Fluorescence mechanism of xylan-derived carbon dots: Toward investigation on excitation-related emission behaviors

Abstract

The thoroughly understanding of photoluminescence (PL) featuring with excitation-dependent emission (EDE) and excitation-independent emission (EIE) are critical for designing carbohydrate-derived carbon dots (CDs) with excellent PL characteristics. Herein, two types of xylan-derived CDs with EDE and EIE were facilely synthesized under the doping effect of NH4OH and polyethyleneimine, respectively. The investigation on optical properties, morphology, and chemical structure of these synthesized CDs revealed that both the EDE and EIE were heavily dependent on the surface states rather than the size and structure of carbogenic cores. Furthermore, the multiple energy levels induced by surface-contained C–OH, C–O–C, and C–O functionalities were responsible for the EDE, while the formation of plentiful C–N or CN like groups, which together with the decreased O-containing groups resulted in a uniform surface state that contained concentrated energy levels, thus generating the EIE behavior of xylan-derived CDs.