Salt effect on molecular orientation at air/liquid methanol interface

引用本文: Xia Li, Gang-Hua Deng, Rong-Juan Feng, Ke Lin, Zhen Zhang, Yu Bai, Zhou Lu, Yuan Guo. Salt effect on molecular orientation at air/liquid methanol interface[J]. Chinese Chemical Letters, 2016, 27(4): 535-539. shu

Citation: Xia Li, Gang-Hua Deng, Rong-Juan Feng, Ke Lin, Zhen Zhang, Yu Bai, Zhou Lu, Yuan Guo. Salt effect on molecular orientation at air/liquid methanol interface[J]. Chinese Chemical Letters, 2016, 27(4): 535-539. shu

Salt effect on molecular orientation at air/liquid methanol interface

Xia Li ^a, ,
Gang-Hua Deng ^b, ,
Rong-Juan Feng ^a, ,
Ke Lin ^c, ,
Zhen Zhang ^a, ,
Yu Bai ^a, ,
Zhou Lu ^a, ,
Yuan Guo ^a,

a Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China;
b Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China;
c School of Physics and Optoelectronic Engineering, Xidian University, Xi'an 710071, China
基金项目:
This work was financially supported by the National Natural Science Foundation of China (Nos. 21227802, 21303216 and 21473217).

摘要: The salt effects on molecular orientation at air/liquid methanol interface were investigated by the polarization-dependent sum frequency generation vibrational spectroscopy (SFG-VS). We clarified that the average tilting angle of the methyl group to be θ=30°±5° at the air/pure methanol surface assuming a δ-function orientational distribution. Upon the addition of 3 mol/L NaI, the methyl group tilts further away from the surface normal with a new θ=41°±3°. This orientational change does not explain the enhancement of the SFG-VS intensities when adding NaI, implying the number density of the methanol molecules with a net polar ordering in the surface region also changed with the NaI concentrations. These spectroscopic findings shed new light on the salt effects on the surfaces structures of the polar organic solutions. It was also shown that the accurate determination of the bulk refractive indices and Raman depolarization ratios for different salt concentrations is crucial to quantitatively interpret the SFG-VS data.

关键词:

English

Salt effect on molecular orientation at air/liquid methanol interface

Xia Li ^a, ,
Gang-Hua Deng ^b, ,
Rong-Juan Feng ^a, ,
Ke Lin ^c, ,
Zhen Zhang ^a, ,
Yu Bai ^a, ,
Zhou Lu ^a, ,
Yuan Guo ^a,

a Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China;
b Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China;
c School of Physics and Optoelectronic Engineering, Xidian University, Xi'an 710071, China
Received Date: 14 December 2015
Revised Date: 23 December 2015
Available Online: 08 January 2016
Fund Project:
This work was financially supported by the National Natural Science Foundation of China (Nos. 21227802, 21303216 and 21473217).

Abstract: The salt effects on molecular orientation at air/liquid methanol interface were investigated by the polarization-dependent sum frequency generation vibrational spectroscopy (SFG-VS). We clarified that the average tilting angle of the methyl group to be θ=30°±5° at the air/pure methanol surface assuming a δ-function orientational distribution. Upon the addition of 3 mol/L NaI, the methyl group tilts further away from the surface normal with a new θ=41°±3°. This orientational change does not explain the enhancement of the SFG-VS intensities when adding NaI, implying the number density of the methanol molecules with a net polar ordering in the surface region also changed with the NaI concentrations. These spectroscopic findings shed new light on the salt effects on the surfaces structures of the polar organic solutions. It was also shown that the accurate determination of the bulk refractive indices and Raman depolarization ratios for different salt concentrations is crucial to quantitatively interpret the SFG-VS data.

Key words:

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Salt effect on molecular orientation at air/liquid methanol interface

English

Salt effect on molecular orientation at air/liquid methanol interface

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Salt effect on molecular orientation at air/liquid methanol interface

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Salt effect on molecular orientation at air/liquid methanol interface

CCS Chemistry：嵌段共聚物自组装成 “三明治”二维有机材料，实现纳米级压力传感功能

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