National Institute Of Materials Physics - Romania

This study presents a systematic approach to engineering the electron transport layer (ETL) in perovskite solar cells using a spray deposition technique to fabricate sequentially compact and mesoporous titanium dioxide (c-TiO2, m-TiO2) films. The spray coating method leads to the development of a distinct reticulated morphology characterized by well-defined wavy-like surface features and significantly increased roughness-at least twice that of spin-coated mesoporous films. The increased interfacial area between the mesoporous TiO2 and the perovskite layer facilitates more efficient charge transfer, contributing to higher device performance. By optimizing the deposition parameters, particularly the number of spray cycles for the m-TiO2 layer, we achieve a significant enhancement in device performance, with improvements in power conversion efficiency (PCE), reduced series resistance, and minimized hysteresis. Our results demonstrate that an optimal film thickness promotes better perovskite anchoring, while excessive deposition impedes light transmission and increases sheet resistance. These findings advance the practical fabrication of high-performance perovskite solar cells using simple solution-processing techniques and highlights the potential of scalable spray deposition methods for industrial-scale fabrication.

Ag-decorated TiO2 aerogels were synthesized using an acid-catalyzed sol-gel method, followed by drying under supercritical CO2 and annealing within the temperature range of 350-500 degrees C, with 50 degrees C increments. This study explores the preparation-structure-performance relationships of Ag-TiO2 aerogels influenced by the annealing process, focusing on their morphological, (micro)structural, optical, and textural properties and surface defects concerning photocatalytic activity. X-ray diffraction (XRD) and Raman spectroscopy confirmed that all aerogels exhibited a single anatase phase of TiO2, while electron microscopy (SEM/TEM) and XPS analysis demonstrated the presence of components. Increasing the annealing temperature resulted in particle size and pore structure changes, reducing the aerogel's overall surface area and porosity, as observed by SEM and nitrogen (N2) sorption analysis. Additionally, according to the Williamson-Hall (W-H) analysis based on the X-ray peak profile, the lattice microstrain value decreased while the crystallite size increased with rising annealing temperature. Optical investigation showed a strong UV light absorption characteristic of TiO2 and a visible light absorption band attributed to the plasmonic effect of silver nanoparticles. Moreover, a gradual photoluminescence (PL) quenching trend was observed with decreasing annealing temperature, indicating a reduction in the recombination rate of photo-induced electrons and holes in Ag-TiO2, alongside the formation of oxygen vacancies and structural defects, consistent with electron paramagnetic resonance (EPR) measurements. The Ag-decorated TiO2 aerogels demonstrated enhanced visible-light photocatalytic activity for methylene blue (MB) degradation, with the Ag-TiO2 aerogel annealed at 500 degrees C exhibiting the highest photocatalytic performance. This improvement can be attributed to the synergistic effects of chemical composition, plasmonic enhancement, morphological properties, and light absorption characteristics.

This study investigates the development of electrochemical genosensors using gold-coated electrospun polymeric fibers electrodes, Au/PMMA/PET and immobilized phosphorothioated oligonucleotides. Scanning electron microscopy (SEM) with energy-dispersive X-rays spectroscopy (EDS) revealed a uniform distribution of oligonucleotides on the fibers, contrary to planar gold electrodes Au/Ti/SiO2/Si, where network-like films were observed. X-ray photoelectron spectroscopy (XPS) confirmed the successful immobilization of the phosphorothioated oligonucleotides via strong covalent gold-sulfur bonds, while surface plasmon resonance (SPR) indicated superior binding affinity, with significantly lower equilibrium dissociation constants, when compared to unmodified probes. The detection of BCR/ABL fusion gene of chronic myeloid leukemia using differential pulse voltammetry and methylene blue as electroactive indicator, showed that the Au/PMMA/PET electrodes achieved a sensitivity of 379 +/- 12 mu A cm(-)(2) pM(-)(1) and a limit of detection of similar to 5.00 +/- 0.01 fM, outperforming the Au/Ti/SiO2/Si planar electrodes. Reduced non-specific adsorption was observed on the Au/PMMA/PET electrodes and attributed to the inherent charges introduced during the electrospinning process, which created localized electrostatic fields that repelled weakly adsorbing molecules. These findings demonstrate the potential of Au/PMMA/PET electrodes as a robust platform for further development of high-performance clinical diagnostic devices.

