Simple Solution-systhesis And Photochromic Properties Of Metastable Hexagonal Tungsten Oxide

Among numerous photocatalytic materials,nanostructured WO₃ is considered to be a promising photocatalytic material because of good stability,short response time,good reversibility and low cost.And it is of great significance to synthesize WO₃ with specific morphology and well-controlled sizes to develop its potential application.Therefore,it's very important to make clear that the influences of different factors on the crystal structure and morphology of WO₃.In this paper,h-WO₃ was synthesized via a facile aqueous method with the assist of the monovalent cations in sulfate,or small simple organic molecule,and we investigated the influences of these additives on morphology and photochromic properties of the final products.The specific research work is given as follows:1.Here we report a facile aqueous method to the synthesis of urchin-like hexagonal tungsten oxides?h-WO₃?in the presence of sulfates at 90 ?.And we choose K₂SO₄,Na₂SO₄ and?NH₄?₂SO₄ as model sulfates in the study.The as-prepared architectures were constructed by elementary nanowire units,and the unit sizes changed with the variety of sulfates.The results show that cation intercalation has a great impact on the formation of h-WO₃ nanowires.We did photochromic examination on the h-WO₃ architectures.The results showed that the introduction of sulfates in the samples increased their optical absorptions in visible-light,but the increased electrochemical impedance means the decrease of charge transfer efficiency at the interfaces of semiconductor.As a result,the designing h-WO₃ architectures with good photochromic property should consider the two facets of influences.2.In this work,we report on the formation of h-WO₃ ordered near-spherical nanostructures via a facile glycine-assisted aqueous approach between Na₂WO₄�2H₂O and glycine acid?HOOC-CH₂-NH₂?in HCl solution.By adjusting the amount of hydrochloric acid,the amount of glycine acid in the solution,the addition way of acid and the reaction time,we successed synthesising h-WO₃ when the ratio of WO₄^2-/H⁺was 1:4.5?1:5.And glycine acid is a crucial factor for the synthesis of h-WO₃ architectures.Glycine acid in the reaction system facilitates the appearance of metastable phase h-WO₃ nuclei through electrostatic interaction between protonated-NH³⁺ and tungstate anion.In addition,we did photochromic examination of the as-synthesized h-WO₃.The results showed that h-WO₃ samples extended preferable photochromic performances.3.Herein,we report a facile aqueous method to the synthesis of pure hexagonal tungsten oxides?h-WO₃?with the assist of urea at 90 ?.By adjusting the amount of urea,the concentration of hydrochloric acid,and the time of urea hydrolysis,we successed synthesising h-WO₃.Upon increasing the amounts of urea,we observed not only a decrease in the dimensions of h-WO₃ nanostructures,but also a red shift in absorption.What's more,h-WO₃ is a potential material used as electrochemical DA sensor.