Photoluminescent Carbon Dot: An Overview on Synthesis Approaches and Applications of Carbon Dot

In recent decade, due to the rapid development of nanotechnology and nanomaterials, carbon quantum dot (CQD) is recognized as a new rising zero-dimensional carbon-based nanomaterial as green substitute of heavy-metal-based nanomaterials with a particle size of less than 10 nm, strong photoluminescence (PL), and similar electrochemical properties as semiconductors. CQD has attracted widespread attention from scientists and researchers due to its excellent and tuneable PL characteristic. This review presents an overview of synthesis approaches, and parameters considered during CQD synthesis and its applications. Photoluminescent CQD can be synthesized through two main approaches, which are top-down (laser ablation, electrochemical etching, ultrasonic treatment and arc discharge) and bottom-up (hydrothermal/solvothermal and microwave-assisted pyrolysis) approaches. The PL characteristic of CQD, which are excitation and emission wavelengths, could be tuned through manipulation of the particle size of CQD, reaction temperature, reaction time, and use of doping agents and solvent during the synthesis of CQD. The tuneable PL property of CQD has widened their applications in the fields of biosensors, biomedical, energy, food engineering, and photosynthesis due to the factors of safety, sustainability, and non-toxicity of photoluminescent CQD. It is believed that the photoluminescent CQD could be further applied into the biomedical, electrochemical applications and lightdependent processes.