Excited-state intramolecular proton-transfer-induced dual fluorescence emission in 2,3-dichloro-5,6-dicyano-1,4-benzoquinone and resorcinol-based carbon dots

Abstract

Herein, we revealed the excited-state intramolecular proton-transfer (ESIPT) process in 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) and resorcinol based carbon dots. The dual-emissive fluorophore, 5,6-diethoxy-4,7-dihydroxyisoindoline-1,3-dione (DDD), is extracted from the products and identified as the main fluorescence origin of the carbon dots. A blue-to-green switching in the emission color of the DDD can be observed as the solution pH decreases and the polarity of the solvent increases. Versatile morphologies including disks, dots and fibers can be formed during the DDD self-assembly in different mediums. By virtue of ESIPT-induced sensitive fluorescence, we not only construct the fluorescent anti-counterfeiting platform based on photoswitching of carbon dots in response to ammonia vapor and dimethyl sulfoxide stimuli, but also develop the picric acid sensing system with high selectivity and sensitivity.