The discovery of the enhancement of Raman scattering by molecules adsorbed on nanostructured metal surfaces is a landmark in the history of spectroscopic and analytical techniques. Significant experimental and theoretical effort has been directed toward understanding the surface-enhanced Raman scattering (SERS) effect and demonstrating its potential in various types of ultrasensitive sensing applications in a wide variety of fields. In the 45 years since its discovery, SERS has blossomed into a rich area of research and technology, but additional efforts are still needed before it can be routinely used analytically and in commercial products. In this Review, prominent authors from around the world joined together to summarize the state of the art in understanding and using SERS and to predict what can be expected in the near future in terms of research, applications, and technological development. This Review is dedicated to SERS pioneer and our coauthor, the late Prof. Richard Van Duyne, whom we lost during the preparation of this article.

The understanding of the localized surface plasmons (LSPs) that occur at the geometrically bounded surface of metal nanoparticles continues to advance as new and more complex nanostructures are found. It has been shown that the oscillation of electrons at the metal dielectric interface is strongly dependent on the size, symmetry, and proximity of nanoparticles. Here, we present a new method to chemically control the shape of silver nanocrystals by using a highly anisotropic etching process. Tuning of the etchant strength and reaction conditions allows the preparation of new nanoparticle shapes in high yield and purity, which cannot be synthesized with conventional nanocrystal growth methods. The etching process produces intraparticle gaps, which introduce modified plasmonic characteristics and significant scattering intensity in the near-infrared. These new silver particles serve as excellent substrates for wavelength-tunable, single-particle surface enhanced Raman spectroscopy (spSERS).

Nanosized Pt and PtRu colloids were prepared by a microwave-assisted polyol process and transferred to a toluene solution of decanthiol. Vulcan XC-72 was then added to the toluene solution to adsorb the thiolated Pt and PtRu colloids. TEM examinations showed nearly spherical particles and narrow size distributions for both supported and unsupported metals. The carbon-supported Pt and PtRu nanoparticles were activated by thermal treatment to remove the thiol stabilizing shell. All Pt and PtRu catalysts (except Pt 23 Ru 77 ) showed the X-ray diffraction pattern of a face-centered cubic (fcc) crystal structure, whereas the Pt 23 Ru 77 alloy was more typical of the hexagonal close-packed (hcp) structure. The electro-oxidation of liquid methanol on these catalysts was investigated at room temperature by cyclic voltammetry and chronoamperometry. The results showed that the alloy catalyst was catalytically more active than pure platinum. The heat-treated catalyst was also expectedly more active than the non-heat-treated ones, because of the successful removal of the organic shell, which might interfere with reactant adsorption in the methanol oxidation reaction. Pt 52 Ru 48 /C had the best electrocatalytic performance among all carbon-supported Pt and PtRu catalysts.