A near-infrared light responsive temperature-sensing switch in a submicro-channel heterogeneous membrane

Abstract

Near-infrared light (NIR) has the advantages of greater radiation depth, less tissue absorption and scattering, and lower risk, and the construction of a high-throughput NIR responsive membrane with ionic current rectification (ICR) characteristics in submicron or micron channels is of great significance for developing photoresponsive biosensors, and photoelectric and thermoelectric energy conversion in the future. In this paper, sulfhydryl- and carboxyl-terminated poly-N-isopropyl acrylamide with thermosensitivity is synthesized by a reversible addition–fragmentation chain transfer polymerization and ammonolysis reaction; it is further grafted at the base end of a polydopamine/Au nanoparticle-modified photothermal responsive heterogeneous membrane via a Au–S bond to achieve the thermosensitive polymer modification. After the asymmetric 808 nm NIR irradiation, the “on” or “off” status of a submicron channel can be realized stably and reversibly for the reversible phase transition of thermosensitive poly-N-isopropyl acrylamide under the photothermal effect of three polydopamine-Au layers. The conductance of the submicro-channel heterogeneous membrane with ICR characteristics increases at the asymmetric pH gradient, the rectification ratio maximally decreases by 11.4, and the photoresponsive current reaches 26.6 μA (0.1 mM KCl). At the same time, the ICR effect is also achieved at a high salt concentration of 1 M KCl and the photoresponsive current can reach 183.7 μA; the intensity of ICR and photoresponsive current can be effectively regulated by the power density, salt concentration and pH, and then the temperature-sensing switch with a NIR response is successfully constructed. This work provides a new way to improve the photoresponsive current and shows great potential in the fields of solar desalination and power generation.