Graphene quantum dot-stabilized gold nanoparticles as a new colorimetric probe for in situ quantification of phenytoin in biological samples

Abstract A rapid, accurate and precise spectrophotometric procedure was described for in situ quantification of phenytoin (PHT) using graphene quantum dots (GQD) stabilized on gold nanoparticles. It was achieved by synchronization of the GQD-gold nanoparticles synthesis and analyte determination via simple mixing PHT, as-prepared GQD obtained by direct pyrolysis of citric acid and HAuCl4 within 30 minutes at room temperature. The X-ray diffraction patterns and Fourier transform infrared spectroscopy clearly confirmed the graphene honeycomb lattice of the graphene in nanoscale structure of gold nanoparticles. In addition, transmission electron microscopy, fluorescence, and ultraviolet–visible spectroscopies revealed the mechanism of aggregation of GQD supported gold nanoparticles for the detection of PHT. The proposed colorimetric assay is able to determine concentrations of PHT in the range of 0.01–0.20 µg·mL-1 with a low limit of detection (5 ng·mL-1) in human plasma obtained from patients taking PHT.