Nanospring electrochemical lithography (NEL): noble metal nanohelices.

We report three-dimensional helical Au nanostructures using anodized aluminum oxide (AAO) and the embedded Pd nanosprings, serving as primary and secondary templates, respectively. The resulting Au nanohelices exhibit strong SERS signals due to the electromagnetic field enhancement originating from the helical morphology; this behavior is seemingly analogous to that of a nano-gap enhancer. Nanospring electrochemical lithography (NEL) represents a new method for synthesizing complex helical nanostructures and has potential for application in materials science.