Fenbendazole is one kind of benzimidazole derivatives which is widely used in the treatment of parasitic infections. Because the drug action mechanism of fenbendazole is consistent with many anticancer drugs and the price is cheaper, it is considered as a potential new anticancer drug, which has caused extensive research attention. Traditional fenbendazole research methods are mostly chemical methods such as liquid chromatography. Although these methods have high precision, they have the disadvantages of cumbersome steps, high cost, and the need for specialized technicians to operate. The research method of molecular vibration information of fenbendazole has not been reported yet. In this paper, the density function theory B3LYP/6-31G* basis set and the pseudopotential basis set Lanl2dz were used to optimize and calculate the Raman activity spectrum of fenbendazole and the theoretical enhanced activity spectrum of Au as the substrate. The characteristic peaks of fenbendazole at 1093cm<sup>-1</sup> , 1453cm<sup>-1</sup> , 1534cm<sup>-1</sup> , and 1633cm<sup>-1</sup> were significantly enhanced. These characteristic peaks can be used for qualitative and quantitative analysis of fenbendazole. The causes of the difference between the theoretically calculated Raman activity spectrum and the experimental Raman spectrum are analyzed. The enhancement principle of Raman activity spectrum with Au substrate was also described. The research results will provide theoretical support for the study of the molecular properties of fenbendazole.
Compared with the traditional spectral analysis methods, such as inductively coupled plasma mass spectrometry method, atomic absorption spectrometry method, the analysis sensitivity, accuracy and spectral resolution of the laser induced breakdown spectroscopy technology is relatively lower. Due to the advantages o f low ablation thresholds, high-spatial resolution, minimal invasion, high-efficiency transportation of femtosecond laser, the femtosecond laser induced breakdown spectroscopy method (fs-LIBS) has become an active topic in recent years. In order to further improve the analysis performance of fs-LIBS, the spatial confinement method is proposed. In this paper, the cavity confinement enhancing effect of fs-LIBS is discussed. Based on the local thermal equilibrium condition (LTE) assumption, the plasma temperature and electron density is obtained. The results shown that the plasma emission intensity, plasma temperature and electron density are improved under the given cavity constraints. In effect, the plasma generated shock wave encounters cavity barriers during its expansion, the shock wave is reflected back to the plasma center. One hand is improved the plasma temperature and electron density, on the other hand is increased the number of particles in the upper energy level, which leads to an increase in the intensity of the plasma emission spectrum. In general, the spatial confinement method combined with the fs-LIBS showed its great potential in improving the figures-of-merit of ultrafast optical LIBS technology.