Nanomaterial-enabled optical techniques for cadmium monitoring in aqueous systems: a comprehensive review

Cadmium contamination in water causes serious environmental and health risks due to its steady, bioaccumulation and is highly toxic in nature. Conventional laboratory-based methods for Cd2+ detection are accurate but expensive, time-consuming and not suitable for rapid on-site use. Recent advances in nanomaterial-assisted optical sensing particularly Ultraviolet-Visible (UV-Vis) spectrophotometry and fluorescence based techniques have enabled the development of cost-effective and highly sensitive platforms for Cd2+ detection. These approaches use the special optical behaviour of noble metal nanoparticles, quantum dots nanoparticles and carbon-based nanostructures to achieve rapid colorimetric or fluorescence responses with better selectivity. Although these sensors still face issues like interference from other ions and inconsistent performance when tested with real samples, recent advances in surface functionalization and the development of hybrid sensing systems are steadily improving their sensitivity, bringing detection limits closer to what is required for practical environmental monitoring. The integration of these sensors into small, user-friendly devices holds strong possibilities for real-time water quality monitoring and early warning systems, addressing both environmental sustainability and public health needs. However, more research is needed to ensure that nanomaterials-based optical sensors remain stable and reliable during long-term, real-world use. Their low material and equipment costs make them affordable alternatives to conventional detection methods. Further improvements in sensor stability and device integration could enable their widespread use in routine water quality monitoring.