Engineering of graphene quantum dots by varying the properties of graphene oxide for fluorescence detection of picric acid

Abstract

The study examines the effect of different forms of graphene oxide (GO) on the synthesis of graphene quantum dots (GQD). GO synthesized at various temperatures i.e. 30, 50, 110 °C possessed different structural and functional properties and was used as a substrate for GQD preparation. Thorough characterization of the GQDs in terms of their structural, morphological, functional, and optical properties was performed. The GQDs exhibited variation in their size and fluorescence properties depending upon the type of GO used. Hydrothermal reduction of GO, prepared at an oxidation temperature of 50 °C (GO-50), minimized the particle size (3.6 nm) and maximized the photoluminescence (PL) intensity and quantum yield (64.8%) of the GQD (GQD-50). GQD-50 was found to detect picric acid (PA) in an aqueous solution via ‘turn-off’ fluorescence quenching, unlike the other GQDs where the initial precursor is synthesized at 30, 110 °C. Experimental studies summarize that interaction between the fluorophore-quencher resulted in static quenching. The limit of detection was estimated to be 1.2 μM with a detection range of 0–200 μM. The work concludes that optimization of the substrate i.e. GO can result in the development of a simple, non-toxic, cost-effective GQD based sensor for PA detection. The study eliminates the need for doping/functionalization of GQDs as reported previously, and hence finds a promising impact on the development of sensors.