)Cl-2] (4) (dmtp: 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine), were synthesized and characterized as new antiproliferative and antimicrobial species. Both complexes (1) and (2) crystallize in the P2(1)/n monoclinic space group, with the tetrahedral surroundings generating a square-planar stereochemistry in the Cu(II) complex and a tetrahedral stereochemistry in the Zn(II) species. The mononuclear units are interconnected in a supramolecular network through pi-pi interactions between the pyrimidine moiety and the phenyl ring in (1) while supramolecular chains resulting from C-H center dot center dot center dot pi interactions were observed in (2). All complexes exhibit an antiproliferative effect against B16 tumor cells and improved antibacterial and antifungal activities compared to the free ligands. Complex (3) displays the best antimicrobial activity against all four tested strains, both in the planktonic and biofilm-embedded states, which can be correlated to its stronger DNA-binding and nuclease-activity traits.

20. 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.

21. Temperature-induced phase transition and tunable luminescence properties of Ce3+-Mn2+-Zr4+ tri-doped LaPO4 phosphor

Authors: AitMellal, O; Oufni, L; Messous, MY; Matei, E; Rostas, AM; Galca, AC; Secu, M

Published: JUL 2022, OPTICAL MATERIALS, 129, 112567, DOI: 10.1016/j.optmat.2022.112567

Tunable blue-white-orange emitting LaPO4:Ce3+/Mn2+/Zr4+(LPCMZ) phosphors have been synthesized by co precipitation followed by calcination. The X-ray diffraction (XRD) shows the phase transition from hexagonal to monoclinic between 600 and 700 ?C, accompanied by the increase of average nanocrystallites size from 8 to 64 nm. The Raman measurements revealed the vibrational modes associated with the LPCMZ crystalline phases, where the band positions and the full width at half maximum values depend on the structural parameters and nanocrystals size. For low-temperature calcination of 500 ?C, scanning electron microscopy (SEM) revealed nanoclusters composed of thinner nanoneedles, which developed into a rod-like self-assembly shape for higher calcination temperatures at around 900 ?C. Electron paramagnetic resonance (EPR) spectroscopy reveals a broad isotropic EPR signal, assigned to agglomerated/clustered Mn2+ ions, which are dispersed only at high temperatures above 900 ?C. The photoluminescence spectra recorded under UV-excitation of Ce3+ ions showed the Mn2+ green/red (546, 630 nm) emissions due to an energy transfer (ET) between Ce3+ and Mn2+. Depending on the calcination temperature, the Mn2+ emission color can be finely adjusted from blue to white and orange.

22. 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%.

23. Antiproliferative Copper(II) Complexes Bearing Mixed Chelating Ligands: Structural Characterization, ROS Scavenging, In Silico Studies, and Anti-Melanoma Activity

Authors: Olar, R; Maxim, C; Badea, M; Bacalum, M; Raileanu, M; Avram, S; Korosin, NC; Burlanescu, T; Rostas, AM

Published: AUG 2022, PHARMACEUTICS, 14, 1692, DOI: 10.3390/pharmaceutics14081692

Melanoma is a skin cancer characterized by rapid growth and spread for which current therapies produce both resistance and increased risk of infection. To develop new anti-melanoma biocompatible species, the series of complexes Cu(N-N)(bzac)(X)center dot nH(2)O (N-N: 1,10-phenanthroline/2,2 '-bipyridine, Hbzac: 1-phenyl-1,3-butanedione, X: NO3/ClO4, and n = 0, 1) was studied. Single-crystal X-ray diffraction revealed a mononuclear structure for all complexes. The ability of the complexes to scavenge or trap reactive oxygen species such as O-2 center dot(-) and HO center dot was proved by EPR spectroscopy experiments. All complexes inhibited B16 murine melanoma cells in a dose-dependent and nanomolar range, but the complexes with 1,10-phenanthroline were more active. Moreover, comparative activity on B16 and healthy BJ cells revealed a therapeutic index of 1.27-2.24. Bioinformatic methods were used to calculate the drug-likeness, pharmacokinetic, pharmacogenomic, and pharmacodynamic profiles of the compounds. The results showed that all compounds exhibit drug-likeness features, as well as promising absorption, distribution, metabolism, and excretion (ADME) properties, and no toxicity. The pharmacodynamics results showed that the neutral species appear to be good candidates for antitumor molecular targets (Tyrosyl-DNA phosphodiesterase 1, DNA-(apurinic or apyrimidinic site) lyase or Kruppel-like factor 5). Furthermore, the pharmacogenomic results showed a good affinity of the copper(II) complexes for the human cytochrome. These results recommend complexes bearing 1,10-phenanthroline as good candidates for developing drugs to melanoma alternative treatment.

