Internally/Externally Bubble-Propelled Photocatalytic Tubular Nanomotors for Efficient Water Cleaning

We describe a highly effective bubble-propelled nanomotor for the photocatalytic decomposition of organic pollutants in water. Two different tubular TiO₂ nanomotor systems are presented: one with Pt nanoparticles decorated on the inner surface and the other with Pt nanoparticles decorated on the outer surface. This is the first time that we have observed the autonomous movement of a tubular nanomotor without the aid of any surfactant, as well as a tubular nanomotor externally decorated with Pt propelled by oxygen bubbles. The synergy between the Pt nanoparticles and the superhydrophilic wetting behavior of the TiO₂ nanotubes endows the two nanomotor systems with high speed at very low H₂O₂ fuel concentrations without the addition of any surfactant. The efficient photodecomposition of rhodamine B demonstrates the intermixing and photocatalytic ability of the two nanomotor systems, which opens new avenues for the development of multifunctional bubble-propelled micro/nanomotors with myriad practical applications.