Ratiometric Dual-Mode Optical Sensor Array for the Identification and Differentiation of Pesticides in Vegetables with Mixed Plasmonic and Fluorescent Nanostructures

In this study, we propose a ratiometric dual-mode sensor array for the identification and differentiation of azinphos-methyl, oxidemeton-methyl, and thiometon as organophosphate pesticides and acetamiprid as a neonicotinoid insecticide. This sensor incorporates unmodified gold nanoparticles (AuNPs) and three fluorescent components─blue carbon dots, fluorescein isothiocyanate, and red quantum dots─integrated into a single well to simultaneously obtain colorimetric and fluorescent responses. The sensor's functionality is based on variations in the fluorescence intensity of the luminous components at different wavelengths. This variation is induced by the inner filter effect mechanism, which is triggered by the aggregation of AuNPs in the presence of pesticides. This effect enables naked-eye detection, with emission color tonalities ranging from ruby to misty rose, pink, lilac, yellow, and green and a color range varying from red to purple, blue, and gray. To facilitate the differentiation of the pesticides, we applied principal component analysis and subsequently linear discriminant analysis. For the quantitative determination of pesticides, the partial least squares regression was employed. Our findings demonstrate that the proposed sensor array can accurately detect pesticides and their mixtures in various environments, including lettuce, cucumber, and water.