Nanostructured Carbon Dots as Ratiometric Fluorescent Rulers for Heavy Metal Detection

Carbon dots (CDs) have garnered significant attention in heavy metal (HM) sensing due to their exceptional optical properties and numerous advantages. Due to the rapid industrialization in the last couple of decades, the accumulation of HM in the environment poses a major threat to humans and marine and terrestrial organisms in the Indian subcontinent. Therefore, the detection of HM in the environment is of paramount importance. This review delineates the latest progress in employing CDs for heavy metal detection, specifically focusing on those with dual-emissive fluorescence characteristics, highlighting their superiority compared to traditional detection approaches. Additionally, eco-friendly synthesis methods and the mechanisms through which heavy metals are sensed by CDs are investigated, with emphasis placed on their benefits, such as high sensitivity and selectivity in metal detection applications. The review examines a variety of detection methods employing CDs, such as fluorescence, colorimetry, electrochemical techniques sensing, and ratiometric fluorescence methods, and elucidates their distinct applications. Furthermore, it focuses on approaches aimed at enhancing the sensing capabilities of CDs through surface functionalization, doping, and composite formation. By providing a comprehensive overview of detection methods and suggesting avenues for further research and development, it aims to contribute to the advancement of this field.