Rapid detection of ziram residues in apple and pear fruits by SERS based on octanethiol functionalized bimetallic core-shell nanoparticles.

ABSTRACT

Existing approaches for the screening of unsafe materials in food matrices are time-consuming, tiresome and destructive in nature. Therefore, in the current study, a surface-enhanced Raman spectroscopy (SERS) method based on octanethiol-functionalized core-shell nanoparticles (Oct/Au@AgNPs) was established for rapid detection of ziram in apple and pear fruits. The morphology of substrate was evaluated using high-resolution TEM images and superimposed HAADF-STEM-EDS elemental mapping images, which confirmed that Au@AgNPs having gold (Au) core size of 28 nm in diameter and silver (Ag) shell of 5.5 nm in thickness were successfully grafted with octanethiol. The SERS method with the sensitive nanoparticles could detect ziram of up to 0.015 and 0.016 ppm in apple and pear with high coefficients of determination (R2) of 0.9987 and 0.9993, respectively. Furthermore, satisfactory recoveries (80-106%) were also accomplished for the fungicide in real samples. This work demonstrated that the functionalized silver-coated gold nanoparticles were easy to prepare and could be used as sensitive SERS platforms for monitoring of other agrochemicals in foods.