Size- and Shape-Controlled Syntheses of Colloidal Sn, Te, and Bi Nanocrystals

Abstract

Abstract We report the synthesis of monodisperse spherical Sn nanocrystals 9.0 nm in size by reduction of SnCl2 using tetrabutylammonium borohydride (TBBH, N(C4H9)4BH4) in a one-pot synthesis using a mixed solvent of oleylamine (OA, C18H35NH2) as a capping agent and tetrahydrofuran (THF). The size and shape of the Sn nanocrystals were found to be influenced by both the amount of OA and THF used and the synthetic temperature. The particle sizes varied from 9 to 83 nm. Spherical nanocrystals were formed at a particular initial concentration of OA, while rod-shaped nanocrystals were formed at reduced initial concentrations of OA. The Sn nanocrystals are used as a bonding material by mixing Cu nanocrystals. The shear strength of Cu plates bonded by the mixture of Cu and Sn nanocrystals at higher than 300 °C is significantly increased, compared with that bonded by Cu nanocrystals without addition of the Sn nanocrystals. The synthetic method was also applied to the synthesis of Te and Bi nanocrystals. The shapes of the Te and Bi nanocrystals were similarly controlled by the amount of OA used and the synthetic temperature. All of the samples were obtained as stable colloidal dispersions.