Vibrationally resonant sum-frequency generation (VR-SFG) spectroscopy is a powerful tool to investigate the molecular structure of surfaces and interfaces.  However, to be a true analytical tool, practitioners must be able to determine the interfacial structure without experimental artifacts affecting the final results.  Analysis of SFG spectra can be problematic because of inherent aspects of the technique and assumptions made in data analysis.  For example, two different thin film structures were reported for the polystyrene/air interface.  Our experiments,however, suggest the structure is independent of substrate.  Normally, spectra of polystyrene films on silicon, fused silica and sapphire substrates look distinctly different, but experimentally suppressing the non-resonant response gives virtually indistinguishable spectra.  This suggests the differences come from non-resonant interference and problems with curve fitting procedures, not structural changes.  We have observed similar problems in additional systems,demonstrating the need for proper experimental design instead of relying solely on complicated data analysis.

Red flags and pitfalls: Challenges in proper analysis and
interpretation of vibrational sum-frequency spectra

241st National Meeting (2011)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.

Red flags and pitfalls: Challenges in proper analysis and interpretation of vibrational sum-frequency spectra