Research On Functional Organic Solid Fluorescent Materials Based On Coumarin

Solid-state fluorescent materials have attracted a surge of interests in recent years due to their wide applications in the field of photoelectric devices,memory storages and fluorescent sensor.Coumarin,as one of the most representative organic fluorescent compounds,has been widely used in functional materials because of its unique photophysical properties,such as reasonable stability and relative ease of synthesis.However,in comparison with abundant reports about the photoluminescent researches of coumarins in solution,the investigation of fluorescent properties as well as potential utilization in the solid state is still rare.In this thesis,a series of coumarin derivatives were synthesized.And especially,we explored the solid state photoluminescence properties and applications of 7-(diethylamino)coumarin-3-aldehyde(DCA)and 7-(diethylamino)coumarin-3-carboxylic acid(DCCA)systematically.(1)Both phosphors DCA,DCCA displayed special concentration-dependent emission behaviour and solvatochromic effect.Importantly,two types of crystal with varied emission color for DCA and DCCA were obtained respectively.Subsequent single crystal analysis revealed the origin of this polymorphism phenomenon.On this basis,their stimuli response was studied.Under the influence of external pressure,both DCA and DCCA have piezochromic properties.Upon thermal treatment,the crystal-to-crystal irreversible transformations were achieved for both fluorophores,which enabled them a potential application in fabrication of thermographic recording materials.(2)The solid powder of DCA and DCCA displayed fluorescent response to HCl and NH3 gas with high sensitivity.The powder of DCA emitted intense orange emission at 560 nm.However,upon exposing to HCl gas for?2 minutes,the fluorescence was completely quenched.After fumed with NH3 gas for a few minutes,the sample gave a red emission color and the emission peak appeared at 600 nm,which red-shifted about 50 nm than the initial sample of DCA.This "off-on" emission switch could be repeated by fuming HCl-NH3 gas.In sharp contrast,different phenomenon was found for DCCA at the same conditions.When DCCA powder was fumed with HCl gas,the emission color was converted from orange to blue,and the emission peak shifted from 570 nm to 420 nm.Subsequently,treated the sample with NH3 gas brought a green emission peaked at 500 nm.The emission color between blue and green could be repeated by using HCl-NH3 gas.Above results declared that DCA and DCCA were able to employ as fluorescent sensor for HCl and NH3 gas with high sensitivity.(3)In addition,by systematic screening assembly methods of DCA and DCCA,it was found that DCA and DCCA were dissolved in tetrahydrofuran,then added to deionized water,ultrasonic,rest,flocculent was produced,filtered,1D micromaterials with good thermal stability,optical transmittance and low optical loss were obtained,are ideal materials for optical waveguide devices.