Carbon nitride-based light-driven microswimmers with intrinsic photocharging ability

Controlling autonomous propulsion of microswimmers is essential for targeted drug delivery and applications of micro/nanomachines in environmental remediation and beyond. Herein, we report two-dimensional (2D) carbon nitride-based Janus particles as highly efficient, light-driven microswimmers in aq...

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Published in:Proceedings of the National Academy of Sciences - PNAS 2020-10, Vol.117 (40), p.24748-24756
Main Authors: Sridhar, Varun, Podjaski, Filip, Kröger, Julia, Jiménez-Solano, Alberto, Park, Byung-Wook, Lotsch, Bettina V., Sitti, Metin
Format: Article
Language:English
Subjects:
Alcohols
Aqueous solutions
Capping
Carbon
Carbon nitride
Chemical reduction
Drug delivery
Drug delivery systems
Energy storage
Environmental restoration
Fuels
Gold
Hydrogen evolution reactions
Hydrogen peroxide
Nanoparticles
Oxygen reduction reactions
Physical Sciences
Platinum
Propulsion
Remediation
Silicon dioxide
Solar energy
Surface reactions
Swimming
Titanium dioxide
Ultraviolet radiation
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Summary:Controlling autonomous propulsion of microswimmers is essential for targeted drug delivery and applications of micro/nanomachines in environmental remediation and beyond. Herein, we report two-dimensional (2D) carbon nitride-based Janus particles as highly efficient, light-driven microswimmers in aqueous media. Due to the superior photocatalytic properties of poly(heptazine imide) (PHI), the microswimmers are activated by both visible and ultraviolet (UV) light in conjunction with different capping materials (Au, Pt, and SiO₂) and fuels (H₂O₂ and alcohols). Assisted by photoelectrochemical analysis of the PHI surface photoreactions, we elucidate the dominantly diffusiophoretic propulsion mechanism and establish the oxygen reduction reaction (ORR) as the major surface reaction in ambient conditions on metal-capped PHI and even with TiO₂-based systems, rather than the hydrogen evolution reaction (HER), which is generally invoked as the source of propulsion under ambient conditions with alcohols as fuels.Making use of the intrinsic solar energy storage ability of PHI, we establish the concept of photocapacitive Janus microswimmers that can be charged by solar energy, thus enabling persistent light-induced propulsion even in the absence of illumination—a process we call “solar battery swimming”—lasting half an hour and possibly beyond. We anticipate that this propulsion scheme significantly extends the capabilities in targeted cargo/drug delivery, environmental remediation, and other potential applications of micro/nanomachines, where the use of versatile earth-abundant materials is a key prerequisite.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.2007362117