A novel self-calibrating strategy for real time monitoring of formaldehyde both in solution and solid phase

Formaldehyde (FA) is a chemical substance with tremendously noxious feature for human health and it causes serious damages to living organisms. The recognition of formaldehyde in the form of fluorescent signals has been extensively explored by using a few molecular scaffolds in buffer mediums. In particular, the study for sensing of formaldehyde both in solution and solid state has generated considerable interests. Herein, a new ratiometric fluorescent probe 1-(5-(9-phenyl-9H-carbazol-3-yl)thiophen-2-yl)but-3-en-1-amine (SO-GJP) has been synthesized for selective detection of FA based on aza-Cope reaction. In the presence of FA from 0 to 1.3 mM, the emission band of SO-GJP varies from 393 nm to 542 nm and the detection limit has been calculated to be 1.55 μM. The entrapment of SO-GJP onto the thin layer chromatography (TLC) plate leads to the successful detection of FA with sensitive color change from white to yellow. Moreover, the response mechanism has been explained by FA-induced 2-aza-Cope rearrangement within SO-GJP and the chemical processes are supported by density functional theory, fluorescence and UV-vis spectra. The integration of responsive units based on carbazole platform can serve as one of the powerful strategies by directly converting signals at different circumstances into fluorescence.