Modulating a D-π-A type diarylethene for on-demand Cu2+ check via photo-switchable detection range and sensitivity

Abstract

Detection range and sensitivity are two important parameters in a sensing system. Unfortunately, in common sensory systems, wide detection range always suffers from low sensitivity and vice versa. Thus, it becomes more and more desirable to design sensors with both wide detection range and high sensitivity. Here, we report a sensory system based on a photo-switchable D-π-A type diarylethene (SDE), which presents both wide detection range and high sensitivity under alternate light modulation. The D-π-A structure endows the sensor with high energy level of HOMO, which enabled the oxidation of both photoisomer SDEo/SDEc by Cu2+. While the discrepancy in energy levels of oxidation potentials in SDE photoisomers leads to their different reactivity, or in another word, sensitivity towards Cu2+. The inherent oxidative cycloreversion of SDEc to SDEo, on the other hand, provides a possibility that two photoisomers would detect Cu2+ in different working concentrations. The open form was employed for the detection of Cu2+ in a wider concentration range (0–13.0 equivalent) with relatively lower sensitivity (6.4×10−7M). While the closed form was able to probe Cu2+ in lower concentration (0–3.0 equivalent) with higher sensitivity (6.6×10−9M). Based on this photo-switchable sensing activity, a molecular multimeter of variable detection range for Cu2+ was then constructed.