National Institute Of Materials Physics - Romania

In the present work, an essential advance in the preparation of novel nanocomposites based on functionalized V2O5 nanostructures with reduced graphene oxide by hydrothermal method, which has great potential for use in photocatalytic processes related to environmental remediation. XRD analysis confirmed V2O5 in an orthorhombic structure. SEM images showed transparent RGO layers well anchored onto the surface of the V2O5 with a homogeneous distribution. Raman spectroscopy further explained the hybridization and interaction between the components. The photocatalytic activity of Rhodamine-B in aqueous solutions has been studied upon irradiation with visible light. A high RhB degradation was obtained using the V2O5/RGO photocatalyst (82 %), compared to the degradation obtained with only V2O5 (60 %). First-principles Density Functional Theory (DFT) simulations reveal a strong interaction between V2O5 molecules and graphene surfaces, with an adsorption energy of -1.673 eV and a significant charge transfer of 0.367 e- to RGO. This interaction modifies the electronic structure, creating semi-metallic behavior near the Fermi level and enhancing catalytic activity through improved charge carrier dynamics and active sites for photocatalytic applications.

The present research explores for the first time the intricate relationship between sulfurization temperature at unusual high temperatures (up to 700 degrees C) and the structural/optoelectronic properties of Cu-2(Zn,Cd)SnS4 (CZCTS) thin films, synthesized via a two-step sequential process involving the precursor film deposition using aprotic molecular ink followed by thermal treatment in sulfur atmosphere. X-ray diffraction patterns confirms the tetragonal structure. Scanning Electron Micrographs revealed significant grain growth, with grain sizes increasing from similar to 0.3 mu m at 620 degrees C to similar to 1.5 mu m at 680 degrees C, effectively reducing grain boundary recombination. Energy dispersive X-ray spectroscopy demonstrated a Cu-poor and Zn-rich composition, with a consistent Cd incorporation of similar to 3.7 at%. Raman spectroscopy showcases the homogeneity and purity of the CZCTS crystalline structure. Precise control of the sulfurization temperature plays a crucial role in determining the photovoltaic characteristics of CZCTS-based solar cells. By increasing the grain size and preventing the thermal decomposition of the CZTS phase, the photovoltaic performance peaked at a sulfurization temperature of 680 degrees C, achieving a power conversion efficiency (PCE) of 10.4%, with an open-circuit voltage of 0.701 V, a short-circuit current density of 24.3 mA/cm(2) and a fill factor of 60.8%. External quantum efficiency reached a maximum of 83.3% at 580 nm. The bandgap of the CZCTS absorber was determined to be 1.48 eV, optimal for photovoltaic applications. However, further increasing the sulfurization temperature to 700 degrees C resulted in a lower PCE of 8.5%, attributed to interface degradation and secondary phase formation. Temperature-dependent current-voltage measurements revealed a reduction in recombination losses, with an activation energy of 1.24 eV at the CZCTS/CdS interface, indicating effective defect passivation by Cd incorporation. The optimized films, sulfurized at 680 degrees C, displayed an absorber thickness of similar to 1.2 mu m after sulfurization, providing efficient light absorption and charge transport. The findings not only emphasize the critical role of sulfurization temperature in engineering CZCTS film and subsequently their functionality but also provide valuable insights for fine tuning their performance in the field of photovoltaic applications.

