Solution Synthesis And Property Studies On Tungsten Oxide Hydrate Mciro/Nano-materials

Nanomaterials have unique chemical, physical and optical properties thatare neither those of bulk materials nor those of molecular compounds. Sothey have attracted much attention from people due to their extensivel yapplicable prospects. With the alternation of shape and dimensions,nanomaterials have gone great changes in physical、 chemical and opticalproperties. So, more efforts have been devoted to the synthesis of onedimensional （1D） nanowires, nanotubes, nanorods and two dimensional （2D）nanoplates, nanodiscs and three dimensional （3D） nanospheres so forth.Now, integrating nanorod/nanowire/nanoplate as building blocks into3Dhierarchical superstructures has been successfully performed. These novelassembled structures offer opportunities for discovering exciting newproperties of materials, and are useful for fabricating complex nanodevices.As important wide gap semiconductors, tungsten oxides and tungstenoxide hydrate have many outstanding properties. They have variedapplications in many areas, especially in photocatalysts, smart windows,gas sensors and lithium battery. Base on major factors impacting materialsnature are their shapes and structures. Hence, it is vital for studying onsynthesis and structure of WO₃nanomaterials. We report a novel synthesisof WO₃·H₂O nanocrystals under relative mild conditions to synthesizeurchin-like hollow spheres, nanoplates and nanoflowers. We systematicallyexamined the reaction parameters on the evolvement of WO₃·H₂Onanomaterials in aqueous phase, and the products will be used forphotocatalysis and reversible color change applications. It was found thathollow spheres extended good photocatalytic property, nanoplates extendedgood photochromism performance, while nanoflowers have good adsorptionperformance. This thesis contains three parts:First, we report a simple approach via a self-sacrifice template methodto synthesize3D WO₃·H₂O hollow spheres with diameters of severalmicrons at low temperature. In this work, Ca WO4was used as the precursor,which was a key factor for getting hollow sphere samples.Temperature, acidamount have prominent influences on the evolution of WO₃·H₂O hollow spheres. In addition, we found that the3D nanoarchitectures could be usedto adsorb and degrade environmental waste of organic contaminants underacidic conditions. The results showed that hollow sphere samples extendedpreferable photocatalytic property to walnut-like samples.Second, we synthesized WO₃·H₂O nanoplates via a solution-phaseapproach with only hydrochloric acid and sodium tungstate as reactants bychanging the reaction parameter, do not add any organic matter, and foundthat extend the good performance of reversible photochromism to UVlight（20W）.Third, we synthesized WO₃·H₂O nanoflowers self-assembled structurewith help of ethylene glycol, and studied the influences of temperature,time, and amount of additive on the final samples. We studied on theadsorption of methylene blue adsorption, found that the adsorptionperformance was very good.