Surface-Enhanced Raman Scattering from Au-Nanorod Arrays with Sub-5-nm Gaps Stuck Out of an AAO Template.

Ordered arrays of Au-nanorod-tips protruding from an anodic aluminum oxide (AAO) template are reported as reproducible and active surface-enhanced Raman scattering (SERS) substrates. The Au-nanorods were grown in the nanochannels of the AAO template by use of alternative current electrodeposition, then the template was strengthened using a polymer, and finally the template bottom side was selectively etched to expose the Au-nanorod tips. By controlling the thinning of the AAO-porewalls, the inter-nanorod-gaps were tuned to ~5 nm, forming dense and uniform nano-gap induced "hot spots" among the adjacent Au-nanorod tips. As a result, the electromagnetic field of the Au-nanorod-tip arrays was uniformly enhanced, and demonstrated high SERS sensitivity with good signal reproducibility. The Au-nanorod-tips have the potential to be used in SERS-based applications in order to rapidly detect trace pollutants in the environment.