Surface-enhanced Raman spectroscopy employing monodisperse nickel nanowire arrays

We have prepared two-dimensional arrays of hexagonally arranged, monodisperse nickel nanowires embedded in an alumina template. The degree of template filling is nearly 100% using an improved electrochemical deposition technique. Optical transmission measurements in the direction parallel to the long axis of the nickel nanowires show a plasmon-enhanced absorption around 400nm. We observe for typically surface-enhanced Raman spectroscopy (SERS) inactive metals like nickel a strong, but locally strongly inhomogeneous SERS signal during in situ Raman microspectroscopy. Supported by our numerical modeling, we suggest that significant SERS enhancement factors are possible only when nanowires in bundles are touching each other.