Synthesis and luminescence properties of carbon quantum dots with core@shell structures

The luminescence stability of carbon quantum dots (CQDs) in air impedes their extensive applications. Ample -NH2 groups on the surface of a green carbon quantum dots (GCQDs) had high organic reactivity, the surface of GCQDs was modified with allyl functional groups through a simple surface substitution reaction (named as GCQD-A). The surface of the GCQD-A was continuously formed a thin organic shell by free radical copolymerization reaction with methyl methacrylate and styrene respectively, and they were named as GCQD@PMMA and GCQD@PS respectively. The allyl functional groups on the surface of GCQD-A, the shell composition of GCQD@PMMA and GCQD@PS were characterized by their 1H nuclear magnetic resonance (1H NMR) data and infrared adsorption spectra. The luminescence stabilities for GCQD@PMMA and GCQD@PS in air were greatly improved compared with that for the GCQDs. The work can provide a novel method to get stable luminescence of CQDs in air, and it will extend their application areas in solid state.