Abstract
To construct efficient room-temperature phosphorescence(RTP)doping systems by simple doping methods,isomers 2-(2-(9H-carbazol-9-yl)benzyl)malononitrile(o-CzCN),2-(3-(9H-carbazol-9-yl)benzyl)malononitrile(m-CzCN)and 2-(4-(9H-carbazol-9-yl)benzyl)malononitrile(p-CzCN)were designed and synthesized by choosing commercial carbazole.Based on the structure-function relationships of three isomers and excellent compatibility between carbazole and benzocarbazole,2-(3-(9H-carbazol-9-yl)benzyl)malononitrile(Lm-CzCN)and 2-(3-(5H-benzo[b]carbazol-5-yl)benzyl)malononitrile(m-BCzCN)were prepared by self-made carbazole and 2-naphthyl-amine.Then,Lm-CzCN/m-BCzCN was constructed and optimized by dissolution and rapid evaporation,as well as tuning the mass ratios between Lm-CzCN and m-BCzCN.Lm-CzCN shows excitation dependent RTP and afterglow lifetimes,as well as concentration dependent RTP emission in poly(vinyl alcohol)(PVA)films,while 1％m-BCzCN@PVA film emits bright green afterglow,with RTP and afterglow lifetimes of 2.303 and 17 s in turn,as well as RTP quantum yield of 0.22.More importantly,Lm-CzCN/m-BCzCN presents ultra-long room temperature phosphorescence,with RTP and afterglow lifetimes of 597.58 ms and 8 s,respectively.Moreover,crystals m-CzCN and p-CzCN,as well as Lm-CzCN/m-BCzCN can be excited by visible light of 440 nm,showing yellow afterglow of 1-4 s.Noteworthy,polymorphism o-CzCNy and o-CzCNB were found,whose different emission was investigated by molecular conformation,intermolecular arrangement and stacking patterns.Finally,multiple encryptions were successfully constructed based on the different luminescent properties.
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