Abstract Glyphosate is a wide spread organophosphate herbicide whose use and associated risks are strongly debated. Many countries are regulating its use in field and it is often found in surface water. Therefore, a simple analytical method, possibly based on portable instruments, would be highly desirable. In case of many other pesticides, surface enhanced Raman scattering (SERS) spectroscopy was shown to be a very effective method to approach the problem. Glyphosate Raman and SERS spectra have been subject of different experimental and theoretical studies but still their interpretation is unclear and sensitivity in SERS experiments is quite low. In this work, SERS spectra on silver nanoparticles dispersion of glyphosate, its 2-13C isotopically substituted derivative, and its degradation product, the aminomethylphosphonic acid, have been obtained. The vibrational spectra of this latter compound allowed us to rule out a possible contribution of this species to the SERS spectra and the observed isotope shifts help to explain the SERS pattern in terms of the orientation of the adsorbed molecules on the metal surface. Therefore, we conclude that the relevant differences both on the intensities and wavenumbers between our SERS and Raman spectra of glyphosate must derive from the effect induced by the adsorption on the nanoparticles.

中文翻译：

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草甘膦在分散的银纳米粒子上的表面增强拉曼散射：基于模型分子的重新解释

摘要 草甘膦是一种广泛使用的有机磷除草剂，其使用和相关风险存在激烈争论。许多国家都在规范其在田间的使用，它经常存在于地表水中。因此，非常需要一种可能基于便携式仪器的简单分析方法。对于许多其他农药，表面增强拉曼散射 (SERS) 光谱被证明是解决该问题的非常有效的方法。草甘膦拉曼光谱和 SERS 光谱已成为不同实验和理论研究的主题，但它们的解释仍不清楚，SERS 实验的灵敏度非常低。在这项工作中，获得了草甘膦银纳米粒子分散体、其 2-13C 同位素取代衍生物及其降解产物氨甲基膦酸的 SERS 光谱。后一种化合物的振动光谱使我们能够排除该物种对 SERS 光谱的可能贡献，并且观察到的同位素位移有助于根据金属表面上吸附分子的取向来解释 SERS 模式。因此，我们得出结论，我们的草甘膦 SERS 和拉曼光谱之间在强度和波数上的相关差异必须源自纳米颗粒上的吸附作用。