Study On The Photochromic Performance And Detection Of Amine Gases Based On Viologen/polyoxometalates Crystalline Materials

With the development of science and technology and the demand of industrial production,a large number of organic amines have been widely used in the chemical industry,but they are only second to the odorous pollutants of organic sulfide.Therefore,the detection of organic amines harmful to human health and ecological environment has gradually become the research focus of scientists.As cations,electron-deficient viologen compounds can be combined with electron-rich polyoxometrates（POMs）to obtain crystalline color-changing materials.So far,viologen/polyoxometalates organic-inorganic hybrid crystalline materials are mainly studied in the field of photochromism,and there are few reports on multifunctional intelligent crystalline materials with amine gas response.In addition,it has only preliminarily explored the recognition of small molecules of amine gases,but has not realized the low concentration sensitive detection of corresponding amine gases.Therefore,in this paper,classical Keggin type or Dawson type polyoxometalates are used as inorganic basic raw materials,and viologen compounds with different substituents are used as organic raw materials.By solvothermal synthesis method,crystalline composite materials are synthesized through the self-assembly reaction of polyoxometalates and viologen compounds.The application of these composites in the field of photochromic and low concentration detection of small molecules of amine gases is studied.The specific work is as follows:Single instead of the viologen one,this article will carboxyethyl essence and more than two kinds of classic configuration acid respectively:Keggin type of twelve tungstophosphoric acid H₃[PW₁₂O₄₀]·10H₂O and Dawson,eighteen tungstophosphoric acid K₆P₂W₁₈O₆₂·14H₂O,using solvent thermal to self-assembly synthesis two crystalline materials:Carboxyethyl monosubstituted viologen/polyoxometrate phosphate and carboxyethyl monosubstituted purpurine/octadungtungsten phosphate.By means of UV-visible diffusing reflection and Raman test,it is found that after 20 min of xenon lamp irradiation,carboxyethyl mono-substituted viologen/polyoxometrate phosphate changes from white to light gray,and the UV absorbance reaches 0.2,while carboxyethyl mono-substituted viologen/polyoxometrate phosphate gradually deepens from white to gray blue,and the absorbance increases to about0.3.Moreover,carboxyethyl-mono-substituted viologen/polyoxometrate phosphate can be used to detect small amine gas molecules.Raman test can be used to detect low concentrations of ethylenediamine,1,3-propylenediamine and 1,5-pentenediamine vapor at low concentrations of10^-6 g/L under the condition of avoiding light.It is of great significance for the accurate detection and identification of toxic amines,and also broadens the application and development of polyoxometalates/viologen hybrid materials.Second,through to replace carboxyethyl single viologen essence further modified into carboxyethyl double instead of viologen,its respectively and Keggin twelve tungstophosphoric acid H₃[PW₁₂O₄₀]·10H₂O and Dawson,eighteen tungstophosphoric acid K₆P₂W₁₈O₆₂·14H₂O,solvent by dicating self-assembly preparation into two crystalline materials:Carboxyethyl-di-substituted viologen/polyoxometrate phosphate and carboxyethyl-di-substituted viologen/polyoxometrate phosphate.Due to the further modification into bilateral substitution,the structure of the compound is more symmetrical,and its photochromic and amine gas response properties are improved compared with carboxyethyl-mono-substituted purpurine/polyoxometalates.By means of UV-visible diffuse reflection and Raman test,it is found that after 20 min of xenon lamp irradiation,carboxyethyl-di-substituted viologen/polyoxometrate phosphate changes from white to dark gray,the ultraviologen absorbance reaches 0.25,and carboxyethyl-di-substituted viologen/polyoxometrate phosphate changes from white to dark gray blue,the absorbance increases to about 0.35.Moreover,carboxyethyl-di-substituted viologen/polyoxometrate phosphate can be used to detect small molecules of amine gases.In the condition of avoiding light,the Raman test can be used to detect ethylene diamine,1,3-malonediamine and 1,5-pentenediamine vapor with low concentration of 10^-7 g/L,so that the detection concentration is lower and more sensitive.Three,this article through to replace carboxyl groups viologen with ammonia propyl double instead of viologen,its respectively and Keggin twelve tungstophosphoric acid H₃[PW₁₂O₄₀]·10H₂O and Dawson,eighteen tungstophosphoric acid K₆P₂W₁₈O₆₂·14H₂O,solvent by dicating self-assembly,A new type of purpurine/polyoxometalates gas chromic crystalline materials:aminopropyl disubstitute viologen/polyoxometrate phosphate and aminopropyl disubstitute viologen/polyoxometrate phosphate were developed.Aminopropyl disubstitute viologen/octadectungstic phosphate has excellent photochromic properties,which can be used as ink-free and erasable printing materials,and has ethylenediamine gas specific detection performance.When ethylenediamine gas molecules react with composite materials,they can first reduce viologen extract,and polyoxometalates further obtain viologen extract electrons.With the reduction of polyoxometalates,the changes caused by the vibration of W-O bond of Raman signal can also indicate the concentration of ethylenediamine gas,realizing highly sensitive and non-destructive Raman detection.Polyoxometalates can also be used as signal molecules in the system to indicate the concentration changes of gas molecules,which has great potential to realize sensitive,simple and nondestructive portable gas sensor for detecting low concentration ethylenediamine.The detection limit can reach 0.1 ppb,which is the lowest detection limit for ethylenediamine gas reported so far.This work provides a new concept for the design of highly sensitive,dual-response,multifunctional viologen/polyoxometalates based crystalline composites using viologen to promote electron transfer,and extends great development potential for the development of selective toxic small molecule aerochromic and Raman sensors..