Publications

Bi-layered ZnO/CuO nanostructured films have been examined for CO2 gas sensing applications. X-ray diffraction, Fourier transform infrared, and Raman spectroscopy confirm the formation of a hexagonal wurtzite ZnO and a monoclinic CuO. Scanning electron and atomic force microscopies' observations reveal homogeneous, dense, and quasi-porous surfaces with smooth spherical sponge-like (ZnO), rough spherical-like (CuO and ZnO/ CuO), and rough flat plate-like (for CuO/ZnO) grains morphologies with a few cracks. UV-visible spectroscopy shows greater transmittance (45-90 %) in the infrared and visible domains, while the energy bandgap decreases significantly from 3.3 eV for ZnO to 1.5 eV for the remaining films. The measurements of the sensor's electrical characteristics at room temperature, including current-voltage (I-V), sensitivity-concentration (S-C), and current-time (I-t), indicate a sensitivity to the presence of CO2 gas and that the fabricated sensor exhibits excellent sensitivity and faster response/recovery times. Indeed, the ZnO thin-film sensor recorded the highest sensitivity of 44.77 % at 31 ppm carbon dioxide concentration at room temperature. Based on the results obtained, a sensing mechanism is proposed. The findings demonstrate that metal oxide multilayered nanostructures are promising candidates for applications such as gas sensing, photocatalysis, and UV photodetection.

We analyze the output mixed states generated when the asymmetric cloners are applied on a pure two-qubit state. We investigate two kinds of cloners: (a) local 1 -> 2 optimal universal asymmetric cloning machines and (b) nonlocal 1 -> 2 optimal universal asymmetric cloning machines. In both cases we find analytical formulae of the geometric quantum discord of the two clones. Finally, we prove that the geometric quantum discord generated by the nonlocal asymmetric cloners is not smaller than the geometric quantum discord given by the local asymmetric cloners.

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.

Magnetic superconductor EuRbFe4As4 is a quite unique system in which macroscopic superconductivity and magnetic ordering coexist, with interesting interactions between Abrikosov vortices and Eu2+ spins that were investigated mostly by static (DC) magnetization measurements. Our aim is to study the dynamic interactions between the two sub-systems using AC susceptibility measurements in a wide range of temperatures and superimposed DC fields. In low DC fields, the magnetic transition at 15 K is clearly visible. We have observed very little difference between the AC susceptibility in different cooling regimes, but large difference for different field orientation. For field perpendicular to the superconducting planes, we have observed an anomalous dependence just below the critical temperature, which is absent in the parallel field orientation. We explained the anomaly by the interplay between the sample dimensions and the temperature dependence of the London penetration depth which may allow the paramagnetic Meissner-like response to be detected in the temperature dependence of the AC susceptibility. We stress that the newly reported phenomenon reflects an AC-susceptibility manifestation of a field-stabilized critical state rather than a thermodynamic phase. In addition, we have observed a paramagnetic AC response in the normal phase, in both field orientations, indicative of interactions between Eu2+ spins and flux lines.

This work reports a systematic study concerning the synthesis of pure polyaniline ultrafine nanofibers (PANI-NFs) and their nanocomposites with oxygen-functionalized carbon nanotubes (PANI-NFs/O-MWCNTs) using diluted chemical polymerization and hydrothermal processes. We investigated the synergistic effects of various synthesis parameters, such as the concentration of the ammonium persulfate oxidant agent and growth temperature, on the physical, chemical, and electrochemical properties of the resulting products through structural, morphological, spectroscopic, and electrochemical characterization. Our study revealed the successful synthesis of thermally resistant polyaniline ultrafine nanofibers (PANI-NFs) in the form of emeraldine salt (ES), exhibiting a mean diameter in the range of 8-17 nm. The PANI-NFs and PANI-NFs/O-MWCNT nanocomposites demonstrated excellent electrochemical properties, with specific capacitances of up to 0.94-1.23 F cm(-2) and 1410-2074 F/g, respectively, and with good rate capability. These characteristics are confirmed by the relaxation time constant tau(0) (41 and 8 ms, respectively) and lower internal R-0/interfacial charge transfer R-Phi resistances of around 0.2 Omega, as well as diffusion coefficients of around 10(-7) and 3.7 x 10(-7) cm(2)/s. This breakthrough in nanofiber synthesis paves the way for practical applications in diverse domains, from high-performance energy storage to biosensing and beyond, where the unique electroactive properties of the nanocomposites can be leveraged to achieve exceptional results. Omega

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.

Zinc oxide (ZnO) and zinc sulfide (ZnS) nanocomposites represent promising multifunctional photocatalysts due to their complementary band structures and synergistic charge separation. ZnO-ZnS nanocomposites with varied ZnS content were synthesized to elucidate the composition-structure-property relationships governing their multifunctional performance. Structural characterization using XRD, SEM/EDS, Raman spectroscopy, and XPS confirmed the coexistence of wurtzite crystalline phases of ZnO and ZnS. SEM analysis revealed ZnS fine deposition on the ZnO surface. XPS measurements showed a gradual increase in the amount of ZnS on the ZnO surface with increasing sulfide content and a shift in the valence band maximum from 2.32 eV (pure ZnO) to 0.77 eV (pure ZnS). Optical measurements (IR, UV-Vis diffuse reflectance, photoluminescence) demonstrated that, despite the evolution of vibrational and luminescence features characteristic of ZnS, the apparent band gap remained nearly constant at 3.16-3.18 eV across the series. Photocatalytic methylene blue (MB) degradation followed pseudo-first-order kinetics, peaking for ZN_2 (1% ZnS, kapp = 103 & times; 10-3 min-1), which is 1.7 times higher than for pure ZnO. This enhanced performance is consistent with an S-scheme-like heterojunction that facilitates electron migration to the ZnS conduction band while retaining ZnO valence band holes for oxidation. Scavenging experiments confirmed that electrons dominate MB degradation (kapp up to 185.1 & times; 10-3 min-1 with EDTA/t-BuOH/Ar), outperforming hole-mediated pathways. Antibacterial assays against Staphylococcus aureus revealed good antimicrobial activity for all nanoparticles. The nanocomposite's antibacterial activity was similar across all samples and was only slightly lower than that of pure ZnS and ZnO.

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.