Design, Preparation, Photophysics, And Sensing Behavior Of Novel Squaraine And Oligothiophene Derivatives

Volatile organic compounds(VOCs)are easy to volatilize into the air at room temperature.VOCs are a kind of important environmental pollutants.Their toxicity,carcinogenicity and irritation can damage human health.In recent years,people generally improve the awareness of indoor environmental protection,strengthen the detection and monitoring of indoor environmental pollutants.Aldehydes,hydrazine and organic amines are important raw materials for chemical production,and they are also important environmental pollutants.Specifically,common aldehydes such as formaldehyde and acetaldehyde are toxic.In the process of beer fermentation,a variety of aldehydes,such as acetaldehyde,are produced.Excessive acetaldehyde will affect the flavor of beer.In addition,hydrazine and some organic amines can cause serious damage to spleen,respiratory tract and thyroid.Therefore,it is of great significance to establish an intuitive,real-time,online and reliable method for the detection of VOCs.At present,there are many methods to detect various kinds of VOCs in the laboratory.These methods mainly include electrochemical method,spectrophotometry and chromatography.However,these methods have the problems of expensive instruments,long time consuming or low sensitivity,which are difficult to popularize.The fluorescence method has the advantages of high sensitivity,good reversibility and strong designability of fluorescent species.From the perspective of sensor core technology and sensor design,it is of great significance to design and develop a conjugated fluorescent compound with excellent comprehensive performance.Among the many developed conjugated fluorescent compounds,squaraines have unique push-pull electron and quaternary nuclear conjugated structures.In many researchs,squaraines as recognition groups have been used to detect amino acids,proteins and metal ions selectively.Literature research shows that there are few reports on the selective detection of aldehydes by squaraines.Oligothiophene derivatives with novel conjugated structure and unique photoelectric activity can be used as fluorescent groups in the design of fluorescent chemical sensors.Many metal cations and anions can be detected by detecting the change of fluorescence characteristics of oligothiophene derivatives.However,there are few reports about the detection of hydrazine and organic amine and other VOCs by oligothiophene derivatives.In addition,it should be noted that the sensor array has the characteristics of interactive response and broad-spectrum response,which is composed of multiple sensor units.Sensor array can not only accurately identify single substance,but also identify mixed samples.For many years,our group has been committed to the innovative preparation of fluorescent sensing thin films,array assembly of thin film devices and other related research work,and has developed a variety of fluorescent sensing thin film materials.Based on the above research status and the research foundation of fluorescent chemical sensors in our laboratory in recent years,this thesis mainly includes the following three sections.In the first section,the composition and sensing mechanism of chemical sensors are briefly introduced.Then,the structural characteristics of colorimetric chemical sensors,especially the combination of squaraines and oligothiophene derivatives,are briefly introduced.The reported fluorescent chemical sensors based on these two kinds of compounds are reviewed.Finally,the research significance and design ideas of this paper are described.In the second section,two water-soluble squaraines,SQOH and SQPY,were designed and synthesized.When existing a certain amount of hydrazine hydrate,the color of squaraines solution changes from blue to colorless.Then,after adding aldehydes to the squaraine-hydrazine adduct,the solution color returned back to blue quickly.The results show that the two kinds of squaraine-hydrazine adducts can be sensitive and rapid to sensing aldehydes.Through analyzing the reaction characteristics,we have experienced the whole "On-Off-On" sensing process.A new sensing mechanism for the detection of aldehydes was proposed,which provides a simple,sensitive and convenient method for the rapid and intuitive detection of aldehydes.The sensing strategy is of great significance for developing a new and sensitive detection system for formaldehyde.In the third section,we designed and synthesized a series of dicyanoethylene functionalized oligothiophene derivatives with push-pull electronic structure.The effects of different capping groups on their photophysical properties were systematically studied,and the relationships between photophysical properties and structure were investigated.Taking one of the compounds NA-3T-CN as an example,the differential detection of hydrazine hydrate,aliphatic amine and aniline by NA-3T-CN was investigated.The results show that NA-3T-CN has sensitive response to hydrazine hydrate,methylamine and ethanolamine,but aniline has no obvious chemical reaction with compound NA-3T-CN,which provides an experimental basis for distinguishing hydrazine hydrate,fatty amine and aniline.At the same time,another kind of zinc porphyrin derivative Zn-TPP was introduced to construct a kind of sensor array based on the color change of hydrazine hydrate,aliphatic amine and aniline.The smart phone camera is used to collect the color information of the sensor array before and after the reaction,and the color information is converted into RGB value by the color processing application.Using the array,the output signals of a series of analysis objects are different,and the detection of hydrazine and aliphatic amine is realized.This method has the advantages of sensitivity,on-line and real-time detection.It has broad potential application value in the field of real-time and visual detection of hazardous chemicals.