A substrate-free graphene oxide-based micromotor for rapid adsorption of antibiotics

Self-propelled micro/nanomotors play a crucial role in the fields of biomedicine, energy and the environment but are limited by low throughput and a tedious fabrication approach. Here, we propose a simple microfluidics-based scheme for fabricating substrate-free graphene oxide (GO)-based micromotors of different shapes and sizes with high throughput. The micromotors are designed to possess a 'Janus'-like porous structure, and half of each micromotor is modified with hierarchical Pt nanoflowers, which can promote the wetting of Pt with an H2O2 solution and result in a high speed of movement. To investigate the applicability of the micromotors, they were employed to rapidly remove an antibiotic, namely, tetracycline, from a solution. It was found that the rapid movement of the micromotors increased the mass transfer of tetracycline and the frequency of collisions between tetracycline molecules and the micromotors, which led to a high removal efficiency. The direction of movement of the micromotors can be conveniently controlled by an external magnetic field. Furthermore, the removal efficiency and removal time as functions of the number of micromotors, the adsorption kinetics and adsorption isotherm, and the removal amount as a function of the pH were investigated. This proved that the micromotors that were constructed exhibit high adsorption capabilities for tetracycline and implied that they hold great promise for the removal of antibiotics with similar structures or other pollutants, including organic compounds, heavy metals and oil droplets.