National Institute Of Materials Physics - Romania

The aim of this work is to highlight the influence of blends based on TiO2 nanoparticles and reduced graphene oxide (RGO) on the photodegradation of acetaminophen (AC). To this end, the catalysts of TiO2/RGO blends with RGO sheet concentrations equal 5, 10, and 20 wt. % were prepared by the solid-state interaction of the two constituents. The preferential adsorption of TiO2 particles onto the RGO sheets' surfaces via the water molecules on the TiO2 particle surface was demonstrated by FTIR spectroscopy. This adsorption process induced an increase in the disordered state of the RGO sheets in the presence of the TiO2 particles, as highlighted by Raman scattering and scanning electron microscopy (SEM). The novelty of this work lies in the demonstration that TiO2/RGO mixtures, obtained by the solid-phase interaction of the two constituents, allow an acetaminophen removal of up to 95.18% after 100 min of UV irradiation. This TiO2/RGO catalyst induced a higher photodegradation efficiency of AC than TiO2 due to the presence of RGO sheets, which acted as a capture agent for the photogenerated electrons of TiO2, hindering the electron-hole recombination. The reaction kinetics of AC aqueous solutions containing TiO2/RGO blends followed a complex first-order kinetic model. Another novelty of this work is the demonstration of the ability of PVC membranes modified with Au nanoparticles to act both as filters for the removal of TiO2/RGO blends after AC photodegradation and as potential SERS supports, which illustrate the vibrational properties of the reused catalyst. The reuse of the TiO2/RGO blends after the first cycle of AC photodegradation indicated their suitable stability during the five cycles of pharmaceutical compound photodegradation.

This study aimed to investigate the biological response induced by hydroxyapatite (HAp) and zinc-doped HAp (ZnHAp) in human gingival fibroblasts and to explore their antimicrobial activity. The ZnHAp (with xZn = 0.00 and 0.07) powders, synthesized by the sol-gel method, retained the crystallographic structure of pure HA without any modification. Elemental mapping confirmed the uniform dispersion of zinc ions in the HAp lattice. The size of crystallites was 18.67 +/- 2 nm for ZnHAp and 21.54 +/- 1 nm for HAp. The average particle size was 19.38 +/- 1 nm for ZnHAp and 22.47 +/- 1 nm for HAp. Antimicrobial studies indicated an inhibition of bacterial adherence to the inert substrate. In vitro biocompatibility was tested on various doses of HAp and ZnHAp after 24 and 72 h of exposure and revealed that cell viability decreased after 72 h starting with a dose of 31.25 mu g/mL. However, cells retained membrane integrity and no inflammatory response was induced. High doses (such as 125 mu g/mL) affected cell adhesion and the architecture of F-actin filaments, while in the presence of lower doses (such as 15.625 mu g/mL), no modifications were observed. Cell proliferation was inhibited after treatment with HAp and ZnHAp, except the dose of 15.625 mu g/mL ZnHAp at 72 h of exposure, when a slight increase was observed, proving an improvement in ZnHAp activity due to Zn doping.

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.

Laser Induced-Thermionic Vacuum Arc (LTVA) technology was used for depositing uniform intermetallic CoNi thin films of 100 nm thickness. LTVA is an original deposition method using a combination of the typical Thermionic Vacuum Arc (TVA) system and a laser beam provided by a QUANTEL Q-Smart 850 Nd:YAG compact Q-switched laser with a second harmonic module. The novelty is related to the simultaneous deposition of a bi-component metallic thin film using photonic processes of the laser over the plasma deposition, which improves the roughness but also triggers the composition of the deposited thin film. Structural analysis of the deposited thin films confirms the formation of face-centered cubic (fcc) as the main phase CoNi and hexagonal Co3Ni as the minority phase, observed mainly using high-resolution transmission electron microscopy. The magneto-optical measurements suggest an isotropic distribution of the CoNi alloy thin films for the in-plan angular rotation. From the low coercive field of H-c = 40 Oe and a saturation field at 900 Oe, the CoNi thin films obtained by LTVA are considered semi-hard magnetic materials. Magnetic force microscopy reveals spherical magnetic nanoparticles with mean size of about 40-50 nm. The resistivity was estimated at rho = 34.16 mu Omega cm, which is higher than the values for bulk Co and Ni.

