Construction of dendritic Janus nanomotors with H2O2 and NIR light dual-propulsion via a Pickering emulsion†
Artificial micro/nanomotors with a dual-propulsion property have attracted considerable attention recently due to their attractive performances in complex fluidic environments. In this work, we successfully constructed Janus nanomotors with H2O2 and NIR light dual-propulsion by employing dendritic porous silica nanoparticles (DPSNs) as carriers via a Pickering emulsion and electrostatic self-assembly. The aminopropyl-modified DPSNs (DPSNs-NH2) with positive charge were semiburied in paraffin wax microparticles in order to achieve electrostatic adsorption of Pt nanoparticles (NPs) with negative charge on the exposed surface for H2O2 propulsion, followed by electrostatic adsorption of negatively charged CuS NPs with excellent NIR light absorption on the other exposed surface of the eluted DPSNs-NH2@Pt for NIR light propulsion. Center-radial large mesopores facilitate the high density loading of Pt NPs and CuS NPs for efficient propulsion. Compared with the commonly used sputtering approach, this Pickering emulsion method can realize relatively large-scale fabrication of Janus NPs. DPSNs-NH2@Pt@CuS Janus nanomotors can be effectively driven not only by self-diffusiophoresis, which results from the decomposition of H2O2 catalyzed by Pt NPs, but also by self-thermophoresis, which is generated from thermal gradients caused by the photothermal effect of CuS NPs. Moreover, the motion speed of the nanomotors can be conveniently modulated by regulating the H2O2 concentration and NIR light intensity. This work provides a novel exploration into the construction of dual-propulsion nanomotors, which are supposed to have significant potential in biomedical and intelligent device applications.