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Indexed by:期刊论文

Date of Publication:2009-09-01

Journal:JOURNAL OF RAMAN SPECTROSCOPY

Included Journals:SCIE、Scopus

Volume:40

Issue:9

Page Number:1172-1177

ISSN No.:0377-0486

Key Words:chemical enhancement; charge transfer; SERRS; binding site; quantum size

Abstract:We describe quantum-size and binding-site effects on the chemical and local field enhancement mechanisms of surface-enhanced resonance Raman scattering (SERRS), in which the pyridine molecule is adsorbed on one of the vertices of the Ag(20) tetrahedron. We first investigated the influence of the binding site on normal Raman scattering (NRS) and excited state properties of optical absorption spectroscopy. Second, we investigated the quantum-size effect on the electromagnetic (EM) and chemical mechanism from 300 to 1000 nm with charge difference density. It is found that the strong absorption at around 350 nm is mainly the charge transfer (CT) excitation (CT between the molecule and the silver cluster) for large clusters, which is the direct evidence for the chemical enhancement mechanism for SERRS; for a small cluster the strong absorption around 350 nm is mainly intracluster excitation, which is the direct evidence for the EM enhancement mechanism. This conclusion is further confirmed with the general Mie theory. The plasmon peak in EM enhancement will be red-shifted with the increase of cluster size. The influence of the binding site and quantum-size effects on NRS, as well as chemical and EM enhancement mechanisms on SERRS, is significant. Copyright (C) 2009 John Wiley & Sons, Ltd.