Branched-arm nanoparticles have been synthesized from several semiconductors, including CdS and ZnO. These approaches succeed by means of the sequential growth of two distinct crystal structures (such as wurtzite and zincblende) and have employed high-temperature conditions.
Chen et al. report on the room-temperature synthesis of gold nanocrystals with either triangular or diamond-shaped centers (which are about 10 nm in diameter) that can grow up to three or four arms, apparently in a stepwise fashion. Ascorbic acid was used to reduce HAuCl4 in the presence of the surfactant cetyltrimethylammonium bromide and much larger silver plates (about 220 nm by 25 nm in size). Further reduction of Au+ complexes was achieved by adding NaOH. The particles formed have no twin boundaries or stacking faults along the arm junctions, indicating that they form as single crystals. Although there are several open questions on how crystal growth is directed, the particles themselves might present an interesting starting point for studies in nanoelectronics. -- PDS
J. Am. Chem. Soc. 10.1021/ja038927x (2003).