In this study, pristine TiO2 and Copper (Cu)-doped TiO2 nanopowders were synthesized using two sol-gel methods: conventional sol-gel (SG) and microwave-assisted sol-gel (MW). The aim was to investigate the effect of the synthesis route and Cu doping on the structural, optical, and photocatalytic properties of TiO2. X-ray diffraction (XRD) analysis confirmed the formation of anatase TiO2 in all samples, with a minor presence of rutile observed in the samples obtained by the MW method. Scanning electron microscopy (SEM) coupled with energy-dispersive X-ray analysis (EDX) showed that the nanopowders obtained by the MW method exhibited a greater tendency for particle aggregation compared to those obtained through the SG method. The presence of Cu2+/Cu+ species in the samples was confirmed by X-ray photoelectron spectroscopy (XPS). UV-Vis reflectance measurements revealed a shift in the absorption edge of the 5% Cu-doped samples toward the visible light range, significantly reducing the band gap. Evaluation of photocatalytic activity demonstrated that doping TiO2 with 5% Cu enhanced the degradation of Congo Red dye under visible light. [GRAPHICS] .

Within the framework of the EUROfusion Consortium, the Characterization of armour, heat sinks materials and joints sub-project of the Work Package Material (WP-MAT) has been dedicated to the development of different tungsten (W) monoblock mock-ups equipped with advanced materials for divertor target applications in the EUDEMO fusion reactor. Assessing the status of the relevant joining interfaces of these mock-ups, not only after fabrication but throughout the whole component lifetime, plays a key role in the qualification process. At the ENEA Special Technologies Laboratory (TES), a number of facilities have been built to perform non-destructive inspections of plasma-facing components for fusion applications by ultrasonic testing (UT). The present work reports on the results of the UT inspections assessing the structural integrity of the relevant joining interfaces of three small-scale mock-ups provided with advanced W armour materials, specifically W-matrix with W2C inclusions consolidated by Spark Plasma Sintering (SPS), K-doped rolled W and K-doped laminated W. The UT examinations are carried out after fabrication and after the high heat flux tests (HHFT) at the neutral beam facility GLADIS. All results confirm the high-quality joining achieved by HIP and HRP. During the HHF tests of mock-ups, after a few hundred HHFT cycles defects are detected at the joining interfaces, due to debonding, delamination and W material cracks mainly affecting the loaded zone. The ultrasonic pulse-echo technique provides not only the size and position of the defects in the plane orthogonal to the ultrasonic beam, but also their depth in the material. During the analysis, the probe is inserted inside the pipe and the mock-up is examined in a cylindrical configuration. The coupling medium (demineralized water) is poured only inside the pipe. The main inspection parameters and the piezoelectric probes are chosen to obtain the maximum resolution in accordance with the thickness and joining interfaces to be analyzed.

Understanding the behavior of biomaterials under physiological conditions is essential for the development of new materials for implants and bone regeneration. This study addresses the critical need to evaluate how exposure to simulated body fluid (SBF) affects hydroxyapatite (HAp) and dextran-coated hydroxyapatite (HApDx) nanoparticles, which are widely considered for biomedical applications due to their bioactivity and biocompatibility. Structural, morphological, and surface property changes induced by SBF immersion were systematically investigated for the first time using advanced characterization techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), FT-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and fractal and Minkowski functional analyses. The results revealed that SBF immersion significantly influenced both HAp and HApDx, leading to reduced crystallite sizes, surface smoothening, and enhanced structural homogeneity. FTIR and FT-Raman spectra indicated subtle structural modifications, while SEM and AFM analyses confirmed the formation of a biomimetic apatite layer and a decrease in surface roughness. These changes are indicative of improved bioactivity, suggesting enhanced potential for osteoconductivity and cellular interaction. Biological evaluations using MG63 osteoblast-like cells demonstrated favorable cell viability and adhesion across 24, 48, and 72 h, particularly for the samples immersed in SBF. AFM further confirmed that surface modifications supported the cell attachment and proliferation. Overall, our findings underscore the importance of SBF exposure in enhancing the physicochemical and biological performance of HAp-based materials, reinforcing their promise for biomedical applications.

