Synthesis, Characterization And Applications Of Zn₂SnO₄Nanocrystals And Related Nanocomposites

Zn2SnO4, with inverse spinel structure, is a very important material with highelectron mobility, high electrical conductivity and low visible absorption, whichmakes it suitable for a wide range of applications in advanced technologies, such asphotovoltaic devices, chemical sensors for humidity, combustible gases and thetransparent conductive electrode. Zn2SnO4, as a material for anode material inphotoelectron chemical cells and lithium-ion batteries, as a photocatalyst todecompose organic wastes in water solution, and as an working electrode for dyesensitized solar cells (DSSC), has drawn great attention recently. These potentialapplications drove people to find simple ways to synthesis this important material.During the past few years, Zn2SnO4has been successfully synthesized via variousmethods, such as thermal evaporation, high-temperature calcinations, sol-gel approach,and ball-milling etc. Nevertheless, these synthesis processes usually involvecomplicated controlling process, which limits its applications. It has been proved thatthe solution-based hydrothermal synthesis is a facile and mild way to produce thismaterial in a large scale to overcome the drawbacks.Single nanocrystals with well-defined shapes and crystal planes have receivedincreasing interest due to their importance in various applications. For example, thephotocatalytic ability of a nanocrystal depends on the exposed crystal planes, whichcan be tuned by the shape of the synthesized nanocrystals. Hence, the design of thecrystal shape is a key factor for developing new materials with high performance orunique characters.The gas-sensing ability of metal oxide semiconductors greatly depends on thecrystal faces of the sensing materials. From the viewpoint of chemical activity,metaloxide nanocrystals with particular exposed crystal planes may be good sensingmaterials, since there are high densities of atom points exist. And it is also feasible toimprove the gas-sensing properties of sensors through surface-engineering strategy,that is selectively exposing high-energy facets on the surface of sensing materials.In this dissertation, we present a simple hydrothermal route for synthesizing of14-faceted polyhedra, truncated octahedral, cubic and amorphism Zn2SnO4particleswith particular exposed faces, and dope SnO2in zinc stannate to improving its gas sensing to ethanol.In chapter II, the truncated octahedral,14-faceted polyhedra and cubic Zn2SnO4were synthesized via hydrothermal method. The results of photodecomposition ofmethyl orange showed that: the amorphism little particle of Zn2SnO4had theadvantage of a fast degradation rate while the14-faceted polyhedra zinc stannatepresented the longest decomposing time. The gas sensing properties of the four zincstannates were investigated in this chapter. It could be found that the14-facetedpolyhedra Zn2SnO4presented higher selectivity and sensitivity to ethanol, acetone and1-butanamine.In chapter III, monodispersed ZnSn(OH)6nanocubes was synthesized by ahydrothermal approach, and taken as precursors to produce heterogeneity compositeproducts Zn2SnO4-SnO2through the thermal decomposition of calcination. TheZn2SnO4-SnO2nanocomposites were also been fabricated into thin film type sensorsto investigated their gas sensing properties to ethanol. The results show that thesensitivity and reversibility to ethanol vapor were greatly improved.