Nanomotors are usually propelled chemically, for example by producing a gas, and can transport cargoes such as drugs. It has been difficult to produce “fuel-free” nanoparticles (propelled by physical means such as electric fields, sound waves, or light), which can be used to transport and release a chemical cargo.

Tieyan Si, Qiang He, Harbin Institute of Technology, China, and colleagues have developed two-faced gold-coated mesoporous silica nanoparticle motors which are driven by near-infrared (NIR) light. The team first synthesized mesoporous silica nanoparticles with sizes of 50–120 nm using a sol-gel process. The particles were spread on a silicon slide in a monolayer and then coated with gold on one side by vacuum sputter deposition.

The resulting two-faced “Janus” nanomotors were suspended in water. They moved rapidly when irradiated with near-infrared light. This is due to the surface plasmon resonance of the gold shells, which generates heat on one side of the particles. The nanomotors reached speeds of 8.1–17.8 μm/s depending on their size, which corresponds to 68–356 body lengths per second. The particles are biocompatible and the mesoporous silica structure has potential for cargo transport.

• Near Infrared Light-Powered Janus Mesoporous Silica Nanoparticle Motors,
  Mingjun Xuan, Zhiguang Wu, Jingxin Shao, Luru Dai, Tieyan Si, Qiang He,
  J. Am. Chem. Soc. 2016.
  DOI: 10.1021/jacs.6b00902