One-step synthesis of PCL/Mg Janus micromotor for precious metal ion sensing, removal and recycling

The field of the micromotor has undergone continuous progresses, especially in the environmental remediation application. However, to the best of our knowledge, there are few micromotors which can sense, remove and recycle metal ions simultaneously. In this paper, we develop a Janus micromotor consisting of polycaprolactone (PCL) and magnesium (Mg) microparticle synthesized by one-step method. Due to the displacement reaction between Mg and the precious metal ions, the resulting micromotor can be self-propelled in hydrogen peroxide (H2O2) solution. Since the motion velocity is highly dependent on both ion species and their concentrations, the micromotor can function as a motion-based metal ion sensor with good selectivity and sensitivity. In addition, since Mg alone is capable of propelling the whole structure in the presence of chloride ion (Cl−), the water-driven PCL/Mg micromotor exhibits higher efficiency when utilized in noble metal removal and recycling as compared to that of the stationary one. We thus believe the one-step fabrication, precious metal ion sensing, removal and recycling capabilities make the current micromotor potentially attractive for polluted water monitoring and treatment.