Benchmarking the placement of hydrosulfide in the Hofmeister series using a bambus[6]uril-based ChemFET sensor.

Hydrosulfide (HS) is the conjugate base of gasotransmitter hydrogen sulfide (HS) and is a physiologically-relevant small molecule of great interest in the anion sensing community. However, selective sensing and molecular recognition of HS in water remains difficult because, in addition to the diffuse charge and high solvation energy of anions, HS is highly nucleophilic and readily oxidizes into other reactive sulfur species. Moreover, the direct placement of HS in the Hofmeister series remains unclear. Supramolecular host-guest interactions provide a promising platform on which to recognize and bind hydrosulfide, and characterizing the placement of HS in the Hofmeister series would facilitate the future design of selective receptors for this challenging anion. Few examples of supramolecular HS binding have been reported, but the Sindelar group reported HS binding in water using bambus[6]uril macrocycles in 2018. We used this HS binding platform as a starting point to develop a chemically-sensitive field effect transistor (ChemFET) to facilitate assigning HS to a specific place in the Hofmeister series. Specifically, we prepared dodeca--butyl bambus[6]uril and incorporated it into a ChemFET as the HS receptor motif. The resultant device provided an amperometric response to HS, and we used this device to measure the response of other anions, including SO, F, Cl, Br, NO, ClO, and I. Using this response data, we were able to experimentally determine that HS lies between Cl and Br in the Hofmeister series, which matches recent theoretical computational work that predicted a similar placement. Taken together, these results highlight the potential of using molecular recognition coupled with ChemFET architectures to develop new approaches for direct and reversible HS detection and measurement in water and further advance our understanding of different recognition approaches for this challenging anion.