This article provides an overview of the development and application of the surface-enhanced Raman scattering (SERS) techniques using metal-coated nanostructures on solid substrates An introduction to theoretical principles of the SERS effect and the different SERS-active media is presented The focus is on nanostructured solid substrates and their practical applications in chemical, environmental and biomedical areas Specific examples of analytical techniques, instruments and sensors developed in the author's laboratory will be discussed to illustrate the usefulness and potential of the SERS techniques

Surface-enhanced Raman spectroscopy using metallic nanostructures

The surface roughness and nanometer scale structure of Ag films used for surface‐enhanced Raman scattering (SERS) are characterized using atomic force microscopy (AFM). Two important types of thin film based SERS‐active surface have been examined in this study: (1) Ag island films (AgIF’s) on smooth, insulating substrates and (2) thick Ag films evaporated over both preroughened and smooth substrates. AFM is demonstrated to be capable of quantitatively defining the three‐dimensional (3D) structure of these roughened surfaces. The effects of mass thickness, dm, and thermal annealing on the nanostructure of AgIF’s are studied in detail. Particle size histograms are calculated from the AFM images for both ‘‘as‐deposited’’ and annealed IF’s with dm=1.8 and 3.5 nm. Quantitative measurements of the SERS enhancement factor (EF) are coupled with the AFM data and interpreted within the framework of the electromagnetic theory of SERS. AFM images for thick evaporated Ag films over a monolayer of polymer nanospheres (AgFON) shows the clear presence of ‘‘random substructure roughness’’ reducing their utility as controlled roughness surfaces. Similar roughness structures are observed for thick evaporated Ag films on smooth, insulating substrates. Nevertheless, AgFON surfaces are demonstrated to be among the most strongly enhancing thin film based surfaces ever studied with EF’s comparable to those found for electrochemically roughened surfaces. Applications of FON surfaces to ultrahigh sensitivity SERS, anti‐Stokes detected SERS, and surface‐enhanced hyper‐Raman spectroscopy (SEHRS) are reported.

Atomic force microscopy and surface-enhanced Raman spectroscopy. I. Ag island films and Ag film over polymer nanosphere surfaces supported on glass

Covalent attachment of nanometer-scale colloidal Au particles to organosilane-coated substrates is a flexible and general approach to formation of macroscopic Au surfaces that have well-defined nanostructure. Variations in substrate (glass, metal, Al2O3), geometry (planar, cylindrical), functional group (−SH, −P(C6H5)2, −NH2, −CN), and particle diameter (2.5−120 nm) demonstrate that each component of these assemblies can be changed without adverse consequences. Information about particle coverage and interparticle spacing has been obtained using atomic force microscopy, field emission scanning electron microscopy, and quartz crystal microgravimetry. Bulk surface properties have been probed with UV−vis spectroscopy, cyclic voltammetry, and surface enhanced Raman scattering. Successful application of the latter two techniques indicates that these substrates may have value for Raman and electrochemical measurements. The assembly method described herein is compared with previous methods for controlling the na...

Two-dimensional arrays of colloidal gold particles : A flexible approach to macroscopic metal surfaces

The analytical potential of a new spectrochemical method based on surface-enhanced Raman spectrometry (SERS) on silver-spheres-coated substrates is presented for the first time in this work. A new method for preparing SERS-active substrate using submicron size silver-coated spheres deposited on filter paper substrates is described in detail. The analytical figures of merit and limitations of the technique are discussed. The detection limits for several organic compounds such as carbazole, 1-aminopyrene, and benzoic acid are 0.2, 1.4, and 0.3 ng, respectively. The results indicate that SERS shows great promise as a useful analytical tool for trace organic analysis.

Surface-enhanced Raman spectrometry for trace organic analysis

The detection of organic traces by surface-enhanced Raman scattering (SERS) requires rough metallic substrates with structures in the nanometer range. Regular metallic structures generated by electron-beam lithography are better reproducible than electrochemical roughened surfaces, island films or films over deposited particles. The lithography also allows optimisation of the dimensions of these structures. The SERS enhancement of optimised periodic structures was found to be at least one order of magnitude larger than that of island films.

E.T. Arakawa

Papers

Surface-enhanced raman scattering on silver-coated teflon sphere substrates