Manipulating the surface structure of quantum dots based on dual response modes triggered by iron ions for the visualization of hydrogen sulfide with a wide detection range

Abstract

Developing fluorescent turn-on probes to monitor hydrogen sulfide (H₂S) in biosystems has attracted significant attention owing to their noninvasiveness, high spatial resolution and superior signal-to-noise ratio. Considering the significant expression level of H₂S in living organisms, it is a great challenge to further expand the response range to several-hundred micromolar levels while maintaining excellent sensitivity for this type of probe. Herein, we proposed a surface manipulation strategy for the highly emissive CuInS₂ quantum dots (CIS QDs) using a recognition group with multiple responses during the assay to construct an H₂S turn-on fluorescent probe. Results demonstrated that the designed CIS/ZnS@Fe³⁺ nanoprobe can react with H₂S via the modes of H₂S-induced reduction of Fe³⁺ and subsequent metal-sulfide precipitation of Fe²⁺, producing a fluorescent signal exhibiting a two-stage linear relationship with the amount of H₂S. As a result, it not only possessed a considerable limit of detection of 0.68 μM and high selectivity but also had an extremely wide detection range of 0–300 μM, and it was capable of H₂S fluorescent imaging in living cells.