Pesticides play an important role in conventional agriculture. Yet, their harmful effects on the environment are becoming increasingly apparent. The occurrence of pesticides is hence being monitored worldwide. For fast, easy, yet sensitive identification, surface-enhanced Raman spectroscopy (SERS) is a powerful tool. In this study, a method is introduced that may be amended to in-field detection of pesticides. Gold and silver nanoparticles were synthesized, size-tailored, and characterized. The herbicide paraquat and the fungicide thiram served as model compounds. The preparation yielded reproducible SERS spectra. Using quantum chemical computation, Raman and SERS spectra were calculated and analyzed. The interpretation of vibrational modes in combination with SERS enhancement and attenuation allowed us to identify compound-specific bands. The assignment was interpreted in terms of the orientation of paraquat and thiram on the gold and silver nanoparticle surfaces. Paraquat preferred a co-planar arrangement parallel to the gold nanoparticle surface and a head-on orientation on the silver nanoparticle. For thiram, breaking of the disulfide bond was recognized, such that interaction with the surface occurred via the sulfur atoms. Successful detection of the pesticides after recollection from vegetable leaves demonstrated the method's applicability for pesticide identification.

中文翻译：

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使用表面增强拉曼光谱和密度泛函理论计算进行农药鉴定：从结构洞察到现场检测

农药在传统农业中发挥着重要作用。然而，它们对环境的有害影响正变得越来越明显。因此，全世界范围内都在监测农药的出现。对于快速、简单且灵敏的识别，表面增强拉曼光谱 (SERS) 是一种强大的工具。在这项研究中，介绍了一种可以修改为农药现场检测的方法。金和银纳米颗粒的合成、尺寸定制和表征。除草剂百草枯和杀菌剂福美双作为模型化合物。该制备过程产生了可重复的 SERS 光谱。使用量子化学计算，计算和分析拉曼和SERS光谱。结合 SERS 增强和衰减对振动模式的解释使我们能够识别化合物特定的谱带。该分配是根据百草枯和福美双在金和银纳米粒子表面上的取向来解释的。百草枯优选与金纳米颗粒表面平行的共面排列以及在银纳米颗粒上的正面取向。对于福美双，发现二硫键断裂，从而通过硫原子与表面发生相互作用。回收蔬菜叶子后对农药的成功检测证明了该方法对于农药鉴定的适用性。