Spatial resolution of tip-enhanced Raman spectroscopy – DFT assessment of the chemical effect

Abstract

Experimental evidence of extremely high spatial resolution of tip-enhanced Raman scattering (TERS) has been recently demonstrated. Here, we present a full quantum chemical description (at the density functional level of theory) of the non-resonant chemical effects on the Raman spectrum of an adenine molecule mapped by a tip, modeled as a single silver atom or a small silver cluster. We show pronounced changes in the Raman pattern and its intensities depending on the conformation of the nanoparticle-substrate system, concluding that the spatial resolution of the chemical contribution of TERS can be in the sub-nm range.

Raman spectroscopy: techniques and applications in the life sciences

“…Zhang et al suggest their resolution originates from a nonlinear process involving luminescence in a plasmonic cavity between tip and sample, but others suggest that the resolution could be due to atomically sharp probes or the steep gradient of the enhanced electric near-field [378]. Further work should continue to unravel the fundamental aspects determining the spatial resolution in order to determine the ultimate achievable limits.…”

Organic acids, siderophores, enzymes and mechanical pressure for black slate bioweathering with the basidiomycete Schizophyllum commune

“…Not all marker bands were present in all spectra, which may result from the extreme resolution effects and molecule orientation dependence that is well known in tip‐enhanced Raman spectrometry (TERS; see Supporting Information Figs. S2 and S3; Deckert‐Gaudig et al ., ; Duan et al ., ; Latorre et al ., ). In some spectra, the presence of protein (amide I bands detection) was seen.…”

“…To identify EPS, more than 800 tip-enhanced Raman spectra were recorded for 10 different areas on the tangled network Duan et al, 2016;Latorre et al, 2016). In some spectra, the presence of protein (amide I bands detection) was seen.…”

The Controversial Orientation of Adenine on Gold and Silver

“…Separately, a theoretical TERS investigation simulated Ag atom or Ag 20 cluster interaction at eight different points on the adenine molecule, with each giving different spectra. Although such hypothetical TERS resolution is beyond current experimental capabilities, it nonetheless demonstrates the importance of fully understanding adenine–surface interaction . A non‐resonant TERS study has also recently examined planar adsorbed adenine with sub‐nanometer spatial resolution …”