Investigation On Properties Of Pure Organic Room Temperature Ultralong Afterglow Materials Based On Benzocabazole

Pure organic room temperature afterglow materials generally have long lifetime and large Stokes shift,which have more unique advantages compared with traditional fluorescent materials.In addition,it shows bright application prospects in the fields of information security and encryption,high-resolution printing,sensors,biomedical imaging and so on.In recent years,researchers have found trace amounts of the impurity benzoindole(Bd)in commercial carbazole(Cz)and confirmed that the presence of even trace amounts of Bd promotes the production of phosphorescence.Recently,our research group successfully obtained Bd through the seven-step reaction,comprehensively and systematically studied the phosphorescent properties of Bd,and revealed the internal mechanism of Bd radical long afterglow emission.However,the complex synthesis and low yield of Bd greatly limit the application of organic phosphorescence.Therefore,the purpose of this paper is to explore the simple and easy replacement of Bd.Specific research contents are as follows:First of all,in the second chapter,we successfully find a new phosphorescence unit that can replace Bd--5H-benzo[b]carbazole,named BCz.BCz shows phosphorescent characteristics similar to Bd in RTUOP.BCz can be obtained by a two-step reaction compared to the seven-step reaction used to synthesize Bd.As a new phosphorescence unit,BCz shows some advantages over Bd: Firstly,BCz and its derivatives can exhibit distinctive red-shifted red ultralong phosphorescence in the self-aggregated state at 77 K while Bd and its derivatives cannot.Secondly,BCz demonstrates remarkable photo-activated yellow ultralong phosphorescence at room temperature while the intrinsic phosphorescence of Bd is difficult to be activated at room temperature.Thirdly,BCz deriva-tives(CNPy BCz and CNBr BCz)display similar photo-activated yellow ultralong phosphorescence with Bd derivatives at room tem-perature but the phosphorescent lifetimes are longer.Fourthly,it is shown that BCz and its derivatives emit yellow RTUOP in the powder matrixes besides their carbazole counterparts.It is revealed that BCz and Bd share the same cation radical-involved phosphorescence mechanism featuring charge separation(CS)and charge recombination(CR)and the redshift of ultralong phosphorescence in the self-aggregated state arises from the enhanced π-πinteractions among the BCz units.Secondly,in Chapter 3,we discuss and compare the influence of substrate on the phosphorescence of guest-substrate doping system at room temperature.We connected BCz(or BCz-1)and two other phosphorescence units(N-2 and BCz-2)to the same skeleton 4-iododiphenyl sulfone,and obtained three guest molecules(ISO2N-2,ISO2Bz-1 and ISO2Bz-2).Then DMAP and ISO2 Cz were used as substrates,and finally constructed six doping systems.To our surprise,all the doping systems at DMAP show longer lifetime and weaker phosphorescence intensity while all the doping systems at ISO2 Cz feature shorter lifetime and higher phosphorescence intensity.Carefully analyzing the single crystals of two matrixes,resemblant chemical structures of guests and ISO2 Cz enable them to approach each other and interact with each other via a variety of interactions thus facilitate the CS and CR process.The HOMO-LUMO energy levels of guest match well with ones of ISO2 Cz,which significantly promotes efficiency of the CS and CR process.In this paper,we demonstrate that the mechanism of cationic radical involvement may be universal in the field of RTUOP,and systematically study how the matrixes influence the RTUOP of the guest matrix doping system,and this work may give deep insight into the development of organic phosphorescence.