Graphene quantum dots (GQDs) have many excellent properties such as strong fluorescence, chemical stability and facile synthesis. In this work, GQDs were prepared by pyrolysis of citric acid. And optimization of the pyrolysis temperature, pyrolysis time, and dispersion pH attained 1.04 times stronger fluorescence intensity.
The appearance of metal oxide nanoparticles in potable water has attracted much public attention. A simple method for quantitative analysis of titanium dioxide (TiO2) nanoparticles was developed by fluorescence quenching of GQDs in this research. Dopamine (DA) was first added to coat TiO2 nanoparticles with polydopamine (PDA) under ultrasonication. GQDs were next added as a fluorescent sensor probe to measure the quenching of its emission intensity by the PDA-coated nanoparticles. Data analysis by the Stern-Volmer equation followed a third-order polynomial fit that indicated static, dynamic and absorptive contributions to the total quenching. Detection of TiO2 nanoparticles down to 0.02 mg/mL was validated.