Micro/nanomotors for metal ion detection and removal from water: A review

Since the mid-to-late-2000s, the emergence of miniaturized machines, namely, micro/nanomotors (MNMs), has taken the nanotechnology research world by storm owing to the distinctive autonomous motion and multifunctionality of MNMs that bring about revolutionary changes in the detection and remediation of various environmental pollutants, including metal ions. MNMs for metal ion detection and removal have been designed with diverse materials and geometries using different methods. Their active motion enhances the mixing and mass transfer, significantly improving the trace metal ion detection in water and speeding up the removal of various metal ions. Confirming this assertion, this review presents an overview of MNMs for metal ion detection and removal from water. A particular emphasis is placed on the classification of MNMs based on their energy sources, along with their materials, geometries, fabrication methods, propulsion mechanisms, and their metal ion detection and removal mechanisms and performance. The major challenges and future prospects towards the large-scale applications of MNMs in water quality monitoring and remediation are also addressed. It is believed that MNMs will rise to the challenge and stand up to the task as optimal solutions for numerous environmental sustainability issues and crises in the 21st century.