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首页> 外文期刊>Journal of environmental science and health >Raman and SERS spectra of thiamethoxam and the Ag_3-thiamethoxam complex: an experimental and theoretical investigation
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Raman and SERS spectra of thiamethoxam and the Ag_3-thiamethoxam complex: an experimental and theoretical investigation

机译：噻虫嗪和Ag_3-噻虫嗪配合物的拉曼光谱和SERS光谱：实验和理论研究

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The insecticide thiamethoxam (TMX) is one of the most important neonicotinoid pesticides. The chromatographic methods currently employed to detect TMX require multiple operational steps. This study proposes a simple method that detects TMX via surface-enhanced Raman scattering (SERS) spectroscopy with Ag nanoparticles (NPs) as the SERS active substrate. Density functional theory (DFT) was used to calculate the structures and vibrational modes of the Ag- and Ag-3-TMX complexes at the B3LYP/6-311++G(d,p)(C,H,N)/LanL2DZ(Ag) level of theory. The results reveal that the atoms in the thiazole ring all lie in the same plane, while the six-membered ring is perpendicular to the thiazole ring. Data from both Ultraviolet-visible and Raman spectroscopy indicated that TMX bonds to Ag through its nitro group, vertically. A weak intramolecular (N22-O23 horizontal ellipsis H26) hydrogen bonding and Ag-O bands shift N-O symmetrical vibration to down to lower wavenumber. This was supported by the appearance of a strong 866 cm(-1) band in the SERS spectrum assigned to the N-O symmetrical vibration coupled with the N-N stretching vibrational mode of different excitation wavelength. Notably, a good linear relationship was observed in the TMX concentration range 1.0 x 10(-6)-1.0 x 10(-4 )mol center dot L-1 (R-2 = 0.9667). SERS is an extremely simple and rapid technique that requires little sample for analysis.
机译：杀虫剂噻虫嗪（TMX）是最重要的新烟碱类农药之一。当前用于检测TMX的色谱方法需要多个操作步骤。这项研究提出了一种简单的方法，该方法通过以银纳米颗粒（NPs）作为SERS活性底物的表面增强拉曼散射（SERS）光谱检测TMX。密度泛函理论（DFT）用于计算B3LYP / 6-311 ++ G（d，p）（C，H，N）/ LanL2DZ处的Ag和Ag-3-TMX配合物的结构和振动模式（Ag）的理论水平。结果表明，噻唑环中的原子全部位于同一平面上，而六元环垂直于噻唑环。来自紫外可见光谱和拉曼光谱的数据均表明，TMX通过其硝基垂直键合至Ag。弱的分子内（N22-O23水平省略号H26）氢键和Ag-O带使N-O对称振动向下移动至更低的波数。这归因于SERS光谱中出现了866 cm（-1）的强带，该带分配给N-O对称振动以及不同激发波长的N-N拉伸振动模式。值得注意的是，在TMX浓度范围1.0×10（-6）-1.0×10（-4）mol中心点L-1（R-2 ＝ 0.9667）下观察到良好的线性关系。 SERS是一种非常简单，快速的技术，几乎不需要样品进行分析。

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