Abstract
In this study, SiO2@Au@4-MBA@Ag (4-mercaptobenzoic acid labeled gold-silver-alloy-embedded silica nanoparticles) nanomaterials were investigated for the detection of thiram, a pesticide. First, the presence of Au@4-MBA@Ag alloys on the surface of SiO2 was confirmed by the broad bands of ultraviolet-visible spectra in the range of 320–800 nm. The effect of the 4-MBA (4-mercaptobenzoic acid) concentration on the Ag shell deposition and its intrinsic SERS (surface-enhanced Raman scattering) signal was also studied. Ag shells were well coated on SiO2@Au@4-MBA in the range of 1–1000 µM. The SERS intensity of thiram-incubated SiO2@Au@4-MBA@Ag achieved the highest value by incubation with 500 µL thiram for 30 min, and SERS was measured at 200 µg/mL SiO2@Au@4-MBA@Ag. Finally, the SERS intensity of thiram at 560 cm−1 increased proportionally with the increase in thiram concentration in the range of 240–2400 ppb, with a limit of detection (LOD) of 72 ppb.
Highlights
The use of pesticides in modern agriculture has improved crop yield and quality by controlling or destroying pests or weeds [1,2,3,4]
Colloidal Au NPs (3 nm) were prepared using tetrakis(hydroxymethyl)phosphonium chloride (THPC) and incubated with the aminated silica NPs by gentle shaking to prepare Au NPs embedded with SiO2 (SiO2@Au NPs), according to the method reported by Pham et al [38,39,40,41]
4-mercaptobenzoic acid (4-MBA) was introduced on the surface of SiO2@Au NPs through the strong affinity between thiol groups and Au, and it was used as an internal standard
Summary
The use of pesticides in modern agriculture has improved crop yield and quality by controlling or destroying pests or weeds [1,2,3,4]. Pesticides have diverse benefits, they are a threat to consumer health because they are toxic to humans and other species [5,6]. When pesticides are used for crops or seeds, their traces could remain in the food [7], and these derivatives are considered to be toxic [8]. Various methods have been proposed for monitoring pesticide residues, such as high-performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS), thin-layer chromatography, and enzyme-linked immunosorbent assay [9,10,11,12,13]. HPLC is the most robust and reliable method for food safety analysis. A fast, simple, highly sensitive, and stable method should be developed for the determination of pesticide residue
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