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.

This study explores the synthesis and characterization of a novel cationic porous organic polymer (cPOP, referred to as POP1) designed as an active material for electrochemical detection of chloramphenicol (CAP) in complex matrices. Unlike conventional sensing platforms, POP1 provides a high density of accessible adsorption sites and tailored chemical functionality, enabling selective host-guest interactions with CAP and improving sensing performance. The polymer was comprehensively characterized using scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), infrared (IR) and Raman spectroscopy and thermogravimetric analysis (TGDTA). The interaction between POP1 and CAP was investigated by isothermal titration calorimetry (ITC), revealing a spontaneous and enthalpy-driven adsorption process that underpins the sensing response. POP1 was incorporated into a chitosan matrix and deposited onto carbon screen-printed electrodes (C-SPE) to fabricate a robust and reproducible electrochemical sensor for CAP. Under optimized conditions, the sensor exhibited a sensitivity of 48 nA mu M- 1, a limit of detection of 1.67 mu M, and a limit of quantification of 5 mu M, along with good repeatability, selectivity, and operational stability over 30 days. Method validation was carried out using pharmaceutical products (topical suspensions, topical gels, injectable suspension, and eye drops) and animal biological samples (cow milk, cow urine and pig urine) containing CAP, yielding satisfactory analytical performance despite the complexity of the matrices and confirming the applicability of the proposed platform for real-sample analysis. These results demonstrate the potential of POPs as effective electrode modifiers for electrochemical sensors.

This study investigates the effect of synthesis parameters on the catalytic performance of Mo-Ti oxide materials in the esterification of levulinic acid (LA) with various alcohols. Three sol-gel synthesis strategies were used for the catalyst's preparation, without additives, using malic acid as complexing agent and polyethylene glycol as surfactant and templating agent. The samples were characterized by structural and surface-sensitive techniques. Detailed kinetic investigations were conducted for the esterification of LA with butanol, assessing the effect of temperature, alcohol-to-acid molar ratio, catalyst loading and activation energy. Catalysts prepared in the absence of any additives or in the presence of a templating agent exhibit comparable activities, both exceeding that of the catalyst obtained with a complexing agent. This behavior is consistent with the smaller Mo6+/Mo5+ surface ratio and with the greater density of acid sites per unit surface area. Our results highlight the critical importance of synthesis strategy in tuning the surface composition and acidity of Mo-Ti catalysts for biomass-derived molecule conversion.

Water pollution poses a major threat to environmental sustainability and human health. Here, we report novel 4'aminobenzo-15-crown-5 ether-functionalized hydrochars as eco-friendly adsorbents for the removal of copper and lead ions from water. The hybrid materials were synthesized via a carbohydrate-assisted hydrothermal route using sucrose, starch, and fructose as carbon sources. Pristine and functionalized hydrochars were characterized by various techniques, including scanning electron microscopy (SEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), thermal analysis (TG/DTG/DTA) and X-ray photoelectron spectroscopy (XPS). The crown ether functionalization and materials integrity were successfully confirmed. Batch adsorption measurements for Cu2+ and Pb2+ removal from aqueous solutions demonstrated that the Freundlich isotherm provided the best fit, suggesting multilayer and heterogeneous adsorption. The adsorption capacities ranged from 10.15 to 16.86 mg center dot g-1 for Cu2+ and from 8 to 11.93 mg center dot g-1 for Pb2+, indicating their potential as sustainable materials for mitigating water pollution.

The aggressive scaling of electronic devices has brought ferroelectric materials to the forefront of nanoscale research, where lateral dimensions strongly influence switching dynamics and device performance. In this context, W/ Hf0.5Zr0.5O2/ p-Ge capacitors with top electrode sizes ranging from 10 & micro;m down to 0.1 & micro;m are investigated using conductive atomic force microscopy (C-AFM). Frequency-dependent measurements reveal that peak switching currents (Isw) increase with sweep rate, yet the total switched charge remains nearly constant, consistent with full polarization reversal in micro- and submicron devices. Positive-Up-Negative-Down (PUND) analysis further isolates the switching current, allowing reconstruction of polarization-voltage (P--V) loops and quantification of remnant polarization. The smallest devices (0.01 & micro;m2) exhibit switching currents below the detection threshold due to parasitic capacitance, masking intrinsic ferroelectric behavior. In contrast, submicron capacitors display an apparent increase of remanent polarization attributed to the larger perimeter-to-area ratio, emphasizing the role of edge-dominated switching. Together, these findings establish C-AFM as a powerful, spatially resolved technique for probing ferroelectric switching in realistic device geometries, providing essential insights for non-volatile memory and neuromorphic applications.

