SEM images of PAA template. (a) PAA surface and (b) continuous oxide-layer present at the bottom of each nanopore in PAA. (c) SEM image of PAA template with Ni nanowires and (d) TEM images of suspended Ni nanowires with dendrites. TEM was performed in a LEO 906E Leica. Sample preparation included PAA dissolution in 0.4 M H3PO4 and magnetic separation, followed by a wash in bi-deionized water and finally re-suspended in 0.5 mL of ethanol.