MnO2 nanosheet-assisted ratiometric fluorescence probe for the detection of sulfide based on silicon nanoparticles and o-phenylenediamine

A ratiometric fluorescence probe was fabricated based on MnO2 nanosheets, silicon nanoparticles (Si NPs), and o-phenylenediamine (OPD) for sulfide detection. In this system, the MnO2 nanosheets play three crucial roles, i.e., fluorescence quencher of the Si NPs, oxidizing of non-fluorescence OPD to produce a fluorescence substance 2, 3-diaminophenazine (OPDox), and sulfide recognition unit. The MnO2 nanosheets were reduced and lost fluorescence quenching capacity and the oxidase-like characteristics after the addition of sulfide, so that the production of OPDox was restricted and the fluorescence of the Si NPs recovered. Therefore, the fluorescence intensity ratio of OPDox at 565 nm to Si NPs at 450 nm was employed as the signal output to construct a novel ratiometric fluorescence sensor for sulfide detection. Under optimal conditions, a linear relationship was noticed between F565/F450 ratio and the sulfide concentration in the range of 2–20 μM with a 0.31 μM detection limit. Moreover, the proposed strategy demonstrates practicability for sulfide detection in real water samples with satisfactory recoveries of 96.0–106%.