Cu²⁺ modulated nitrogen-doped grapheme quantum dots as a turn-off/on fluorescence sensor for the selective detection...

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 0-35μmolL^-1, with a detection limit of 72.2nmolL^-1. The proposed method is successfully applied to detect His in samples with a recovery range of 96-102%.