L. Z. Pei

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.

Single crystalline Sr germanate nanowires and their photocatalytic performance for the degradation of methyl blue

Single crystalline Sr germanate nanowires have been synthesized by a facile hydrothermal process without any surfactants at a low temperature. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), Fourier transform infrared (FTIR) and ultraviolet-visible (UV-vis) diffusion reflectance spectra have been used to characterize the structure, morphology, size and optical properties of the Sr germanate nanowires. The nanowires with the orthorhombic SrGeO3 phase have the diameter of 50 to 200 nm. The morphology and size of the Sr germanate nanowires can be controlled by adjusting the hydrothermal temperature, reaction time and surfactant species. The photocatalytic activity of the Sr germanate nanowires has been evaluated by the degradation of methylene blue (MB) under UV-vis light irradiation. The roles of the irradiation time, the content of the Sr germanate nanowires and the MB concentration on the MB degradation have been investigated. The Sr germanate nanowires present a degradation ratio of 83.22% after irradiation for 4 h over 10 mg Sr germanate nanowires in a 10 ml 10 mg L−1 MB solution.

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.

Effect of Fe content on the properties of perovskite-related oxides

A series of SrFexCo0.5O3 − δ (x = 0.5, 0.75, 1.0, 1.25) powders have been synthesized by the citrate method. The effect of Fe content on the properties of the SrFexCo0.5O3 − δ was investigated by X-ray diffraction (XRD), thermo-gravimetric analysis and differential scanning calorimeters (TGA/DSC). XRD results reveal that the phases of the SrFexCo0.5O3 − δ powders depend upon the content of Fe. Variations in Fe-content and temperature play important effects on the oxygen loss of the SrFexCo0.5O3 − δ samples. The phase transition from brownmillerite to perovskite structure in helium is strongly dependent on the content of Fe by TGA/DSC analysis. The phase transition temperature is 795, 853, 828 and 874°C for SrFe0.5Co0.5O3 − δ, SrFe0.75Co0.5O3 − δ, SrFeCo0.5O3 − δ and SrFe1.25Co0.5O3 − δ, respectively. The oxygen sorption capacity of the products is closely related to the Fe content and temperature. The oxygen sorption capacity of the SrFe1.25Co0.5O3 − δ sample increases rapidly from 790°C with the highest oxygen sorption capacity of 6.83 × 10−3 mmol/g at 870°C exhibiting the good oxygen sorption capacity from 860 to 880°C.

Polyvinyl pyrrolidone-assisted synthesis of crystalline manganese vanadate microtubes

Manganese vanadate microtubes have been synthesized by a facile polyvinyl pyrrolidone-assisted hydrothermal route. X-ray diffraction pattern confirms that the microtubes are composed of monoclinic MnV2O6, tetragonal V2O5 and orthorhombic MnO2 phases. The outer diameter and inner diameter of the microtubes are about 300 nm-3 µm and 200 nm-1 µm, respectively. The tube wall thickness of the microtubes is about 50 nm-1 µm. The possible formation process of the manganese vanadate microtubes has been proposed as a polyvinyl pyrrolidone-assisted growth mechanism.

Low temperature synthesis of CuGeO3 nanoflowers from n-heptane solvent

Abstract CuGeO3 nanoflowers have been synthesized by solvothermal treatment of GeO2 and Cu(CH3COO)2 · H2O in n-heptane solvent without using any surfactants. The influence of temperature and reaction time on the formation of the CuGeO3 nanoflowers has been analyzed. The room temperature photoluminescence spectrum of the CuGeO3 nanoflowers has also been investigated. The synthesized nanoflowers are composed of orthorhombic phase, based on X-ray diffraction and scanning electron microscopy characterizations. The temperature and reaction time have important roles in the formation and size of the CuGeO3 nanoflowers. The room temperature photoluminescence spectrum of the CuGeO3 nanoflowers demonstrates strong blue light emission centered at 421 nm and 488 nm and a poor green light emission centered at 530 nm and 543 nm, suggesting that the CuGeO3 nanoflowers have good optical properties.

Synthesis of binary bismuth–cadmium oxide nanorods with sensitive electrochemical sensing performance

Abstract Binary bismuth–cadmium oxide nanorods have been synthesized by a simple hydrothermal process without templates and additives. X-ray diffraction and high-resolution transmission electron microscopy reveal that the nanorods possess single crystalline tetragonal Bi2CdO4 phase. Scanning electron microscopy and transmission electron microscopy images show that the length and diameter of the nanorods are 20–300 nm and 5–10 μm, respectively. The formation of the binary bismuth–cadmium oxide nanorods is closely related to the hydrothermal parameters. The electrochemical sensing performance of the binary bismuth–cadmium oxide nanorods has been investigated using the nanorods as glassy carbon electrode modifiers. The detection limit is 0.19 μM with a linear range of 0.0005–2 mM. The nanorod-modified glassy carbon electrode exhibits good electrocatalytic activity toward L-cysteine and great application potential for electrochemical sensors.

Synthesis and formation process of zirconium dioxide nanorods

Crystalline zirconium dioxide nanorods have been prepared by a simple hydrothermal process using zirconium hydroxide as the zirconium raw material. Zirconium dioxide nanorods are composed of monoclinic zirconium dioxide phase, which has been confirmed by the X-ray diffraction analysis. Electron microscopy observations show that the zirconium dioxide nanorods have a single crystal structure, with the rod diameter of less than 100 nm and length of 1–2 μm. Hydrothermal temperature and reaction time play essential roles in the formation and growth of the zirconium dioxide nanorods. Nucleation and crystal growth process are proposed to explain the formation and growth of the zirconium dioxide nanorods.