Ultrasensitive SERS detection and efficient flotation removal of nanoplastics from water using bubble-spouting micromotor swarms

Abstract Nanoplastics are ubiquitous in aquatic environments. Most of the nanoplastics suspend in the water column, facilitating their transportation and increasing their influence on the ecosystems. Owing to their small size and good dispersion in water, detection and separation of the nanoplastics from an extremely large volume of water are very challenging. Here, we demonstrate a concept to employ carefully engineered microbubble-spouting magnetic Ag/Co micromotors to sensitively detect the nanoplastics by the surface-enhanced Raman spectroscopy (SERS) technique, as well as remove the nanoplastics from a large volume of water with the “microbubble armies” to attract, capture, and transport the nanoplastics to the water surface ( i.e. , flotation method) resembling the white blood cells chasing and swallowing nanointruders in biology. The SERS detection sensitivity reaches single nanoplastic debris level, enabled by the microscale cavities on the micromotor surface and the slippery substrate facilitating nanoplastic enrichment during water evaporation. The removal efficiency of nanoplastics from water reaches 94.3% arising from the strong interactions between the “microbubble armies” spouted from the Ag/Co micromotor swarms and the nanoplastics via the hydrophobic interactions. The Ag/Co micromotors can be separated from water after nanoplastics removal by a magnet for recycling usage. The practical applicability of the flotation method was proved by the high flotation removal efficiency of the PS nanospheres spiked into the lake and tap water using the Ag/Co micromotors. The high SERS sensitivity and the high nanoplastic removal efficiency, as well as the high throughput production and the recyclability of the Ag/Co micromotors provide valuable multifunctional materials for simultaneous detection and treatment of nanoplastic pollution in contaminated water.