SERS-Active Substrate with Collective Amplification Design for Trace Analysis of Pesticides.

Jiunn-Der Liao,Wei-En Fu,Bernard Haochih Liu,Han Lee,Jaya Sitjar

doi:10.3390/nano9050664

Jiunn-Der Liao, Wei-En Fu + Show 3 more

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https://doi.org/10.3390/nano9050664

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Abstract

Health risks posed by the exposure to trace amounts of pesticide residue in agricultural products have gained a lot of concerns, due to their neurotoxic nature. The applications of surface-enhanced Raman Scattering (SERS) as a detection technique have consistently shown its potential as a rapid and sensitive means with minimal sample preparation. In this study, gold nanoparticles (Au NPs) in elliptical shapes were collected into a layer of ordered zirconia concave pores. The porous zirconia layer (pZrO2) was then deposited with Au NPs, denoted as Au NPs (x)/pZrO2, where x indicates the deposition thickness of Au NPs in nm. In the concave structure of pZrO2, Au-ZrO2 and Au-Au interactions provide a synergistic and physical mechanism of SERS, which is anticipated to collect and amplify SERS signals and thereafter improve the enhancement factor (EF) of Au NPs/pZrO2. By taking Rhodamine 6G (R6G) as the test molecule, EF of Au NPs/pZrO2 might reach to 7.0 × 107. Au NPs (3.0)/pZrO2 was then optimized and competent to detect pesticides, e.g., phosmet and carbaryl at very low concentrations, corresponding to the maximum residue limits of each, i.e., 0.3 ppm and 0.2 ppm, respectively. Au NPs (3.0)/pZrO2 also showed the effectiveness of distinguishing between phosmet and carbaryl under mixed conditions. Due to the strong affinities of the phosphoric groups and sulfur in phosmet to the Au NPs (3.0)/pZrO2, the substrate exhibited selective detection to this particular pesticide. In this study, Au NPs (3.0)/pZrO2 has thus demonstrated trace detection of residual pesticides, due to the substrate design that intended to provide collective amplification of SERS.

Highlights

Trace detection of contaminant or target substance has gained a lot of interests to be effective for various applications, including food safety, environmental monitoring, and medical diagnostics among others [1]
With increasing deposition thickness (x), Au NPs appeared to increase in quantity and eventually exhibited agglomeration, as shown in x = 5.0 nm
A substrate specially designed for collective surface-enhanced Raman Scattering (SERS) amplification by taking into consideration substrate geometry and materials, as well as its interactions with target analytes, was presented in this study

Summary

Introduction

Trace detection of contaminant or target substance has gained a lot of interests to be effective for various applications, including food safety, environmental monitoring, and medical diagnostics among others [1]. Analytical methods for such applications have already been established, for example, the techniques of chromatography [2] and mass spectroscopy [3]. The said methods are mostly suitable for cases wherein the analyte component in a sample is present at a relatively high concentration, and could follow a time-consuming process for sample preparation. There has been a growing public concern on the residuals of pesticides being present in agricultural products intended for consumption and eventually posing health risks. Regulations have set maximum residue limits for the residuals of pesticides in products; these limits may range from 0.01 to 0.1 ppm, which would require a sensitive detection method [4].

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