Various embodiments of the present invention relate to plasmonic electric-field concentrators and to systems incorporating the plasmonic electric-field concentrators to perform Raman spectroscopy. In one aspect, a plasmonic electric-field concentrator comprises two or more large features, and a relatively small feature similar in shape to large features positioned adjacent to the two or more large features. The features are arranged so that when light of an appropriate wavelength is incident on the features, surface plasmon polaritons form on the outer surfaces of the features. The surface plasmon polaritons have associated electric fields extending perpendicular to the surfaces of the features. The electric fields are concentrated in the space between features forming an electric field hot spot that enhances Raman scattered light emitted from an analyte proximate to or absorbed on the features.