Resolving sub-angstrom ambient motion through reconstruction from vibrational spectra

Tracking single molecule movements is a challenging task, but highly desired for applications and fundamental studies. Here the authors reconstruct the sub-angstrom relative movements of a molecule interacting with a metal adatom, by measuring its vibrational spectrum in a self-assembled monolayer, continuously modified by the adatom in a nanoparticle-on-mirror construct. Metal/organic-molecule interactions underpin many key chemistries but occur on sub-nm scales where nanoscale visualisation techniques tend to average over heterogeneous distributions. Single molecule imaging techniques at the atomic scale have found it challenging to track chemical behaviour under ambient conditions. Surface-enhanced Raman spectroscopy can optically monitor the vibrations of single molecules but understanding is limited by the complexity of spectra and mismatch between theory and experiment. We demonstrate that spectra from an optically generated metallic adatom near a molecule of interest can be inverted into dynamic sub-angstrom metal-molecule interactions using a comprehensive model, revealing anomalous diffusion of a single atom. Transient metal-organic coordination bonds chemically perturb molecular functional groups > 10 bonds away. With continuous improvements in computational methods for modelling large and complex molecular systems, this technique will become increasingly applicable to accurately tracking more complex chemistries.

Automated summary

The study reconstructs sub-angstrom relative movements of a molecule interacting with a metal adatom using vibrational spectrum measurements in a self-assembled monolayer, showcasing the potential of tracking complex chemistries at the atomic scale.