Tiny carpets of gold rods, all standing upright, can be manufactured more easily and accurately thanks to a method exploiting capillary action. These nanorods have precise optical properties that can be used in sensors and solar energy harvesting.
Udo Bach at Monash University in Clayton, Australia, and his team patterned silica-coated wafers with gold squares 2 micrometres wide and 4 micrometres apart. The wafers are placed in tubes with an aqueous solution of gold nanorods modified with thiol and polyethyleneglycol (PEG). When the solvent evaporates, the nanorods crystallize upwards from the gold squares. Thiol and PEG molecules bind the rods together as capillary action from the evaporating solvent drags them upright. The process can be controlled easily by changing the solution concentration and evaporation temperature.
Angew. Chem. Int. Edn. http://dx.doi.org/10.1002/anie.201204609 (2012)