This study synthesized Mg-doped ZnO nanoparticles using the co-precipitation method with doping concentrations ranging from 2 % to 8 %. The structural, morphological, and optical properties of the synthesized nanoparticles were systematically characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and UV-Visible spectroscopy. XRD analysis confirmed the successful incorporation of Mg2+ ions into the ZnO lattice, evidenced by lattice parameter shifts and a significant reduction in crystallite size from 30.91 nm (pure ZnO) to 18.10 nm (6 % Mg doping). SEM images showed uniform morphology with reduced particle agglomeration at optimal doping levels, while FTIR analysis identified characteristic Zn-O and Mg-O bonding vibrations, confirming structural integrity. UV-Vis spectroscopy revealed strong absorbance in the UV region, with the band gap energy decreasing from 3.68 eV (pure ZnO) to 3.16 eV (6 % Mg doping), indicating enhanced optical properties conducive to improved photocatalytic performance. The photocatalytic activity of Mg-doped ZnO nanoparticles was evaluated by degrading Basic Fuchsin (BF) dye under UV light irradiation. The Mg-doped ZnO nanoparticles exhibited significantly enhanced photocatalytic performance compared to undoped ZnO, achieving a maximum degradation efficiency of 99.38 % at 6 % Mg doping within 100 min. Optimal photocatalytic conditions were observed at pH 6, using 0.1 g of catalyst and an initial dye concentration of 10 ppm. These enhancements were attributed to improved electron-hole pair separation and increased generation of reactive oxygen species (ROS), facilitated by the strategic incorporation of Mg. To complement the experimental findings, Density Functional Theory (DFT) simulations were performed, integrating the Conductor-like Screening Model for Realistic Solvation (COSMO-RS), Reduced Density Gradient (RDG), and Quantum Theory of Atoms in Molecules (QTAIM). The DFT analysis revealed enhanced charge separation, optimized electron transfer dynamics, and stronger adsorption interactions at Mg-doped sites, which promoted efficient ROS generation. The calculated valence band (VB) and conduction band (CB) edge potentials supported the formation of a Z-scheme heterojunction mechanism, enhancing charge separation and minimizing recombination. These theoretical insights aligned with the experimental observations, confirming that Mg doping effectively enhances photocatalytic efficiency by optimizing electronic interactions and promoting reactive surface dynamics. This integrated experimental and theoretical investigation demonstrates that Mgdoped ZnO nanoparticles exhibit superior photocatalytic properties, making them highly effective for environmental remediation applications, particularly in degrading organic pollutants in wastewater treatment. The study highlights the potential of Mg-doped ZnO as a promising photocatalyst for sustainable environmental solutions.

