National Institute Of Materials Physics - Romania

This study describes the development of a pyruvate kinase (PyK)-biosensor for the evaluation of PyK activity, as a diagnostic tool for early cancer screening and detection of kinase inhibitors used in cancer treatment, with the evaluation of the inhibition mechanism. The biosensor was constructed by co-immobilizing the enzymes PyK and pyruvate oxidase (PyOx) on Au film electrodes by crosslinking with glutaraldehyde (GA) and evaluated electrochemically by cyclic voltammetry (CV) and fixed potential amperometry (CA). First, the experimental conditions were optimized in terms of applied potential, enzyme ratio PyK:PyOx and enzyme substrate concentration: phosphoenolpyruvate (PEP) and adenosine diphosphate (ADP). The biosensor sensitivity towards PEP detection was 2.11 +/- 0.08 mu A mM- 1 cm- 2, with very high reproducibility and repeatability, which made it suitable for inhibition studies of PyK inhibitor. The inhibition mechanism of shikonin was determined in relation to both PEP and ADP, with the calculation of IC50 values and binding constants (Ki). Detection of shikonin was possible at very low concentrations in the linear range of 0.1-4.0 pM. The electrochemical results were validated by UV-Vis spectrophotometry. The developed biosensor is a valuable tool for drug screening by enabling enzyme catalytic function examination with applicability to identify inhibitors, estimate their affinity, inhibition mechanism linked to their molecular mechanisms of action and evaluate selectivity, of great interest in both pharmaceutical and medical domains.

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 the present work, an essential advance in the preparation of novel nanocomposites based on functionalized V2O5 nanostructures with reduced graphene oxide by hydrothermal method, which has great potential for use in photocatalytic processes related to environmental remediation. XRD analysis confirmed V2O5 in an orthorhombic structure. SEM images showed transparent RGO layers well anchored onto the surface of the V2O5 with a homogeneous distribution. Raman spectroscopy further explained the hybridization and interaction between the components. The photocatalytic activity of Rhodamine-B in aqueous solutions has been studied upon irradiation with visible light. A high RhB degradation was obtained using the V2O5/RGO photocatalyst (82 %), compared to the degradation obtained with only V2O5 (60 %). First-principles Density Functional Theory (DFT) simulations reveal a strong interaction between V2O5 molecules and graphene surfaces, with an adsorption energy of -1.673 eV and a significant charge transfer of 0.367 e- to RGO. This interaction modifies the electronic structure, creating semi-metallic behavior near the Fermi level and enhancing catalytic activity through improved charge carrier dynamics and active sites for photocatalytic applications.

In this study, we developed a ternary nanocomposite using graphene oxide (GO), multiwalled carbon nanotubes (MWCNTs), and tungsten trioxide (WO3), nanostructures, synthesized via a straightforward chemical process with ultrasound assistance. The initial composition was GO/MWCNT, later combined with WO3 to form the GO/ MWCNT: WO3 (25/25:50) structure. Characterization was performed using X-ray diffraction, which revealed the multiphase nature of the WO3 nanostructures. Scanning Electron Microscopy showed the one-dimensional CNTs interwoven with graphene oxide sheets decorated with densely populated WO3 nanopetals. Fourier transform infrared and Raman spectroscopy confirmed the chemical composition of the system. The photocatalytic degradation of Rhodamine-B in water under visible light irradiation was significantly enhanced using the GO/

The present paper evidences the beneficial effect that the combination of Pt with WO3 and silicotungstic acid (STA) brings to the methanol oxidation electroactivity. To avoid substrate interferences boron doped diamond (BDD) was used as the electrocatalysts support. SEM measurements have shown that the use of a STA/WO3/BDD substrate allows the electrodeposition of smaller Pt clusters, exhibiting better dispersion, higher homogeneity in terms of size and enhanced electrochemically active surface area. Cyclic voltammetry, polarization and EIS experiments demonstrated than STA addition on the WO3/BDD support induces to the deposited Pt higher activity and improved resistance to fouling during methanol anodic oxidation. Based on the XPS results such behavior was tentatively ascribed to the higher surface concentration of Pt(OH)2 species and adsorbed water that STA presence enables, which may assist in the oxidative desorption of reaction intermediates.

The gas sensitivity of field-effect structures with 2D-MoS2 channels selectively grown between Mo electrodes using the Mo-CVD method was investigated by measuring the effect of molecular adsorption from air on the device source-drain current (Isd). The channels were composed of interconnected atomically thin MoS2 grains, with their density and average thickness varied by choosing two different distances (15 and 20 mu m) between the Mo contacts. A high response to the tested stimuli, including molecule adsorption, illumination and gate voltage changes, was observed. A significant, persistent photoconduction was induced by positive charge accumulation on traps, most likely at grain boundaries and associated defects. Isd increased under high vacuum, both in the dark and under illumination. The relative dark current response to the transition from air to high vacuum reached up to 1000% at the turn-on voltage. When monitored during the gradual change in air pressure, Isd exhibited a non-monotonic function, sharply peaking at about 10-2 mbar, suggesting molecular adsorption on different defect sites and orientations of adsorbed H2O molecules, which were capable of inducing electron accumulation or depletion. Despite the screening of disorder by extra electrons, the #20 mu m sample remained more sensitive to air molecules on its surface. The high vacuum state was also investigated by annealing devices at temperatures up to 340 K in high vacuum, followed by measurements down to 100 K. This revealed thermally stimulated currents and activation energies of trapping electronic states assigned to sulfur vacancies (230 meV) and other shallow levels (85-120 meV), possibly due to natural impurities, grain boundaries or disorder defects. The results demonstrate the high sensitivity of these devices to molecular adsorption, making the technology promising for the easy fabrication of chemical sensors.

