| The development of a “green” design and preparation of organic long persistent luminescence(LPL)materials is a highly challenging yet promising direction for the research and development of efficient organic luminescence.The recent investigation suggested that the host-guest doped design with donor-acceptor(D-A)structure may significantly improve the LPL performance(afterglow time and brightness).In this thesis,a series of novel fluorene-based guest-doped organic LPL crystals with D-A structure are designed and prepared.This is to obtain excellent LPL properties induced by the longlived charge separated states in water and air and rich application prospects.The structureperformance relationship between the molecular structure of the compound,the configuration of the D-A doped crystal,the LPL performance and the relative photophysical process are elucidated.The potential application of such materials in biomedical sensing and anti-counterfeiting were explored.1)Organic long-persistent luminescent materials can be easily quenched in aqueous solutions or air;which limits their wide applications.Here we report five novel doped organic crystals to overcome this challenge,wherein five fluorenyl molecules are modified with different lengths of alkyl chains at the 7 and 9-positions as the guest and small-molecule diphenylamine and methyl diphenylamine as the host.The stable LPL performance of this series of crystalline material is visible for over 8 s and can be maintained for at least one year even in aqueous solution or in air.2)Three crystalline materials are prepared by a convenient host-guest doping method at room temperature under ambient surrounding,i.e.,in the presence of oxygen.Two kinds of crystals with long-lived charge separated states exhibit visible LPL emission over 8 s and 6 s,respectively.The persistent room-temperature phosphorescence effect caused by different generation efficiency of charge separated states is the main reason for the difference of LPL duration time.The crystal without charge separation has no LPL phenomenon because it is not a donor-acceptor system.Therefore,this work indicates that the generation of charge-separated states and their generation efficiency are two key factors affecting the LPL properties and it provides a new understanding of the design of organic LPL materials.3)The doped crystals mixed with polyvinylpyrrolidone(PVP)are used to prepare a waterbased paste.Based on this,a two-dimensional code is printed to show the potential application of host-guest doped crystal material with LPL property in the field of security and information encryption.On the other hand,the doped organic material has been tested for quantification of DNA.Doped material reacted with DNA to lose its LPL phenomenon and the loss in OLPL is directly corresponding to the amount of DNA in sample.This turn-off analysis and detection technology provides a new design idea for the field of DNA detection.The successful implementation of the thesis is expected to develop a "green" preparation of the new functional crystal system,which will shine new light on the design of high-performance organic luminescence models and the exploration of high-efficiency LPL system based on new mechanism. |
