Abstract

Khanitta Saenwong¹, Chawangorn Putthasehn¹, Atipa Tunsawat¹, Prawit Nuengmatcha² and Saksit Chanthai¹

DOI : http://dx.doi.org/10.13005/ojc/340106

This research was aimed to prepare graphene quantum dots (GQDs) by thermolysis of citric acid using paraffin oil bath, preferably regarding weight of citric acid and heating temperature. Fluorescence spectrum of the blue GQDs solution (under UV light), with excitation l_max 365 nm was characterized. The fluorescence intensity at l_max 460 nm was used to calibrate their uniformity.  The as-prepared GQDs were achieved with 0.25 g citric acid at 225°C for 5 min. The GQDs solution at pH 6-13 gave high fluorescence intensity without any effect of ionic strength and masking agent. Effect of some anionic salts using their corresponding mineral acids (1%, w/w) to decorate the GQDs was investigated. The results showed that each of HCl, HNO₃ and H₃PO₄ enhances its fluorescence intensity of the GQDs decorated with Cl^-, NO₃^-& PO₄^3-, respectively, while the matrix effect of ClO₄^-, SO₄^2- and BO₃^3-gave very large extent of the quenching effect compared with that of bare GQDs. In addition, these anionic–decorated GQDs were applied for selective screening test with various metal ions. It was found that each kind of these anions shows strong intrinsic quenching and enhancing of their fluorescence intensity of the GQDs, suggesting further trends in their fluorescence determination of some metal ions.

Fluorescence Sensor; Metal Ions; Graphene Quantum Dots; Thermolysis; Citric Acid; Mineral Acids

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