Engineering Nanostructures for Single‐Molecule Surface‐Enhanced Raman Spectroscopy

Abstract Surface‐enhanced Raman spectroscopy (SERS), an effect discovered in the 1970s and studied systematically in the 1980s, received a significant “second wind” with the report (primarily by Nie and by Kneipp) of enhancements large enough to allow the Raman spectrum of single molecules to be obtained. It is now understood that this occurs as a result of the extremely high electromagnetic fields that can exist at appropriately configured gaps and interstices between nanoparticles and other nanostructures composed of suitable materials (such as silver). With this insight one is now in a position to fabricate structures that will dependably and repeatably produce single‐molecule SERS. We describe three such strategies: using molecular linkers to self‐assemble silver clusters possessing the correct geometry; fabricating nanowire rafts in which the gaps between nanowires are “hot”; and structuring the interior of nanopores so as to produce finely‐architectured nanostructured arrays.