Preparation And Microstructure And Properties Of ZnFe₂O₄Nanoparticles And Nanocomposites

As a normal spinel structure indirect gap semiconductor, ZnFe₂O₄nanoparticlesreceive more and more attentions since their excellent magnetic property,photocatalytic performance and electrochemical performance. In this work,ZnFe₂O₄nanoparticles and MWCNTs/ZnFe₂O₄nanocomposites are synthesized bya sample and inexperience method based on a polyols method. Also, the structure,morphology, ingredients as well as the photocatalytic performance andelectrochemical performance are conducted by XRD, TEM, XPS, TG/DTA, PPMS,UV-vis, electrochemical workstation and LAND system.Monodisperse water-soluble ZnFe₂O₄nanoparticles with the particle size of6.3nm and band gap of2.04eV are prepared by heating the mixture of iron（III）acetylacetonate and zinc acetate in triethylene glycol. The ZnFe₂O₄nanoparticlesdisplay photoluminescence and exhibit excellent superparamagnetic properties atroom temperature. Photocatalytic activity studies confirm the as-synthesizedZnFe₂O₄nanoparticles have photoactive property towards the photodegradeation ofmethyl orange in the aqueous solution. The photodecomposition rate of ZnFe₂O₄nanoparticles maintains the highValue for the third time by retrieving the catalystusing the magnet.Monodisperse ZnFe₂O₄nanoparticles with sizes less than10nm have beensuccessfully assembled on multi-walled carbon nanotubes （MWCNTs） by in situhigh-temperature decomposition of the precursor iron（III） acetylacetonate, zincacetate and MWCNTs in polyol solution. It was found that the coverage density onthe MWCNTs could be easily controlled by changing the concentration of theprecursor. A possible formation mechanism was proposed, which suggests that theZnFe₂O₄nanoparticles are formed on the surface of MWCNTs through anaggregation thermochemical reaction process between ZnO and γ-Fe2O3subparticles.Magnetic and optical measurements showed that the MWCNTs/ZnFe₂O₄nanocomposites are superparamagnetic and photoluminescence at room temperatureand the magnetization of the samples can be controlled by the reaction conditions.The as-synthesized MWCNTs/ZnFe₂O₄nanocomposites are water dispersible andcan be manipulated by an external magnetic field.As anode materials for Li-ion batteries, the MWCNTs/ZnFe₂O₄nanocompositesshowed high rate capability and superior cycling stability with a specific capacity of1152mAh/g, which was much higher than that of ZnFe₂O₄nanoparticles （<100mAh/g）. The MWCNTs served as good electron conductors and volumebuffers in improving the lithium performance of MWCNTs/ZnFe₂O₄nanocomposites during the discharge–charge process.