Styrylisoxazole-based fluorescent probes for the detection of hydrogen sulfide

Styrylisoxazoles bearing a nitro group linked to bulky aromatic rings have been synthesized and examined for their absorption and emission studies in organic solvents and water. The molecules showed emission in the visible region with significant solvatochromic emission shifts influenced by the extended conjugation of aromatic rings and intramolecular charge transfer. These absorption and emission changes were used for the efficient and sensitive detection of trace concentrations of hydrogen sulfide (H<inf>2</inf>S) through the reduction of the nitro group to the amine group in the presence of aqueous sodium sulfide. The experimental results indicated that the probes exhibit an excellent emission response with large shifts in the emission and sensitivity with a micromolar detection limit.