Metal-Free Visible-Light Photoactivated C3N4 Bubble-Propelled Tubular Micromotors with Inherent Fluorescence and On/Off Capabilities

Photoactivated micromachines are at the forefront of the micro- and nanomotors field, as light is the main power source of many biological systems. Currently, this rapidly developing field is based on metal-containing segments, typically TiO2 and precious metals. Herein, we present metal-free tubular micromotors solely based on graphitic carbon nitride, as highly scalable and low-cost micromachines that can be actuated by turning on/off the light source. These micromotors are able to move by a photocatalytic-induced bubble-propelled mechanism under visible light irradiation, without any metal-containing part or biochemical molecule on their structure. Furthermore, they exhibit interesting properties, such as a translucent tubular structure that allows the optical visualization of the O2 bubble formation and migration inside the microtubes, as well as inherent fluorescence and adsorptive capability. Such properties were exploited for the removal of a heavy metal from contaminated water with the concomitant optical monitoring of its adsorption by fluorescence quenching. This multifunctional approach contributes to the development of metal-free bubble-propelled tubular micromotors actuated under visible light irradiation for environmental applications.