In situ Raman spectroscopy of Langmuir monolayers at air-water interface

A new approach for the acquisition of in situ Raman spectra of Langmuir monolayers at air-water interface with minimal interference was presented. An in situ Raman instrument was designed, which comprises a Raman spectrometer (JY-U1000), a micro Langmuir-Blodgett trough, and a CCD imaging system. By lowering the subphase slowly until Langmuir monolayer deposited on a surface-enhanced Raman scattering (SERS) substrate that was placed under subphase in advance, Raman spectra of Langmuir monolayers of octadecylamine (ODA) and dipalmitoylphosphatidylcholine (DPPC) have been acquired with good signal-to-noise ratio. These spectra present informations of the headgroup interaction and the ordering degree of alkane chains at different surface pressures. This new method could expand SERS application in the study of Langmuir monolayers at the air-water interface.