In this work a method in two steps for the preparation of the composites based on poly(ortho-toluidine) (POT) and the MoS2 and WS2 sheets was reported. In the first step, by ball-milling of mixtures of MoS2 and WS2 particles, the sheets of MoS2 and WS2 (MoS2: WS2) with weight ratio equal to 3:1, 1:1 and 1:3 were prepared. In the second step, the interaction in solid-state of the MoS2: WS2 samples with POT in emeraldine-base (POT-EB) and emeraldine-salt (POT-ES) was used to obtain composites of the type MoS2: WS2/POT-EB and MoS2: WS2/ POT-ES. Using X-ray diffraction (XRD), FTIR spectroscopy, Raman scattering and X-ray photoelectron spectroscopy (XPS), we demonstrate that: i) the ball-milling method can allow the preparation of the MoS2 and WS2 sheets with different stacking order, ii) the interaction of POT-EB with the MoS2: WS2 samples involves the transformation of some repeating units of the type EB into ES; and iii) the interaction of POT-ES with the MoS2: WS2 samples leads to the appearance of new positive charges onto macromolecular chains which are compensated by S2- ions. According to thermogravimetric analysis (TG) and differential scanning calorimetry (DSC), all samples are demonstrated to be stable up to 230 degrees C. Dielectric spectroscopy data reveal a complex dependence of DC electrical conductivity on frequency, temperature, and composite concentration. We use the apparent activation energy, defined as the derivative of the logarithm of conductivity with respect to the inverse temperature. The obtained results indicate that apparent activation energy is influenced by system composition via filling factors. The electrical properties of these heterogeneous materials are described using Lichtenecker's mixing laws. For components with similar electrical properties, the effective conductivity and apparent activation energy were determined as linear combinations of the individual conductivities and activation energies, respectively, weighted by the component concentrations. Our findings align with experimental data, offering a framework for understanding conductivity and activation energy in multi-component systems.

Pathogenic microorganisms such as bacteria, virus, and fungi present in water matrices are cause of infections and epidemic diseases worldwide. Photocatalytic deactivation is emerging as a promising, powerful method for water disinfection and microbial control. Transition metal oxide semiconductor photocatalysts has been widely investigated, being non-toxic, eco-friendly, and cost effective. However, their use in practical applications is limited due to their relatively wide band gap, reducing their optical absorption range to the UV domain of the solar radiation, and high recombination rate of photo-induced electron-hole pairs. The synthesised Mg doped TiO2 / graphene-like reduced graphene oxide nanocomposites are highly effective in deactivating nucleic acid molecules extracted from model Saccharomyces cerevisiae yeast cells as well as Saccharomyces cerevisiae yeast cells cultures, both under simulated sunlight and visible-light irradiation. The morphology, structure, and composition of the layers were thoroughly investigated by high resolution scanning electron microscopy, transmission electron microscopy, high-angle annular dark field scanning transmission microscopy, energy dispersive X-ray spectroscopy, as well as X-ray photoelectron spectroscopy. In accordance with the energy band structure of the synthesised nanocomposite catalysts, hydrogen peroxide and hydroxyl radicals are the major oxidative species (ROS) involved in the deactivation process. This study reveals a highly efficient approach for ROS generation for cell components decomposition and pathogen deactivation under visible light, and it can serve as an essential confirmation of the efficiency of visible-light-responsive photocatalysts in water disinfection.

Biodegradable polymers like poly(epsilon-caprolactone) (PCL) are widely studied for their potential applications in biomedical and environmental fields. To enhance PCL's thermal, and bioactive properties, researchers have explored composite formulations with other polymers or bioactive compounds. Oleic acid (OA), a naturally occurring fatty acid, has been identified as a promising modifier. This study investigates the modification of PCL with OA using an eco-friendly catalyst to improve its functional properties. PCL was grafted with OA using Maghnite-H+, a heterogeneous solid catalyst clay activated via sulfuric acid treatment. A response surface methodology with a central composite design was applied to optimize synthesis parameters, including reaction temperature, duration, and catalyst concentration. The resulting composite was characterized using FTIR and NMR to confirm structural modifications, while its thermal stability was evaluated. Antioxidant activity was assessed using the DPPH radical scavenging assay, and antimicrobial potential was tested against various microorganisms. The PCL-OA composite exhibited enhanced antioxidant activity, with increased radical scavenging efficiency compared to unmodified PCL. Antimicrobial tests revealed strain-dependent effects, with improved inhibition observed in specific combinations of caprolactone, OA, and PCL-OA. The findings suggest that OA incorporation enhances PCL's bioactivity, making it a promising material for biomedical and packaging applications.