Synthesis Of Oxide Semiconductor Nanocomposites With Oxygen Vacancies For Constructing Photochromic Fabrics

Photoreversible color switching systems?PCSSs?have attracted the increasing attention in various applications,because they can change the color under the irradiations of light.Light as stimulus is favorable due to noninvasiveness,remote control,easy control of intensity and wavelength as compared to other stimuli.However,in most PCSSs,the discoloration process usually relies on harmful UV light as stimulus source,and the recoloration requires high temperature.To solve these problems,we have developed three kinds of oxide semiconductor nanocomposites with oxygen vacancies,including CeO_2-x,Ag/CeO_2-x and Cu2O/TiO_2-x.They have the broadened absorption band and narrowed bandgap.These nanocomposites have been used to construct smart fabric,and the fabrics exhibit color switching features under different light irradiation.The main results are listed as follow:?1?CeO_2-x nanodots for constructing photochromic smart fabrics.CeO2 have been developed as photocatalysts and oxygen sensors,but their wide band gap?3.2 eV?limits the photoresponse only in UV region.Herein,we have designed and prepared CeO_2-x nanodots with oxygen vacancies as novel photocatalytic components in PCSS that responds two kinds of visible light CeO_2-x nanodots are prepared by solvothermal route with L-ascorbic acid as the reducing agent.CeO_2-x nanodots with size of?2 nm have high concentration of oxygen vacancies,which confers a narrowed bandgap?2.38 eV?,broadened photoabsorption edge at?500 nm as well as weak tail at 500-800 nm.To realize the color switching,both CeO_2-x/Dye/H2O solution and CeO_2-x/Dye/HEC-coated fabric have been prepared.Under blue?450 nm?light irradiation,both solution and fabric show a rapid discoloration in 30 s and 150 s,respectively,because of the effective photocatalytic reduction of the MB by CeO_2-x.Conversely,red?630 nm?light irradiation with air conters the rapia recoforation in 35 s for solution and 200 s for fabric,resulting from CeO_2-x-mediated self-catalyzed oxidation.In particular,the desired designs and letters could be printed remotely on CeO_2-x/Dye/HEC-coated T-shirts.?2?Ag-decorated CeO_2-x nanospheres for photochromic smart fabricsCeO_2-x nanodots have weak absorption tail at 500-800 nm.To enhance the visible to NIR photoabsorption,herein we designed and prepared Ag/CeO_2-x nanospheres sample by hydrothermal route with ethylenediamine tetraacetic acid?ETDA?and NaOH as reducing agents.The sample is composed of CeO_2-x nano spheres with size of?200 nm,which are decorated by Ag nanoparticles,as well as it has enhanced photoabsorption in visible to NIR light.Ag/CeO_2-x nanospheres are mixed with dye to prepare PCSS solution and films.Under visible?450 nm?light irradiation,both the PCSS solution and film showed discoloration of dye?MB?in?40 s and 200 s,respectively,due to efficient photocatalytic reduction of redox dye by Ag/CeO_2-x nanospheres.On the other hand,NIR light irradiation with air confers the rapid recoloration of dye?MB?in?45 s for solution and 250 s for film,resulting from the efficient oxidation by O2 at high temperature from photothermal effect of Ag/CeO_2-x nanospheres.Especially,the desired designs and letters can be printed remotely on Ag/CeO_2-x/dye/HEC-coated films by visible light laser pen,and afterwards removed by NIR light with good reversibility.?3?Cu2O/TiO_2-x nanosheets for constructing photochromic smart fabrics.TiO_2-x has been prepared previously for color switching in fabrics,but it still relies on UV light because of wide band gap?3.17 eV?.To address this problem,we have developed Cu2O/TiO_2-x nanosheets by a modified solvothermal method with TiF4,TiCl3 and CuSO4 as precursors.The sample consists of Cu2O nanosheets with length??150 nm?and width??50 nm?,which are surrounded by TiO_2-x nanoparticles,Cu2O/TiO_2-x sample has the enhanced photoabsorption from visible to NIR?400-1200 nm?region.To analyze the color switching,both Cu2O/TiO_2-x/Dye/H2O solution as well as,Cu2O/TiO_2-x/Dye/HEC-coated films have been prepared.Under visible light irradiation,both solution and film show a rapid discoloration in?21 s and?180 s respectively.On the other hand,NIR light irradiation with air confers the rapid recoloration in?20 s and 160 s respectively Specially,the desired designs and letters could be printed remotely on smart PCSS ink coated films by visible light laser pen and later on,erased by using NIR light,having efficient stability and reversibility...