Design,Synthesis And The Application In Sensors Of Donor-acceptor Molecules With Aniline

In recent years,fluorescence sensors have attracted broad attention because of the advantage of fluorescent visualization and real-time detection without the need of instrument and equipment in the detection process.So it has been widely used in pharmacy,industry,environmental testing and many other fields,nowadays,fluorescence sensors have become a major detection method.But in the detection of the past,the aggregation of the fluorescent molecules which may be caused by self-aggregation or analytes together lead to the fluorescence quenching,greatly limit the application of fluorescent sensor.Fortunately,the discovery of the aggregation induced fluorescence enhancement(AIE)breaks the impasse.Scientists have designed and synthesized a large number of fluorescent molecules with AIE units,from organic fluorescent small molecules,metal complexes,to linear polymers,hyperbranched polymers,although unfortunately,many fluorescent probes with AIE properties have been designed and synthesized.However,the fluorescence sensors still have the problem of low sensitivity.Therefore,how to use the advantage of AIE molecule to design the sensor with high sensitivity is still an urgent problem to be solved.In the first part of the thesis,D-A small molecule(DBPA)has been designed and synthesized with a hybridized local and CT state(HLCT),so that it has both high fluorescence intensity and high sensitivity.Moreover,the existence of the HLCT state is verified by the study of the relationship between the polarity of the solution of the fluorescent molecules and the Stokes shift and the detection of the molecular life.And the reaction of DBPA molecule,in which pyridine serves as recognition site,with different concentration of acid solution was carried out,which realized the conversion of fluorescence intensity and color.Besides,the self-supporting films fabricated by incorporation of DBPA molecules with AIE properties in a SEBS elastomer exhibited highly stretchable and flexible ability,which promoted the real applications of HCl sensing.In contrast to drop-casting membranes(DMs),the sensitivity and the response time of stretchable nanofiber films(SNMs),fabricated by electro-spinning process,were evidently improved as a consequence of its large surface area and high porosity.The detection limit of SNMs reached as low as 0.37 ppm,got very close to the new standard of maximum allowable limit(~0.3 ppm)set.In the second part,TPA-CO fluorescent probe was synthesized with D-A structure,in which carbonyl group serves as recognition site.Based on the principle of fluorescence quenching,when the amount of picric acid is increasing,the color of the solution changes from colorless to yellow,and the fluorescence color is quenched from bright blue to colorless.The phenomenon is due to the protonation of the carbonyl group of the molecule with picric acid,which consumes the energy of the fluorescence molecule and quenches the fluorescence,so that the rapid and sensitive detection of picric acid can be achieved.Moreover,when the probe of TPA-CO contact with PA in the presence of water,instead of fluorescent quenching,it displayed superior sensitivity and the limit of detection was calculated of 2×10~-55 mol/L.It has greatly promoted the detection in the actual environment and greatly improved the value of its wide application in real life.In the last part,we design and synthesize a small molecule oMe-TPA,with high fluorescence intensity and mechanical chromic property,and analyzed by fluorescence spectrum,ultraviolet absorption spectrum,Raman spectrum,infrared spectrum and lifetime test.In addition,basing on the molecular properties of AIE,the electrospinning film prepared by incorporating oMe-TPA into the polymeric host(PVA),revealed self-supporting ability as well as piezochromic behaivor.Further,by comparing the mechanochromic properties of the films prepared with different doping ratios with the crystals,it can be concluded that the change of color and fluorescence intensity of oMe-TPA is mainly due to the enhancement of the interaction between molecules rather than the conformational changes,this discovery is of great significance to the understanding of the piezochromic luminescent properties.What's more the film prepared by electrospinning has realized the materialization of the electrochromic molecule and laid the foundation for its later application.