Synthesis of highly fluorescent nitrogen-doped graphene quantum dots for sensitive, label-free detection of Fe (III) in aqueous media

Heteroatom doping can drastically alter the electronic characteristics of graphene quantum dots (GQDs), thus resulting in unusual properties and related applications. Herein, we develop a simple and low-cost synthetic strategy to prepare nitrogen-doped GQDs (N-GQDs) through hydrothermal treatment of GQDs with hydrazine. The obtained N-GQDs with oxygen-rich functional groups exhibit a strong blue emission with 23.3% quantum yield (QY). Compared to GQDs, the N-GQDs exhibit enhanced fluorescence with blue-shifted energy. Due to the selective coordination to Fe3+, the N-GQDs can be used as a green and facile sensing platform for label-free sensitive and selective detection of Fe (III) ions in aqueous solution and real water samples. The N-GQDs fluorescence probe shows a sensitive response to Fe3+ in a wide concentration range of 1-1945 mu M with a detection limit of 90 nM (s/N=3). Interestingly, it is also found that both dynamic and static quenching processes occur for the detection of Fe3+ by N-GQDs, while the quenching effect of Fe3+ on the fluorescence of GQDs is achieved by affecting the surface states of GQDs. (c) 2014 Elsevier B.V. All rights reserved.