Abstract-Terahertz spectroscopic investigation of gallic acid and its monohydrate

Bo Zhang, Shaoping Li, Chenyang Wang, Tao Zou,  Tingting Pan, Jianbing Zhang, Zhou Xu, Guanhua Ren, Hongwei Zhao,

http://www.sciencedirect.com/science/article/pii/S1386142517307084


The low-frequency spectra of gallic acid (GA) and its monohydrate were investigated by terahertz time-domain spectroscopy (THz-TDS) in the range of 0.5 to 4.5 THz. The dehydration process of GA monohydrate was monitored on-line. The kinetic mechanism of the dehydration process was analyzed depending on the THz spectral change at different temperatures. The results indicate that the diffusion of water molecule dominates the speed of the entire dehydration process. Solid-state density functional theory (DFT) calculations of the vibrational modes of both GA and its monohydrate were performed based on their crystalline structures for better interpreting the experimental THz spectra. The results demonstrate that the characterized features of GA mainly originate from the collective vibrations of molecules. And the interactions between GA and water molecules are responsible for THz fingerprint of GA monohydrate. Multi-techniques including differential scanning calorimetry and thermogravimetry (DSC-TG) and powder X-ray diffraction (PXRD) were also carried out to further investigate GA and its monohydrate.

Abstract-Terahertz Spectra of Ninhydrin and Indane-1,2,3-Trione

Tao Zou, Shaoping Li, Tingting Pan, Bo Zhang, Zheng Yu, Xindi Li, Jianbing Zhang, Hongwei Zhao,

https://link.springer.com/article/10.1007%2Fs10762-017-0376-z

Distinctive terahertz (THz) absorption spectra of ninhydrin and indane-1,2,3-trione ranging from 0.5 to 4.5 THz were observed firstly in our experiment by terahertz time-domain spectroscopy (THz-TDS). The dehydration process of ninhydrin was also monitored online. The experimental results indicate that THz spectroscopy is highly sensitive to the crystal structure, weak intermolecular interactions, and the environmental change. Multitechniques including differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD) were also carried out to further investigate ninhydrin and indane-1,2,3-trione. And the results support the reliability of THz spectroscopy. Density functional theory (DFT) calculations based on the samples’ crystalline structures were performed for better understanding the THz characteristic spectra. The calculations agree with the experimental observation, and the corresponding vibrational modes of ninhydrin and indane-1,2,3-trione are assigned.