Highly sensitive surface-enhanced Raman scattering detection of organic pesticides based on Ag-nanoplate decorated graphene-sheets

Organic pesticides are widely used in the modern agriculture. Their residues in food, water and soil pose a huge threat to human health. Surface-enhanced Raman scattering (SERS) spectroscopy is a powerful tool for detecting trace organic pesticides due to its high sensitivity and rich fingerprinting structure information for molecules. In this work, we construct a highly sensitive SERS substrate based on Ag-nanoplates decorated graphene-sheets for ultra-sensitive SERS detection of organic pesticides. The Ag-nanoplates are holded by the graphene and stay closely to each other, creating "hot spots" for SERS-signal amplification. On the other hand, the graphene sheets can serve as pesticides molecules assemblier because of its strong absorption ability and π − π interaction with pesticides molecules. Therefore, the Ag-nanoplates@graphene hybrids (Ag-NP@GH) substrate shows high sensitivity for detecting trace-level organic pesticides, including thiram and methyl parathion (MP), and their mixtures. The limit of detection for thiram and MP was as low as 40 nM and 600 nM, respectively. In addition, a good linear relationship between the Raman intensity and molecular concentration was obtained, indicating the potential application of the Ag-NP@GH substrate for quantitative SERS detection. Importantly, the Ag-NP@GH substrate shows good SERS-signal reproducibility with a relative signal deviation down to 5.6%. These results show high potential of the Ag-NP@GH as effective SERS substrates for rapid detection of trace-level organic pesticides in environment.