Application Of Carbon Dot-Based Room Temperature Phosphorescent Materials In Anti-Counterfeiting,Information Encryption,Fingerprint Detection And In Vivo Imaging

In recent years,room temperature phosphorescence(RTP)materials have attracted considerable attention owing to their many promising applications,such as in optoelectronic devices,sensing,biological imaging,and document security.However,the preparation of RTP materials is still a huge challenge due to the non-radiative nature of triplet excitons transition.So far,RTP materials are still mainly limited to organometallic complexes and metal-free pure organic compounds,but all of them suffer from high cost and toxicity,sensitivity to atmospheric oxygen,complex preparation or only in the crystalline/composite form.In addition,most of the currently reported RTP materials exhibit relatively short emission lifetimes(ie microseconds to several milliseconds).This rapid decay is inconvenient in some applications,because people usually need tens of milliseconds to effectively identify afterglow.As a new type of luminescent nanomaterials,carbon dots(CDs)have the characteristics of excellent water solubility,strong light stability,low cytotoxicity and good biocompatibility.Therefore,they have caused more and more attentions in the construction of RTP materials.At present,the synthesis of RTP materials has been successfully achieved by dispersing carbon points in polyvinyl alcohol,polyurethane,urea,zeolite,mesoporous materials and other substrates.The advantages of this strategy lie in that the synthetic method is simple,the materials are cheap,the host and guest can be designed and synthesized as needed.Therefore,a variety of materials with long-persistent luminescence are expected to be synthesized by using this strategy.In this thesis,CDs-based room temperature phosphorescent materials are synthesized by confining CDs in a matrix of boric acid(BA)and metal salt shells,and they have been successfully applied in the fields of anti-counterfeiting,information encryption,fingerprint detection and in vivo imaging.The main research contents of the thesis are as follows:(1)By using boric acid and citric acid as raw materials,we successfully prepared phosphorescent CDs(named as BD50)with long-lifetime(1.17 s),through a simple one-step pyrolysis method.BD50 has a bright yellow RTP.Utilizing the effect of external heavy atoms,BD-X was synthesized by introducing halogen anions,BD-X has an ultra-long phosphorescence lifetime of 2.61 s.Based on the excellent optical properties of BD50 and BD-X,we further appled them in anti-counterfeiting and information encryption.(2)The CDs-based RTP material(CD71)with good water dispersibility was successfully synthesized by the molten salt method.The optimal phosphorescence emission of the CD71 in the aqueous solution was located at 520 nm,and the phosphorescence lifetime was 616 ms.Due to the unique phosphorescence properties and excellent dispersibility of CD71 in water,we further applied it to fingerprint detection and in vivo imaging.This work provides a new idea for the practical application of phosphorescent materials in fingerprint detection and in vivo imaging.