Research On The Design, Synthesis And Application Of New Aggregation-induced Luminescent Materials

In recent years,novel aggregation-induced emission(AIE)materials have been widely used in organic light-emitting diodes(OLEDs),optical devices,fluorescent sensors,biological imaging and disease diagnosis due to their special optical behavior and high solid quantum yield.Therefore,the development of AIE materials with new functions has gradually become one of the research hotspots of researchers.This thesis will focus on the following two aspects to design and synthesis novel aggregation-induced emission materials:(1)Novel organic fluorescent materials are developing rapidly,and 1ore and more researchers are committed to developing new types of fluorescent materials.Compared to the many studies that focus on the development of novel molecular frameworks pertaining to functionalized fluorescent materials,there is lesser emphasis on side chains even though they have a significant impact on the properties and applications of fluorescent materials.In this study,a series of pyridinium-functionalized tetraphenylethene salts(TPEPy-1 to TPEPy-4)possessing different alkyl chains are synthesized,and the influence of chain length on their optical performance and applications is thoroughly investigated.By changing the alkyl chain,the fluorogens exhibit opposite emission behavior(ACQ-AIE)in aqueous media because of their distinct hydrophobic nature.Unlike the emission behavior in aqueous media,all fluorogens emitted intense fluorescence in the solid state and the emission color could be tuned from green to red by simply controlling the length of the alkyl chain.In addition,by increasing the chain length,the microstructure of the self-assembled fluorogens converts from microplates to microrods with various emission colors.Moreover,TPEPy-1 exhibits dual-mode fluorescence "turn-on" response toward NO3-and ClO4-in aqueous media because the anions induce the self-assembly of fluorogens.Furthermore,the fluorogens display cellular uptake selectivity while the proper alkyl chain impels the fluorogens to penetrate the cell membrane and accumulate in the mitochondria with high specificity.(2)The luminescence of solid-state fluorescent materials is affected by the arrangement of molecules usually.The arrangement and accumulation of molecules can be different in one compound,which lead to obvious differences in luminescence.This fancy phenomenon of polymorphism has now attracted wide interests of scientist.In this study,we designed three compounds(2a,2b,2c)based on 2,2-dicyanovinylphenyl backbone and then investigated the effects of substituents on the optical properties and applications of compounds.A series comprehensive research indicated that all the three compounds are typical AIE compounds and possess significant solvent effects.In addition,we found that compound 2a and 2b are both possess the property of polymorphism,in which different packing patterns of crystals in different solvents display optical phenomena differences of the compound.Compound 2a can also self-assemble to form needle-shaped crystallites which held a regular morphology.It is worth noting that 2a-green crystal exhibits specific detection of volatile organic compounds methanol vapor.The most important thing is that the process of detecting volatile organic compounds methanol vapor is cyclically reversible.This unique property makes 2a-green a potential prospect in the field of volatile organic compounds detection.