# 15. In-Depth Investigation on THz Spectrum of 1-Butyl-3-Methylimidazolium Dicyanamide Spreading on Graphene Surface by Computational Calculation (Times cited = 0)

### Abstract

Understanding dynamic change of ionic liquid (IL) THz spectrum under certain conditions is a real challenge. Herein, through spreading 1-butyl-3-methylimidazolium dicyanamide ([Bmim][DCA]) nanodroplet on graphene surface, dynamic change of [Bmim][DCA] THz spectrum in the range from 30 to 300 cm$^{-1}$ is probed by computational calculation at 300 K. Analyzing the calculated THz spectra it can be found that vibrational bands at 49.95 (cation-anion bend), 216.45 cm$^{-1}$ (rocking of CH$_{3}$ in alkyl chain) show a 16.65 cm$^{-1}$ blue shift as spreading time increases from 0 to 5 ns and further blue-shift 16.65 cm$^{-1}$ as spreading time increases from 10 to 20 ns, while vibrational band at 266.40 cm$^{-1}$ (bend of CH$_{3}$ in methyl) only blue-shifts 16.65 cm$^{-1}$ as spreading time increases from 0 to 20 ns. The underlying mechanism is revealed to be the stronger adsorbed layer forming on graphene-IL interface which enhances the hydrogen bonds between cations and anions, and constrains the torsion and out-of-plane bend of CH$_{3}$ group in alkyl chain and methyl respectively. The findings described here represent an important step in developing a comprehensive understanding of dynamic manipulation IL THz spectrum by spreading IL nanodroplet on graphene surface.

Publication
Journal of Molecular Liquids, 2020, 311, 113353

Supplementary files can be found here, including Additional Methods and Data.

Journal and Conference Articles
##### Yongji Guan
###### Postdoc Research Fellow

Yongji Guan is currently a postdoc research fellow of Physical chemistry who specializes in the theoretical caculation of ionic liquids.