Analyte-triggered cascade signal amplification strategy for highly sensitive detection of iodate in table salt with dual-readout signals.

A novel and highly sensitive upconversion fluorescence and colorimetric dual readout iodate (IO) nanosensor system was constructed by using both the outstanding optical performance of NaYF:Yb, Tm upconversion nanoparticles (UCNPs) and the analyte-triggered cascade signal amplification (CSA) technique. The construction of the sensing system consisted of three processes. First, IO oxidized o-phenylenediamine (OPD) to diaminophenazine (OPDox), while IO was reduced to I. Second, the generated I can further oxidize OPD to OPDox. This mechanism has been verified by H NMR spectra titration analysis and HRMS measurement, which effectively improves the selectivity and sensitivity of the measurement of IO. Third, the generated OPDox can effectively quench the fluorescence of UCNPs via the inner filter effect (IFE), realize analyte-triggered CSA, and allow quantitative determination of IO. Under the optimized conditions, the fluorescence quenching efficiency showed a good linear relationship to IO concentration in the range of 0.06-100 μM, and the detection limit reached 0.026 μM (3RSD/slope). Moreover, this method was applied to detect IO in table salt samples, yielding satisfactory determination results with excellent recoveries (95.5-105%) and high precision (RSD <5.5%). These results suggest that the dual-readout sensing strategy with well-defined response mechanisms has promising application prospects in physiological and pathological studies.