Surface properties are essential for many applications. Surface properties of reconfigurable surfaces are tunable using external stimuli. Light, a non-contact stimulus, provides high spatiotemporal resolution to control surface properties. UV-light-controlled reconfigurable surfaces have been developed in recent years. However, UV light easily damages biological components and shortens lifetime of organic materials. Thus, it is highly desirable to use noninvasive visible light to reconfigure surface properties.
Our group is working on the visible-light-responsive Ru complexes. These complexes undergo ligand photosubstitution induced by visible light. Based on photosubstitution of Ru complexes, we have developed functional polymers [1-3] and nanomaterials [4-7].
Two years ago, my institute was under construction. When I walked through the constructed hallway, I was disturbed by the noise from an electric screwdriver. As my group was working on photoresponsive Ru complexes, I noticed that Ru complexes may act as molecular screwdrivers that are a hundred million times smaller than the real one. Molecular screwdrivers may be used to construct nano world. Inspired by the screwdriver, we designed a Ru complex (Ru-H2O), which acts as the molecular “screwdriver”, and thioethers with different functional groups act as molecular “bits”. The removal of the bit on the screwdriver is driven by visible light, while the attachment of another bit to the screwdriver is achieved in the dark via thermal substitution. Based on the reversible ligand substitution, we constructed surfaces that can be reconfigured into user-defined functions.
As a proof of concept, we demonstrate rewriting surface patterns, manipulating protein adsorption, and controlling wettability based on visible-light-controlled metal-ligand coordination. Our surface is responsive to red light, which can penetrate deeply into tissue and causes less damage to biological systems than UV light. Our strategy is versatile for customizable surface functionalization and opens exciting opportunities for a wide range of applications.
To learn more about our work, please read our article: “Reconfiguring Surface Functions Using Visible-Light-Controlled Metal-Ligand Coordination” in Nature Communications.
1. Sun, W. et al. Red-light-controlled release of drug-Ru complex conjugates from metallopolymer micelles for phototherapy in hypoxic tumor environments. Adv. Funct. Mater., 1804227 (2018).
2. Sun, W. et al. An amphiphilic ruthenium polymetallodrug for combined photodynamic therapy and photochemotherapy in vivo. Adv. Mater. 29, 1603702 (2017).
3. Sun, W. et al. Ruthenium-containing block copolymer assemblies: Red-light-responsive metallopolymers with tunable nanostructures for enhanced cellular uptake and anticancer phototherapy. Adv. Healthcare Mater. 5, 467-473 (2016).
4. Chen, Z., He, S., Butt, H. J. & Wu, S. Photon upconversion lithography: Patterning of biomaterials using near-infrared light. Adv. Mater. 27, 2203-2206 (2015).
5. Chen, Z. et al. Upconversion nanocarriers encapsulated with photoactivatable ru complexes for near-infrared light-regulated enzyme activity. Small 13, 1700997 (2017).
6. Chen, Z., Xiong, Y., Etchenique, R. & Wu, S. Manipulating pH using near-infrared light assisted by upconverting nanoparticles. Chem. Commun. 52, 13959-13962 (2016).
7. He, S. et al. Ultralow-intensity near-infrared light induces drug delivery by upconverting nanoparticles. Chem. Commun. 51, 431-434 (2015).