Ion-imprinted polymer-based sensors for toxic metal-ion detection in water: coordination chemistry, transduction strategies, and environmental applications.

Toxic metal contamination in aquatic environments remains a persistent threat to human health and ecosystems. Yet, the high cost, infrastructure demands, and centralized nature of conventional analytical methods constrain routine monitoring. Ion-imprinted polymers (IIPs), a subclass of molecularly imprinted polymers, have emerged as promising synthetic recognition materials for metal-ion sensing because they generate coordination-defined binding sites with high selectivity, chemical stability, low cost, and reusability. This review summarizes recent advances in Ion-imprinted polymer (IIP)-based sensing technologies for toxic metal-ion detection in water from 2016 to 2026. It examines the fundamental recognition chemistry of IIPs, major synthesis strategies used to generate selective binding cavities, and the principal sensing platforms, including electrochemical, optical/fluorescence, and piezoelectric systems. Attention is given to the role of conductive nanomaterials in enhancing electron transfer. Additional emphasis is placed on multiplex metal-detection strategies and validation in real environmental samples. Across literature, electrochemical platforms dominate the field owing to their sensitivity, portability, and compatibility with miniaturized devices, although analytical performance often depends strongly on interfacial engineering and matrix conditions. Current challenges, including reproducibility, selectivity in complex waters, and field deployment, are discussed together with future directions needed to enable practical water-quality monitoring technologies.