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.

ROS TRENDS in BiotechnologyFigure 3. Schematic representation of toxicology effect of multifunctional nanoparticles (NPs) in bacterial biofilms. Monodisperse superparamagnetic iron oxide NPs (SPIONs; black spheres) are coated with silver (gray shell), gold (yellow shell), and silver ring-coated, gold-coated SPIONs; silver ring-coated SPIONs and silver ring-coated, gold-coated SPIONs have strong toxic effects on bacterial biofilms, by penetration into the biofilms. Both SPIONs cores and the intermediate gold shell have the capability to induce heat by applying alternative magnetic and laser fields, respectively; the produced heat can be used as additional means to escalate bacterial death using these NPs. The magnified section in the center illustrates the irreversible effects of NPs and their ions on the various parts of the bacteria. § DOI of original article: http://dx

The optimization of the enhancement of Raman scattering by plasmonic effects is largely determined by the properties of the enhancing substrates. The main parameters behind this effect are related to the morphology of plasmonic nanoparticles and their relative distribution within the substrate. We focus this tutorial review on the effects of nanoparticle morphology, for the particular case of anisotropic metal nanoparticles. Anisotropy in silver and gold nanoparticles offers the possibility to tailor their plasmonic properties and intrinsic electromagnetic "hotspots". We describe the effect of varying particle size and shape on the SERS signal, focusing on the most common anisotropic morphologies used for SERS. Especial emphasis is made on existing comparative studies that shed light on the effect of nanoparticle anisotropy on their enhancement capabilities. We aim at providing a general perspective toward understanding the general key factors and highlighting the difficulty in quantitatively determining SERS performance.