Abstract
Conventional photocatalytic micromotors are limited to the use of specific wavelengths of light due to their narrow light absorption spectrum, which limits their effectiveness for applications in biomedicine and environmental remediation. We present a multiwavelength light-responsive Janus micromotor consisting of a black TiO2 microsphere asymmetrically coated with a thin Au layer. The black TiO2 microspheres exhibit absorption ranges between 300 and 800 nm. The Janus micromotors are propelled by light, both in H2O2 solutions and in pure H2O over a broad range of wavelengths including UV, blue, cyan, green, and red light. An analysis of the particles' motion shows that the motor speed decreases with increasing wavelength, which has not been previously realized. A significant increase in motor speed is observed when exploiting the entire visible light spectrum (>400 nm), suggesting a potential use of solar energy, which contains a great portion of visible light. Finally, stop-go motion is also demonstrated by controlling the visible light illumination, a necessary feature for the steerability of micro- and nanomachines.
Highlights
Catalytic micromotors are autonomously propelled by harvesting fuel from their surrounding environment.[1, 2] While the propulsion direction must be controlled for precise locomotion, conventional catalytic micromotors show only random motion
We present a multi-wavelength light responsive Janus micromotor consisting of a black TiO2 microsphere asymmetrically coated with a thin Au layer
The absorbance of as-synthesized TiO2 and black TiO2 (B-TiO2) powders was measured by diffuse reflectance spectrum (DRS)
Summary
Catalytic micromotors are autonomously propelled by harvesting fuel from their surrounding environment.[1, 2] While the propulsion direction must be controlled for precise locomotion, conventional catalytic micromotors show only random motion. Dai et al have recently demonstrated that by changing the incident light orientation, photocatalytic Janus Au/TiO2 nanowires can be precisely maneuvered along a desired trajectory.[17] Despite these efforts, existing photocatalytic micromotors, such as TiO2-,13-19 -Fe2O3-,20-24 Cu2O-,25 WO3,26 and BiOI-27based motors, operate in narrow light spectra. This limits the efficient use of the entire available solar energy and the range of applications for which such motors are useful. Compared to other photocatalytic micromachines, the reported Janus micromotors can be used for a larger range of applications due to their higher photocatalytic activity over the entire spectrum of UV and visible light
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