This study presents an ultrasound-assisted synthesis of (3-cyclodextrin/hydroxyapatite composites to be used as green and safe auxiliaries in the tanning process. A combination of spectroscopic and non-spectroscopic techniques such as DLS (dynamic light scattering), ZP (zeta potential), XRD (X-ray diffraction), SEM (scanning electron microscopy) and ATR-FTIR (attenuated total reflectance-Fourier transform infrared spectroscopy) were used to thoroughly characterize the eight composites obtained by varying the ultrasound process parameters. While not cytotoxic, all composites had strong antibacterial action against Brevibacterium lines, Staphylococcus aureus, Escherichia coli, and Staphylococcus epidermis. All composites underwent lab-scale tanning tests, but only those exhibiting the most suitable set of tanning abilities underwent pilot-scale testing. The composites' interaction with the collagen matrix was assessed by micro-DSC (micro-differential scanning calorimetry), TG/DTG/ DTA (thermal analysis), 1H unilateral NMR (proton nuclear magnetic resonance), ATR-FTIR, in-situ temperature synchrotron-based XRD and standard tests (UNI EN ISO 3380: 2015, UNI EN ISO 2589: 2016, UNI EN ISO 105B02:2014). Thermal stability, dye penetration, thickness, colour fastness, surface appearance and microbiological protection were all improved for the leather treated with a small amount of composite added to the wet finish float. These findings demonstrate the benefits of (3-cyclodextrin/hydroxyapatite composites as safe and sustainable tanning additives.

Developing new glass electrolytes with the necessary room-temperature ionic conductivity (similar to 10(-3) Scm(-1)) for solid-state batteries, especially sodium-ion (Na+) batteries, has been impeded by the lack of a clear relationship between composition, structure, and conductivity in glass materials. This study highlights the impact of the mixed glass formers on the structure, Na+-ion dynamics, and glass conductivity. To this end, we substituted SiO2 for P2O5 in sodium alumino-phosphate glass while maintaining a constant molar concentration of Al2O3 and Na2O. A detailed analysis combining molecular simulations and experiments revealed that the glass containing 15 mol% SiO2 exhibited the highest DC ionic conductivity of similar to 9 x 10(-6) Scm(-1) at 473 K, followed by a decrease for 20 mol% SiO2. To understand this behavior, microscopic characteristic length such as critical hopping distance and Na+ diffusion coefficients were correlated with structural changes using AC conductivity analysis. Altogether, we elucidate the composition-dependent Na+ ion dynamics in the alumino-phosphate glass system, with factors like mobile charge carrier concentration, ion mobility, and coulombic forces influenced by the structure of different glass compositions.

Photoanodes based Ce-doped ZnO nanorods arrays were prepared by hydrothermal method in order to improve photoelectrochemical efficiency of ZnO photoanodes in water splitting process. Scanning electron microscopy investigation showed ZnO based nanorods with length of around 500 nm and different thicknesses and growth directions. Some morphological changes were noted following the thermal treatment. Energy-dispersive X-ray analysis and X-ray photoelectron spectroscopy measurements proved the presence of cerium species both in bulk and on the surface of ZnO nanorods. A current density of 2.44 mA/cm(2) at 1.23 V against the reversible hydrogen electrode (0.265 V vs. Ag/AgCl) was obtained for Ce-doped ZnO sample, which is >162% increase over that of ZnO sample. The increased photocurrent value obtained for this sample was correlated with the passivation of surface defects evidenced by photoluminescence study and the increased concentration of Ce3+ on the surface. Also, the electrochemical impedance spectroscopy measurements suggested that Ce doping improves the charge transfer in bulk.

This article describes a new synthesis of nanoscaled Y2O3 that is bioinspired. It has been confirmed that Callistemon viminalis flower extract works well as a chelator when used to bioengineer high-shape anisotropy nanorods of single-phase Y2O3 . X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy and photoluminescence spectroscopy were used to analyse the structural, morphological, surface and optical features. The photoluminescent spectra of the bio-engineered nanorods show blue emissions. As the annealing temperature was increased from 300 to 500 degrees C, the blue colour purity values of the synthesized Y2O3 nanorods were 58.1, 80.7 and 77.0% at 300, 400 and 500 degrees C respectively. The chromaticity coordinates (0.2020, 0.1931), (0.1660, 0.1082) and (0.1714, 0.1226) from the photoluminescence spectra of the biosynthesized Y2O3 nanorods were used to determine these values. The CIE y-component coordinate values of the bioengineered blue-emitting nanophosphors suggest their potential for applications in display technology and white light-emitting diodes.

