除虫脲和高效氯氟氰菊酯的太赫兹光谱及密度泛函理论研究

摘要

利用太赫兹时域光谱技术及密度泛函理论对两种常用的卫生杀虫剂除虫脲和高效氯氟氰菊酯的低频振动光谱进行了研究.室温下观测到两种物质在0.2～2.2 THz内的实验谱分别有5和7个吸收峰,可作为其在THz波段的指纹谱用于分子识别.为了深入理解太赫兹吸收峰的振动特性,我们采用Gaussian03和CRYSTAL09软件分别进行了单分子和晶体的密度泛函理论模拟.晶体模拟结果预测出两种物质在0.2～2.2 THz实验谱中所有的吸收峰,明显优于单分子模拟结果.最后通过晶体密度泛函理论模拟的简正模式分析获得不同吸收峰处的振动模式归属.结果证明太赫兹光谱技术在农药分子识别以及晶体密度泛函理论模拟在太赫兹吸收峰指认和振动模式归属方面的可行性.%The low frequency vibrational spectra of two common hygienic insecticide diflubenzuron and λ-cyhalothrin were investigated using terahertz time-domain spectroscopy (THz-TDS) and density functional theory (DFT) simulations.The experimental spectra of the two molecules had 5 and 7 absorption peaks within 0.2～2.2 THz at room-temperature,which can be used as fingerprints for the molecular recognition.To understand the nature of the vibrational motions leading to absorptions in THz spectra,the Gaussian03 and CRYSTAL09 were used for isolated-molecule and solid-state simulation,respectively.The solid-state simulation predicted all the observed experimental features,which was clearly better than the isolated-molecule.The assignment of IR-active vibrational modes was performed from the solid-state DFT simulation.The overall results indicate that THz technique is quite potential for pesticide molecular discrimination,and solid-state density functional theory simulation is very effective in accurately calculating the vibrational modes to assign the absorption peaks observed in terahertz spectrum.