One-step synthesis of sulfur-incorporated graphene quantum dots using pulsed laser ablation for enhancing optical properties

To tune the electronic and optoelectronic properties of graphene quantum dots (GQDs), heteroatom doping (e.g., nitrogen (N), boron (B), and sulfur (S)) is an effective method. However, it is difficult to incorporate S into the carbon framework of GQDs because the atomic size of S is much larger than that of C atoms, compared to N and B. In this study, we report a simple and one-step method fur the synthesis of sulfur-doped GQDs (S-GQDs) via the pulsed laser ablation in liquid (PLAL) process. The as-prepared S-GQDs exhibited enhanced fluorescence quantum yields (0.8% -> 3.89%) with a huge improved absorption band in ultraviolet (UV) region (200 similar to 400 nm) and excellent photo stability under the UV radiation at 360 nm. In addition, XPS results revealed that the PLAL process can effectively facilitate the incorporation of S into the carbon framework compared to those produced by the chemical exfoliation method (e.g., hydrothermal method). And also, the mechanisms related with the optical properties of S-GQDs was investigated by time-resolved photoluminescence (TRPL) spectroscopy. We believe that the PLAL process proposed in this study will serve as a simple and one-step route for designing S-GQDs and opens up to opportunities for their potential applications. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement