Bimetallic Au-Ag nanoparticles with homogeneous dispersion in amine-modified SBA-15 mesoporous silica channels were successfully synthesized by the post-modification method. The obtained nanocomposites with different component ratios were studied by structural, Physico-chemical, and optical analysis. The structural and Physico-chemical properties were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and nitrogen adsorption-desorption isotherm measurement (BET). The optical properties were characterized by photoluminescence (PL) and UV-Vis spectroscopy. The photoluminescence and absorption spectra were strongly affected by the change in the compositional ratio of gold to silver nanoparticles due to the interactions of Au-Ag nanoparticles, the configuration of conduction electrons and their plasmonic properties. A significant enhancement was observed in the photoluminescence spectrum in the long-wavelength red emission at 640 nm for a one-to-one composition ratio of Au/Ag/SBA-15 nanocomposite. Since the light emission of most microorganisms is in the visible range, the nanocomposite produced can be proposed for applications in biosensor technology. تفاصيل المقالة

AbstractIn this work, a new sensitive enzyme-based electrode for electrochemical cholesterol biosensor was fabricated based on a nanocomposite of Au nanoparticles, ZnO nanoparticles and multi-wall carbon nanotubes (Au/ZnO/MWCNTs). The nanocomposite was prepared by sol–gel method and deposited on FTO substrate by dip coating, followed by cholesterol oxidase (ChOx) enzyme immobilized (ChOx/Au/ZnO/MWCNTs). Structural properties and morphology of the nanocomposite have been studied using X-ray diffraction (XRD) and Field emission scanning electron microscopy (FESEM). The sample was subjected to Fourier transform infrared spectroscopy (FTIR) to determine functional groups. Electrochemical behavior of the electrode was studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques as a function of cholesterol concentration. Electrochemical impedance spectroscopy (EIS) was also considered to study of surface modified electrodes. The ChOx/Au/ZnO/MWCNTs electrode has been found to have enhanced electron transfer and display excellent analytical linear performances. The fabricated electrode exhibited low detection limit (0.1 μM), high sensitivity (25.89 μA/μM) evaluated from DPV data in the detection range of 0.1–100 µM and high selectivity in the determination of cholesterol over glucose and uric acid. The application of the ChOx/Au/ZnO/MWCNTs electrode in detection of cholesterol in human serum was also confirmed. تفاصيل المقالة