Imidazole-assisted film-based fluorescent sensor for the ultrasensitive detection of hydrazine

Abstract

A substituted imidazole-based small molecule fluorescent probe R-1 was designed for the ultrasensitive, selective and quick detection of hydrazine in solid, gel, solution as well as in thin film. The response of R-1 to hydrazine in liquid or vapour form was very effective. The emission band (λ_em = 560 nm) of R-1 in DMSO solution with Stokes shift of 8598 cm⁻¹ was diminished significantly. Most intriguingly, R-1 also exhibited gelation capabilities in DMSO (R-1_gel), and it changed into the sol form (R-1_sol) when it came into contact with hydrazine directly or through its vapour. Rheological and morphological studies revealed that a crystalline self-assembled fibrillar network supported the gelation properties. Density functional theory (DFT) calculations and ¹H NMR spectroscopy both supported the mechanism of recognition. R-1 was also studied for the cell imaging in C6 (glioma) cell lines. This makes R-1 a complete, simple, quick, and visible to the naked eye approach to detect an extremely low amount of hydrazine with high sensitivity (0.08 ppb) and selectivity in every possible state of the receptor as well as hydrazine. The sensing ability of R-1 in the form of a free-standing fluorescent polymeric film is also significant for examining the leakage of the hydrazine vapour.