Numerical Analysis of Visible Light Driven Gold/Ferric Oxide Nanomotors

The nanomotors consisted of gold and ferric oxide in this study are driven by visible light. Actuation of nanomotors results from the comprehensive effect of diffusion and migration of species in solution. In view of electrons, internal and external electric fields of a gold/ferric oxide nanomotor are analyzed to showthe propulsion mechanism based on self-electrophoresis, especially for electron distribution resulted from light illumination on the semiconductor part. Induced photovoltage triggers decomposition of hydrogen peroxide. Local electric field, formed bymoving electrons in a nanomotor and charged particles in solution, drives protons to migrate as primary effect. However, the concentration gradient, impelling protons to move from ferric oxide to gold, works little in start and moving period. A gold/ferric oxide nanomotor model is established. Local moving environment of nanomotors varies and is shown by the proton concentration distribution, velocity field, and electric field. Light with wavelength shorter than 552.2 nm can actuate nanomotors, realizing start and stop control in visible light band. Stronger light intensity and lower wavelength result in higher velocity.