National Institute Of Materials Physics - Romania

Copper-zinc-tin-sulfide (Cu2ZnSnS4, CZTS) kesterites a promising earth-abundant and non-toxic absorber for next-generation thin-film photovoltaics. However, sulfur-based CZTS solar cells remain limited in performance, largely due to intrinsic defects and interfacial recombination losses. Here, we systematically investigate the impact of solvent chemistry and extrinsic doping and compositional engineering on the quality of solution-processed CZTS absorbers. A comparative study of three solvents, 2-methoxyethanol (MOE), dimethylformamide (DMF), and dimethyl sulfoxide (DMSO) reveals that all yield phase-pure, and compact films due to a robust Cu+-Sn4+ molecular precursor system, with MOE producing the most uniform morphology and superior optoelectronic properties. Rather than focusing on pure CZTS, the solvent screening is conducted on Cd-alloyed CZTS (CZCTS), as Cd incorporation substantially alters precursor coordination and crystallization behavior. Building on the optimized processing route, a synergistic compositional strategy combining silver (Ag) - cadmium (Cd) co-alloying with lithium (Li) doping is introduced to suppress cation disorder, passivate grain-boundary defects, and enhance carrier transport. As a result, the optimized he optimized absorber delivers a champion device with a power conversion efficiency of 10.6%, placing it among the highest efficiencies reported for solution-processed, selenium-free CZTS solar cells. These results highlight the critical role of solvent engineering coupled with targeted extrinsic doping in overcoming the long-standing limitations of CZTS photovoltaics and provide a scalable pathway toward environmentally benign thin-film solar technologies.

We present a simple and intuitive tabletop experiment designed to generate gravitational wave-like signals. This toy model serves as a physical analogy for the motion of compact astrophysical objects in curved spacetime and is intended primarily for educational and outreach purposes. The experimental setup consists of a circular solid frame over which an elastic fabric is tightly stretched and secured with clips. Solid spheres of different masses represent astrophysical objects, and their motion is recorded using a webcam connected to a laptop running the TableTopGW software. A heavy sphere is placed at the center of the fabric to simulate a massive compact object, such as a black hole or neutron star, that distorts the surrounding spacetime. A lighter sphere is then released onto the curved surface, where it spirals inward toward the central mass under the influence of Earth's gravity and friction with the fabric. The webcam continuously records the motion of both spheres. From this video data, the separation between the two masses is computed. Using the quadrupole formalism from general relativity, as applied to binary systems, the TableTopGW software uses this separation to simulate gravitational wave-like signals. This setup establishes a direct and visually engaging connection between the physical motion of orbiting bodies and the corresponding gravitational waveform, offering students and the general public an accessible and hands-on introduction to complex astrophysical concepts.

Alloys (A) of crystalline Ge50Te50 and partially amorphous Ge20Te80 were added to MgB2 superconductor. Samples with composition (MgB2)A0.01 were ex situ spark plasma sintered (SPS) and characterized. Results are compared with pristine and Te ((MgB2)Te0.01) or Ge, ((MgB2)Ge0.01) added samples. Samples with Ge-Te alloys show the fastest densification rate of 3.4 to 5.2 times larger than for the other samples. Although there is a strong influence of Te, alloys synergistically contribute structural and microstructural development and superconducting properties as determined by magnetometry. The proposed methodology of densification curves analysis allows prediction of the final bulk density, MgO and MgB4 amounts, the amount of carbon substituting boron and critical temperature. The alloys addition promotes MgB4 formation and a slightly lower critical current density Jc for Ge50Te50. For Ge20Te80, Jc is approximately similar to pristine sample, while the highest Jc is for Te. Samples with Ge-Te have lower maximum pinning force values.

Silicon-tin (Si-Sn) nanocomposites are viable anode substitutes for lithium-ion batteries (LIBs) as they have the high theoretical storage capacities of lithium (4200 mAh g-1 (Si) and 994 mAh g-1 (Sn)), which are significantly more than those of graphite (372 mAh g-1). The Si and Sn cannot be used widely due to their extreme volume expansion during cycling, which results in limited structural stability and quick capacity deterioration. Herein, a nanocomposite based on reduced graphene oxide and nanoparticles containing silicon and tin species (Sn/Si@reduced graphene oxide (RGO)) is presented as a potential solution to mitigate these challenges by incorporating rGO to enhance the electrochemical performance. This nanocomposite demonstrates a high discharge capacity of 1506.91 mAh g-1 at a current density of 0.55 A g-1 after 205 cycles. In contrast, the Sn/Si nanoparticles only kept 125.85 mAh g-1 after the same number of cycles. Sn/Si@rGO nanocomposite improved electrochemical performance due to the conductive network provided by rGO, which adapts to volume variations during cycling and facilitates charge transfer. Results from galvanostatic testing, cyclic voltammetry, and electrochemical impedance spectroscopy support the idea that Sn/Si @rGO nanocomposites could be a high-performance anode material for next-generation LIBs.

