National Institute Of Materials Physics - Romania

The primary objective of this research was to develop efficient solid catalysts that can directly convert the lactic acid (LA) obtained from lignocellulosic biomass into alanine (AL) through a reductive amination process. To achieve this, various catalysts based on ruthenium were synthesized using different carriers such as multi-walled carbon nanotubes (MWCNTs), beta-zeolite, and magnetic nanoparticles (MNPs). Among these catalysts, Ru/MNP demonstrated a remarkable yield of 74.0% for alanine at a temperature of 200 degrees C. This yield was found to be superior not only to the Ru/CNT (55.7%) and Ru/BEA (6.6%) catalysts but also to most of the previously reported catalysts. The characterization of the catalysts and their catalytic results revealed that metallic ruthenium nanoparticles, which were highly dispersed on the external surface of the magnetic carrier, significantly enhanced the catalyst's ability for dehydrogenation. Additionally, the -NH2 basic sites on the catalyst further facilitated the formation of alanine by promoting the adsorption of acidic reactants. Furthermore, the catalyst could be easily separated using an external magnetic field and exhibited the potential for multiple reuses without any significant loss in its catalytic performance. These practical advantages further enhance its appeal for applications in the reductive amination of lactic acid to alanine.

For the development of memory devices for the continuous advancement of IT engineering, a good understanding of the charging-discharging mechanisms in nanocrystalline floating gate memories is crucial to overcoming the current limitations. The charging-discharging mechanism in Al2O3/Ge/Al2O3 trilayer memory structures obtained by magnetron sputtering deposition is investigated as a function of the postdeposition annealing temperature, up to 900 degrees C. The change by annealing of C-V hysteresis curves from a clockwise type at low temperatures to counterclockwise one in a sample annealed within the intermediary temperature range of 550 to 650 degrees C, and then, a return to a clockwise type for annealing within the higher temperature range of 800-900 degrees C was observed. Up to 700 degrees C, memory performances are constantly improved reaching for 600 degrees C annealed samples, a memory window of 5.6 V for voltage sweep in the range -1 to +15 V, and good retention characteristics for 650 degrees C annealed structures, in which the charge loss is only similar to 2% after 10(8) s. When the annealing temperature was increased above 700 degrees C, a rapid decrease in the memory performance takes place. The annealing-induced changes are explained based on the Ge fast diffusion and nanocrystallization process, in correlation with morphological and structural high-resolution transmission electron microscopy results.

This study reports the development of a novel biocomposite for potential applications in the environmental remediation. The hydroxyapatite/sodium bicarbonate (HAp-SB) biocomposite obtained by a cheap method could offer promising characteristics to be used in environmental applications. The obtaining of HAp-SB ceramic composites was studied with the aim of increasing the adsorption efficiency of lead ions from contaminated waters. A composite material (HAp-SB) with good crystallinity that preserves the hexagonal structure of pure hydroxyapatite was obtained. For the powder recovered after decontamination of the lead solution (PbHAp-SB), the XRD model highlighted additional maxima belonging to Ca10(PO4)5(OH)2, Ca0.805Pb4.195(PO4)(OH) and PbH2P2O7. The FTIR spectra of PbHAp-SB are similar to those of HAp-SB composites showing a broadening of the vibration peaks and a slight shift. The XPS and EDS studies illustrated the purity of the HAp-SB sample. Moreover, the presence of lead in the powder recovered after decontamination was also highlighted by XPS and EDS studies. The efficiency of HAp-SB in the adsorption of Pb2+ ions from the contaminated solution was also highlighted by ultrasound studies using double-distilled water as the reference liquid. The adsorption kinetics were investigated with the aid of Langmuir and Freundlich theoretical models. The results demonstrated that the HAp-SB ceramic composite has a strong affinity for the adsorption of Pb2+ ions from contaminated solutions. The removal efficiency of Pb2+ ions was about 92% for the initial Pb2+ concentration above 50 mg/L. The results of the cell viability and cytotoxicity studies demonstrated that HAp-SB nanoparticles did not influence negatively the HeLa cell's viability and did not induce any significant changes of the morphological features of HeLa cells after 24 h of incubation. The batch adsorption results as well as the cytotoxicity assay results suggested that the HAp-SB powder could be successfully used for the removal of Pb2+ from contaminated water.

The paper describes the chemical modification of the graphene oxide (GO) surface with glucosamine, which was conjugated to GO via a carbodiimide-mediated amidation-type reaction. The efficiency of the reaction was confirmed by FT-IR and Raman spectroscopy and elemental analysis. The elaborated functionalization significantly reduces the agglomeration of graphene oxide platelets. The interactions at the interface of GO and two types of ceramic nanoparticles (ZrO2 and Al2O3 with particle sizes of 58 nm and 158 nm, respectively) were examined by zeta potential measurements at different pH values. The viscosity of ZrO2 suspensions (35 vol% of solid loading) at 1.5 s- 1 increases from 24.8 Pas to 170.7 Pas and 142.7 Pas with the addition of GO and f-GO, respectively. The interfaces at ceramic-graphene heterostructures obtained by slip casting method have been analyzed by SEM. The investigations revealed the presence of multilayer graphene oxide and flexible single-layer f-GO within the ceramic matrix.

