Abstract
A nanoprobe is described for the ratiometric fluorometric determination of sulfite ions. Upconversion nanoparticles (UCNPs) of the type β-NaYF4:Yb(III),Er(III),Tm(III) were covalently modified with the molecular probe HIAN which is a hydroxynaphthalimide fluorophore modified with a (cationic) indolinium moiety. Under excitation at 980nm, the green emission of the UCNPs (peaking at 543nm) is almost totally quenched, while the NIR emission (peaking at 802nm) remains unaffected. In the presence of sulfite or bisulfite(hydrogen sulfite), the green fluorescence is restored and can be visually observed. A ratiometric method was worked out by measurement of the ratio of the green and NIR emissions. The analytical range extends from 10 to 250μM, the limit of detection is 0.14μM, and the assay can be performed within 40s. Graphical abstract Based on the use of a molecular probe for sulfite and hydrogen sulfite, and by exploitinganinner filter effect (IFE), an assay for sulfite/hydrogensulfite was developed by using upconversion nanoparticles (UCNPs). Addition reaction of sulfite/bisulfite with the material results in weakened IFE and enhancedgreen fluorescence of the UCNPs at excitation/emission wavelengths of 980/543nm.
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