A highly selective and easily acquisitive near-infrared fluorescent probe for detection and imaging of hydrogen sulfide in cells.

Hydrogen sulfide (H2S) plays a substantial role as a messenger in the physiological and pathological processes of many diseases. Recently, the fluorescence probe of H2S based on organic dye has attracted great attention. However, the emission of many probes is in the UV-vis region (400-600 nm), so it has the disadvantages of shallow tissue penetration and more vulnerable to spontaneous fluorescence interference. Although several H2S probes have been developed that emit more than 650 nm, there is a complex structure difficult to synthesize or unstable in storage. Aimed at simply structural and easily synthesized H2S fluorescent probes with emission wavelength more than 650 nm, a novel near-infrared (NIR) probe (NIR-H2S) here was rationally designed with 4-(2-carboxyphenyl)-7-(diethylamino)-2-(4-hydroxystyryl)chromenylium (NIR-OH) as a fluorescent dye and 2,4-dinitrophenyl moiety as a recognition group. Addition of H2S, the "turn-on" NIR fluorescence response at 736 nm of NIR-H2S was displayed, accompanied by a visual colour change from purple to green when excited at 686 nm. As an easily acquisitive H2S probe, NIR-H2S has been successfully applied to cell imaging for H2S detection with the advantages such as long fluorescence emission, low toxicity, high sensitivity and strong selectivity.