Anchoring Carbon Nanodots onto Nanosilica for Phosphorescence Enhancement and Delayed Fluorescence Nascence in Solid and Liquid States

摘要

Carbon nanodots (CDs) anchored onto inorganic supporter (amorphous nanosilica, SiO_2) like a core-satellite structure have enhanced the room-temperature phosphorescence (RTP) intensity along with ultralong lifetime of 1.76 s. Special and quite stable structure should account for these superiorities, including hydrogen network, covalent bond, and trap-stabilized triplet-state excitons that are responsible for the generation of phosphorescence. These multiple effects have efficaciously protected CDs from being restrained by the external environment, providing such long-lived emission (LLE) that can subsist not only in powdery CDs-SiO_2 but also coexist in aqueous solution, pushing a big step forward in the application prospects of liquid-state phosphorescence. Through construction of CDs-SiO_2 compound, electron trap is reasoned between CDs and SiO_2 by analyzing thermoluminescent glow curve. Electron trap can capture, store, and gradually release the electrons just like an electron transporter to improve the intersystem crossing (ISC) and reserved ISC, having provided the more stabilized triplet excitons, stronger and longer phosphorescence, and also triggered the formation of thermally activated delayed fluorescence (TADF), offering a new mechanism for exploiting LLE among CD-based field. Moreover, it is more beneficial to the formation of TADF as temperature increases, thus the afterglow color can change with the temperature.