Long-Lived Room-Temperature Phosphorescent Nitrogen Doped CQDs/PVA Composites: Fabrication, Characterization and Application
Abstract
Room-temperature phosphorescent (RTP) materials have attracted significant attention because of their potential applications in anticounterfeiting and optical imaging. However, most RTP materials developed to date have short-lived lifetimes, because the triplet excited states are easily quenched by atmospheric oxygen, thus limiting their full potential. Herein, nitrogen-doped carbon quantum dots (NCQDs), prepared by hydrothermal method, are dispersed into a poly(vinyl alcohol) matrix to fabricate phosphorescent materials with ultralong lifetimes at ambient temperature and atmosphere. The N-CQDs/PVA composites, which are 3D aerogel and thin film respectively, display a long lifetime of 442 ms and an average lifetime of 416 ms at ambient conditions. The efficient room-temperature phosphorescence phenomenon can be attributed to the small energy gaps between the singlet and triplet states (ΔES,T) of 0.246 eV and 0.23 S,T eV of the RTP materials (aerogel and thin film, respectively), thus facilitating state population through intersystem crossing. In addition, PVA molecule is able to inhibit quenching of the triplet excited state by oxygen, consequently promoting phosphorescence production at ambient conditions. Furthermore, the N-CQDs/PVA composites can be prepared in different physical forms, i.e., as solution, film, or aerogel as per the requirements of varied potential applications in optical imaging, writing, anti-counterfeiting, or sensors.