Surface-enhanced Raman scattering (SERS) has become a mature vibrational spectroscopic technique during the last decades and the number of applications in the chemical, material, and in particular life sciences is rapidly increasing. This Review explains the basic theory of SERS in a brief tutorial and-based on original results from recent research-summarizes fundamental aspects necessary for understanding SERS and provides examples for the preparation of plasmonic nanostructures for SERS. Chemical applications of SERS are the centerpiece of this Review. They cover a broad range of topics such as catalysis and spectroelectrochemistry, single-molecule detection, and (bio)analytical chemistry.

Nanoscale localization of electromagnetic fields near metallic nanostructures underpins the fundamentals and applications of plasmonics. The unavoidable energy loss from plasmon decay, initially seen as a detriment, has now expanded the scope of plasmonic applications to exploit the generated hot carriers. However, quantitative understanding of the spatial localization of these hot carriers, akin to electromagnetic near-field maps, has been elusive. Here we spatially map hot-electron-driven reduction chemistry with 15 nm resolution as a function of time and electromagnetic field polarization for different plasmonic nanostructures. We combine experiments employing a six-electron photo-recycling process that modify the terminal group of a self-assembled monolayer on plasmonic silver nanoantennas, with theoretical predictions from first-principles calculations of non-equilibrium hot-carrier transport in these systems. The resulting localization of reactive regions, determined by hot-carrier transport from high-field regions, paves the way for improving efficiency in hot-carrier extraction science and nanoscale regio-selective surface chemistry.

Label-free in situ surface-enhanced Raman scattering (SERS) monitoring of reactions catalyzed by small gold nanoparticles using rationally designed plasmonic superstructures is presented. Catalytic and SERS activities are integrated into a single bifunctional 3D superstructure comprising small gold satellites self-assembled onto a large shell-isolated gold core, which eliminates photocatalytic side reactions.

Experimental results obtained in different laboratories world‐wide by researchers using surface‐enhanced Raman scattering (SERS) can differ significantly. We, an international team of scientists with long‐standing expertise in SERS, address this issue from our perspective by presenting considerations on reliable and quantitative SERS. The central idea of this joint effort is to highlight key parameters and pitfalls that are often encountered in the literature. To that end, we provide here a series of recommendations on: a) the characterization of solid and colloidal SERS substrates by correlative electron and optical microscopy and spectroscopy, b) on the determination of the SERS enhancement factor (EF), including suitable Raman reporter/probe molecules, and finally on c) good analytical practice. We hope that both newcomers and specialists will benefit from these recommendations to increase the inter‐laboratory comparability of experimental SERS results and further establish SERS as an analytical tool.

Noble metals are important photocatalysts due to their ability to convert light into chemical energy. Hot electrons, generated via the non-radiative decay of localized surface plasmons, can be transferred to reactants on the metal surface. Unfortunately, the number of hot electrons per molecule is limited due to charge–carrier recombination. In addition to the reduction half-reaction with hot electrons, also the corresponding oxidation counter-half-reaction must take place since otherwise the overall redox reaction cannot proceed. Here we report on the conceptual importance of promoting the oxidation counter-half-reaction in plasmon-mediated catalysis by photorecycling in order to overcome this general limitation. A six-electron photocatalytic reaction occurs even in the absence of conventional chemical reducing agents due to the photoinduced recycling of Ag atoms from hot holes in the oxidation half-reaction. This concept of multi-electron, counter-half-reaction-promoted photocatalysis provides exciting new opportunities for driving efficient light-to-energy conversion processes.

The synthesis of bifunctional Au/Pt/Au nanoraspberries for use in quantitative in situ monitoring of platinum-catalyzed reactions by surface-enhanced Raman scattering (SERS) is presented. Highly convolved SERS spectra of reaction mixtures can be decomposed into the contributions of distinct molecular species by multivariate data analysis.

Surface-enhanced Raman scattering (SERS) microscopy is a novel method of vibrational microspectroscopic imaging for the selective detection of biomolecules in targeted research. This technique combines the advantages of biofunctionalized metal nanoparticles and Raman microspectroscopy for visualizing and quantifying the distribution of target molecules such as proteins in cells and tissues. Advantages of SERS over existing labeling approaches include the tremendous multiplexing capacity, quantification using the characteristic SERS signatures and high photostability. This review summarizes current designs of nanoparticle-based SERS probes and highlights first biomedical applications of SERS microscopy for protein localization ex and in vivo.

In a glass house: Silica-encapsulated self-assembled monolayers (SAMs) on tunable gold/silver nanoshells were used as labels for surface-enhanced Raman scattering (SERS). This concept combines the spectroscopic advantages arising from maximum surface coverage and uniform molecular orientation of the Raman reporter molecules within the complete monolayer together with the high chemical and mechanical stability of the glass shell.