Metal-Doped Carbon Dots (MCDs) as Efficient Nano-adsorbents for Detection, Monitoring, and Degradation of Wastewater Pollutants: Recent Progress, Challenges, and Future Prospects

The surging global demand for food, textiles, and medicines has led to widespread exploitation, maltreatment, and contamination of water sources. The ecological and health impacts of this situation have become increasingly evident. Industries generate untreated or partially treated waste liquids known as effluents, which include wastewater, human sewage, and cooling water, as well as various inorganic and organic components. These contaminants differ among industries, making it challenging to categorize them. To tackle this pressing issue, innovative water treatment technologies are required, with recent efforts focusing on the use of modern chemicals for the adsorption and photocatalytic removal of hazardous water pollutants. One promising development in this field is the use of carbon dots, or fluorescent carbon nanoparticles. These nanomaterials have great potential for environmental monitoring and remediation. Metal-doped carbon dots (MCDs) have been shown to improve their photoluminescence capabilities and expand their application range. Compared to unmodified carbon dots, MCDs possess more catalytically active centers and enhanced catalytic activity, making them valuable in photocatalysis, electrocatalysis, chemical catalysis, and biocatalysis. This comprehensive review provides a synopsis of the most recent advancements in metal-doped carbon dots, highlighting their sensing, adsorption, and degradation applications in the remediation of water effluents. It also presents the novel and unique synthesis methods employed by recent studies in creating MCDs, along with the challenges and future prospects for their implementation.