24. Facile synthesis of low toxicity iron oxide/TiO2 nanocomposites with hyperthermic and photo-oxidation properties

Authors: Popescu, T; Matei, CO; Culita, DC; Maraloiu, VA; Rostas, AM; Diamandescu, L; Iacob, N; Savopol, T; Ilas, MC; Feder, M; Lupu, AR; Iacoban, AC; Vlaicu, ID; Moisescu, MG

Published: APR 27 2022, SCIENTIFIC REPORTS, 12, 6887, DOI: 10.1038/s41598-022-11003-3

The present study aimed to assess the feasibility of developing low-cost multipurpose iron oxide/TiO2 nanocomposites (NCs) for use in combined antitumor therapies and water treatment applications. Larger size (approximate to 100 nm) iron oxide nanoparticles (IONPs) formed magnetic core-TiO2 shell structures at high Fe/Ti ratios and solid dispersions of IONPs embedded in TiO2 matrices when the Fe/Ti ratio was low. When the size of the iron phase was comparable to the size of the crystallized TiO2 nanoparticles (approximate to 10 nm), the obtained nanocomposites consisted of randomly mixed aggregates of TiO2 and IONPs. The best inductive heating and ROS photogeneration properties were shown by the NCs synthesized at 400 degrees C which contained the minimum amount of alpha-Fe2O3 and sufficiently crystallized anatase TiO2. Their cytocompatibility was assessed on cultured human and murine fibroblast cells and analyzed in relation to the adsorption of bovine serum albumin from the culture medium onto their surface. The tested nanocomposites showed excellent cytocompatibility to human fibroblast cells. The results also indicated that the environment (i.e. phosphate buffer or culture medium) used to disperse the nanomaterials prior to performing the viability tests can have a significant impact on their cytotoxicity.

25. Biological Activity of Triazolopyrimidine Copper(II) Complexes Modulated by an Auxiliary N-N-Chelating Heterocycle Ligands

Authors: Ruta, LL; Farcasanu, IC; Bacalum, M; Raileanu, M; Rostas, AM; Daniliuc, C; Chifiriuc, MC; Marutescu, L; Popa, M; Badea, M; Iorgulescu, EE; Olar, R

Published: NOV 2021, MOLECULES, 26, DOI: 10.3390/molecules26226772

Novel complexes of type [Cu(N-N)(dmtp)(2)(OH2)](ClO4)(2)& BULL;dmtp ((1) N-N: 2,2 & PRIME;-bipyridine; (2) L: 1,10-phenantroline and dmtp: 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine) were designed in order to obtain biologically active compounds. Complexes were characterized as mononuclear species that crystallized in the space group P-1 of the triclinic system with a square pyramidal geometry around the copper (II). In addition to the antiproliferative effect on murine melanoma B16 cells, complex (1) exhibited low toxicity on normal BJ cells and did not affect membrane integrity. Complex (2) proved to be a more potent antimicrobial in comparison with (1), but both compounds were more active in comparison with dmtp-both against planktonic cells and biofilms. A stronger antimicrobial and antibiofilm effect was noticed against the Gram-positive strains, including methicillin-resistant Staphylococcus aureus (MRSA). Both electron paramagnetic resonance (EPR) and Saccharomyces cerevisiae studies indicated that the complexes were scavengers rather than reactive oxygen species promoters. Their DNA intercalating capacity was evidenced by modifications in both absorption and fluorescence spectra. Furthermore, both complexes exhibited nuclease-like activity, which increased in the presence of hydrogen peroxide.

