Sensing Activity of Green Synthesized Carbon Quantum Dots for Detecting Heavy Metal Ions

The presence of hazardous contaminants, particularly, highly toxic heavy metal ions (Cr6+, Hg2+, Pb2+, Cd2+, Sn2+, Cu2+, and As3+), is a big issue to access safe drinking water. Evidences say that the uptake of these metal ions above permissible limit may cause severe metabolic disorder, organ failure, and cancer growth in living organisms. Therefore, sensing of heavy metal ions in water is a vital task. Green carbon dots (GCDs) have shown immense potential to detect these metal ions in water as well as in biological systems. The biomass-based GCDs are advantageous over chemical counterparts due to the abundant and cheap availability of non-toxic starting precursor along with the simple, energy-saving, and rapid synthetic procedure. This chapter deals with a comprehensive overview of biomass-based GCDs in terms of synthesis, structural/optical properties, and sensing attributes towards heavy metal ions. Involvement of various mechanisms for the fluorescence quenching-based detection of metal ions along with the possibility of fluorescence enhancement with some metal ions is also discussed. Hence, we strongly believe that GCDs have an admissible opportunity for the development of efficient, selective, and sensitive sensor platform for toxic metal ions to identify the quality of water and tracking in biological medium.