Bibliographic Details
| Title: |
Investigation of the double layer structure of 1-butyl-3-methylimidazolium thiocyanate at the air–water interface using sum-frequency generation vibrational spectroscopy. |
| Authors: |
Wang, Baihui1 (AUTHOR), Duan, Yiyi1 (AUTHOR), Bai, Yimin1 (AUTHOR), Zhang, Weiting1 (AUTHOR), Peng, Jiahui1 (AUTHOR), Bian, Hongtao1 (AUTHOR) htbian@snnu.edu.cn |
| Source: |
Journal of Chemical Physics. 10/7/2024, Vol. 161 Issue 13, p1-10. 10p. |
| Subject Terms: |
*SURFACE tension measurement, *SURFACE tension, *GIBBS' free energy, *MOLECULAR orientation, *MOLE fraction |
| Abstract: |
The interfacial structure and adsorption behavior of 1-butyl-3-methylimidazolium thiocyanate ionic liquids (ILs) aqueous solutions were investigated using sum-frequency generation vibrational spectroscopy (SFG-VS) and surface tension measurements. Polarization-dependent measurements revealed a dramatic increase in the SFG signal for both CH and CN stretching modes with increasing ILs concentration, reaching a maximum at a mole fraction of 0.01. This concentration dependence was accompanied by a dramatic drop in surface tension. Upon further increasing the concentration, surface tension varied slightly and reached a constant value, while the SFG signal decreased significantly. Quantitative polarization analysis showed that as the bulk concentration increased, the apparent molecular orientation of the SCN− transition dipole at the interface changed from 51° to 46°, and the tilt angle of CH3 group of the butyl chain attached to the imidazole cationic ring changed from 18° to 32°. The decrease in the SFG signal can be explained by the formation of a double layer adsorption structure at the air/water interface. It was also demonstrated that the anions were adsorbed at the interface simultaneously with the cationic group, rather than by successive adsorption as proposed in a previous study. Using the Shereshefsky model, the thermodynamic Gibbs free energy of adsorption deduced from surface tension data was compared with SFG results. [ABSTRACT FROM AUTHOR] |
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| Database: |
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