Subnanometer-resolved chemical imaging via multivariate analysis of tip-enhanced Raman maps

Advanced multivariate analysis can dramatically improve the chemical sensing capabilities of tip-enhanced Raman spectroscopy (TERS). A powerful surface analysis technique, TERS is hampered by inherently weak Raman signals, which have not permitted complex molecular architectures to be distinguished at the subnanometer scale. By employing advanced multivariate analysis, Song Jiang and co-workers from the University of Science and Technology of China used TERS to unambiguously identify adjacent molecules on a surface. The scheme’s spatial resolution of just 0.4 nanometers opens up the possibility of gathering information on a submolecular scale, such as mapping local vibrations and structural units within a single molecule. Experiments with a mixture of ZnTPP and H2TBPP molecules adsorbed on the edge of a silver step confirmed the advantages of the multivariate approach over conventional single-peak spectral analysis.