26. Activation ability of Gd dopant in the ZnSe single crystals

Authors: Goncearenco, EP; Rostas, AM; Galca, AC; Colibaba, G; Nedeoglo, DD

Published: OCT 2021, JOURNAL OF LUMINESCENCE, 238, DOI: 10.1016/j.jlumin.2021.118314

Rare-earth elements are widely used as doping materials as they considerably change the semiconductor optical, electrical, magnetic and radiative properties. This work explores the influence of Gadolinium (Gd) as a dopant on the radiative, optical and magnetic properties of the Zinc Selenide (ZnSe). ZnSe single crystals were grown by the physical transport method and doped during the growth process using a GdSe source. A wide range of characterization equipment was employed to analyze the obtained ZnSe:Gd single crystals. Intracenter radiative transition of the Gd has not been detected. Gd ions activate the background impurities, causing radiative transitions from the conduction band to the Cu2+ level and intracenter transitions within V3+, V2+ and Cr2+ ions. At the same time, the edge band intensity is dependent on the dopant concentration. Optical transmittance decreases, but the position of the fundamental absorption band is unchanged. Single crystals have a zinc blende crystal structure, and Gd ions do not form complexes with native defects or background impurities.

27. Thermal Gating of Magnon Exchange in Magnetic Multilayers with Antiferromagnetic Spacers

Authors: Polishchuk, DM; Tykhonenko-Polishchuk, YO; Lytvynenko, YM; Rostas, AM; Gomonay, OV; Korenivski, V

Published: JUN 4 2021, PHYSICAL REVIEW LETTERS, 126, DOI: 10.1103/PhysRevLett.126.227203

We observe a strong thermally controlled magnon-mediated interlayer coupling of two ferromagnetic layers via an antiferromagnetic spacer in spin-valve type trilayers. The effect manifests itself as a coherent switching as well as collective resonant precession of the two ferromagnets, which can be controlled by varying temperature and the spacer thickness. We explain the observed behavior as due to a strong hybridization of the ferro- and antiferromagnetic magnon modes in the trilayer at temperatures just below the Neel temperature of the antiferromagnetic spacer.

28. Enhancing stability of hybrid perovskite solar cells by imidazolium incorporation

Authors: Tomulescu, AG; Leonat, LN; Neatu, F; Stancu, V; Toma, V; Derbali, S; Neatu, S; Rostas, AM; Besleaga, C; Patru, R; Pintilie, I; Florea, M

Published: AUG 1 2021, SOLAR ENERGY MATERIALS AND SOLAR CELLS, 227, DOI: 10.1016/j.solmat.2021.111096

Hybrid perovskites based solar cells have demonstrated high conversion efficiency but poor long-term stability. This study reports on the results obtained after doping the CH3NH3PbI2.6Cl0.4 mixed halide perovskite with imidazolium (C3N2H5+, denoted IM) on the "A site" position of a perovskite, to improve photovoltaic performances and stability of hybrid perovskite solar cells. The perovskite films were investigated exhaustively by different characterization techniques: X-ray diffraction, Atomic Force Microscopy, Scanning Electron Microscopy, UV-Vis, X-ray Photoelectron Electron Paramagnetic Resonance spectroscopies, Impedance Spectroscopy and Incident Photon-to-Electron Conversion Efficiency. The photovoltaic parameters were determined by measuring the IV curves of the corresponding solar cells. The amount of IM inserted in the perovskite play a key role on the film properties. The calculated new tolerance factors according to the "globularity factor" are experimentally proved and thus at doping concentrations greater than 20% for CH3NH3PbI2.6Cl0.4 perovskite the 3D structure is no longer obtained. However, below this value, the IM substituted perovskite film possesses an improved film quality and crystallinity as compared to the pristine film. Substituting MA+ with IM+ provides a favorable way to reduce recombination processes and shows great potential to achieve high stability, and an improved charge generation, resulting in increased PCE values. We find that the optimal percentage of imidazolium incorporation to achieve better stability of solar cells is 6%.

