Photogravitactic MXene-derived microrobots for nanoplastics capture and detection.

Nanoplastics pollution represents an increasing concern due to the easier diffusion and higher hazard associated with their small sizes, justifying the pressing demand for effective strategies to quantify and remove nanoplastics in wastewater. This contribution presents the on-the-fly capture of nanoplastics in the 3D space by multifunctional MXene-derived oxide microrobots and their further detection. A thermal annealing process converts titanium carbide MXene into photocatalytic multi-layered titanium dioxide, followed by metal layer deposition and magnetic nanoparticles decoration. The MXene-derived microrobots show negative photogravitaxis, resulting in a powerful fuel-free motion with six degrees of freedom under light irradiation. Owing to the unique combination of self-propulsion and programmable Zeta potential, the microrobots quickly attract and trap nanoplastics on their surface. Utilized as self-motile preconcentration platforms, they enable nanoplastics electrochemical detection using low-cost and portable electrodes. This proof-of-concept study paves the way toward the on-site screening of nanoplastics in wastewater and its successive remediation.