Synthesis, Photophysical Properties And Sensing Applications Of Nonplanar Perylene Monoimide Derivatives

In the past 100 years,people's unremitting research on the phenomenon of fluorescence and its essence,as well as the rapid development of science and technology and the joint efforts of multiple disciplines,the fluorescence technology has been greatly popularized.Among them,fluorescence sensors,especially film-based fluorescence sensors,have attracted much attention due to their strong designability,high sensitivity,rich output signals,simple operation,easy miniaturization and devocalization.Prof.Fang's research group has focused on thin film-based fluorescent sensors for more than 20 years,including the design and preparation of new fluorescent compounds with various photophysical properties,the innovative development of sensitive thin-film preparation strategies,and the development of related portable devices.Group has achieved some outstanding results in hidden explosives detection,multi-drug detection and early disease detection.Fluorescent molecules play a key role in the sensitive film of the film-based fluorescence sensor,because their chemical and physical nature largely determines the performance of the fluorescent film.Compared to other fluorescent molecules like pyrene,perylene monoimide(PMI)derivatives,as a member of the large family of perylene dyes,have the merits of strong designability,high molar extinction coefficient,and good photoelectric properties.Taking advantages of the good photochemical stability and high fluorescence quantum yield of PMI derivatives,it is expected to develop new PMI derivatives as high-performance fluorescent film materials.Based on the work about fluorescent sensors in our laboratory and other research groups,we designed and prepared several new PMI derivatives,and studied their photophysical properties,as well as their sensing performance.The main content of this dissertation includes the following three parts:The first chapter includes three parts:(1)introduction of the existence and toxicity of BTEX(i.e.,benzene,toluene,ethylbenzene,xylene)in air,and BTEX detection methods;(2)the overview of the film-based fluorescence sensors,such as the common structure of a sensor,the fluorescence sensing principle,and the current research progress;(3)chemical structures and modification strategy of PMI derivatives.The second chapter focuses on the design and synthesis of new PMI derivatives.To our knowledge,nonplanar structure can hinder ?-? stacking,and further improve the fluorescence intensity of the PMI derivatives in solid state.Therefore,a new nonplanar PMI-CB was synthesized through incorporating a three-dimensional o-carborane with the PMIA.To illustrate the role of nonplanar structure in reducing intermolecular aggregation,a series of planar PMI derivatives were synthesized as reference as they possess the same fluorescent unit.All the PMI derivatives in this work show good solubility in common organic solvents,and show a typical solvatochromic property.Particularly,the PMI-CB shows the highest fluorescence intensity,which lay the foundation for sensing applications.The third chapter focuses on the photophysical property and sensing performance of the as-synthesized PMIA and PMI-CB in film state.The PMIA and PMI-CB films were prepared using the drop coating method,and a home-made sensing platform was built.The photochemical stability test showed both PMIA and PMI-CB films have good stability with only 1%decrease in fluorescence intensity under continuous light irradiation(?ex=470 nm)for 3 hours.For gas sensing test,the PMI-CB film exhibits relatively high response than the PMIA film,which can be ascribed to the nonplanar structure that hinder ?-? stacking,as well as form microporous structure during the formation of the PMI-CB film.The PMI-CB film shows fluorescence enhancements for BTX,while fluorescence quenching for other interfering compounds,endowing the PMI-CB-based sensor with the ability for selection detection of BTX.The sensitivity test shows the PMI-CB film can detect benzene vapor at a concentration of as low as 1 ppm without any preconcentration procedures,and exhibits a good linear relationship.We also examined the response behavior of the PMI-CB film to mixture solvent vapors of benzene and ethanol with different volume ratios.The PMI-CB film can detect benzene even at high ethanol volume percentage of 95%without and preconcentration and separation.On the basis of these results,a portable detector with high selectivity,sensitivity,reusability,and low power consumption can be adapted for the on-site BTX detection.