Multifunctional Visible‐Light Powered Micromotors Based on Semiconducting Sulfur‐ and Nitrogen‐Containing Donor–Acceptor Polymer

Abstract

Photosensitive micromotors that can be remotely controlled by visible light irradiation demonstrate great potential in biomedical and environmental applications. To date, a vast number of light‐driven micromotors are mainly composed from costly heavy and precious metal‐containing multicomponent systems, that limit the modularity of chemical and physical properties of these materials. Herein, a highly efficient photocatalytic micromotors based exclusively on a purely organic polymer framework—semiconducting sulfur‐ and nitrogen‐containing donor–acceptor polymer, is presented. Thanks to precisely tuned molecular architecture, this material has the ability to absorb visible light due to a conveniently situated energy gap. In addition, the donor‐acceptor dyads within the polymer backbone ensure efficient photoexcited charge separation. Hence, these polymer‐based micromotors can move in aqueous solutions under visible light illumination via a self‐diffusiophoresis mechanism. Moreover, these micromachines can degrade toxic organic pollutants and respond to an increase in acidity of aqueous environments by instantaneous colour change. The combination of autonomous motility and intrinsic fluorescence enables these organic micromotors to be used as colorimetric and optical sensors for monitoring of the environmental aqueous acidity. The current findings open new pathways toward the design of organic polymer‐based micromotors with tuneable band gap architecture for fabrication of self‐propelled microsensors for environmental control and remediation applications.

Polymeric Micro/Nanocarriers and Motors for Cargo Transport and Phototriggered Delivery

“…Moldable organic polymeric systems have demonstrated biodegradability and solubility in aqueous media-features amenable for environmental applications, promoting high interaction with pollutants and salts compared with precious metal systems with limited modularity and worse properties [347]. Moreover, semiconductor polymers can exert photocatalytic activity for pollutant degradation, constituting another approach for water purification [356].…”

“…The visible irradiation photocatalyzed the micromotors, causing the disaggregation of the polymer because the material absorbed the light in a situated energy gap, causing the donor/acceptor dyes to break apart. This degraded the organic pollutants and increased the acidity of aqueous media, changing their color, showing great potential for colorimetric-based acidity sensors, and opening new environmental control options and novel opportunities for remediation applications (Figure 10D) [347].…”

“…Figure10. Schematic representation of light-stimulated polymeric micro/nanomotors for propulsion, by (A) an azobenzene-coated crosslinked polystyrene nanomotor, reprinted with permission from[341], copyright 2011, American Chemical Society; (B) cargo transport-an NIR-photoactive polymersome nanomotor for doxorubicin delivery, reprinted with permission from[345], copyright 2020, John Wiley and Sons; (C) visible-light-photosensitive micromotors, reprinted with permission from[346], copyright 2017, American Chemical Society; (D) an organic polymer sulfur semiconductor and nitrogen donor/acceptor polymer, reprinted with permission from[347], copyright 2020, John Wiley and Sons; (E) light-stimulated and catalytic micromotors enhance the biosensing detection, reprinted with permission from[348], copyright 2017, John Wiley and Sons; and (F) NIR thermal and catalytic polymeric nanomotors, reprinted with permission from[349], copyright 2018, American Chemical Society.…”

Self‐Propelled Micro‐/Nanomotors as “On‐the‐Move” Platforms: Cleaners, Sensors, and Reactors

“…Reproduced with permission. [ 108 ] Copyright 2020, Wiley‐VCH. F) Reductive detoxification of 4‐nitrophenol facilitated by Pd/Ti/Fe/Cr rolled‐up micromotors using NaBH 4 as reductant and fuel.…”

Polymeric Micro/Nanomotors and Their Biomedical Applications

“…A state-of-the-art photocatalytic micromotor that could work as a pH sensor was based on sulfur-and nitrogen-containing donor-acceptor polymers. [66] It was noteworthy that sulfur and nitrogen-containing polymer network, a versatile framework that could trigger propulsion of micro or nanoparticles in aqueous system under illumination, brought mobility and pH-responses to the micromotor. Under visible-light irradiation, stable photoexcited charge carriers were generated.…”