Xu Meng-Lei, Gao Yu, Jin Jing, Xiong Jin-Feng, Han Xiao Xia, Zhao Bing
College of Food Science and Engineering, Jilin University, Changchun 130062, China.
State Key Laboratory of Supramolecular Structure and Materials, Jilin University, Changchun 130012, China.
Nanomaterials (Basel). 2020 Dec 17;10(12):2539. doi: 10.3390/nano10122539.
Glyphosate is one of the most commonly used and non-selective herbicides in agriculture, which may directly pollute the environment and threaten human health. A simple and effective approach to its detection is thus quite necessary. Surface-enhanced Raman scattering (SERS) spectroscopy was shown to be a very effective method to approach the problem. However, sensitivity in SERS experiments is quite low, caused by different orientation/conformation of the adsorbed molecules on the metal surface, which limit its detection by using SERS. In this paper, 2‒C‒glyphosate (hereafter: 13-GLP) was designed as a model molecule for theoretical and experimental studies of the molecule structure. Vibrational modes were assigned based on the modeling results obtained at the B3LYP/6-311++G** level by density functional theory (DFT) calculations, which were performed to predict the FT‒IR and Raman spectra. Band downshifts were caused by C atom isotopic substitution with mass changed. Moreover, SERS spectra of 13-GLP by combining ninhydrin reaction on Ag NPs were obtained. Isotopic Raman shifts are helpful in identifying the components of each Raman band through vibrations across the molecular system. They are coupled by probe molecules and thus bind to the substrates, indirectly offering the opportunity to promote interactions with Ag NPs and reduce the complex equilibrium between different orientation/conformation of glyphosate molecules on the metal surface.
草甘膦是农业中最常用的非选择性除草剂之一，它可能直接污染环境并威胁人类健康。因此，一种简单有效的检测方法非常必要。表面增强拉曼散射（SERS）光谱被证明是解决这个问题的一种非常有效的方法。然而，SERS实验中的灵敏度相当低，这是由吸附在金属表面的分子的不同取向/构象引起的，这限制了使用SERS对其进行检测。在本文中，设计了2-C-草甘膦（以下简称：13-GLP）作为分子结构理论和实验研究的模型分子。基于密度泛函理论（DFT）计算在B3LYP/6-311++G**水平获得的建模结果对振动模式进行了归属，这些计算用于预测傅里叶变换红外（FT-IR）和拉曼光谱。由于C原子同位素取代导致质量变化而引起谱带下移。此外，通过在银纳米颗粒（Ag NPs）上结合茚三酮反应获得了13-GLP的SERS光谱。同位素拉曼位移有助于通过分子系统中的振动识别每个拉曼谱带的成分。它们通过探针分子耦合，从而与底物结合，间接地提供了促进与Ag NPs相互作用的机会，并减少了草甘膦分子在金属表面不同取向/构象之间的复杂平衡。
