Towards a comprehensive model of Surface Enhanced Raman Scattering (SERS)
(1) a simple introduction , (2) the main points of the enhancemen by the local electromagnetic field (EM) at spherical silver particles. (3)the experimental evidence for SERS active sites of atomic dimensions . The average signal from the SERS active sites(SAS) mimics a non-genuine" first layer effect” which is often interpreted as “Chemical effect". (4) The SAS are quenched by oxygen, therefore plasmonic enhancers in air are pure EM enhancers . (5) This allows the quantitative experimental separation of the EM and “chemical” enhancement for different kinds of silver samples. (6) If the surface concentration of SAS is known the extra enhancement at SAS can be evaluated.(7) The extra enhancement is caused by transient electron transfer metal-adsorbate.(8) charge transfer calculations at clusters covered by one adsorbed molecule may be considered as models of SAS.
Prof. Andreas Otto，University of Düsseldorf
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