Raman spectroscopy of model membrane monolayers of dipalmitoylphosphatidicacid at the air-water interface using surface enhancement from buoyant thin silver films

A novel method for the acquisition of surface enhanced Raman (SER) spectra of model membranes of dipalmitoylphosphatidic acid (DPPA) in Langmuir layer s at the air-water interface is reported. The approach is based on the elec trochemical formation of a buoyant thin layer of coalesced silver colloids in the vicinity of the phosphatidic acid head groups at the interface. This Ag layer is an excellent platform for SER scattering, which shows the spec tral features from all parts of the molecule and water between the Ag surfa ce and the DPPA layer. The observation of the spectral response from the ph osphatidic acid head groups is of particular significance, allowing insight into their chemical state and orientation at the air-water interface. (C) 2000 John Wiley & Sons, Inc.