Water-soluble boron carbon oxynitride dots with excellent solid-state fluorescence and ultralong room-temperature phosph
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Water-soluble boron carbon oxynitride dots with excellent solid-state fluorescence and ultralong room-temperature phosphorescence Shenghui Han1, Gang Lian1 (), Xiaoliang Zeng2, Zhaozhen Cao3, Qilong Wang3, Deliang Cui1, and Ching-Ping Wong4 () 1
State Key Lab of Crystal Materials, Shandong University, Jinan 250100, China Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China 3 Key Laboratory for Special Functional Aggregated Materials of Education Ministry, School of Chemistry & Chemical Engineering, Shandong University, Jinan 250100, China 4 School of Materials Science and Engineering, Georgia Institute of Technology, Georgia 30332, USA 2
© Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 25 March 2020 / Revised: 17 July 2020 / Accepted: 20 July 2020
ABSTRACT Developing metal-free and long lifetime room-temperature phosphorescence (RTP) materials has received tremendous interest due to their numerous potential applications, of which stable triplet-excited state is the core challenge. Here, boron carbon oxynitride (BCNO) dots, emitting stable blue fluorescence and green RTP, are reported for the first time. The obtained BCNO dots exhibit an unexpected ultralong RTP lifetime of 1.57 s, lasting over 8 s to naked eyes. The effective doping of carbon and oxygen elements in boron nitride (BN) actually provides a small energy gap between singlet and triplet states, facilitating the intersystem crossing (ISC) and populating of triplet excitons. The formation of compact cores via crystallization and effective inter-/intra-dot hydrogen bonds further stabilizes the excited triplet states and reduces quenching of RTP by oxygen at room temperature. Based on the water-soluble feature of BCNO dots, a novel advanced security ink is developed toward anti-counterfeiting tag and confidential information encryption. This study extends BCNO dots to rarely exploited phosphorescence fields and also provides a facile strategy to prepare ultralong lifetime metal-free RTP materials.
KEYWORDS boron carbon oxynitride dots, room-temperature phosphorescence, fluorescence, colourless security ink, anti-counterfeiting
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Introduction
Stimuli-responsive optical materials have received growing attention owing to their promising applications in optoelectronic devices, bioimaging, display devices, sensors, and so on [1–7]. Particularly in information encryption field, exploiting novel stimuli-responsive smart materials is extremely significant to avoid the anti-counterfeiting technologies mimicked. Recently, room-temperature phosphorescence (RTP) materials are expected promising candidates in this field. To achieve effective RTP, it is generally required efficient spin-orbit coupling for singletto-triplet intersystem crossing (ISC) and stable triplet-excited states [8, 9]. Unfortunately, because of the spin-forbidden transition feature of triplet-excited states and the non-radiative deactivation, most of the reported RTP materials face the issues of sh
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