National Institute Of Materials Physics - Romania

Graphene oxide (GO) provides a versatile platform for the development of antimicrobial and anti-adhesive materials, particularly when combined with covalently immobilized bioactive compounds but translating antibiotic activity into a stable layer without clinically relevant drug leaching remains challenging. Here, we report a covalently engineered GO-moxifloxacin (GO-MOX) composite obtained by grafting MOX onto ethylenediaminefunctionalized GO via carbodiimide coupling. The successful functionalization was supported by complementary physicochemical analyses, including FTIR, NMR, Raman, XPS, TGA, SEM/EDS and XRD. TGA indicated a high MOX loading of approximately 44.75 wt%, while HPLC analysis revealed that extractable/free MOX represented only 0.0586% of the total MOX content, supporting the predominantly covalent and minimally releasing character of the material. GO-MOX showed pronounced antimicrobial activity against representative ESKAPEE pathogens, with MIC values of 7.81 & micro;g/mL against E. coli and 62.5 & micro;g/mL against the tested Gram-positive strains. In the antimycobacterial assay, GO-MOX markedly inhibited the growth of both drug-susceptible and rifampicin/isoniazid-resistant Mycobacterium tuberculosis strains under the tested conditions. Anti-adherence activity was observed at sub-inhibitory concentrations, with MBEC values of 1.95 & micro;g/mL for E. coli and 7.81 & micro;g/mL for S. aureus, suggesting interference with early bacterial attachment. Additional analyses on mature biofilms formed on titanium substrates showed that GO-based treatments, particularly GO-MOX, affected biofilm viability, promoted membrane permeabilization, and altered extracellular matrix components, including extra-cellular proteins, nucleic acids/eDNA-like fractions and polysaccharides. In vitro cellular assays showed that normal MRC-5 fibroblasts recovered metabolic activity to >= 80% after 72 h, whereas A549 cells displayed a concentration-and time-dependent decrease in viability. ROS generation and Caspase-3 activity further suggested that the selective antiproliferative response observed in A549 cells may be associated, at least in part, with oxidative stress-mediated apoptotic mechanisms. In silico target prediction and structural inspection of MOX-topoisomerase complexes suggested that GO-MOX may retain a MOX-related contribution involving bacterial DNA gyrase/topoisomerase IV, while GO may provide additional contact-associated interfacial effects. Overall, GO-MOX emerges as a promising antimicrobial and anti-adhesive nanoplatform with cell-selective antiproliferative effects, supporting its further investigation for the future development of biomedical antimicrobial surfaces and coatings.

Structural and electronic transport features of high quality epitaxial metastable fcc W and beta-W2N thin films compatible with spintronic multilayer nanosystems are reported in a parallel approach. The epitaxial layers have been successfully prepared in a broad range of thicknesses from a few to tens of nanometers. The scalable method of auxiliary plasma assisted substrate magnetron sputtering was used. The epitaxy relationship between the thin films and MgO (100) single-crystal substrate is highlighted by high resolution XRD investigations of the reciprocal space. Electron transport properties are discussed with respect to the striking behavior observed via resistivity over temperature cycles. The chemical stability as active buffer layers of both fcc W and beta-W2N thin films is shown in spintronic configurations, where a thin film of Fe is interposed between W or W2N layers. The reported results show that the obtained high quality W based epitaxial layers are superior template-matched buffers for epitaxial Fe layers, enabling a new class of functional spintronic heterostructures.

Multilayer oxide/metal/oxide (OMO) structures emerge as suitable alternative to indium tin oxide (ITO) in transparent conductive electrode (TCE) field mainly due to their high visible light transmittance and low resistivity. Moreover, OMO structures are appropriate for flexible organic optoelectronic devices being less susceptible to cracking than single-layer ITO electrodes. Therefore, the present study is focused on the assessment of the properties of ZnO/Ag/ZnO (ZAZ) structures deposited by consecutive radio frequency magnetron sputtering (ZnO) and thermal vacuum evaporation (Ag) on flexible substrates such as polyethylene terephthalate, polyethersulfone and flexible glass. Additionally, the ZAZ deposition was carried out on patterned polyethersulfone in order to evaluate the nanopatterning effect on the properties of the multilayer structures. For comparison, ZAZ structures were also deposited on rigid glass substrate, this being commonly used in optoelectronic devices. The optical and electrical measurements reveal that the roughness of the deposition substrate has a significant impact on the transmittance and sheet resistance of the ZAZ multilayers. Thus, the best performance in terms of transmittance at 550 nm wavelength (82.7%), sheet resistance (9.5 52/square) and figure of merit (15.75x10-3 52-1), correlated with the lowest roughness (2.3 nm), is achieved for the structure fabricated on flexible glass. The values of the TCE key parameters endorse the developed ZAZ structures for optoelectronic applications.