Electrospun nanofibres based on poly(styrene sulfonate) doped poly(3,4-ethylenedioxythiophene) (PEDOT:PSS) were fabricated using a straightforward procedure which combines electrospinning, sputtering deposition and electrochemical synthesis. In general, electrospun fibre meshes based on conducting polymers are prepared by mixing the conducting polymer with a carrier polymer or chemically coverage of the fibres. In contrast, freestanding nylon 6/6 nanofibre webs were prepared through electrospinning and were coated by sputtering with gold in order to make them conductive. Further, a PEDOT:PSS layer was electrochemically deposited onto the metalized nanofibre meshes and the synthesis parameters were chosen in such a way to preserve the high active area of the fibres. The prepared material was morphologically characterized and the formation of PEDOT:PSS was also demonstrated. The PEDOT:PSS coated nanofibres revealed remarkable electrical properties (sheet resistance of about 3.5 Omega cm(-2)), similar to those of metalized nanofibres (sheet resistance around 3 Omega cm2). The in vitro studies using L929 fibroblast mouse cells showed that the bioactive material has no cytotoxic effect and allows proliferation. Moreover, after 72 h of incubation, the fibroblasts shrunk their nuclei and spread suggesting that a differentiation in myofibroblast occurs without application of any kind of external stimuli. These results will be helpful for developing efficient materials for wound healing applications that work without energy consumption.

For the development of memory devices for the continuous advancement of IT engineering, a good understanding of the charging-discharging mechanisms in nanocrystalline floating gate memories is crucial to overcoming the current limitations. The charging-discharging mechanism in Al2O3/Ge/Al2O3 trilayer memory structures obtained by magnetron sputtering deposition is investigated as a function of the postdeposition annealing temperature, up to 900 degrees C. The change by annealing of C-V hysteresis curves from a clockwise type at low temperatures to counterclockwise one in a sample annealed within the intermediary temperature range of 550 to 650 degrees C, and then, a return to a clockwise type for annealing within the higher temperature range of 800-900 degrees C was observed. Up to 700 degrees C, memory performances are constantly improved reaching for 600 degrees C annealed samples, a memory window of 5.6 V for voltage sweep in the range -1 to +15 V, and good retention characteristics for 650 degrees C annealed structures, in which the charge loss is only similar to 2% after 10(8) s. When the annealing temperature was increased above 700 degrees C, a rapid decrease in the memory performance takes place. The annealing-induced changes are explained based on the Ge fast diffusion and nanocrystallization process, in correlation with morphological and structural high-resolution transmission electron microscopy results.

Undoped and Sm3+doped 45P2O5-45Na2O-2Al2O3-8BaO glasses were synthesized by the melt-quenching technique. The glass structure and luminescence properties were investigated by using Raman spectroscopy, scanning electron microscopy (SEM), spectroscopic ellipsometry, Judd-Ofelt theory and photoluminescence. Electron microscopy showed the homogeneity of samples. Raman spectroscopy revealed that the overall struc-ture of the glass was unaffected by the doping of Sm3+ and ellipsometry was used to measure the optical constants. Judd-Ofelt (JO) analysis was performed on the absorption bands of Sm3+ (4f5) and the three phenomenological parameters (omega 2, omega 4, and omega 6) were computed and then used to determine radiative properties such as the radiative transition probability (Ar), the fluorescent branching ratio (beta r), the stimulated emission cross-section (sigma e) and the radiative lifetime (tau rad). Photoluminescence (PL) spectrum showed the typical four transitions of Sm3+ at wavelengths of 564, 600, 645 and 703 nm corresponding to 4G5/2 -> 6H5/2, 6H7/2, 6H9/2 and 6H11/2, respectively. The spectroscopic quality factors omega 4/omega 6, the predicted lifetime (tau rad) calculated using the JO method and the experimentally lifetime (tau exp) for the 4G5/2level were calculated and discussed. The glass color purity is as high as 98%, which makes it a potential candidate for laser emission.

In the present study, we report the development and characterization of composite layers (by spin coating) based on magnesium-doped hydroxyapatite in a chitosan matrix, containing human osteosarcoma MG63 cells anchored. Studies regarding the biocompatibility of the composite layers were performed with the aid of a MTT (3-4,5-Dimethylthiazol 2,5-diphenyltetrazolium bromide) assay. The data determined that the composite layers did not inhibit the growth and adhesion of MG63 cells to their surfaces exhibiting good biocompatibility properties. Furthermore, the attachment and development of MG63 cells on the surface of MgHApCh composite layers were investigated using atomic force microscopy (AFM). AFM topographical maps emphasized that the HApCh and 8MgHApCh composite layers surface promoted the attachment and proliferation of MG63 cells on their surface. Meanwhile, in the case of 30MgHApCh layers incubated for 48 h, a slight modification of the morphological features of the MG63 cells. In addition, the effects of the composite layers against Candida albicans ATCC 10231 were also evaluated. The data results from the in vitro antifungal assay depicted that the composite layers successfully inhibited the growth of the fungal cells onto their surface. Morphological and fractal analyses unveil cancer cell surfaces on Mg-containing composite layers with intricate 3D patterns, driven by highfrequency components. Their remarkable complexity and roughness arises from a strong multifractal nature, supporting more effective vertical growth compared to Si and HApCh surfaces. The cell viability reduced of uncoated Si surface is highlighted by its less intense 3D pattern growth. Our results show that the uncoated Si surface promotes lower viability of MG63 cancer cells, with less rough and complex 3D spatial patterns.