Construction And Properties Of Thermochromic Fluorescent Materials

Organic luminescent materials can be used in various fields such as organic lightemitting diode(OLED),biological imaging,sensing,and anti-counterfeiting.However,most organic luminescent materials either suffer from aggregation-caused quenching(ACQ)or aggregation-induced emission(AIE),making it difficult to achieve dualemission characteristics.At the same time,most solid-stated luminescent molecules cannot possess temperature-responsive properties due to their strong intermolecular forces,which prevent these molecules from changing conformation or existential state.Therefore,it is necessary to find suitable carriers enabling molecules to undergo their existential state changes even in the solid state.In recent years,phase-change materials have been utilized to manipulate the existential states and luminescent properties of luminescent molecules due to their flexible ability of phase transitions at different temperatures.This paper focuses on doping fluorescent and delayed fluorescent molecules into phase-change materials,enabling the regulation of their luminescent properties by thermal stimulation.And these novel luminescent systems can be used in anti-counterfeiting and temperature sensing.In Chapter 2,a kind of D-π-A type delayed fluorescence molecules(TPABN,TPABNC,and TPABS)were synthesized by combining triphenyl amine with benzoheterocyclic ring.Their solution-stated photophysical tests showed the presence of intramolecular charge transfer between these molecules.In addition,the photophysical properties tests of these molecules in solid state demonstrated hey all possessed a bright blue delayed fluorescence with long lifetime when excited at 365 nm.And these compounds both exhibited bright emission in solution and solid state.Then,these molecules were co-doped with phase change material lauric acid.At room temperature,these doped systems exhibited blue luminescence.However,as the temperature gradually increased,the luminescence of these doped systems changed from blue to white,confirming their temperature-responsive characteristic.In conclusion,a class of doped systems with two-stated delayed fluorescence and temperature-responsive properties was successfully obtained through reasonable structural design.In Chapter 3,according to our previous work,a D-A-π type molecule MEPPA was synthesized with benzyloxy(BO),cyanostilbene(CS),and diphenyl-diacetylene(DPDA)structures as the donor part,acceptor part,and π unit,respectively,which showed strong monomer and excimer emission characteristics.Based on this,a temperature responsive fluorescence system(MEPPA@LA)was constructed by doping MEPPA into the thermal-responsive matrix lauric acid(LA).In addition,a new doped system MEPPA-RB@LA was developed by doping Rhodamine B dye into MEPPA@LA,achieving multi-color fluorescence emission through the combined emission of MEPPA and Rhodamine B.At the same time,this system exhibited wide prospects in temperature monitoring and advanced information encryption.This research sheds new light on designing more advanced multipurpose luminescent materials.