Synthesis And Electrochemical Properties Of Calcium Vanadate And Manganese Vanadate Microscale And Nanoscale Structures

Vanadate microscale and nanoscale materials exhibit excellent application potential inthe fields of nanoscale optical devices, sensors and lithium ion battery owing to their goodelectrochemical and optical properties. The current research situation and recentdevelopment on the calcium vanadate and manganese vanadate microscale and nanoscalematerials and electrochemical analysis of tartaric acid and cysteine have beendemonstrated. Calcium vanadate nanorods, manganese vanadate microtubes, andmanganese vanadate nanorods have been synthesized by hydrothermal method. Thestructure, morphology and optical properties were analyzed by X-ray diffraction (XRD),scanning electron microscopy (SEM), transmission electron microscopy (TEM),high-resolution TEM (HRTEM), infrared (IR) and photoluminescence (PL) spectra. Therole of the growth conditions and raw materials on the formation of the vanadatemicroscale and nanoscale materials and growth mechanism have been researched. Theelectrochemical behaviors of tartaric acid and cysteine at the vanadate microscale andnanoscale material modified glassy carbon electrode have been analyzed. It is greatsignificance for the controlled synthesis, formation mechanism and application of thevanadate microscale and nanoscale materials.Single crystalline calcium vanadate nanorods with sheaf-shaped structure have beensynthesized by a hydrothermal route using calcium acetate and sodium orthovanadate asthe raw materials without any surfactants. Electron microscopy observations show that theaverage diameter and length of the calcium vanadate nanorods are about50nm and3μm,respectively. XRD and HRTEM observation exhibit that the calcium vanadate nanorods arecomposed of single crystalline hexagonal Ca10V6O25phase. PL spectrum of the calciumvanadate nanorods shows that the calcium vanadate nanorods exhibit strong violet lightand blue light emission centered at425nm and488nm, respectively. The nucleation andcrystal growth combined with crystal splitting process have been proposed to explain theformation and growth of calcium vanadate nanorods. Calcium vanadate nanorods havebeen obtained using CaCl2as the Ca source material. Calcium sulfate nanosheets andcalcium vanadate flower-like structure composed of nanorods have been synthesized usingcalcium sulfate as the Ca raw material. Calcium vanadate microrods with hexagonalCa10V6O25phase have been obtained using ammonium vanadate as the V raw material. Theelectrochemical cyclic voltammogram (CV) of the tartaric acid at the calcium vanadate nanorods modified glassy carbon electrode shows a pair of semi-reversible oxidation andreduction electrochemical peaks. The calcium vanadate nanorod modified glassy carbonelectrode exhibits good performance for the electrochemical detection of tartaric acid witha detection limit of2.4μM and linear range of0.005-2mM.Manganese vanadate microtubes have been synthesized by the hydrothermal processusing manganese acetate and sodium vanadate as the raw materials, polyvinyl pyrrolidone(PVP) as the surfactant. XRD analysis shows that the manganese vanadate microtubes arecomposed of monoclinic MnV2O6phase, tetragonal V2O5and orthorhombic MnO2phases.Electron microscopy observations display that the manganese vandate microtubes havesmooth surface. The outer diameter and inner diameter of the manganese vanadatemicrotubes are about300nm-3μm and200nm-1μm, respectively. The tube wallthickness of the microtubes is about50nm-1μm. PVP concentration, hydrothermaltemperature, reaction time and raw materials play essential roles on the formation andgrowth of the manganese vanadate microtubes. Only irregular particles can be obtainedusing Mn sulfate, Mn chloride and Mn nitrate as the Mn raw materials. Mn vanadatenanosheets and microrods with monoclinic MnV2O6phase have been synthesized usingammonium metavanadate and sodium metavanadate as the V raw material, respectively.The electrochemical CV of the L-cysteine at the manganese vanadate microtube modifiedglassy carbon electrode shows a pair of semi-reversible oxidation and reductionelectrochemical peaks. The manganese vanadate microtube modified glassy carbonelectrode exhibits good performance for the electrochemical detection of L-cysteine with adetection limit of9.2μM and linear range of0.01-2mM.Manganese vanadate nanorods have been synthesized through a hydrothermal processusing Mn acetate and sodium vanadate as the raw materials, sodium lauryl sulfonate (SDS)as the surfactant. XRD results show that the manganese vanadate nanorods are composedof triclinic Mn2V2O7phase. Electron microscopy observations show that the nanorods havesmooth surface and single crystalline structure. The length and diameter of the nanorodsare in the range of5to20μm and50to300nm, respectively. SDS has essential role on theformation and growth of the manganese vanadate nanorods. The formation and growthprocess has been explained as a nucleation and SDS adsorption growth mechanism. Theelectrochemical CV of the L-cysteine at the manganese vanadate nanorod modified glassycarbon electrode shows a pair of semi-reversible oxidation and reduction electrochemicalpeaks. The manganese vanadate nanorod modified glassy carbon electrode exhibits goodperformance for the electrochemical detection of L-cysteine with a detection limit of0.026μM and linear range of0.00005-2mM, respectively.