Single Layer Graphene for Estimation of Axial Spatial Resolution in Confocal Raman Microscopy Depth Profiling

Carol Korzeniewski, Jay P. Kitt, Saheed Bukola, Stephen E. Creager, Shelley D. Minteer, Joel M. Harris

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Single layer graphene (SLG), with its angstrom-scale thickness and strong Raman scattering cross section, was adapted for measurement of the axial (Z-direction) probe beam profile in confocal Raman microscopy depth-profiling experiments. SLG adsorbed to a glass microscope coverslip (SLG/SiO 2 ) served as a platform for the estimation of axial spatial resolution. Profiles were measured by stepping the confocal probe volume through the SLG/SiO 2 interface while measuring Raman scattering from the sample. Using a high numerical aperture (1.4 NA) oil immersion objective, axial profiles were derived from the graphene 2D vibrational mode and fit to a Lorentzian instrument response function (IRF). Subsequently, the Z-direction spatial resolution in depth-profiling studies of polymer interfaces was estimated through convolution of the Lorentzian IRF with a step function representing the ideal junction separating the phases of interest. In the study of a bipolar polymer membrane, confocal Raman depth profiles of the AEM/CEM (anion exchange membrane/cation exchange membrane) interface show that the transition region is broader than the limiting response and are consistent with roughness at the boundary on the order of a few micrometers. Using ClO 4 - as a Raman active mobile ion probe, application of self-modeling curve resolution (SMCR) to spectral data sets within a profile showed ClO 4 - ions track the spatial distribution of the AEM phase. Finally, in measurements on a liquid-solid interface formed between 1-octanol and a polydimethylsiloxane (PDMS) membrane, the IRF derived from fitting the experimental profile was slightly narrower than those obtained from profiling SLG, indicating the potential to use polymer-liquid interfaces formed from widely available materials and reagents for estimation of axial spatial resolution in confocal Raman depth-profiling.

Original languageEnglish
Pages (from-to)1049-1055
Number of pages7
JournalAnalytical Chemistry
Issue number1
StatePublished - Jan 2 2019


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