The acceptor removal process is the most detrimental effect encountered in irradiated boron-doped silicon. This process is caused by a radiation-induced boron-containing donor (BCD) defect with bistable properties that are reflected in the electrical measurements performed in usual ambient laboratory conditions. In this work, the electronic properties of the BCD defect in its two different configurations (A and B) and the kinetics behind transformations are determined from the variations in the capacitance-voltage characteristics in the 243-308 K temperature range. The changes in the depletion voltage are consistent with the variations in the BCD defect concentration in the A configuration, as measured with the thermally stimulated current technique. The A & RARR;B transformation takes place in non-equilibrium conditions when free carriers in excess are injected into the device. B & RARR;A reverse transformation occurs when the non-equilibrium free carriers are removed. Energy barriers of 0.36 eV and 0.94 eV are determined for the A & RARR;B and B & RARR;A configurational transformations, respectively. The determined transformation rates indicate that the defect conversions are accompanied by electron capture for the A & RARR;B conversion and by electron emission for the B & RARR;A transformation. A configuration coordinate diagram of the BCD defect transformations is proposed.

Hydroxyapatite doped with magnesium and zinc in chitosan matrix biocomposites have great potential for applications in space technology, aerospace, as well as in the biomedical field, as a result of coatings with multifunctional properties that meet the increased requirements for wide applications. In this study, coatings on titanium substrates were developed using hydroxyapatite doped with magnesium and zinc ions in a chitosan matrix (MgZnHAp_Ch). Valuable information concerning the surface morphology and chemical composition of MgZnHAp_Ch composite layers were obtained from studies that performed scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), metallographic microscopy, and atomic force microscopy (AFM). The wettability of the novel coatings, based on magnesium and zinc-doped biocomposites in a chitosan matrix on a titanium substrate, was evaluated by performing water contact angle studies. Furthermore, the swelling properties, together with the coating's adherence to the titanium substrate, were also analyzed. The AFM results emphasized that the composite layers exhibited the surface topography of a uniform layer, and that there were no evident cracks and fissures present on the investigated surface. Moreover, antifungal studies concerning the MgZnHAp_Ch coatings were also carried out. The data obtained from quantitative antifungal assays highlight the strong inhibitory effects of MgZnHAp_Ch against C. albicans. Additionally, our results underline that after 72 h of exposure, the MgZnHAp_Ch coatings display fungicidal features. Thus, the obtained results suggest that the MgZnHAp_Ch coatings possess the requisite properties that make them suitable for use in the development of new coatings with enhanced antifungal features.

This study aims to design and test different formulations composed of dextran-coated iron oxide nanoparticles (IONPs) loaded with 5-Fluorouracil (5-FU) with varying nanoparticle:drug ratios on colorectal cancer cells. The stable suspension of IONPs s was synthesized by the adapted co-precipitation method. The stable suspension of IONPs was mixed with a solution of dextran and 5-FU solubilized in a saline solution. The final suspensions with optimized ratios of IONP:5-FU in the final suspension were 0.5:1, 1:1, and 1.5:1. The information on the morphology and size distribution of the IONPs suspension and IONP loads with 5-FU was obtained using scanning electron microscopy (SEM). The presence of 5-FU and dextran on the surface of the IONPs was highlighted by energy-dispersive X-ray spectroscopy (EDS) studies. The determination of the surface charge of the nanoparticles in the final suspensions of IONP:5-FU was achieved by measuring the zeta potential (& zeta;). The hydrodynamic diameter of the resulting suspensions of IONP:5-FU was determined by dynamic light scattering (DLS). A cytocompatibility analysis was performed using Caco-2 (human epithelial colorectal adenocarcinoma) cells. In this research, our goal was to find a relationship between the formulation ratio of nanoparticles and drug, and the cellular response after exposure, as a strategy to increase the efficacy of this drug-delivery system. The nanoparticle uptake and antitumor activity, including modulation of oxidative stress, apoptosis, and proliferation biomarkers, were analyzed. The present study showed that the nanoformulation with the ratio IONP:5-FU 1.5:1 had the highest anti-tumor efficiency. Moreover, decreased MCM-2 expression in Caco-2 cells exposed to dextran-coated iron oxide nanoparticles loaded with 5-FU was demonstrated for the first time.