29. Comparative investigation of structural, EPR, optical and photoluminescence properties of nanostructured LaPO4:Ce/RE/Me and LaPO4:Yb/Er phosphors prepared by co-precipitation method

Authors: AitMellal, O; Oufni, L; Messous, MY; Trandafir, MM; Chirica, IM; Florea, M; Neatu, S; Rostas, AM; Secu, M; Neatu, F

Published: SEP 2021, JOURNAL OF SOLID STATE CHEMISTRY, 301, DOI: 10.1016/j.jssc.2021.122310

In this work, the structural, thermal, vibrational, morphological, magnetic and optical properties of LaPO4:Ce/RE/Me (RE=Nd3+, Tb3+; Me-Cr3+, Mn2+) and LaPO4:Yb3+/Er3+ phosphors prepared by the co-precipitation method are presented. The obtained materials crystallized in monoclinic structure with the P2(1)/n space group and the particles were of nanorod shape with about 200 nm in length and the diameter approximately 19 nm. The presence of dopant ions was confirmed by both electron paramagnetic resonance (EPR) and UV-visible spectroscopies. In addition, the down-conversion (DC) and up-conversion (UC) of the LaPO4 nanophosphors via the 275 and 980 nm excitations, respectively, were considered, and a wide range of electronic transitions was observed. Based on the photoluminescence (PL) spectra, there is an efficient energy transfer (ET) process from Ce3+ donors to Nd3+ and Tb3+ acceptors, and the computed ET efficiency was 70% and 88%, respectively. The Ce3+/Cr3+ and Ce3+/Mn2+ doped LaPO4 showed weak far-red and green luminescence with much smaller ET efficiency of about 3.7 and 0.4%, respectively. LaPO4:Yb3+/Er3+ showed UC luminescence under the 980 nm laser radiation, and the resulted red and green light was attributed to the Er3+ transitions.

30. 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.

31. Antiproliferative and antibacterial properties of biocompatible copper(II) complexes bearing chelating N,N-heterocycle ligands and potential mechanisms of action

Authors: Olar, R; Badea, M; Bacalum, M; Raileanu, M; Ruta, LL; Farcasanu, IC; Rostas, AM; Vlaicu, ID; Popa, M; Chifiriuc, MC

Published: OCT 2021, BIOMETALS, 34, 1172, DOI: 10.1007/s10534-021-00334-9

In an attempt to propose new applications for the biomedical field, complexes with mixed ligands {[Cu(bpy)(2)(mu 2OClO3)]ClO4}n (1) and [Cu(phen)(2)(OH2)](ClO4)(2) (2) (bpy: 2,2'-biyridine; phen and 1,10-phenantroline) were evaluated for their antibacterial and cytotoxicicity features and for the elucidation of some of the mechanisms involved. Complex (2) proved to be a very potent antibacterial agent, exhibing MIC and MBEC values 2 to 54 times lower than those obtained for complex (1) against both susceptible or resistant Gram-positive and Gram-negative strains, in planktonic or biofilm growth state. In exchange, complex (1) exhibited selective cytotoxicity against melanoma tumor cells (B16), proving a promising potential for developing novel anticancer drugs. The possible mechanisms of both antimicrobial and antitumor activity of the copper(II) complexes is their DNA intercalative ability coupled with ROS generation. The obtained results recommend the two complexes for further development as multipurpose copper-containing drugs.

