Spatial Resolution in Raman Spectroscopy
in: Faraday Discussions (2015)
We presented the high resolution aspects of Raman spectroscopy using different approaches. By studying homogeneous samples under controlled conditions, a comparison of signal position fluctuations indicates that TERS probes very small sample volumes where individual orientation effects are not averaged. Complementary studies on proteins and protein fibrils reveal a surprising capability to distinguish amino acid distributions locally on a length scale of at least 1 nm, also confirming the high spatial resolution of TERS. Interestingly, no consistent theory is at hand to explain this resolution with the usual approach using “macroscopic” tip parameters. Last but not least we presented a general method that allows a direct sequencing of single polymer stands with TERS that would already work with the current theoretically predicted resolution. The time resolution aspects of TERS have not been addressed here, but are currently being successfully investigated by the van Duyne group. In this way the goal to combine ultimate temporal, spatial and spectral resolution as a general tool should be reached in the not too distant future.