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ÏÂÔØÒѸüУ¡Ð¡µÜµÚÒ»´Î·¢×ÊÔ´£¬Ï£Íû´ó¼ÒÖ§³Ö£¡ Expanding generality of surface-enhanced Raman spectroscopy with borrowing SERS activity strategy Zhong-Qun Tian,* Bin Ren,* Jian-Feng Li and Zhi-Lin Yang Xiamen University Chem. Commun., 2007, 3514¨C3534 ABSTRACT Surface-enhanced Raman scattering (SERS) was discovered three decades ago and has gone through a tortuous pathway to develop into a powerful diagnostic technique. Recently, the lack of substrate, surface and molecular generalities of SERS has been circumvented to a large extent by devising and utilizing various nanostructures by many groups including ours. This article aims to present our recent approaches of utilizing the borrowing SERS activity strategy mainly through constructing two types of nanostructures. The first nanostructure is chemically synthesized Au nanoparticles coated with ultra-thin shells (ca. one to ten atomic layers) of various transition metals, e.g., Pt, Pd, Ni and Co, respectively. Boosted by the long-range effect of the enhanced electromagnetic (EM) field generated by the highly SERS-active Au core, the originally low surface enhancement of the transition metal can be substantially improved giving total enhancement factors up to 104¨C105. It allows us to obtain the Raman spectra of surface water, having small Raman cross-section, on several transition metals for the first time. To expand the surface generality of SERS, tip-enhanced Raman spectroscopy (TERS) has been employed. With TERS, a nanogap can be formed controllably between an atomically flat metal surface and the tip with an optimized shape, within which the enhanced EM field from the tip can be coupled (borrowed) effectively. Therefore, one can obtain surface Raman signals (TERS signals) from adsorbed species at Au(110), Au(111) and, more importantly, Pt(110) surfaces. The enhancement factor achieved on these single crystal surfaces can be up to 106, especially with a very high spatial resolution down to about 14 nm. To fully accomplish the borrowing strategy from different nanostructures and to explain the experimental observations, a three-dimensional finite-difference time-domain method was used to calculate and evaluate the local EM field on the core¨Cshell nanoparticle surfaces and the TERS tips. Finally, prospects and further developments of this valuable strategy are briefly discussed with emphasis on the emerging experimental methodologies. ÏÂÔØÁ¬½Ó£º http://www.divshare.com/download/2860029-690 Raman Spectroscopy of nanomaterials: How spectra relate to disorder, particle size and mechanical properties Gwe´nae¡§l Gouadec*, Philippe Colomban Laboratoire de Dynamique, Interactions et Re´activite´ (LADIR), UMR7075 e CNRS & Universite´ Pierre et Marie Curie e Paris 6, 2 rue Henry Dunant, 94320 Thiais, France Progress in Crystal Growth and Characterization of Materials xx (2007) 1e56 Abstract The purpose of this review is to provide non-specialists with a basic understanding of the information micro-Raman Spectroscopy (mRS) may yield when this characterization tool is applied to nanomaterials, a generic term for describing nano-sized crystals and bulk homogeneous materials with a structural disorder at the nanoscale e typically nanoceramics, nanocomposites, glassy materials and relaxor ferroelectrics. The selected materials include advanced and ancient ceramics, semiconductors and polymers developed in the form of dots, wires, films, fibres or composites for applications in the energy, electronic and aeronauticseaerospace industries. The text is divided into five sections: Section 1 is a general introduction. Section 2 outlines the principles of conventional mRS. Section 3 introduces the main effects for nanomaterials, with special emphasis on two models that connect Raman spectra features to ¡®¡®grain size¡¯¡¯, namely the Phonon Confinement Model (PCM) and the Elastic Sphere Model (ESM). Section 4 presents the experimental versatility of mRS applied to nanomaterials (phase identification, phase transition monitoring, grain size determination, defect concentration assessment, etc.). ÏÂÔØÁ¬½Ó£º http://www.divshare.com/download/2860030-182 [ Last edited by mossback on 2007-11-26 at 05:02 ] |
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