Composites based on TiO2 and single-walled carbon nanotubes (SWCNTs), highly separated in semiconducting tubes (S-SWCNTs) and as a mixture of metallic and semiconducting tubes (M + S-SWCNTs), were obtained by the interaction in the solid state. This interaction induces a change in the size of TiO2 particles from 23.67 nm to 28.2 and 150 nm, respectively, accompanied by an increase in the disorder state of the graphitic lattice of SWCNTs. We demonstrate by UV-VIS spectroscopy that the best performance in terms of rhodamine 6G (Rh6G) photodegradation is obtained in the case of the TiO2/S-SWCNT composite. The highest values of the Rh6G photodegradation efficiency were equal to 92% for an S-SWCNT concentration in the photocatalyst mass of 10 wt% and 94% for a 0.1 mM Rh6G solution with a pH equal to 1. We demonstrate that an important role is played by the O2(center dot)- and (OH)-O-center dot species in the photodegradation mechanism of Rh6G. This study contributes to a better understanding of the role of metallic and semiconducting carbon nanotubes in the photocatalysis field, highlighting that composites based on semiconducting SWCNTs and semiconducting metallic oxides are those that contribute essentially to the removal of dyes by exposure to the light emitted by a halogen lamp.

Functionalized gold nanoparticles (AuNPs) have emerged as versatile platforms in therapeutic research, yet their specific roles in regenerative medicine, particularly in modulating prokaryotic and eukaryotic cell responses, enhancing antioxidant defense, and supporting tissue repair mechanisms, remain insufficiently elucidated. In this study, we have obtained gold nanoparticles initially functionalized with the well-established antioxidant lipoic acid and subsequently with thiosalicylic acid. Their final modification with the 6-amino-chromen-2-one, a coumarin derivative with recognized antioxidant and pharmacological relevance, generated novel composite systems, distinguished by enhanced biological performance. The novel structures have been comprehensively characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (IR), and thermal analysis. Their biological properties were evaluated through antimicrobial and anti-adherence assays against standard and clinical strains, as well as antioxidant and biocompatibility (hemolytic/anti-hemolytic/cytotoxicity) assays. The findings highlight the strong therapeutic potential of functionalized AuNPs, demonstrating enhanced antimicrobial efficacy, antioxidant protection, and cytocompatibility. Their capacity to reduce oxidative stress and combat microbial infections show promise for advanced biomedical applications, such as controlled drug delivery and tissue regeneration.

Developing magnetic nanocomposites (NCPs) based on magnetite (Fe3O4) and cerium dioxide (CeO2) nano-particles can be a beneficial solution to obtain multifunctional nanomaterials with pronounced bioactivity, which are promising for use in biomedical fields. In this study, we demonstrate that the synthesis conditions directly determine the morphology and surface chemical state of Fe3O4@CeO2 NCPs, and consequently the balance of Fe2+/Fe3+ and Ce3+/Ce4+ redox couples, which is crucial for their bioactivity. Controlled synthesis enables the formation of nanocomposites with a uniform CeO2 shell, optimized redox balance, and enhanced structural homogeneity compared to composites obtained via conventional precipitation methods. Experimental data confirmed that the morphology and surface chemical state directly influence the nanozymatic and anti-amyloid activities of the NCPs. The bioactivity of Fe3O4@CeO2 significantly exceeds that of individual Fe3O4 and CeO2 nanoparticles, indicating a synergistic effect arising from the balanced participation of both redox couples in biocatalytic processes. Furthermore, a potential mechanism for the synergistic enhancement of bioactivity is proposed, in which the Fe2+/Fe3+ and Ce3+/Ce4+ couples actively interact at the nanocomposite surface, enhancing redox processes and increasing the efficiency of antioxidant and anti-amyloid actions. The synthesized Fe2+/Fe3+ and Ce3+/Ce4+ nanocomposites also retain the ability to heat effectively under an alternating magnetic field, further boosting their biomedical potential. Overall, this work highlights that the choice of synthesis conditions is a key factor in controlling morphology, redox balance, and synergistic bioactivity of Fe3O4@CeO2 NCPs, opening new opportunities for the rational design of multifunctional bioactive nanomaterials.

This study explores how catalysts containing a low palladium loading (0.5 wt%) contribute to the selective hydrogenation of cinnamaldehyde. High specific surface area (SSA) mesoporous (2 wt%) TiO2 - SiO2 (UVM-7) materials were prepared by two different approaches: a one-step procedure, in which titania and silica precursors were added from the beginning to generate Ti2@UVM-7 support, and a two-step procedure, where TiO2 was deposited onto the UVM-7 silica surface via wet impregnation technique (Ti2/UVM-7). Both types of supports were decorated with Pd nanoparticles (NPs) through the deposition-precipitation technique. The obtained catalysts were thoroughly characterized by using different techniques, including XRD, N2 adsorption-desorption isotherms at liquid N2 temperature, ATR-FTIR, TEM-EDX, SEM-EDX, and XPS. Characterization data revealed that one-step procedure largely preserves the textural and structural properties of the support following the deposition-precipitation of the noble metal, whereas the two-step procedure slightly alters the UVM-7 morphology. Moreover, the preparation method of the supports impacts the Pd particle sizes and the metal-support interaction (MSI). The one-step procedure tends to promote the growth of larger Pd NPs, likely due to the TiO2 species being well embedded within the SiO2 matrix. In contrast, the two-step procedure yields well-dispersed Pd NPs smaller than 2 nm, due to the confinement of TiO2 nanodomains within the UVM-7 cavities, which enhances the MSI. Consequently, enhanced catalytic performance and stability were achieved with 0.5Pd/Ti2/UVM-7 (similar to 99% hydrocinnamaldehyde yield, TOF 4.81 s-1), due to the formation of very small Pd nanoparticles on the support that promote the MSI.

