Propulsion of Au nanorod@TiO2/PNIPAm copolymer Janus nanomotors under the influence of visible/NIR-light via the self-electrophoretic propulsion mechanism

Scientists are exploring light-propelled micro/nanomotors for their potential applications and unique performance. Here, we have created match-like Janus nanomotors powered by visible/ near-infrared (NIR) light. These motors were fabricated from gold nanorod-titanium dioxide structure coated with a thermo-responsive polymer. The multi-segment metal nanorods (Au-Fe-Au) were fabricated using the porous anodic alumina (PAA) templates by electrodeposition method. The gold-iron oxide-gold nanorods were obtained after thermal annealing and dissolving the PAA membrane in a NaOH solution. The wet-chemistry method cultivated the titanium dioxide on both tips of the gold-iron oxide-gold nanorods. The Au nanorod@TiO2 heterostructure was prepared by removing the iron oxide segment in a hydrochloric acid solution. The reversible addition-fragmentation chain transfer (RAFT) polymerization was used to synthesize a thermo-responsive copolymer, N-isopropyl acrylamide-co-acrylamide. By reducing the RAFT agent residue, -SH groups were created at the end of each polymer chain, providing better conditions for coating the surface of the Au domain with thiolated copolymer. The motion of Janus nanorods was studied using varying monochromatically visible and NIR lights that lead to the self-electrophoresis mechanism. Optical microscopy data revealed that the Janus nanomotors can move within the wavelength range of visible and NIR light. The nanomotors' motion velocity increased with an increase in light intensity.