Hydrogen bond regulated hydrogen sulfate ion recognition: an overview

Hydrogen sulfate possesses substantial biological importance, having a colossal impact on physiological and environmental events. Therefore, several scientific groups have devoted serious effort to the development of versatile colorimetric and fluorimetric HSO4- sensors. Along with the scope, challenges, and significance, this review emphasizes the advancement of the optical recognition of HSO4- based on hydrogen bonding during the past two decades. Moreover, hydrogen-bond-driven proton transfer, ESIPT, ICT, PET, CHEF, and TBET mechanisms that allow for the optical detection of HSO4- are also discussed concisely. The foundation of this review includes the key points of the sensing process, like the nature of spectroscopic changes, selectivity and sensitivity, naked-eye color changes, the reusability of sensors, and the in vivo detection of HSO4-, if any. Special attention is focused on the correlation between the photophysical changes and the underlying interaction mechanisms that triggered the recognition aspect.

Fluorogenic naked-eye sensing and live-cell imaging of cyanide by a hydrazine-functionalized CAU-10 metal–organic framework

A hydrazine-functionalized Al(iii) based metal–organic framework was utilized for the detection of lethal cyanide in water and in living cells.

Optical sensing of hydrogen sulphate using rhodamine 6G hydrazide from aqueous medium

This communication reports the application of rhodamine 6G hydrazide (L) for the selective colorimetric and turn-on fluorescent sensing of hydrogen sulphate ions from aqueous medium. The ring opening of the colourless spirocyclic form of L was selectively triggered in the presence of HSO₄^- among the other tested anions (F^-, Cl^-, Br^-, I^-, AcO^-, H₂PO₄^-, NO₃^-, ClO₄^-, CN^-, HO^-, AsO₃^3- and SO₄^2-), which gives rise to a pink colour and strong fluorescence in the visible region. Sensor L showed a detection limit down to micromolar range without any interference from the other tested competitive anions. Sensor L was applied for the construction of two inputs (HO^- and HSO₄^-) INHIBIT type molecular logic gate and naked-eye detection of HSO₄^- using test paper strips.