Exploration of the potential efficacy of natural resource-derived blue-emitting graphene quantum dots in cancer therapeutic applications

Abstract

Coal being the most abundant natural resource is used worldwide and shows graphite-like clusters. Here, for the first time, we report an innovative and cost-effective oxidative functionalization approach, followed by an acid-free and oxone oxidant-assisted solvothermal synthesis of graphene quantum dots from coal. This method involving the oxidative functionalization of coal was performed through the heat treatment of nitric acid, followed by an acid recovery process. Indeed, the solvothermal method used was entirely free from the utilization of strong acids, and involved a simple, eco-friendly, and salt-free purification process with a high production yield (∼45%). Due to the synergistic synthesis technique, our developed GQDs were found to exhibit a strong blue photoluminescence (PL) characteristic with a significantly high quantum yield (∼14.42%). High-resolution transmission electron microscopy (HRTEM) images indicated that the nanocrystalline GQDs had a uniform and narrow particle-size distribution in the range of 2.5–5 nm. The anticancer efficacy of the as-synthesized GQD nanomaterial was validated through cellular morphological pattern analysis and DAPI-staining images of neuroblastoma cells and breast cancer cells. In addition, the alteration of the mitochondrial membrane potential was scrutinized using JC-1 micrographs. Interestingly, the RITC-tagged GQDs showed cellular internalization within breast cancer cells. The robust functionality, luminescence stability, nanosecond lifetime, biocompatibility, and low toxicity of our developed GQDs suggest they could be promising probes for cancer therapeutic applications. This study unveils new opportunities for the sustainable production of GQDs with novel attributing features due to the easily availability of the raw materials, their cost-effective production, and fascinating photoluminescence property.