衰减全反射模式的傅里叶变换红外光谱仪(ATR-FTIR)可以用来确定固体粉末样品的远红外光谱性质, 并根据其指纹特征对未知物样品进行鉴定, 且具有快速、 简便、 灵敏、 样品用量少等优点, 已成为分析与表征染料的常用的手段。 运用ATR-FTIR在真空条件下测试了汽巴蓝2B、 去氧紫草素、 靛蓝、 靛红、 硫靛红等五种染料在50~610 cm-1范围内的吸收光谱。 实验结果表明这五种染料在此波段内均有明显的特征吸收峰并对其峰位进行了指认与描述。 使用Gaussian09软件对硫靛红分子进行模拟计算与指纹谱指认, 并根据可视化结果可以看出: 硫靛红分子在50~610 cm-1范围内的特征吸收峰主要源于分子的集体振动, 且其高频与低频的振动模式并不一致。 模拟结果与实验结果相对符合较好, 但仍然存在一定的差异: 比如峰值位置的差异、 吸收峰位的移动、 模拟得到的新峰位等, 主要是由于二者所基于的温度不同、 理论计算没有考虑分子间的相互作用、 ATR晶体与样品粉末的接触效果略差以及系统分辨率不够等因素导致的结果。

Attenuated total reflectance Fourier transform infrared spectrograph (ATR-FTIR) has become a common way to analyze and represent dyes as it can be used to acquire the far infrared spectra of powder samples (only less dosage) conveniently, easily, and sensitively apart from being able to identify the unknown samples in terms of their finger-print features. Five dyes, including ciba blue 2B, deoxyshikonin, indigo, 1H-Indole-2, 3-dione, and thioindigo, were measured by ATR-FTIR with the condition of vacuum. We acquired the absorption spectra within the region of 50~610 cm-1. The experimental results showed that there were obvious characteristic peaks in these five dyes and the corresponding peak positons were identified. And then Gaussian 09 software was used for simulating the vibrational assignments of thioindigo molecule and identifying the fingerprint spectra. It can be seen from the visualization results that the absorption peaks of thioindigo from 50~610 cm-1 were mainly caused by the collective vibration and the vibration modes ranged from low frequency to high frequency. Although the simulation results corresponded well with the experimental results, there were some differences between experimental and simulated results. For example, the values between experimental and simulated results were dissimilar; the positions of absorption peaks in the experiment shifted; the new peak positions were acquired in simulation. The main reason was that the temperature of simulation went far from that of experiment; the intermolecular activity was not considered in the theory calculation; the weak effect of contacting between the ATR crystal and powder; and the resolution of the instrument was not high enough.