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Total internal reflection Raman spectroscopy as a method to study water structure near Langmuir–Blodgett films
Author(s) -
Nickolov Z. S.,
Earnshaw J. C.,
McGarvey J. J.
Publication year - 1993
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1250240705
Subject(s) - raman spectroscopy , prism , raman scattering , vicinal , analytical chemistry (journal) , langmuir–blodgett film , chemistry , laser , excited state , materials science , total internal reflection , optics , molecule , optoelectronics , atomic physics , physics , organic chemistry , chromatography
A single‐pass total internal reflection (TIR) Raman technique for studying the stretching modes of water close to Langmuir–Blodgett (LB) films of amphiphilic molecules is described. The method is based on efficient collection of the 458 nm (argon ion laser) excited Raman scattering from water layers adjacent to a sapphire prism coated with LB films. The experimental arrangement permitted comparison between scattering from vicinal water and that from bulk water. Polarized TIR Raman spectra for D 2 O of reasonable signal‐to‐noise ratio were obtained at moderate laser excitation powers (50–100 mW). However, the levels of parasitic scattering from the prism compromised the collection of corresponding spectra of good quality for H 2 O. Comparisons were made between the OD Raman band for D 2 O layers adjacent to the prism coated with LB films of ω‐tricosenoic acid with that for D 2 O near the uncoated prism. Small but well defined increases in the intensity of the low‐frequency shoulder of the OD band near 2400 cm −1 for the coated compared with the uncoated case are discussed in terms of possible structuring of the vicinal water by the hydrophobic film. Refinements to the experimental set‐up to increase further the sensitivity for probing water layers near surfaces are briefly considered.