Structure, composition, and transport properties of Mg2-xAgx(Si0.3Sn0.7)1-yGay (x = {0, 0.021, y = {0, 0.02, 0.04, 0.061) solid solutions produced by melting followed by spark plasma sintering are investigated. The preparation method is adjusted to control sample stoichiometry and phase composition. Doping with two types of dopants at different sites, while employing synthesis methods which generate a small amount of secondary phase, is an uncommon approach in this materials, expected to enhance their thermoelectric performance. An enhanced carrier concentration but diminished mobility is observed in the samples with higher amounts of dopant, which leads to the highest values of the power factor, for Mg1.98Ag0.02Si0.27Sn0.67Ga0.06 in a narrow temperature range (575-675 K) around the peak value, of 9.10-4 Wm-1 K-2 at 625 K. The two types of dopants have opposing effects on the thermal conductivity, with Ag promoting strong phonon scattering and decreasing its values while Ga increases them because of its en-hanced carrier concentration. The rather high thermal conductivity values of the double doped compounds produce low values of the ZT without exceeding 0.29 at 627 K for Mg1.98Ag0.02Si0.3Sn0.7 sample.(c) 2023 Elsevier B.V. All rights reserved.

Zinc substituted nickel-cobalt ferrites, i.e., ZnxNi0.8-xCo0.2Fe2O4 (x = 0.0, 0.05, 0.10 and 0.20) with average crystallite size 100 nm were synthesized by citrate-gel auto-combustion method to investigate effects of Zn2+ substitution on the structural and dielectric properties. Both X-ray diffraction (XRD) and IR spectroscopy studies confirms the formation of pure cubic spinel structure. Variation of lattice parameter infers Vegard's law linear dependence with the addition of Zn2+ concentration. The temperature-dependent behavior of dielectric and modulus spectra has been studied within the frequency range 100 Hz-100 kHz for different temperatures between 100 K and 400 K. It was concluded that the dielectric responses of ZnxNi0.8-xCo0.2Fe2O4 are found to be frequency dependent and thermally activated. Also, In the Zn doped ferrites variations of dielectric loss (tan d) and the imaginary part of electric modulus (M") show the presence of the non-Debye type of dielectric relaxation. Rise in Zinc concentration leads to a decrease in dielectric constant (e (r)) due to the declining of Fe3+-O-M2+ conducting network (M is Co or Ni). Here, we report a low loss tangent factor of the order of 8x10-3 0.6Zn(0.2)Co(0.2)Fe(2)O(4) make this composition suitable for high frequency-applications at room temperature. The activation energy is calculated from electric modulus formalism and DC electrical conductivity and found to increase with further substitution of Zn2+ concentration.

Zinc substituted nickel-cobalt ferrites, i.e., ZnxNi0.8-xCo0.2Fe2O4 (x = 0.0, 0.05, 0.10 and 0.20) with average crystallite size 100 nm were synthesized by citrate-gel auto-combustion method to investigate effects of Zn2+ substitution on the structural and dielectric properties. Both X-ray diffraction (XRD) and IR spectroscopy studies confirms the formation of pure cubic spinel structure. Variation of lattice parameter infers Vegard's law linear dependence with the addition of Zn2+ concentration. The temperature-dependent behavior of dielectric and modulus spectra has been studied within the frequency range 100 Hz-100 kHz for different temperatures between 100 K and 400 K. It was concluded that the dielectric responses of ZnxNi0.8-xCo0.2Fe2O4 are found to be frequency dependent and thermally activated. Also, In the Zn doped ferrites variations of dielectric loss (tan d) and the imaginary part of electric modulus (M") show the presence of the non-Debye type of dielectric relaxation. Rise in Zinc concentration leads to a decrease in dielectric constant (e (r)) due to the declining of Fe3+-O-M2+ conducting network (M is Co or Ni). Here, we report a low loss tangent factor of the order of 8x10-3 0.6Zn(0.2)Co(0.2)Fe(2)O(4) make this composition suitable for high frequency-applications at room temperature. The activation energy is calculated from electric modulus formalism and DC electrical conductivity and found to increase with further substitution of Zn2+ concentration.