Nitrogen and Sulfur Co‐doped Graphene Quantum Dots: A Strategy for Utilizing Coal as a Precursor for Functional Material

Graphene quantum dots (GQDs) have caught significant attention in recent years due to their potential applications across various scientific disciplines. Heteroatom doping has emerged as a promising strategy to enhance the intrinsic properties of GQDs. Thus, the hunt for suitable dopants and low‐cost precursors for GQD synthesis is a future‐demanding topic. Herein, we report a simple and cost‐effective top–down approach synthesis method of nitrogen and sulfur co‐doped GQDs using semi‐bituminous coal and coke as precursors in which naturally present chemically bound sulfur and nitrogen also contribute to the dopant precursor. The synthesized nitrogen and sulfur co‐doped GQDs were characterized using various analytical techniques to examine their structural, morphological, and pH‐dependent photoluminescence properties. The synthesized CL‐NS‐GQDs exhibit a particle size of around 16–20 nm, having 3 to 4 layers of graphene confirmed by TEM and AFM analysis. We investigated the fluorescence behavior of N, S co‐doped GQDs across different pH levels (pH‐2, pH‐7, and pH‐10), and further enhanced the Photoluminescence properties by increasing the dopant concentration. Moreover, computational studies have also been conducted to examine the role of nitrogen and sulfur in GQD. Thus, this paper illustrates the fundamental understanding of utilizing low‐cost precursors to synthesize functional materials for diverse applications.