Cu2+ modulated nitrogen-doped grapheme quantum dots as a turn-off/on fluorescence sensor for the selective detection of histidine in biological fluid

A highly sensitive sensor for detection of histidine (His) based on the nitrogen-doped graphene quantum dots (N-GQDs)-Cu2+ system has been designed. The N-GQDs were synthesized by one-step hydrothermal approach according to previous report. The fluorescence of N-GQDs can be effectively quenched by Cu2+ due to the binding between Cu2+ and functional groups on the surface of N-GQDs. The high affinity of His to Cu2+ enables Cu2+ to be dissociated from the surface of N-GQDs and recovering the fluorescence. The sensor displayed a sensitive response to His in the concentration range of 0-35 mu mol L-1, with a detection limit of 72.2 nmol L-1. The proposed method is successfully applied to detect His in samples with a recovery range of 96-102%. (C) 2017 Elsevier B.V. All rights reserved.