Colorized TEM image of gold nanowires in a template of nano-porous alumina.

An aluminum foil was anodized in sulfuric acid at 0 °C and 25 V, which leads to the formation of an oxide with vertically aligned pores which are self-organized in a honeycomb-like structure. The pores were used as a template for the growth of gold nanostructures using the pulse electrodeposition method, resulting in a facile and scalable way of fabricating ordered arrays of nanorods with a height of approximately 500 nm. To examine the encapsulate nanorods, a thin (approx. 100 nm) lamella was extracted from the nano-porous alumina matrix combining the operation of a focused ion beam and a nano-manipulator.

The profile of the nanorods resembles the skyline of a big city, although their size is a billion times smaller than a skyscraper. Similarly to a skyscraper, however, these nanorods were formed from the bottom up. The starry sky in the background is made of Bragg reflections of a selected area electron diffraction pattern arising from the gold nanorods. The colorization was done in ImageJ, while the water-like reflection of the “skyline” was added in GIMP.

Credits: Crispin Hetherington - TEM, Giuseppe Abbondanza - sample preparation and image processing.