Gold nanoparticles are proving to be highly successful for delivering drugs to specific targets, exploiting carefully designed functionalizations. This work creates and optimizes the synthesis of gold nanorods (AuNRs), subsequently functionalized with a peptide, TAT, appropriately modified to allow attachment to the rods and guide their entry into the cell nucleus and nuclear growth. Various chemical and physical characterizations were performed to verify and optimize the AuNRs-TAT system. DLS, Z-potential, UV-vis, and FT-IR spectroscopies confirmed the nanosize, monodispersity, colloidal stability, and successful functionalization. Furthermore, structural characterizations conducted using synchrotron radiation were crucial for understanding the actual interaction between the gold surface and the modified TAT peptide. The study highlighted how this material is indeed a good drug delivery system, stable over time, and promising for reaching the cell nucleus.

Lithium borohydride (LiBH4) is a promising hydrogen storage material releasing 13.8 wt% H2 upon decomposition in lithium hydride and boron, significantly surpassing other complex hydrides. However, sluggish dehydrogenation kinetics still hinder the use for practical applications. The infiltration of LiBH4 into carbon nanoscaffolds has proved to be effective in improving the hydrogen absorption/desorption (a/d) kinetics. Further improvement of storage kinetics can be achieved by modification of the nanocarbon with dopant elements. The present work compares nanoporous carbon (C-MSU-H) and C-MSU-H doped either with 1 at% N or 1 at% Ni as the matrix for infiltration of LiBH4. The catalytic effect of nitrogen proved to be superior to that of nickel (keeping the same doping level) for improving the hydrogen a/d kinetics of LiBH4 infiltrated in doped C-MSU-H. X-ray photoelectron spectroscopy was used to detect the amount and chemical proximity of nitrogen in nanoporous carbon following the thermal treatment in ammonia flow. The morphology and porosity of doped C-MSU-H were investigated by X-ray diffraction, FTIR, TEM, and BET. Hydrogen a/d kinetics of LiBH4@C-MSU-H nanocomposites was investigated by a volumetric method. The desorption peak temperatures (measured at 2 degrees C min-1 rate) are 339 degrees C for the undoped LiBH4@C-MSU-H, 328 degrees C for the LiBH4@C-MSU-H doped with 1 at% Ni and 318 degrees C for the LiBH4@C-MSU-H doped with 1 at% N nanocomposites. The activation energies of hydrogen desorption for the investigated nanocomposites were obtained from Kissinger plots: 142.7 kJ mol-1 for undoped LiBH4@C-MSU-H, 123.8 kJ mol-1 for LiBH4@C-MSU-H 1 at% Ni and 119.5 kJ mol-1 for LiBH4@C-MSU-H 1 at% N nanocomposites. The catalytic effect on LiBH4 dehydrogenation due to N-doping of nanocarbons is discussed.

This study presents the development and analysis of a highly sensitive SnO2-based gas sensor for acetone detection, enhanced through the wet impregnation with WO3. Structural and morphological investigations confirm the tetragonal structure of the SnO2 crystalline phase and reveal irregular grain boundaries that become less pronounced with increasing WO3 content. Surface chemistry analyses confirm the presence of well-dispersed WO3 on the SnO2 surface. Thick and porous sensing layers were fabricated by screen printing onto commercial alumina substrates. The influence of operating temperature on surface interactions was evaluated by measuring the sensor response at a fixed acetone concentration. This enabled the selection of SnO2:WO3 5 % for sensing measurements, at an operating temperature of 280 degrees C, over a wide range of acetone concentrations, dosed in dynamic airflow with variable relative humidity. Simultaneous DC electrical resistance and Contact Potential Difference measurements allow decoupling of ionosorption from dipolar effects on the SnO2:WO3 5 % surface and explain the rise in the sensor response to acetone as relative humidity increases. The chosen concentration range for acetone, between 0.25 and 5 ppm, and for relative humidity, between 10 and 90 %, creates the premises for the further development of applications for non-invasive monitoring of diabetic exhalation.

