Site-Selective Superassembly of a Multilevel Asymmetric Nanomotor with Wavelength-Modulated Propulsion Mechanisms.

Micro-/nanomotors with advanced motion manipulation have recently received mounting interest; however, research focusing on the motion regulation strategies is still limited, as the simple construction and composition of micro-/nanomotors restrict the functionality. Herein, a multifunctional TiO2-SiO2-mesoporous carbon nanomotor is synthesized via an interfacial superassembly strategy. This nanomotor shows an asymmetric matchstick-like structure, with a head composed of TiO2 and a tail composed of SiO2. Mesoporous carbon is selectively grown on the surface of TiO2 through surface-charge-mediated assembly. The spatially anisotropic distribution of the photocatalytic TiO2 domain and photothermal carbon domain enables multichannel control of the motion, where the speed can be regulated by energy input and the directionality can be regulated by wavelength. Upon UV irradiation, the nanomotor exhibits a head-leading self-diffusiophoretic motion, while upon NIR irradiation, the nanomotor exhibits a tail-leading self-thermophoretic motion. As a proof-of-concept, this mechanism-switchable nanomotor is employed in wavelength-regulated targeted cargo delivery on a microfluidic chip. From an applied point of view, this nanomotor holds potential in biomedical applications such as active drug delivery and phototherapy. From a fundamental point of view, this research can provide insight into the relationship between the nanostructures, propulsion mechanisms, and motion performance.