Facile Growth of Multi-twined Au Nanostructures

Abstract

We describe a facile growth of chain-like Au nanostructures and their spontaneous transformation to multi-twined nanostructure using a mild reducing agent bisphenol A (BPA). The growth Au nanostructures involves the chemical reduction of HAuCl4 by BPA in the presence of cetyltrimethylammonium bromide (CTAB) as capping agent in alkaline condition without any seeds. Wire and chain-like Au nano-network structures with diameter in the range of 4 to 9 nm are obtained in the initial stage of the reaction. These chain-like nanostructures undergo spontaneous transformation into multi-twined nanostructures within 24 h. These nanocrystalline multi-twined structures have an average size of 80-90 nm. X-ray and selected area electron diffraction measurements reveal that the Au nanoparticles have (111), (200), (220) and (311) planes of a face centered cubic structure. High resolution transmission electron microscopic measurement shows that the nanostructures are mainly composed of (111) lattice plane with twin boundaries. The concentration of HAuCl4, BPA and CTAB has pronounced effect in the growth of nanostructures. The multi-twined nanostructures are highly stable at room temperature over a period of one month and can be used for catalytic applications. Growth of chain-like Au nanoaggregates and the spontaneous transformation to multitwined Au nanostructure are described.