首页 > 新闻公告 > CEM研究国际动态 CEM研究国际动态
Distinguishing adjacent molecules on a surface using plasmon-enhanced Raman scattering

Unambiguous chemical identification of individual molecules closely packed on a surface can offer the possibility to address single chemical species and monitor their behaviour at the individual level. Such a degree of spatial resolution can in principle be achieved by detecting their vibrational fingerprints using tip-enhanced Raman scattering (TERS). The chemical specificity of TERS can be combined with the high spatial resolution of scanning probe microscopy techniques, an approach that has stimulated extensive research in the field. Recently, the development of nonlinear TERS in a scanning tunnelling microscope has pushed the spatial resolution down to …0.5 nm, allowing the identification of the vibrational fingerprints of isolated molecules on Raman-silent metal surfaces. Although the nonlinear TERS component is likely to help sharpen the optical contrast of the acquired image, the TERS signal still contains a considerable contribution from the linear term, which is spatially less confined. Therefore, in the presence of different adjacent molecules, a mixing of Raman signals may result. Here, we show that using a nonlinear scanning tunnelling microscope-controlled TERS set-up, two different adjacent molecules that are within van der Waals contact and of very similar chemical structure (a metal-centred porphyrin and a free-base porphyrin) on a silver surface can be distinguished in real space. In addition, with the help of density functional theory simulations, we are also able to determine their adsorption configurations and orientations on step edges and terraces.




Nature Nanotechnology (2015) doi:10.1038/nnano.2015.170
Received 17 February 2015 Accepted 02 July 2015 Published online 27 July 2015
http://www.nature.com/nnano/journal/vaop/ncurrent/full/nnano.2015.170.html

发布日期:2015/08/10 发布者: 点击数: