A multi-stimuli responsive carbazole based low molecular weight gelator: nanomolar sensing of cyanide ions and electrochromic switching in real-time

Abstract

Multi-stimuli responsive polycyclic aromatic hydrocarbons offer advantages of high selectivity, sensitivity, and versatility as they can integrate multiple inputs and outputs to achieve the desired applications in a flexible manner. In this context, carbazole and its derivatives have been extensively studied due to their tunability, outstanding electrochemical properties and good environmental stability. However, most of the studies used the polymeric forms of carbazole derivatives which requires energy-intensive synthesis. Recently, it has been reported that the self-assembled monolayers of carbazole derivatives offer more advantages over their polymeric forms in terms of stability and efficiency. Herein, we introduce a carbazole-based low molecular weight gelator achieved with synthetic ease, exhibiting a multi-stimuli response behaviour, i.e. sensing of cyanide ions and electrochromism, in its solution state. Further, the compound forms a gel in dioxane–H₂O and DMF–H₂O mixtures and exhibits aggregation-induced emission (AIE). The mechanistic pathways of sensing have been investigated and the limit of detection is found to be 1.25 nM, which is significantly lower than the permissible limit established by the WHO. Furthermore, possibilities of extending the electrochromism and sensing in the gel state using carbazole derivatives have been explored and the results indicate that low molecular weight carbazole derivatives are promising candidates for electrochromism and sensing applications.