In this report, we use a sum-frequency generation vibrational spectroscopy to measure SFG spectra from 1-Butanol monolayers on pure water and halide saline solution interfaces. These spectra indicate that halide anions have different effects on the structure of 1-Butanol monolayer/water interfaces. The obtained SFG spectra suggest that the I¯ anions mostly disturb the interfacial structure due to their largest surface propensity among those investigated. | VNU Journal of Science: Mathematics – Physics, Vol. 33, No. 1 (2017) 8-13 Effect of Halide Anions on Structure of 1-butanol Monolayer/water Interface Probed by Sum-frequency Vibrational Spectroscopy Nguyen Thi Hue1,2, Vu Thi Thanh Tam1, Nguyen Anh Tuan1,* 1 Department of Physics, VNU University of Science, Hanoi, Vietnam 2 Hung Vuong University, Phu Tho Province, Vietnam Received 15 January 2017 Revised 16 February 2017; Accepted 20 March 2017 Abstract: In this report, we use a sum-frequency generation vibrational spectroscopy to measure SFG spectra from 1-Butanol monolayers on pure water and halide saline solution interfaces. These spectra indicate that halide anions have different effects on the structure of 1-Butanol monolayer/water interfaces. The obtained SFG spectra suggest that the I¯ anions mostly disturb the interfacial structure due to their largest surface propensity among those investigated. Keywords: Interfacial structure, Sum-frequency vibrational spectroscopy, 1-Butanol, halide salt. 1. Introduction Halide ions in seawater have been recognized as reactants in ozone depletion processes [1]. However, a detailed effect of halogen ion on the water surface structure has not been suggested due to the lack of tools to probe liquid surfaces specifically. As ultrafast laser technology has been developed recently, the sum-frequency generation vibrational spectroscopy (SFGVS) gives not only static information on surfaces but also dynamic properties of surface molecules [2]. Sum-frequency generation (SFG) is a second-order nonlinear optical process that has an intrinsic sensitivity to the struture at surfaces and interfaces. In the SFVS we can control the polarization of both two incident waves as well as the output (sum-frequency) wave. By choosing an appropriate polarization combination for each SFG measurement we can also get the information of molecular orientation at the surface or interface. Molecules like fatty acids, lipids, and long-chain alcohols,