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.

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.

We approach a cost effective, environmentally friendly, synthesis route of a non-precious electrocatalysts for the anodic oxidation of bioethanol. SnO2 and SnO2-Graphene Nanoplatelets are decorated with nano-crystallized Ni filaments and clusters with peculiar surface chemistry. The electrocatalysts are obtained by subsequently depositing different Ni species by wet impregnation in the presence or absence of a reducing agent (Na borohydride). The effect of the Ni deposition parameters on the crystalline and porous structures, on the surface chemistry and on the electrochemical behavior is highlighted. It is found that the use of a lower temperature (200 degrees C) thermal treatment in the presence of a reducing agent leads to an increase of more than five times of the specific surface area. Electrocatalytic performance is assessed in alkaline medium and, apparently, graphene addition to the SnO2-nickel support allows diminishing the Tafel slope with ca. 20 %, down to 106 mV decade(-1). Such value, that favorably compares to those in the literature, together with the good resistance to fouling that the results of the chronoamperometric and electrochemical impedance spectroscopy (EIS) measurements demonstrate, show that the composites are worthy of development as active materials for biofuel cell applications.

Chronic inflammation and persistent infections represent major obstacles to effective wound healing, underscoring the urgent need for innovative, eco-friendly biomaterials capable of combating microbial contamination and oxidative stress. In this study, we investigated the in vitro biological activities of a gold-titanium dioxide (AuNPs/TiO2) composite, synthesized via an environmentally friendly approach, employing an ethylenediamine-hyaluronic acid derivative as both a reducing and stabilizing agent. The composite was analyzed using various techniques, including Transmission Electron Microscopy, X-ray elemental mappings, X-ray diffraction, and X-ray spectroscopy. We evaluated the biological properties of the material through antimicrobial and anti-adherence assays, alongside hemolysis, cytotoxicity, oxidative stress levels, and wound healing potential. The green-derived AuNPs/TiO2 demonstrated moderate to potent antimicrobial and anti-adhesion activity (minimum inhibitory concentrations ranging from 0.625 to 5 mg/mL) against both standard and clinical isolates. The material showed low hemolysis rates (<5 %) at bioactive concentrations. Additionally, keratinocyte viability and membrane integrity were largely preserved at the tested concentrations, with no detectable increase in pro-inflammatory nitric oxide levels. Intracellular antioxidant defenses were maintained, and lipid peroxidation was minimal. In an in vitro scratch assay, AuNPs/TiO2 promoted keratinocyte migration, suggesting a promising potential to enhance tissue repair. In summary, the biomaterial exhibits promising multifunctional properties, including effective antimicrobial and anti-adhesion activity, excellent biocompatibility with minimal hemolysis, and the ability to enhance keratinocyte migration and intracellular antioxidant defenses. These findings highlight its potential as a safe and effective biomaterial for accelerating wound healing and addressing infection-related challenges.

The rapid growth of the global population has increased the need for efficient fabrication methods and materials to purify polluted water. In this study, we report the fabrication and characterization of reusable and efficient three-dimensional (3D) polydimethylsiloxane (PDMS) sponge composites designed for water treatment applications. By varying the ratios (10/90, 30/70, and 50/50) of large and small sacrificial templates' particles used in the fabrication method, we tailored the sponge's morphology and the interconnected pores' distribution. To achieve an enhanced photocatalytic activity, we incorporated titanium dioxide (TiO2) at different concentrations (1 % TiO2, 5 % TiO2, and 10 % TiO2 w/w) into the PDMS matrix. Scanning electron microscopy (SEM) was used to evaluate the structure of both 3D PDMS and TiO2@PDMS sponges, while energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD) confirmed the successful incorporation of TiO2 into the sponge framework. The photocatalytic performance of the 3D TiO2@PDMS composites was assessed by monitoring the degradation of Rhodamine B (RhB) under solar light irradiation, and the results were compared to those obtained using reference (TiO2-free) sponges under identical conditions. Very low Ti leaching effect have been evidenced by using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The reusability of the sponges was demonstrated through complete bleaching of the 554 nm RhB absorption band after four consecutive degradation cycles.