Room-Temperature Phosphorescence Of Carbon Dots And Their Application In The Detection Of Warfarin Sodium

Carbon dots(CDs)have been actively researched in the past decades due to their excellent photoluminescence(PL)properties.And the optical properties of fluorescence(FL)and room-temperature phosphorescence(RTP)have been utilized in the field of biology,chemistry,environment,and physics.Warfarin sodium,as an anticoagulant drug commonly used in clinical practice,is of great significance for its fast and effective detection.However,the most common used detection methods suffered narrow linear range and insufficient sensitivity.Hence,it is urgent to develop new detection methods.In addition,RTP of CDs have been limited by weak spin-orbit coupling(SOC)and super-fast deactivation of triplet exciton.Nowadays,the most common ways to acquire RTP are doping heavy atoms,heteroatom,and aromatic carbonyl which could enhance SOC,or utilizing hydrogen bonds,covalent bonds,and space restriction to immobilize triplet excitons which could inhibit non-radiative transition.Thus,the simple and efficient preparation of RTP CDs with long lifetime and strong phosphorescence is still a challenge for researchers.Therefore,focusing on the FL and RTP properties of CDs,we mainly conducted in-depth research from the following two parts:(1)The green FL carbon dots(pm-CDs)were initially synthesized,and then a long RTP lifetime of 1.01 s was obtained through embedding pm-CDs in dicyandiamide(DCDA)forming the composite of pm-CDs@DCDA.And their bright and long-lived afterglow with 365 nm of UV excitation was observed by the naked eyes for more than17 s.Importantly,the phosphorescence intensity and lifetime of pm-CDs@DCDA were remarkably promoted owing to the intermolecular hydrogen bonds and rigid environment,hence facilitating the intersystem crossing(ISC)process and restricting the non-radiative transition of triplet excitons.Taking advantage of the superior solid-state luminescence of pm-CDs@DCDA,we further innovatively prepared the white light-emitting diodes(WLEDs)with tunable color temperatures by regulating the composite mass ratios of pm-CDs@DCDA.This proposed study originally employed DCDA as a matrix to separate and immobilize pm-CDs,which built up a new avenue to improve the RTP property and offered a promising application in WLEDs.(2)A facile strategy was designed to synthesize P and N co-doped carbon dots(CDs@creatine).The as-prepared CDs@creatine exhibited bright blue FL and green RTP.Significantly,the FL of the CDs@creatine was quenched by warfarin sodium,whereas the RTP was enhanced.To be more specific,the FL intensity drop chiefly ascribed to inner filter effect and static quenching effect.Additionally,the abundant hydroxyl groups and amino functional groups on the CDs@creatine surface could react with the carbonyl groups of warfarin sodium to form intermolecular hydrogen bonds,which would rigidify the triplet states excitons against non-radiative deactivation,leading to the RTP intensity enhancement.Therefore,a dual-channel detecting strategy of warfarin sodium has been proposed with concentrations ranging from 10 nM to 8mM(LOD = 9.33 nM,S/N = 3),which may widen the detection ways.The above work was based on the photoluminescence properties of CDs,and the CDs were analyzed by means of morphology,structure,and optical characterization.Mechanisms of the change of FL and RTP signals of CDs composite materials were mainly discussed,and the excellent FL properties of CDs were used to prepare WLEDs with different color temperatures.In addition,the detection of warfarin sodium with high sensitivity and wide linear range was realized by the FL and RTP properties of CDs.These studies provide a new effective way to enhance the RTP intensity and prolong the lifetime,and offer strong evidence for the application of CDs in WLEDs preparation and small molecule drug detection.