In situ exsolution has emerged as a powerful strategy for tailoring fuel electrode catalysts in solid oxide fuel cells (SOFCs), yet its integration with reversible exsolution-dissolution processes and its application to symmetricalcapable electrode design remain largely unexplored. Here, we demonstrate controlled exsolution-dissolution in nanofiber double perovskites as a rational route to engineer high-performance SOFC electrodes operable in both symmetrical and anode-supported configurations. Sm0.9Ba0.9Mn1.8-xFexCo0.1Ni0.1O5+delta nanofiber perovskites enable composition-dependent control of nanoparticle evolution. Under reducing conditions, socketed Co-Ni-Fe alloy nanocatalysts exsolve and partially embed into the perovskite lattice, while oxidation induces their transformation into Fe3-x-yNixCoyO4-type hollow core-shell nano-oxides via a Kirkendall-type mechanism. The nanofiber architecture promotes smaller and more densely distributed nanoparticles compared to powders, enhancing catalytic activity and redox stability. The optimized composite electrode delivers a low polarization resistance of 0.046 Omega cm2 at 800 degrees C. Anode-supported cells achieve a peak power density of 1112 mW cm-2 at 850 degrees C and 877 mW cm-2 at 800 degrees C, while symmetrical cells deliver 816 mW cm-2 at 800 degrees C with stable operation. This work establishes controlled exsolution-dissolution as a versatile platform for designing symmetrical-capable high-performance SOFC electrodes and highlights hollow core-shell nanostructure engineering as a powerful strategy for durable solid oxide electrochemical systems.

Simonkolleite nano-platelets, with the chemical formula Zn-5(OH)(8)Cl-2 center dot H2O (ZHC), both undoped and Mndoped, were synthesized by a wet-chemical synthesis method. The physicochemical properties of the materials have been investigated using several complementary experimental techniques, including powder X-ray diffraction, specific surface area and porosity measurements, Fourier-transform infrared spectroscopy, scanning electron microscopy, X-ray Fluorescence, X-ray photoelectron spectroscopy, and electron paramagnetic resonance spectroscopy. On the one hand, the morpho-structural characteristics of the material are not significantly affected by the dopant used at low concentrations; however, the textural characteristics, specifically the specific surface area and porosity, vary with the Mn concentration. On the other hand, the cellular response of skin cells (human fibroblasts and mouse melanoma) exposed to undoped and Mn-doped ZHC was assessed, revealing a certain dependency on the Mn concentration. It was observed that the cells' response could be correlated with both the dopant concentration and the exposure time of the cells, independent of the morpho-textural characteristics of the materials. Even at the low Mn amounts used in this study, the cells' response depends on the Mn concentration, thus showing drastic cytotoxicity in human fibroblast cells at concentrations higher than 0.25 mu g/mL, irrespective of the exposure time (24 or 48 h), but showing low cytotoxicity at concentrations lower than 0.25 mu g/mL. In contrast, the presence of Mn does not drastically affect mouse melanoma cells, even at concentrations higher than 0.5 mu g/mL, but this depends on the exposure time. To our knowledge, this is the first study on the effects of Simonkolleite on skin cells, and it is of great interest considering the current and potential applications of this material in skin wound treatment and animal food supplements.

Topological materials are promising electrocatalysts for the hydrogen evolution reaction (HER) because of their protected electronic states and exceptional carrier mobility. Among them, the topological metal Pt3Te4 (mitrofanovite) exhibits low Tafel slopes in the nanocrystals. Realizing this potential in scalable catalyst systems requires nanoscale texturing coupled with precise control of the surface chemistry under operating conditions. Herein, we demonstrate that hydrogen peroxide (H2O2)-assisted liquid-phase exfoliation (LPE) of bulk Pt3Te4 yields nanoporous nanosheets that retain their metallic character and are chemically preconditioned to develop a bias-controlled PtO2 skin that governs the catalytic activity. Crucially, spectromicroscopy resolves termination-selective oxidation: PtO2 forms exclusively on PtTe2-like terminations, whereas Pt2Te2 terminations remain metallic. Operando ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) in an electrochemical cell revealed the bias-dependent emergence of surface oxide phases in H2O2-treated nanosheets. The joint effect of the higher accessible site density imparted by nanoporosity and the emergence of a bias-controlled PtO2/PtTe2-terminated Pt3Te4 surface junction rationalizes the improved catalytic activity: the overpotential at 10 mA cm-2 decreases by similar to 30% (from 113.1 to 78.7 mV), while the exchange current density more than triples (from 0.106 to 0.347 mA cm-2), all with an unchanged Tafel slope (similar to 53 mV dec-1) and sustained stability over 50 h in acid. By combining a single scalable top-down step with operando proof that the catalytically active oxide is switched on by bias rather than being a static passivation layer, this study establishes a precise interface-engineering principle for Pt3Te4 nanosheets and a practical path to efficient, scalable HER catalysts based on nanosheets of topological metals.