Carbon quantum dots: Comprehensively understanding of the internal quenching mechanism and application for catechol detection

Abstract

Abstract Carbon quantum dots (CQDs), a new member of the nanocarbon family, are emerging as attractive optical sensing material. At present, there is still a lack of in-depth investigation on internal responsive mechanism of CQDs as their fluorescence is quenched by analytes. In this work, ethylenediamine (EDA) functionalized carbon quantum dots (N-CQDs) are synthesized through the protection/deprotection of one amine group and the amidation reaction on CQDs surface. According to the fluorescence response of N-CQDs in catechol (CTC) solution and under different environmental conditions, it is found that the EDA on the surface of N-CQDs could spontaneously combine with CTC via Michael addition or Schiff base reaction to form static compounds, which serve as electron donor to effectively quench the fluorescence originated from sp2 carbogenic core area and “surface state” of N-CQDs, but have little impact on the emission from “edge state” of N-CQDs. This is the first time that the “inertness” of “edge state” was observed. Based on the comprehensive analysis of quenching mechanism, the excitation wavelength (λex=310nm) corresponding to the “core state” of N-CQDs was selected, and a simple, highly sensitive and selective detection platform for CTC quantification is established.