Selective homocysteine detection of nitrogen-doped graphene quantum dots: Synergistic effect of surface catalysis and photoluminescence sensing

As a new photoluminescence functional material, graphene quantum dots have aroused widely entertaining. However, the complicated surficial chemistry micro-circumstance of graphene quantum dots hinders the further study of graphene quantum dots. In this paper, we demonstrate that the selectivity and sensitivity photoluminescence (PL) detection of homocysteine based on the synergistic effect of surface catalysis and photoluminescence sensing for nitrogen-doped graphene quantum dots (N-GQDs). Due to the localized superacid microenvironment of N-GQDs, the homocysteine cyclized into homocysteine thiolactone efficiently and selectively. Meanwhile, the aromatic N in N-GQDs adsorbs homocysteine thiolactone selectively. The following static quenching results in the outstanding selectivity and sensitivity PL quenching of N-GQDs with the presence of homocysteine. The detection limit is 5 x 10(-11) M, which is much lower than most reported detection methods. We also demonstrate that N-GQDs are able to display a PL response to homocysteine in the living cells.