Visual sensing of formaldehyde via a solution-to-gel transition with cholesteryl naphthalimide-based derivatives

Abstract It is relevant for individual and public health security to develop a simple protocol for visual sensing of formaldehyde (FA). Herein, two cholesteryl naphthalimide-based derivatives (1a and 1b) were developed to be FA chemosensors with a hydrazine group as the receptor based on Schiff-base reaction. These two compounds were found to be organogelators for several organic solvents. Besides, either 1a or 1b in DMSO could be used to determine FA in an aqueous solution via fluorescence spectral changes with relatively low detection limits. More interestingly, FA could trigger gelation of the DMSO solutions of gelator 1a in a high gelator concentration. However, 1b failed to have such behaviour. The easy-to-visualize solution-to-gel transition in combination with quantitatively fluorescent detection leads us to propose that 1a and related systems could have a role play analyzing FA either in an aqueous solution or in air. Furthermore, this is the first instance ever of a chemosensor using such a sensing mode for FA.