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Unparalleled time, spectral resolution benefit surface science studies at EMSL

Only HR-BB-SFG-VS can resolve the two peaks and determine the orientation for methyl groups at the air/DMSO interface. Enlarge Image

Femtosecond time resolution. Sub-wavenumber spectral resolution. These combined features are now available in EMSL’s unique, in-house designed and custom-built high-resolution broadband sum-frequency generation vibrational spectroscopy capability (HR-BB-SFG-VS). Ideal for characterizing surfaces and interfaces, HR-BB-SFG-VS offers ultrahigh surface selectivity and sub-monolayer sensitivity, yielding new information about the structure, conformation, and chemical dynamics of homogeneous and heterogeneous systems. Details about HR-BB-SFG-VS are reported in the December issue of The Journal of Chemical Physics. In their article, the development team demonstrates the capabilities of HR-BB-SFG-VS detailing the fine spectral features at the air/liquid interface of DMSO. HR-BB-SFG-VS revealed an unexpected split in the spectra showing two methyl groups on the DMSO surface that were previously observed to be spectroscopically identical. Rather, the two methyl groups reside in distinct chemical environments and have distinct spectral features and geometries. Further, the spectral lineshape and width resolution afforded by HR-BB-SFG-VS uncovered previously hidden information about dynamics and interactions at the liquid surface at interfaces. This new addition to EMSL’s suite of surface science tools is helping researchers obtain a deeper fundamental understanding of surface chemistry, particularly for otherwise difficult-to-analyze interfaces such as solid/liquid, solid/solid, and gas/liquid, and apply that deeper understanding to a broad family of surface chemistry applications—from predicting and mitigating drug interactions involving biological membranes and attenuating corrosion processes to building better solar cells and catalysts for alternative energy. 

Reference: Velarde L, X Zhang, Z Lu, AG Joly, Z Wang, and H Wang. 2011. “Communication: Spectroscopic phase and lineshapes in high-resolution broadband sum frequency vibrational spectroscopy: Resolving interfacial inhomogeneities of “identical” molecular groups.” The Journal of Chemical Physics 135:241102. DOI: 10.1063/1.3675629.

Acknowledgement: This work was supported by Pacific Northwest National Laboratory’s Laboratory Directed Research and Development program, EMSL’s Intramural Research and Development Program, and the Department of Energy’s Subsurface and Biological Research Program’s National Laboratory Scientific Focus Area Program.  Portions of the work were performed at EMSL, a national scientific user facility located at PNNL.

Released: February 29, 2012