Terahertz Time-domain Spectroscopy Of Azo Dyes Intermediates And Several Textile Fibers

THz locates in the far-infrared electromagnetic radiation with the frequency of 1012Hz, which internationally recognized as a new the radiation source having many unique advantages. It is also the only band in the electromagnetic spectrum that is not recognized by people. Terahertz time-domain spectroscopy is a new detection technology based on the production and development of THz radiation,which has broad application prospects.The reason why it has a wide range of applications.first, because the structure vibrational frequencies of a lot of material nature is in the THz segment.secondly,The terahertz spectroscopy can quickly obtain the optical properties of the material, which has the great significance of studying the internal structure of the material in this band.We first apply the terahertz technology in the research of the textile materials and Azo dye molecules,and then obtain their spectral features in the THz segment.At the same time,we carried out theoretical calculations of the Azo dyes intermediates and simulated the molecular vibration combining with quantum chemistry.Studies have shown that the different textile fiber materials and Azo molecules have their own characteristic spectral, therefore ,terahertz time-domain spectroscopy can be used to identify.The main reasearch work in this paper as follows:1. Using terahertz time-domain spectroscopy system measured two typical chemical fibers (polyester and aramid) in the THz section and obtained absorption features by extracting the optical parameters of their THz absorption spectra.Experimental results show that different chemical fibers exist obvious difference in THz spectrum, so it can identify the different fiber materials; even the same type of fiber, because their different production process can lead to the difference of crystallization conditions of the internal structure and Intermolecular forces,so this will also lead to differences in spectrum.Therrfore,.different production processes of the same fibers can also be identified by the THz spectra.2. Testing four kinds of prohibited Azo dyes intermediates THz spectroscopy to study their physical and chemical properties in the THz section. Test results show that they also have absorption characteristic peaks in the THz and can serve as a fingerprinting database in the THz band. On this basis, we measure THz spectrum of the mixture of them according to their fingerprinting characteristic spectral of pure substance.Spectrum of the mixture shows that THz spectrum of the mixture can still identify their special absorption peak in the THz spectrum of pure substance.The only difference is the absorption intensity.3. Using Gussian03 software Carry out quantum chemical calculations. We optimizate the molecular geometry structure of the 2 - amino -4 - nitrotoluene and p-chloroaniline in the 0 ~ 10THz frequency domain with DFT B3LYP method and 6-31G(d) basis and calculate the vibrational frequencies with the same method and base group.We Comparatively study the experimental and theoretical simulated spectra and figure out the ownership of the vibration frequency using Gussian View 3.07.