32. Structural and Optical Investigations of Ce3+/Mn2+-Doped LaPO4 Phosphors

Authors: Aitmellal, O; Oufni, L; Messous, MY; Neatu, F; Florea, M; Neatu, S; Rostas, AM; Secu, M

Published: APR 2021, JOURNAL OF ELECTRONIC MATERIALS, 50, 2147, DOI: 10.1007/s11664-020-08678-7

Lanthanum orthophosphate (LaPO4) and La0.95-xCe0.05MnxPO4 (x = 0.00, 0.03, 0.10) phosphors were synthesized by a simple and cost-efficient co-precipitation method and the formation of LaPO4 nanorods with a monoclinic P21/n crystal structure was observed. X-ray diffraction pattern analysis indicated a slight distortion of the LaPO4 crystalline structure and an increase of the lattice strain as a consequence of the Mn2+ and Ce3+ dopants incorporation in the host matrix. Scanning electron microscopy revealed that the microstructure of all powders consists of agglomerations of nanorods, which are around 17 +/- 3 nm in diameter and length ranging from 100 nm to 300 nm. Electron paramagnetic resonance measurements have indicated the presence of Mn2+ in isolated species, but also as agglomerates. Ce3+ and Mn2+ doping of LaPO4 resulted also in a decrease of the band gap up to 4.70 eV compared to the un-doped sample. Because of an energy transfer effect from Ce3+ to Mn2+ ions, green emission of Mn2+ ions at around 550 nm was observed upon 275 nm excitation.

33. 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.

34. 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.

35. Investigations of BaCl2:Eu2+ nanophosphor using electron paramagnetic resonance, structural analysis and thermoluminescence

Authors: Secu, CE; Rostas, AM

Published: JAN 30 2020, JOURNAL OF ALLOYS AND COMPOUNDS, 815, DOI: 10.1016/j.jallcom.2019.152400

Structural analysis of the Eu2+-doped BaCl2 nanocrystals and the doping process was monitored and characterized via electron paramagnetic resonance spectroscopy. Structural analysis has shown a slight distortion of the cell which is reflected in the low value of microstrain and the Eu2+-doping effect is limited to the first order chlorine ions neighbors of Ba2+. Electron paramagnetic resonance measurements have indicated the presence of the Eu2+-dopant ions in the BaCl2 host matrix with a solubility limit of about 2%. From the spectra simulation, the isotropic g-value g(iso) = 1.9951(7), the isotropic hyperfine coupling constant A(iso)= 42.4 MHz and the high-order zero-field splitting parameters from the crystal field B-2(0) = 21 MHz and B-2(2)= -493 MHz were obtained. During X-ray irradiation, defects are produced and stabilized by the Eu2+ dopant ions. The single dominant thermoluminescence peak at 132 degrees C (activation energy E = 1.1 eV) was assigned to the recombination of the F(Cl)-center with Eu2+ related hole centers. (C) 2019 Elsevier B.V. All rights reserved.

36. Magneto-functionalities of La 1-x A x MnO 3 (A = K; Ba) synthesized by flash combustion method

Authors: Bouzid, SA; Galca, AC; Sajieddine, M; Kuncser, V; Rostas, AM; Iacob, N; Enculescu, M; Amarande, L; Pasuk, I; Essoumhi, A

Published: OCT 25 2020, JOURNAL OF ALLOYS AND COMPOUNDS, 839, DOI: 10.1016/j.jallcom.2020.155546

37. Copper(II) Complexes with Mixed Heterocycle Ligands as Promising Antibacterial and Antitumor Species

Authors: Rostas, AM; Badea, M; Ruta, LL; Farcasanu, IC; Maxim, C; Chifiriuc, MC; Popa, M; Luca, M; Korosin, NC; Korosec, RC; Bacalum, M; Raileanu, M; Olar, R

