Publication Details (including relevant citation information):
Smith, B. D.; Kirby, D. J.; Keating, C. D. Vertical Arrays of Anisotropic Particles by Gravity-Driven Self-Assembly. Small 2011, 7 (6), 781-788.
Anisotropic particles assemble to spontaneously form columnar arrays. Hybrid nanotube/nanowire particles (silica nanotubes partially filled with metallic cores) deposit with their denser metallic ends towards the surface, orienting them vertically. Up to 84% are observed to be standing over a 0.64 cm2 area within 15 min. Standing percentage is found to be dependent on particle surface concentration.