Monodispersed Snowman-Like Ag-MoS2 Janus Nanoparticles as Chemically Self-Propelled Nanomotors

Silver (Ag)-based Janus nanoparticles (NPs) are of broad interest for extensive applications due to their excellent photoelectric performances and special structure. However, it still remains challenging to prepare this type of Janus NP with high uniformity in a large scale. Here, we present a facile wet-chemical strategy to synthesize Ag-MoS2 Janus NPs via adding an appropriate amount of AgNO3 into the MoS2 nanosphere (200 nm in size)-contained aqueous solution. These Janus NPs represent a new type of heterogeneous nanostructure. Each Janus NP is made up of one tiny-Ag-dot-decorated MoS2 nanosphere and one polyhedral Ag single crystal (∼100 nm in size), and both of them attach together, showing a snowman-like dimer. Such Janus NPs or dimers can not be detached by the ultrasonic vibration even with a high power, showing strong adhesion between them. Further, the morphology and size of the polyhedral Ag nanocrystals attached on MoS2 nanospheres can be controlled by the AgNO3 addition amount, reaction time, and temperature. A growth model is proposed to understand the formation of these Janus NPs, which is based on the tiny Ag dots' aggregation and oriented connection mechanism. Importantly, such Ag-MoS2 Janus NPs can be used as nanomotors, due to their asymmetric catalytic component structure, and self-propelled in H2O2 fuel solutions. They show good directional motion and significant dependence of their speed on fuel concentration. This study expands our understanding of the formation of heterogeneous Janus particles and provides a promising platform to investigate active colloids as nanomotors.