Seedless Synthesis of Monodisperse Cuboctahedral Gold Nanoparticles with Tunable Sizes

Abstract

Polyhedral gold nanoparticles are of great current interest because of their unique optical and chemical properties which are attributable to their well-defined facets, corners, and size. While various polyhedral gold nanoparticles of different sizes mostly synthesized by the seed-mediated method have been reported, synthesis of gold cuboctahedra with tunable sizes still remains challenging. Here, we report for the first time a seedless method of synthesizing monodisperse gold cuboctahedra with finely tunable sizes ranging from 40 to 80 nm using cetyltrimethylammonium 4-vinylbenzoate (CTAVB) as a selective capping and mild reducing agent in the presence of a high concentration of HCl in aqueous solution. The HCl provides strong oxidative etching power to remove structural defects, resulting in single-crystal seeds, and significantly reduces the particle growth rate. This slow particle growth provides an easy and reliable way of tuning the particle size by stopping the reaction at different times and allowing sufficient time for the surface self-diffusion of Au atoms. Combined with the selective capping of {100} facets with CTA+, the surface self-diffusion of Au atoms from {111} to {100} facets is considered to be the key mechanism for the formation of Au cuboctahedra and their stable growth without morphological deformation.

One-Pot Synthesis of Ultrasmooth, Precisely Shaped Gold Nanospheres via Surface Self-Polishing Etching and Regrowth

“…39 Previous studies indicate that H + ions can dramatically enhance the oxidation power of O 2 /Cl − pairs. 11 In this reaction system, almost all the H + and a high proportion of Cl − ions are generated from HCl; thus, the oxidative etching ability of O 2 /Cl − pairs and reduction kinetics can be influenced by the concentration of HCl. 11,39 First, in the absence of HCl, Au quasi NSs (ϑ = 1.0125 ± 0.0010) with little facets were formed due to the feeble etching process (Figures 4b and S10 and Table S3).…”

Synthesis of Gold Nanoparticles Using Cetyltrimethyammonium 4-Vinylbenzoate as a Reducing and Capping Agent

“…The role of CTAVB which works as a capping and reducing agent has been investigated in our previous report. 19 CTAVB contains a hydrophobic tail with an ammonium head group (CTA + ) and 4-vinylbenzoate (VB -) as its counter ion. The results show that in the absence of CTA + , aggregated Au NPs were produced in which it confirmed the role of VBas a reducing agent.…”

“…Currently, the synthesis of Au NPs with the two-step seed-mediated method has been simplified to a onestep synthesis. [18][19][20][21][22] This approach is done to remove the preparation of seed, i.e. by adding a reducing agent directly into the growth solution.…”

“…Recently, a seedless method of synthesizing Au NPs using cetyltrimethylammonium 4-vinyl benzoate (CTAVB) which serves as a mild reducing as well as a capping agent has been reported by our group. 19 Few different shapes and sizes of Au NPs had been produced by controlling the concentration of surfactant, Au precursor, and pH. While the ability of CTAVB molecules as a reducing agent in low pH (pH < 3) has been well elaborated in the previous study, its ability in neutral pH has not been explored.…”

Diameter-controlled Cu nanoparticles on saponite and preparation of film by using spontaneous phase separation

“…[35][36][37] In addition, their diameter control on clay has not been achieved, even though the diameter strongly affects the reactivity of the Cu NPs. The diameter of metal NPs can be affected by various parameters, for instance reaction temperature, 38 reaction time, 39 metal salts, 40 the ratio of ligand to metal salt, 41 and the presence of templates such as dendrimers. 42 However, no signicant change in the diameter has been achieved simply by changing [Cu 2+ ] on an adsorbent, for example graphene oxide.…”