title: Molecular orientation of organic thin films on dielectric solid substrates: a phase-sensitive vibrational SFG study.
abstract: Broadband phase-sensitive vibrational sum frequency generation (SFG) spectroscopy was utilized to study the molecular orientation of molecules adsorbed on dielectric solid substrates. A gold thin film was employed to generate a SFG signal as a local oscillator (LO). To simplify the phase measurement, a self-assembled monolayer (SAM) of octadecyltrichlorosilane (OTS) was used as a standard sample for phase correction of the phase-sensitive SFG measurements on the solid/air interface. It was demonstrated that the absolute orientation of molecules in the LB films on a fused quartz surface can be clearly distinguished by phase-sensitive SFG measurement. In addition, the observation on the SAM of d35-OTS reveals that the two C-H stretching modes for α-CH2 group are in opposite phase. Furthermore, by using the present phase-sensitive SFG setup, the orientation flipping of water molecules on positively and negatively charged solid/liquid interface can be distinguished.
authors.affiliation: Catalysis Research Center, Hokkaido University, Sapporo 001-0021, Japan. ye@cat.hokudai.ac.jp.
authors.forename: Aimin
authors.initials: A
authors.lastname: Ge
authors.forename: Qiling
authors.initials: Q
authors.lastname: Peng
authors.forename: Lin
authors.initials: L
authors.lastname: Qiao
authors.forename: Nageshwar R
authors.initials: NR
authors.lastname: Yepuri
authors.forename: Tamim A
authors.initials: TA
authors.lastname: Darwish
authors.forename: Michiya
authors.initials: M
authors.lastname: Matsusaki
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Akashi
authors.forename: Shen
authors.initials: S
authors.lastname: Ye
mesh_terms: D000388:Air; D004573:Electrolytes / Q000737:chemistry; D006046:Gold / Q000737:chemistry; D012821:Silanes / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D013499:Surface Properties; D014867:Water / Q000737:chemistry
chemical_list: D004573:Electrolytes; D012821:Silanes; D014867:Water; C061189:octadecyltrichlorosilane; D006046:Gold