Label-Free, Reusable, Equipment-Free, and Visual Detection of Hydrogen Sulfide Using a Colorimetric and Fluorescent Dual-Mode Sensing Platform

In this work, we have found for the first time that the fluorescence of rhodamine B (RhB) would be dramatically reduced after it bound to hemin/G-quadruplex and reacted with •OH. Based on this finding, we have designed a colorimetric and fluorescent dual-mode sensing platform for visual detection of hydrogen sulfide (H₂S). The constructed sensor is based on the formation of dsDNA and the G-quadruplex structure by the cytosine-Ag⁺-cytosine mismatch, causing H₂O₂-mediated catalysis to oxidize ABTS or RhB to induce a colorimetric or fluorescent change. In the presence of H₂S, the solution color for colorimetric and fluorescent assays would change from dark green to pink and from green (fluorescence off) to bright yellow (fluorescence on), respectively. This dual-mode assay showed high selectivity toward H₂S over other interference materials with a low measurable detection limit value (below than 2.5 μM), and it has been successfully applied to H₂S visual detection in real samples. Moreover, the dual-mode sensing strategy presented an excellent reutilization character both in colorimetric and fluorescent assays. This method was employed as a label-free, simple, fast, and equipment-free platform for H₂S detection with high selectivity and reusability. This work realized naked-eye detection both in colorimetric and fluorescent analysis at a lower concentration of H₂S, demonstrating a promising strategy for on-site visual detection of H₂S.