Published: SEP 2020, MOLECULES, 25, DOI: 10.3390/molecules25173777

Complexes with mixed ligands [Cu(N-N)(2)(pmtp)](ClO4)(2)((1) N-N: 2,2 '-bipyridine; (2) L: 1,10-phenanthroline and pmpt: 5-phenyl-7-methyl-1,2,4-triazolo[1,5-a]pyrimidine) were synthesized and structurally and biologically characterized. Compound (1) crystallizes into space groupPaand (2) inP-1. Both complexes display an intermediate stereochemistry between the two five-coordinated ones. The biological tests indicated that the two compounds exhibited superoxide scavenging capacity, intercalative DNA properties, and metallonuclease activity. Tests on various cell systems indicated that the two complexes neither interfere with the proliferation ofSaccharomyces cerevisiaeor BJ healthy skin cells, nor cause hemolysis in the active concentration range. Nevertheless, the compounds showed antibacterial potential, with complex (2) being significantly more active than complex (1) against all tested bacterial strains, both in planktonic and biofilm growth state. Both complexes exhibited a very good activity against B16 melanoma cells, with a higher specificity being displayed by compound (1). Taken together, the results indicate that complexes (1) and (2) have specific biological relevance, with potential for the development of antitumor or antimicrobial drugs.

38. Structural and Optical Investigations of Ce3+/Mn2+-Doped LaPO4 Phosphors

Authors: Aitmellal, O; Oufni, L; Messous, MY; Neatu, F; Florea, M; Neatu, S; Rostas, AM; Secu, M

Published: , JOURNAL OF ELECTRONIC MATERIALS, DOI: 10.1007/s11664-020-08678-7

39. Copper(II) species with 1-(o-tolyl)biguanide: Structural characterization, ROS scavenging, antibacterial activity, biocompatibility and in silico studies

Authors: Maxim, C; Badea, M; Rostas, AM; Chifiriuc, MC; Pircalabioru, GG; Avram, S; Olar, R

Published: , APPLIED ORGANOMETALLIC CHEMISTRY, DOI: e6471

The species cis-[Cu(tbg)(2)](ClO4)(2) (CuTP) (tbg: 1-(o-tolyl)biguanide) was designed as a novel antimicrobial and biocompatible agent. The single-crystal X-ray diffraction revealed a mononuclear species with a very interesting structure consisting of two tautomeric forms of tbg arranged in a cis-configuration. A complex hydrogen bond network with perchlorate anions involved in different interactions leads to a supramolecular structure. The EPR data indicated the formation of a stable cis-trans mixture in dimethylsulfoxide. Moreover, the EPR experiments evidenced no activity against the superoxide radical (O-2 center dot(-)) but scavenging ability of the hydroxyl radical (HO center dot). This complex exhibited excellent antibacterial properties against planktonic and biofilm embedded gram-negative (Klebsiella pneumoniae, Enterobacter cloacae) and gram-positive (Bacillus subtilis, Lysteria monocytogenes) bacteria. The best efficiency was noticed against E. cloacae and L. monocytogenes with minimal inhibitory concentration and minimal biofilm eradication for a concentration value of 1.95 mu g/ml. One of the possible mechanisms of antimicrobial activity is represented by reactive oxygen species (ROS) generation. The complex was not cytotoxic on L929 fibroblasts. The in silico analysis confirmed the drug-likeness and safety profile of the tested compound and its potential for developing novel antimicrobial and therapeutic tools, targeting other clinical conditions besides infectious diseases.

40. Antiproliferative and antibacterial properties of biocompatible copper(II) complexes bearing chelating N,N-heterocycle ligands and potential mechanisms of action

Authors: Olar, R; Badea, M; Bacalum, M; Raileanu, M; Ruta, LL; Farcasanu, IC; Rostas, AM; Vlaicu, ID; Popa, M; Chifiriuc, MC

Published: , BIOMETALS, DOI: 10.1007/s10534-021-00334-9

Dr. Arpad ROSTAS

Scientific Researcher III

Publications

1. Effect of transition metal ions on the dielectric properties of chromium potassium phosphates

2. Interaction of Low-Density Polyethylene Nanofragments with Autotrophic and Chemotrophic Bacteria

3. Nitrogen-Doped WO3 Nanoparticles as Electrode Materials in All-in-One Supercapacitor Devices

4. Adsorption-catalysis synergy in the visible-light-driven removal of 17 β-estradiol by (Au)TiO 2 nanotubes-graphene composites

