Cost-effective diagnostic kits for selective detection of gaseous H2S

Bay-functionalization of perylene diimide (PDI) dyes provides the scope for modulating the optical properties of PDI. Symmetrical functionalization at the 1,7-position of the bay-region of PDI offered limited scope for the tunability of photophysical properties, whereas unsymmetrical functionalization at the bay-position met with limited success. We have synthesized unsymmetrical bay-functionalized PDI 3 bearing -OCH3 and -NO2 substituents and studied its properties using the UV-Vis technique, powder X-ray diffraction, thermogravimetric method and NMR spectroscopy. PDI 3 selectively responds to thiols such as H2S, Cys, and Hcy with discriminative behaviour among them. We fabricated several colorimetric kits for the detection of gaseous and aqueous H2S: (a) solution-based colorimetric kits using PDI 3 offer high-resolution colour change with different concentrations of H2S with initial to final colour change from purple to green and (b) PDI 3 impregnated silica nanoparticle and TLC strip/paper-based solid-state colorimetric kits. These colorimetric kits can find potential applications in checking the spoilage of food materials and detecting intracellular H2S.