Sum-frequency vibrational spectroscopy SFVS

In another study which used a support more relevant to supported ionic liquid catalysts, sum-frequency vibrational spectroscopy (SFVS) was used to study the structure of ionic liquid cations present at the interface between a silica support and imidazolium ionic liquids [RMIM][X], with R = hex)d, oct)4 or decyl, and X = (CF3(CF2) S02)2N with = 0 or 1 [46]. The measurements were performed by introducing the ionic liquids in a thoroughly cleaned fused silica prism. 

Abstract Vibrational sum-frequency spectroscopy in conjunction with interfacial pressure measurements are used to provide the first direct spectroscopic information about the structure of amphiphillic molecules adsorbed to the interface between two immiscible liquids by total internal reflection sum-frequency vibrational spectroscopy (TIR SFVS). The effect of the ionic head group on the conformational order of sodium dodecyl sulfate (SDS), sodium dodecylsulfonate (DDS), dodecyltrimethylammonium chloride (DTAC), and dodecylamine hydrochloride (DAC) adsorbed at the D2O/CCI4 interface has been examined. In addition, the effect of the length of the alkyl chain on the conformation and orientation of sodium hexylsulfonate (HS), sodium undecylsulfonate (UDS), and sodium dodecylsulfonate (DDS) is also presented. SF vibrational spectra indicate the presence of gauche conformations in the hydrocarbon chains of all the surfactants examined. An increase in the surface coverage results in the reduction of gauche defects in the hydrocarbon chains as determined from the intensity ratio of the methyl to methylene symmetric... 

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