Carbon quantum dots: synthesis, properties and multifaceted applications in biomedical imaging, environmental remediation and sensing technologies

Abstract With a dimension of roughly 10 nm, carbon quantum dots (CQDs) are an intriguing family of carbon nanoparticles. Various fabrication techniques, such as ultrasonication, electrochemical oxidation, hydrothermal reaction, laser ablation, microwave irradiation and reflux lead to CQD synthesis through processes including pyrolysis, carbonization, oxidation and polymerization. Sustainable raw materials are often utilized, aligning with environmental concerns and waste reduction efforts. CQDs exhibit low toxicity, chemical inertness, remarkable biocompatibility and highly adjustable photoluminescence behaviour owing to their semiconductor-like properties and oxygen based functional groups. Their tiny particle sizes contribute to highly photoluminescent emissions and controllable fluorescence. In biomedical applications, CQDs show promise for imaging, drug delivery and sensing due to their biocompatibility and tunable optical properties. In environmental contexts, they hold potential for wastewater treatment, heavy metal detection and ion sensing leveraging their adsorption capabilities and photoluminescence. This review explores the synthesis methods, physical and chemical characteristics and diverse applications of CQDs particularly focusing on their potential in biomedical imaging, environmental remediation and sensing technologies.