C. G. Fan

Low temperature synthesis of magnesium oxide and spinel powders by a sol-gel process

Magnesium oxide and magnesium aluminate (MgAl2O4) spinel (MAS) powders have been synthesized by a simple aqueous sol-gel process using citrate polymeric precursors derived from magnesium chloride, aluminium nitrate and citrate. The thermal decomposition of the precursors and subsequent formation of cubic MgO and MAS were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry-differential scanning calorimetry (TG-DSC) and Fourier transform infrared spectra (FTIR). The single phase cubic MgO powder and MAS powder form after heat treatment at 800 and 1200 °C, respectively. The particle size of the MgO and MAS powders is about 100 nm and several micrometers, respectively. Ball milling eliminates the size of MgO and MgAl2O4 spinel powders by decreasing the conglomeration of the powders.

Electrochemical determination of L-cysteine using polyaniline/CuGeO3 nanowire modified electrode

The 10 wt % polyaniline/CuGeO3 nanowire modified glassy carbon electrode has been used for the electrochemical determination of L-cysteine. The electrochemical behavior of L-cysteine at the 10 wt % polyaniline/CuGeO3 nanowire modified glassy carbon electrode has been investigated. The intensities of the anodic cyclic voltammogram (CV) peaks of L-cysteine at the modified electrode increase linearly with the increase of the L-cysteine content in the range of 0.001–2 mM and scan rate ranging from 25 to 200 mV s−1. 10 wt % polyaniline/CuGeO3 nanowire modified glassy carbon electrode exhibits good reproducibility, stability and low detection limit of 1.7 and 0.44 μM for cvpl and cvp2, respectively. The polyaniline combined with the CuGeO3 nanowires can improve the electrochemical detection ability of L-cysteine.

Synthesis and characterization of manganese vanadate nanorods as glassy carbon electrode modified materials for the determination of L-cysteine

Manganese vanadate nanorods with a single crystalline triclinic Mn2V2O7 phase have been synthesized through a hydrothermal process using sodium lauryl sulfonate (SDS) as the surfactant. The manganese vanadate nanorods have a typical length in the range of 5 to 20 μm and a diameter of about 50 to 300 nm. The morphology of the manganese vanadate products is influenced by SDS concentration, hydrothermal temperature and duration time. SDS promotes the phase transformation of the products from irregular particles with an orthorhombic MnV2O5 phase to nanorods with a triclinic Mn2V2O7 phase. The growth process has been proposed as a nucleation and SDS adsorption growth process based on the analysis of the influence of growth conditions on the morphology of the manganese vanadate products. The manganese vanadate nanorods are used as glassy carbon electrode modified materials to analyze the electrochemical responses of L-cysteine. The manganese vanadate nanorod modified glassy carbon electrode exhibits a good analytical performance for the electrochemical determination of L-cysteine with a detection limit of 0.026 μM and linear range of 0.00005–2 mM.

Electrochemical determination of benzoic acid using CuGeO3 nanowire modified glassy carbon electrode

Copper germanate (CuGeO3) nanowires are applied as the electrochemical modified materials for the electrochemical determination of benzoic acid (BA) in neutral solution. The electrochemical responses of BA at the CuGeO3 nanowire modified glassy carbon electrode (GCE) show two pairs of electrochemical cyclic voltammogram peaks (cvp) which originate from the nanowires. The linear range is 0.01–2 mM and detection limit is 6.3 µM for cvp1 at a signal-to-noise ratio of 3. The linear range and detection limit, respectively, are 0.001–2 mM and 0.91 µM for cvp2. Scan rate plays an important role on the electrochemical behavior of BA at the CuGeO3 nanowire modified GCE. There is a linear correlation between the anodic current and scan rate in the range of 25–200 mV s−1. The CuGeO3 nanowire modified GCE exhibits good stability and reproducibility. The good analytical performance indicates that the CuGeO3 nanowires have a potential application for the determination of BA.

Copper germanate nanowire electrode for the electrochemical detection of glyoxalic acid using cyclic voltammetry method

Glyoxalic acid was determined by electrochemical cyclic voltammetry method using copper germanate (CuGeO3) nanowires as the modified glassy carbon electrode (GCE) materials. The CuGeO3 nanowire modified GCE exhibited good detection performance for glyoxalic acid in neutral solution. The intensities of two anodic peaks vary linearly with the increase of the scan rate from 25 to 200 mVs−1 and glyoxalic acid concentration from 0.001 to 2 mM. The detection limit was 8.5 μM and 0.78 μM for cvp1 and cvp2 with the correlation coefficient of 0.991 and 0.998, respectively. The CuGeO3 nanowire modified GCE exhibited good reproducibility and stability.