This paper presents an in-depth study of Surface Enhanced Raman Scattering (SERS) enhancement factors (EFs) and cross-sections, including several issues often overlooked. In particular, various possible rigorous definitions of the SERS EFs are introduced and discussed in the context of SERS applications, such as analytical chemistry and single molecule SERS. These definitions highlight the importance of a careful characterization of the non-SERS cross-sections of the probes under consideration. This aspect is illustrated by experimental results for the non-SERS cross-sections of representative SERS probes along with average SERS EFs for the same probes. In addition, the accurate experimental determination of single molecule enhancement factors is tackled with two recently developed techniques, namely:  bi-analyte SERS (BiASERS) and temperature-dependent SERS vibrational pumping. We demonstrate that SERS EFs as low as 107, as opposed to the figure of 1014 often claimed in the literature, are sufficient for...

Surface Enhanced Raman Scattering Enhancement Factors: A Comprehensive Study

In the mid-1970s, surface-enhanced Raman scattering (SERS) was discovered which impacted on surface science and spectroscopy because of its extremely high surface sensitivity. However, SERS had not developed as many people had hoped to be a powerful surface diagnostic technique that can be widely used because of some obstacles. For example, only three noble metals Au, Ag, and Cu could provide large enhancement, severely limiting the widespread applications involving other metallic materials of both fundamental and practical importance. In this article, emphasis is put on the recent work of our group to directly generate SERS on net transition metals (e.g., Pt, Ru, Rh, Pd, Fe, Co, Ni, and their alloys) by developing various roughening procedures and optimizing the performance of the confocal Raman microscope. An approach of replacing the randomly roughened surface with ordered nanorod arrays of transition metals is introduced as a promising class of highly SERS-active substrates. The surface enhancement fa...

Surface-Enhanced Raman Scattering: From Noble to Transition Metals and from Rough Surfaces to Ordered Nanostructures

After over 30 years of development, surface-enhanced Raman spectroscopy (SERS) is now facing a very important stage in its history. The explosive development of nanoscience and nanotechnology has assisted the rapid development of SERS, especially during the last 5 years. Further development of surface-enhanced Raman spectroscopy is mainly limited by the reproducible preparation of clean and highly surface enhanced Raman scattering (SERS) active substrates. This review deals with some substrate-related issues. Various methods will be introduced for preparing SERS substrates of Ag and Au for analytical purposes, from SERS substrates prepared by electrochemical or vacuum methods, to well-dispersed Au or Ag nanoparticle sols, to nanoparticle thin film substrates, and finally to ordered nanostructured substrates. Emphasis is placed on the analysis of the advantages and weaknesses of different methods in preparing SERS substrates. Closely related to the application of SERS in the analysis of trace sample and unknown systems, the existing cleaning methods for SERS substrates are analyzed and a combined chemical adsorption and electrochemical oxidation method is proposed to eliminate the interference of contaminants. A defocusing method is proposed to deal with the laser-induced sample decomposition problem frequently met in SERS measurement to obtain strong signals. The existing methods to estimate the surface enhancement factor, a criterion to characterize the SERS activity of a substrate, are analyzed and some guidelines are proposed to obtain the correct enhancement factor.

Surface-enhanced Raman spectroscopy: substrate-related issues

Surface-enhanced Raman spectroscopy is widely used for rapid and sensitive molecular detection in chemistry and biology, but typically relies on noble metals. Here the authors report a non-stoichiometric semiconducting material with defect-rich surface that displays excellent detection limits and enhancement factors.

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Noble metal-comparable SERS enhancement from semiconducting metal oxides by making oxygen vacancies.

A Review on Surface-Enhanced Raman Scattering.

Investigation of surface-enhanced Raman scattering from platinum electrodes using a confocal Raman microscope: dependence of surface roughening pretreatment

Surface-enhanced Raman spectroscopy has almost been restricted to the study of only three noble metals of Au, Ag and Cu for two decades. Recently, a new confocal Raman microscope and special surface pretreatments have allowed the acquisition of high-quality surface Raman spectra of organic and inorganic molecules adsorbed on bare Pt, Ni, Co, Fe, Pd, Rh, Ru and Si electrodes over a wide applied potential range for the first time. The present results demonstrate several advantages of in situ surface Raman spectroscopy that could probably make it a general technique widely used in surface science and electrochemistry. © 1998 John Wiley & Sons, Ltd.

Can surface Raman spectroscopy be a general technique for surface science and electrochemistry

Extending surface Raman spectroscopic studies to transition metals for practical applications: III. Effects of surface roughening procedure on surface-enhanced Raman spectroscopy from nickel and platinum electrodes

X.Q. Li

Papers

Investigation of surface-enhanced Raman scattering from platinum electrodes using a confocal Raman microscope: dependence of surface roughening pretreatment

Can surface Raman spectroscopy be a general technique for surface science and electrochemistry

Extending surface Raman spectroscopic studies to transition metals for practical applications: III. Effects of surface roughening procedure on surface-enhanced Raman spectroscopy from nickel and platinum electrodes