Tailoring Metal/TiO₂ Interface to Influence Motion of Light-Activated Janus Micromotors

Catalytic light-powered micromotors have become a major focus in current autonomous self-propelled micromotors research. The attractiveness of such machines stems from the fact that these motors are “fuel-free,” with their motion modulated by light irradiation. In order to study how different metals affect the velocities of metal/TiO₂ micromachines in the presence of UV irradiation in pure water, Pt/TiO₂, Cu/TiO₂, Fe/TiO₂, Ag/TiO₂, and Au/TiO₂ Janus micromotors are prepared. The metals have different chemical potentials and catalytic effects toward water splitting reaction, with both the effects expected to alter the photoelectrochemically-induced reaction and propulsion rates. Analysis of structures, elemental compositions, motion patterns, velocities, and overall performances of different metals (Pt, Au, Ag, Fe, Cu) on TiO₂ are observed by scanning electron microscopy, energy dispersive X-ray spectroscopy, and optical microscopy. Electrochemical Tafel analysis is performed for the different metal/TiO₂ structures and it is concluded that the effective velocity is a result of the synergistic effect of chemical potential and catalysis. It is found that the Pt/TiO₂ Janus micromotors exhibit the fastest motion compared to the rest of the prepared materials. Furthermore, after exposure to UV light, every fabricated micromotor shows high possibility of forming assembled chains which influence their velocity.