Wet chemical synthesis of gold nanoparticles using silver seeds: a shape control from nanorods to hollow spherical nanoparticles

Abstract

A seed-mediated method was employed here for CTAB-assisted gold nanoparticle growth. 3-4 nm silver aqueous colloid was stabilized by sodium citrate and used as seed solution to initial gold particle growth. The concentration of seed solution was calculated based on its relationship with silver atom concentration and seed particle statistical mean volume. It was found that there is a maximum seed concentration of 8.57 × 10 −12 M (∼25 μl 0.343 × 10 −8 M seed solution added) in 10 ml 2.5 × 10 −4 M HAuCl 4 growth solution for growth of rodlike particles. Below this seed amount, the aspect ratio of nanorods could be controlled by varying the silver seed amount, i.e. nanorods with aspect ratio ∼18.9 were obtained when the seed concentration in the growth solution was 0.343 × 10 −12 M by adding 1 μl 0.343 × 10 −8 M silver seed solution and nanorods with aspect ratio ∼9.69 were obtained when the seed concentration in the growth solution was 1.715 × 10 −12 M by adding 5 μl 0.343 × 10 −8 M silver seed solution. As the seed concentration in the growth solution was more than 8.58 × 10 −12 M (25 μl 0.343 × 10 −8 M silver seed solution was added), there were no rodlike particles formed but spherical ones instead. These spheres were further studied by TEM and found to all be hollow structures. It was suggested that there were probably two different nucleation processes for growth of nanorods and spheres. For hollow spheres, the reaction between Ag seeds and Au ions formed hollow structures based on the Ag particle template effect. Then further growth of Au on these hollow structures produced hollow gold nanospheres. For nanorods, due to the very low concentration of silver seed (molar ratio of Ag seed: Au = 3.426 × 10 −8), the growth process here probably was started by silver-induced Au nucleation, in which reduction of gold ions by silver resulted in small gold clusters. These gold clusters further grew up into nanoparticles and nanorods in the presence of CTAB. S Supplementary data are available from stacks.

Nanoparticles: synthesis and applications

“…In this method, the stabilizers are used to control the size and shape of growing nanoparticles. This method was developed over the years using various types of seeding, reductant agents, and stabilizers (Xu et al, 2007;Han et al, 2009;Perrault and Chan, 2009;Ziegler and Eychmuller, 2011;Rioux and Meunier, 2015). For example, the method which was developed by Perrault and Chan in 2009, reduces HAuCl 4 in gold nanoparticles seed-contained aqueous solution using hydroquinone.…”

Encapsulation of Gold Nanorods with Porphyrins for the Potential Treatment of Cancer and Bacterial Diseases: A Critical Review

“…The wet chemical techniques involve the reduction of metal ions at gold surfaces in the presence of various surfactants; the technique however produces hybrids of nanospheres and other shapes clearly dominated by rods and that affects the ideal optical response of the gold nanorods. For high purity nanorods, the hard template directed methods are utilized by making use of the polycarbonate membrane and the anionic aluminum oxide (AAO) as templates [86, 87]. A typical example of the wet chemical method is the synthesis of AuNRs by seeding.…”

Arbitrary Form Plasmonic Structures: Optical Realization, Numerical Analysis and Demonstration Applications

“…Au NPs possessing particular shapes, such as nano-sphere, nano-rod, and nano-prism, are often fabricated by standard chemical methods, for example, the Turkevich [22], Brust [23] seeded growth [24] or other miscellaneous methods [25]. Those NPs are usually randomly distributed and initially suspended in a solvent such as water.…”