Plasmon-enhanced fluorimetric and colorimetric dual sensor based on fluorescein/Ag nanoprisms for sensitive determination of mancozeb

A plasmon-enhanced fluorimetric and colorimetric dual sensor was designed to detect mancozeb based on fluorescein (as a fluorimetric reporter) and AgNPRs (as a fluorescence enhancer and colorimetric reporter). The sensing mechanism was based on the shape transformation of AgNPRs due to etching and anti-etching effect of S2O32- and mancozeb. We observed that AgNPRs enhanced the fluorescence intensity of fluorescein around 4-fold. By adding S2O32-, the AgNPR florescence enhancement effect decreased, also SPR peak of AgNPRs blue-shifted and the solution color altered from blue to purple. The fluorescein fluorescence intensity and AgNPR's SPR peak position restored in the presence of mancozeb due to its protecting effect on AgNPRs. The restored fluorescence intensity and the SPR wavelength shift were proportional to the mancozeb concentration at the range of 0.005-0.1 and 0.005-0.075 mg/L, respectively. The developed sensor was successfully applied to measure mancozeb in fruit juice samples.