Graphene quantum dots: preparation and detection of ethanol content in an aqueous solution

Improved graphene quantum dot preparation method based on incomplete carbonization of citric acid was developed. X-ray powder diffraction demonstrates the formation of graphene structure. The produced quantum dots have an average particle size of approximately 6 nm. The wavelengths of excitation, emission, and uv-visible absorption peaks are 355, 458, and 360 nm, respectively. Because ethanol may inhibit the protonation of the zigzag sites of graphene quantum dots, protecting the emissive triple carbine and active quantum dot fluorescence states, its content in water can be estimated by the fluorescence intensity of the quantum dots. In the scope of 0.01 to 100%, the ethanol volume ratio increases linearly with increasing fluorescence intensity at the emission peak with a fluorescence-to-volume ratio constant of about 0.125. This research provides reference information for graphene quantum dot preparation. And it also presents a facile method to measure the ethanol content in water at a relatively wide range. (authors)