Highly fluorescent graphene quantum dots as turn off-on nanosensor for detecting toxic metal ions to organic pollutant

A high photoluminescence (PL)-based nanosensor based on graphene quantum dots (GQDs) is fabricated for the detection of toxic ions Ag+, Ce2+, Cd2+, Cu2+, Cr2+, Pb2+, Sn2+, and Fe3+, p-nitrophenol, and thioacetamide in water. The quenching of PL spectra indicates that the complex of GQDs/Fe(III) shows a high florescent quenching efficiency (similar to 75%) toward the hydrophobic surface of the GQDs. The limit of detection for Fe(III) concentration 40 +/- 2 nM, with high linearity and sensitivity. The change of the zeta potential value proves the attachment of Fe (III) ions to the surface of the GQDs. The GQDs/ Fe(III) complexes can be utilized as a turn-OFF or turn-ON type fluorescence probe for p-nitrophenol (turn-OFF) detection with 5 +/- 1 pM concentration and the sulfur (turn-ON) detection with 7.6 +/- 1 pM. The proposed method is facile, sensitive and fast, which makes it ideal for nanosensors to detect water quality of rivers, ponds, or industrial wastes.

Automated summary

A high photoluminescence nanosensor based on graphene quantum dots was developed for the detection of toxic ions and compounds in water. The GQDs/Fe(III) complexes showed a high fluorescent quenching efficiency for the hydrophobic surface of the GQDs, enabling the detection of Fe(III) with a concentration of 40 +/- 2 nM. This method is facile, sensitive, and fast, making it ideal for water quality detection in rivers, ponds, or industrial wastes.