Preparation And Properties Of Films Based On Tungstophosphate And Dyes

Electrochromism has attracted extensive research interest due to the highly reversible and durable optical property.Developing cost-effective strategy to fabricate electrochromic materials with fast switching speed and long cycle life is significant for the next generation high performance electrochromic materials.Polyoxometalates?POMs?represent a well-known class of metal oxide nanoclusters.POMs are promising candidates due to their diverse structures and good reversible redox activity.Classic POMs can achieve colorless to blue reversible changes,the electrochromic performance of materials can be improved by incorporating dye into POMs-based materials.In this paper,we focus on the preparation of POMs/dye materials by Layer-by-Layer method?LbL?.The composite films were characterized by UV-vis spectroscopy,infrared spectroscopy?IR?,scanning electron microscopy?SEM?and cyclic voltammetry?CV?,and the electrochromic properties of composite films were studied by electrochemical test.The specific work is as follows:Three kinds of Dawson-type phosphotungstate K₁₀[P₂W₁₇O₆₁]·20H₂O(P₂W₁₇),vanadium substituted Dawson-type phosphotungstate?-K_6+n[P₂W_18-nV_nO₆₂]·18H₂O(P₂W_18-nV_n,n=1,2,3),Preyssler phosphotungstate K_12.5Na_1.5[NaP₅W₃₀O₁₁₀]·15H₂O(P₅W₃₀)and dye congo red?CR?and color-adjustable[Fe(C₁₂H₈N₂)₃]Cl₂·7H₂O?Fe?phen?₃?The following composite membranes are constructed:1.[PEI/P₂W₁₇/PEI/CR]₂₀0 and[PEI/P₂W₁₇]₂₀;2.[PEI/P₂W₁₇V/PEI/CR]₂₀,[PEI/P₂W₁₆V₂/PEI/CR]₂₀and[PEI/P₂W₁₅V₃/PEI/CR]₂₀;3.[P₅W₃₀/PAH-Fe?phen?₃]₂₀0 and[P₅W₃₀/Fe?phen?₃]₂;The transition from red to light purple to dark purple was realized through congo red doped composite film 1.In order to further improve the electrochromic properties,vanadium substituted Dawson type phosphotungstate with color was selected to prepare the composite film 2,in which the electrochromic performance of the composite film[PEI/P₂W₁₇V/PEI/CR]₂₀0 was the best,which not only realized the reversible change of color,but also increased the light contrast by 71.1%and 56.7%,respectively,compared with the composite film[PEI/P₂W₁₆V₂/PEI/CR]₂₀0 and[PEI/P₂W₁₅V₃/PEI/CR]₂₀,The coloring efficiency increased by 27.8%and 19.4%respectively;In order to improve the cycle life of the composite film,polyelectrolyte polymerization was introduced to prepare the composite film 3.The light contrast loss rate of the composite film before and after polyelectrolyte PAH coating was 63.23%and 16.12%,respectively.The coating of polyelectrolyte PAH increased the cycle life of the composite film and enriched the types of electrochromic materials.In summary,in this paper,based on the synergistic effect of phosphotungstate and dyes,this paper separately prepared three types of phosphotungstate/dye composite electrochromic materials.This work can be Provide a reference for development.