A simple one-pot synthesis of highly fluorescent nitrogen-doped graphene quantum dots for the detection of Cr(vi) in aqueous media

Abstract

A new method for selective determination of Cr(VI) in environmental water samples was developed based on its quenching effect on the fluorescent N-doping graphene quantum dots (N-GQDs). The N-GQDs were synthesized by a simple one-step method using citric acid as the carbon source and ammonia as the nitrogen source with a 65% yield, showing that mass production of the N-GQDs is possible. The obtained N-GQDs with oxygen-rich functional groups exhibited a strong blue emission with a quantum yield of 18.6%, which was 7 times greater than that of graphene quantum dots (GQDs). Due to the selective coordination to Cr(VI), the N-GQDs can be used as a green and facile sensing platform for label-free sensitive and selective detection of Cr(VI) ions in aqueous solution and real water samples.Compared to GQDs, the N-GQDs as a fluorescent probe promises much improved selectivity for sensing of Cr(VI). The N-GQDs fluorescence probe shows a sensitive response to Cr(VI) in a wide concentration range of 0-140 mM with a detection limit of 40 nM. The N-GQDs-based fluorescence method was successfully used to selectively detect Cr(VI), and discriminate it and Cr(III) as well in aqueous samples.

Graphene quantum dots combined with copper(II) ions as a fluorescent probe for turn-on detection of sulfide ions

“…1c, the fluorescence spectrum peaks of the GQDs shift from 427 to 436 nm with the excitation wavelength increasing from 320 to 350 nm. This excitation-dependent fluorescence behavior may result from the optical selection of differently sized GQDs and surface defects of GQDs [30]. As shown in the inset, the GQDs exhibit an intense blue fluorescence color under irradiation with 365 nm UV light.…”

Graphene quantum dots in analytical science

“…GQD-based probe sensors have been used to determine Fe 3+ [22,23,42,48,58,60,76], Cu 2+ [68,82,83], Al 3+ [84] and the hazardous species Hg 2+ [85,86], Cr 6+ [87] and Ni 2+ [88]. Analytical applications of these sensors has focused largely on Fe 3+ , probably because of its prominent role in biological systems (particularly in regulatory processes).…”

Ultrafast ammonia-driven, microwave-assisted synthesis of nitrogen-doped graphene quantum dots and their optical properties

“…For example, NGQDs have been synthesized using glycine [21], glucose [14], or citric acid [22][23][24][25][26][27] as carbon source or using ammonia [14,22,23], dicyandiamide [24,25], tris(hydroxymethyl) aminomethane [26], 3,4-dihydroxy-L-phenylalanine [27], or glycine [21] as nitrogen source through hydrothermal reaction [14,[21][22][23][24][25] or high-temperature treatment [26,27]. Such one-step methods usually require high temperature and/ or high pressure.…”