Biodegradable templates are sought for targeted antibiotic administration/delivery in bone infections to avoid detrimental reactions during bone regeneration. We investigated two key-aspects in this direction: 1) the optimal antibiotic delineation, with thermal stability equivalent to the temperature involved for templates preparation and 2) the antibacterial templates development by a two-step homogenization process. The selected antibiotic - ampicillin (AMP) was mechanically and then thermally mixed with the prime materials: poly(lactic acid) (PLA) - the polymeric matrix, biogenic bovine bone-derived hydroxyapatite (HA, particles <40 mu m), and graphene nanoplatelets (GnP, micrometric range). For the first time, all materials were used in simultaneous modulated ratios for the synthesis of PLA/AMP (1-5 wt.%)/HA (0-30 wt.%)/GnP (0-3 wt.%) composites. The influence of the concomitant materials modulation was surveyed through several assays. The FTIR-ATR spectroscopy depicted a three-level model of overlapping structures asserting the solid molecular cross-linking between all materials, without structural alterations induced to any material (XRD analysis). The addition of AMP to the PLA matrix caused a slight particle conglomeration, alleviated through GnP addition. The microporous HA particles supported the adhesion to the PLA matrix and promoted the AMP particles' entrapment/attachment. Linked to the enhanced wettability of the composite materials, the phosphate buffered saline solution (PBS) degradation profiles revealed a pronounced burst during the first 14-28 days of incubation and a long-term, low-level process hereafter. Thus, the formation of pores and cavities were signalled along with the HA particles' fragmentation. The released AMP (percentage) pictured an ascending trendline during the 24 h of analysis, at all targeted ratios. The preservation of AMP features at 200 degrees C was endorsed by the strong antibacterial activity of composite materials against Staphylococcus aureus (S. Aureus) growth and the medium response against Escherichia coli (E. Coli) - the higher the drug release, the higher the inhibitory effect on bacteria evolution.

Featured Application Optoelectronic devices in space missions.Abstract Transparent conductive oxides are essential materials for many optoelectronic applications. For new devices for aerospace and space applications, it is crucial to know how they respond to the space environment. The most important issue in commonly used low-Earth orbits is proton radiation. This study examines the effects of high-energy proton irradiation (226.5 MeV) on thin films of aluminium-doped zinc oxide (AZO) and indium tin oxide (ITO). We use X-ray diffraction and electron microscopy observations to see the changes in the structure and microstructure of the films. The optical properties and homogeneity of the materials are determined by spectrophotometry and spectroscopic ellipsometry (SE). Analysis of the chemical states of the elements with X-ray photoelectron spectroscopy (XPS) gives insight into what proton irradiation changes at the surface of the oxides. All measurements show that ITO is less influenced than AZO. The proton energy and fluence used in this study simulate about a hundred years in low Earth orbit. This research demonstrates that both transparent conductive oxide thin films can function under simulated space conditions, with ITO showing superior resilience. The ITO film was more homogenous in terms of the total thickness measured with SE, had fewer defects and adsorbates present on the surface, as XPS analysis proved, and did not show a difference after irradiation regarding its optical properties, transmission, refractive index, or extinction coefficient.

Capitalizing on invasive plant species and stopping their aggressive spread might be achieved by using them as a renewable source of useful products such as cellulose. The study aimed to develop new cellulose-based food packaging materials with antioxidant and antimicrobial activity. The cellulose was extracted from the invasive plant species Robinia pseudoacacia pods, crosslinked with citric acid, used as reinforcement for polyvinyl alcohol (PVA) and functionalized with ferulic acid (FA). The obtained materials were characterized by XRD, ATR-FTIR, contact angle and SEM. The materials exhibited low solubility in water and the swelling degree was proportional to the FA content. The FA release from the matrix was assessed by HPLC and the antioxidant profile by CUPRAC, FRAP, and TEAC methods. The obtained materials inhibited the growth of bacteria, yeasts and molds, being especially active on Gram-positive bacteria and yeasts. Overall, the most promising formulation for further developing new packaging materials for products with water activity less than 0.95 was the one with the highest FA content.

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.