An unusual example of hyperbranched metal nanocrystals and their shape evolution

The preparation of hyperbranched metal nanocrystals in aqueous solutions at room temperature without using surfactants was investigated. The branch growth was believed to be kinetically controlled while the growth directions were nonspecific. The prepared structures had relatively uniform overall size and the bodies have dark contrast three dimensional (3D) structures. The size of the nanocrystals were also effectively controlled by increasing the concentration of L-ascorbic acid and/or trisodium citrate. Hyperbranched silver nanocrystals were successfully confined in aqueous solution at room temperature. The structures were shown to exist either as 2D gearlike or self-organized 3D objects. The results show that dissimilar reaction kinetics of trisodium citrate and L-ascorbic acid leads to formation of hyperbranched metal nanocrystals even in the absence of an explicit structure-directing agent.