Rapidly solidified Fe-Pd-Ga ferromagnetic shape memory ribbons, containing 1 and 3 at. % Ga, were obtained, and annealed at 950 degrees C for 15 and 30 min. Gallium substitution destabilizes the cubic lattice but preserves ferromagnetic order; thereby, it modifies phase stability and magnetic sensitivity. The combined effects of composition and heat treatment on microstructure, martensitic transformation temperatures, transformation heat, kinetics, and magnetic-field-induced transformation shift are presented. Magnetic sensitivity is evaluated using thermomagnetic and magneto-elastic measurements, being further validated through Clausius-Clapeyron analysis. Short-time heat treatment enhances structural relaxation and significantly increases the transformation heat, whereas prolonged annealing promotes grain growth and precipitate formation without suppressing thermoelastic behavior. Increasing Ga content results in a pronounced linear increase of the martensitic transformation temperature with magnetic field, from approximately 0.6 K T-1 for 1 at. % Ga to about 1.45 K T-1 for 3 at. % Ga. The good agreement between thermomagnetic measurements and Clausius-Clapeyron analysis confirms that the transformation shift is primarily governed by intrinsic thermodynamic parameters. The smaller magneto-elastic response indicates that microstructure limits strain expression. Therefore, functional control requires tuning the balance between intrinsic thermodynamic driving forces and microstructure-dependent magneto-elastic effects through composition and heat treatment. This enables the design of thermally adaptive and magnetically programmable materials, where 3 at. % Ga composition is suitable for active magnetic control and that of 1 at. % Ga is optimized for enhanced thermal stability and precision sensing.

Capacitive energy storage is part of a promising energy harvesting and storage solution to power Internet of Things (IoT) sensors, overcoming the critical limitations of conventional supercapacitors and micro-batteries. Moreover, achieving high recoverable energy storage density (ESD) and high efficiency (eta) simultaneously is a key goal in energy storage, often requiring hybrid systems (e.g., combining batteries and supercapacitors) to balance the trade-offs. Here, we demonstrate a ultra-thin film capacitor with unprecedented high ESD that can be efficiently released at low operating voltage. This is achieved by using a novel heterostructure design combining ferroelectric La-doped HfO2 and a ferroelectric perovskite that is a relaxor induced by polar nanoregions, which enables a low hysteresis loss in the capacitor, thereby leading to an improved eta. Additionally, the relaxor ferroelectric layer thickness was optimized to give an optimum voltage drop to allow high maximum polarization and low remnant polarization, the former to allow an ESD of over 50 J/cm3, and the latter to allow & eng; to be maximized at similar to 95%. Therefore, our fluorite/perovskite heterostructure design and unique materials strategy have together provided a novel way to achieve unprecedented dielectric energy storage properties, proving a new route to electrostatic energy storage for autonomous IoT sensors.

New approaches for the synthesis of magnetite (Fe3O4) nanoparticles (NPs) are of considerable interest due to their potential applications in various fields, such as biomedicine, industry, environmental remediation, and catalysis. This study presents a novel approach for synthesizing Fe3O4 NPs using high-energy electron beam (EB) irradiation starting from organic (acetylacetonates) iron precursors. EB irradiation is a challenging nanoparticle synthesis method, being at the same time efficient and rapid. The synthesis is carried out at room temperature and is based on the water radiolysis process. This eliminates the need for chemical-reducing agents and may provide precise control over particle formation. Using high-energy EB irradiation of an organic Fe precursor, we demonstrate the successful synthesis of well-dispersed Fe3O4 NPs with controlled size, morphology and magnetic properties, as proven by morpho-structural, M & ouml;ssbauer spectroscopy and magnetic investigations. In particular, using organic iron precursors, such as iron acetylacetonates, NPs with distinct surface characteristics and improved thermal stability compared to those synthesized from inorganic precursors were obtained. These findings suggest that integrating organic precursors in EB-assisted synthesis can enhance the functional properties of Fe3O4 NPs, making them more suitable for specific applications. The versatility of this method opens up new avenues for the targeted design of nanomaterials with specific functionalities, paving the way for advanced applications in various technological fields. The current study is also motivated by the lack of literature data on the synthesis of metallic iron or iron oxide NPs mediated by EB radiolysis.