Photoanodes based Ce-doped ZnO nanorods arrays were prepared by hydrothermal method in order to improve photoelectrochemical efficiency of ZnO photoanodes in water splitting process. Scanning electron microscopy investigation showed ZnO based nanorods with length of around 500 nm and different thicknesses and growth directions. Some morphological changes were noted following the thermal treatment. Energy-dispersive X-ray analysis and X-ray photoelectron spectroscopy measurements proved the presence of cerium species both in bulk and on the surface of ZnO nanorods. A current density of 2.44 mA/cm(2) at 1.23 V against the reversible hydrogen electrode (0.265 V vs. Ag/AgCl) was obtained for Ce-doped ZnO sample, which is >162% increase over that of ZnO sample. The increased photocurrent value obtained for this sample was correlated with the passivation of surface defects evidenced by photoluminescence study and the increased concentration of Ce3+ on the surface. Also, the electrochemical impedance spectroscopy measurements suggested that Ce doping improves the charge transfer in bulk.

This article describes a new synthesis of nanoscaled Y2O3 that is bioinspired. It has been confirmed that Callistemon viminalis flower extract works well as a chelator when used to bioengineer high-shape anisotropy nanorods of single-phase Y2O3 . X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy and photoluminescence spectroscopy were used to analyse the structural, morphological, surface and optical features. The photoluminescent spectra of the bio-engineered nanorods show blue emissions. As the annealing temperature was increased from 300 to 500 degrees C, the blue colour purity values of the synthesized Y2O3 nanorods were 58.1, 80.7 and 77.0% at 300, 400 and 500 degrees C respectively. The chromaticity coordinates (0.2020, 0.1931), (0.1660, 0.1082) and (0.1714, 0.1226) from the photoluminescence spectra of the biosynthesized Y2O3 nanorods were used to determine these values. The CIE y-component coordinate values of the bioengineered blue-emitting nanophosphors suggest their potential for applications in display technology and white light-emitting diodes.

When used as the active layers-either as a light absorber in photovoltaic devices or as an electroluminescent material in light-emitting devices-lead-free perovskites significantly impact the performance of optoelectronic devices. This study focuses on antimony-based perovskites, which are promising for lighting applications. These types of perovskites enable the formation of self-trapped excitons (STEs) with higher dissociation energy than lead-based perovskites, which generate excitons with lower dissociation energy. The (CH3NH3)3Sb2I9 crystals are synthesized using two methods, resulting in distinct spatial configurations - dimer and dimer/layered mixtures, each exhibiting unique structural and spectroscopic properties, as revealed by comprehensive multi-parametric complementary analyses. Their emissive properties underscore the efficiency of the STE photoluminescence, driven by electron-phonon interactions and influenced by Sb-Sb distances in (CH3NH3)3Sb2I9 powder, whether dispersed in polymethyl-methacrylate or solution. The phase transition from monoclinic to hexagonal (dimer) and trigonal (layered) structures enabled the tuning of the optical properties in direct correlation with the structural and electrical features. The photoluminescence behavior of the STEs, analyzed in conjunction with the Raman spectroscopy, elucidates the dynamic process of the electron-phonon coupling effects in the dimer (face-capping Sb-I octahedra) and layered (corner-sharing Sb-I octahedra) crystallographic structures.

In this work, we report for the first time the development and complex characterization of new bioceramics based on hydroxyapatite (HAp, Ca10(PO4)6(OH)2). On the other hand, the lyophilization process was used for the first time in this research. The samples were obtained by a modified coprecipitation method and were dried by lyophilization (lyophilized hydroxyapatite (HApLF) and lyophilized zinc-doped hydroxyapatite (5ZnHApLF)). Valuable information about the HApLF and 5ZnHApLF stability was obtained through nondestructive ultrasound measurements. The X-ray diffraction (XRD) studies revealed the phase and the effects of the incorporation of Zn ions into the HAp structure. The chemical composition of the samples was evaluated by energy dispersive X-ray analysis (EDS) and X-ray photoelectron spectroscopy (XPS). Information about the functional groups present in the HApLF and 5ZnHApLF was obtained using Fourier Transform Infrared Spectroscopy (FTIR) studies. The morphology of HApLF and 5ZnHApLF pellets was observed by scanning electron microscopy (SEM). The surface topography of HApLF and 5ZnHApLF pellets was studied with the aid of atomic force microscopy (AFM). Details regarding the roughness of the samples were also obtained using AFM topographies and SEM images. A complementary study was also carried out on a larger analysis surface using a Scanning Acoustic Microscope (SAM). The SAM was used for the first time to analyze the surface of HAp and 5ZnHAp pellets. The biological properties of the HApLF and 5ZnHApLF pellets was investigated with the aid of MG63 and human gingival fibroblasts (HGF-1) cell lines. The results of the cell viability assay highlighted that both the HApLF and 5ZnHApLF pellets exhibited good biological activity. Moreover, SEM and AFM studies were conducted in order to emphasize the development of MG63 and HGF-1 cells on the pellet's surface. Both SEM and AFM images depicted that the pellets' surface favored the cell attachment and development of MG63 and HGF-1 cells. Furthermore, the antimicrobial properties of the HApLF and 5ZnHApLF were evaluated against Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, and Candida albicans ATCC 10231. The results of the antimicrobial assays highlighted that the 5ZnHApLF exhibited a strong antimicrobial activity against the tested microbial strains. The results of the biological assays suggested that the samples show great potential for being used in the development of novel materials for biomedical applications.