Nanoarchitectonics with designed sulfur-based functionalized azobenzene ionic liquids for low-temperature UV light switching systems

Ionic liquids (ILs) have been widely used as flexible sensors due to their tunable properties, low vapor pressure, and high electrical conductivity. ILs containing sulfonium cations have exhibited low melting points, high conductivity, and excellent stability comparable to imidazolium-based ILs, rendering them promising candidates for low-temperature sensing applications. Nevertheless, the unique properties of functionalized sulfonium-based ILs pose challenges for their synthesis using conventional methods, thereby limiting their widespread utilization. In this study, we propose an efficient approach for the preparation of functionalized sulfonium-based ILs and, for the first time, obtain ILs capable of ultraviolet (UV) light sensing at −10 °C. The synthesized ILs maintain their liquid state over a broad temperature range (−30 °C to 150 °C) and exhibit sensitive responses to UV light under complex environments, including low and high temperatures, as well as underwater, demonstrating great potential for their applications as flexible sensors.