5. Hybrid supercapacitors based on X-site Ba(II) ions substituted by Sr(II) in Langbeinite-type phosphates

6. α-MoO3 Micro- and Nanoparticles as Catalysts for Biofuel Production

7. Antiferromagnet-mediated interlayer exchange: Hybridization versus proximity effect

8. Characterization of defect structures in nanoscaled W-doped TiO2 tested as supercapacitor electrode materials

9. Structural and Electrical Properties of Novel Cr/Fe Mixed Transition-Metal Phosphates

10. Multi-analytical characterization of the white inlaid decoration on the prehistoric pottery from southern Romania

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

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

13. Characterization of defect structures in nanoscaled W-doped TiO2 tested as supercapacitor electrode materials

14. Structural and Electrical Properties of Novel Cr/Fe Mixed Transition-Metal Phosphates

15. Photo-stable, 1D-nanofilaments TiO2-based lepidocrocite for photocatalytic hydrogen production in water-methanol mixtures

16. TiO2 Phase Ratio's Contribution to the Photocatalytic Activity

17. Analysis and characterization of magneto-structural transformations and critical exponent analysis of La0.8Ca0.2-xPbxMnO3

18. 'Put variety in White': Multi-analytical investigation of the white pigments inlaid on Early Chalcolithic pottery from Southern Romania

19. Insights into Structure and Biological Activity of Copper(II) and Zinc(II) Complexes with Triazolopyrimidine Ligands

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

21. Temperature-induced phase transition and tunable luminescence properties of Ce3+-Mn2+-Zr4+ tri-doped LaPO4 phosphor

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

23. Antiproliferative Copper(II) Complexes Bearing Mixed Chelating Ligands: Structural Characterization, ROS Scavenging, In Silico Studies, and Anti-Melanoma Activity

24. Facile synthesis of low toxicity iron oxide/TiO2 nanocomposites with hyperthermic and photo-oxidation properties

25. Biological Activity of Triazolopyrimidine Copper(II) Complexes Modulated by an Auxiliary N-N-Chelating Heterocycle Ligands

26. Activation ability of Gd dopant in the ZnSe single crystals

27. Thermal Gating of Magnon Exchange in Magnetic Multilayers with Antiferromagnetic Spacers

28. Enhancing stability of hybrid perovskite solar cells by imidazolium incorporation

29. Comparative investigation of structural, EPR, optical and photoluminescence properties of nanostructured LaPO4:Ce/RE/Me and LaPO4:Yb/Er phosphors prepared by co-precipitation method

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

31. Antiproliferative and antibacterial properties of biocompatible copper(II) complexes bearing chelating N,N-heterocycle ligands and potential mechanisms of action

32. Structural and Optical Investigations of Ce3+/Mn2+-Doped LaPO4 Phosphors

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

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

35. Investigations of BaCl2:Eu2+ nanophosphor using electron paramagnetic resonance, structural analysis and thermoluminescence

36. Magneto-functionalities of La 1-x A x MnO 3 (A = K; Ba) synthesized by flash combustion method

37. Copper(II) Complexes with Mixed Heterocycle Ligands as Promising Antibacterial and Antitumor Species

38. Structural and Optical Investigations of Ce3+/Mn2+-Doped LaPO4 Phosphors

39. Copper(II) species with 1-(o-tolyl)biguanide: Structural characterization, ROS scavenging, antibacterial activity, biocompatibility and in silico studies

40. Antiproliferative and antibacterial properties of biocompatible copper(II) complexes bearing chelating N,N-heterocycle ligands and potential mechanisms of action

3. Nitrogen-Doped WO₃ Nanoparticles as Electrode Materials in All-in-One Supercapacitor Devices

6. α-MoO₃ Micro- and Nanoparticles as Catalysts for Biofuel Production

13. Characterization of defect structures in nanoscaled W-doped TiO₂ tested as supercapacitor electrode materials

16. TiO₂ Phase Ratio's Contribution to the Photocatalytic Activity

17. Analysis and characterization of magneto-structural transformations and critical exponent analysis of La_0.8Ca_0.2-xPb_xMnO₃