Facile synthesis of sulfur-doped graphene quantum dots as fluorescent sensing probes for Ag+ ions detection

Sulfur-doped graphene quantum dots (S-GQDs) with bright blue emission have been prepared by a facile one-pot hydrothermal treatment. A specific compound, 1,3,6-trinitropyrene, which has a mother nucleus structure similar with graphene, was chosen as the carbon source and 3-mercaptopropionic acid (MPA) was employed for S-doping and carboxyl groups modification. The synthesized S-GQDs were characterized by atomic force microscopy (AFM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and fluoscence (FL) spectrum. Results indicated that S-GQDs possessed single layer graphene structure with mean size of about 2.5   nm and presented an excitation-independent photoluminescence behavior with maximum excitation/emission wavelength at 360/450   nm, respectively. The sulfur-doping of GODs drastically improved their electronic and chemical properties, which afforded the S-GQDs a sensitive response to Ag + ions. Furthermore, the S-GQDs were successfully explored as a sensing probe for Ag + detection with high sensitivity and selectivity. A wide linear range of 0.1-130.0   μM with a low detection limit of 30   nM was obtained. The facile preparation method and the high performace of the as-prepared S-GQDs present promising potential for their applications in sensing, biological imaging and catalysis.