Kinetically Controlled Growth of Gold Nanoplates and Nanorods via a One-Step Seed-Mediated Method

Abstract

In this research, we further developed the one-step seed mediated method to synthesize gold nanoparticles (GNPs) and control their resulting shapes to obtain hexagonal, triangular, rod-shaped, and spherical gold nanostructures. Our method reveals that the reaction kinetics of formation of GNPs with different shapes can be controlled by the rate of addition of ascorbic acid, because this is the critical factor that dictates the energy barrier that needs to be overcome. This in turn affects the growth mechanism process, which involves the adsorption of growth species to gold nanoseeds. There were also observable trends in the dimensions of the GNPs according to different rates of addition of ascorbic acid. We performed further analyses to investigate and confirm the characteristics of the synthesized GNPs.

Kinetically controlled growth of gold nanotriangles in a vesicular template phase by adding a strongly alternating polyampholyte

“…Noteworthy that these findings are quite opposite to the seed-mediated synthesis of nanoplatelets in the presence of CTAB, where the best results were found at the lowest addition rate. [8] A furthermore temperature increase to 70°C induces the opposite effect (Figure 3). This means the second absorption maximum is shifted to lower values, becomes less pronounced, and is decreased from 699 to 645 nm by increasing the dosage rate.…”

“…From the energetic point of view spherical particles should be formed, which means for the formation of anisotropic particles a higher activation energy is required. [8] The formation of energetically unfavorable anisotropic nanorods or nanoplatelets can be forced: 1. By adding symmetry breaking components Polymers, like poly(vinyl pyrrolidone) (PVP), [9] surfactants, e.g., CTAB, [7,10] as well as ions, e.g., iodide, [11][12][13] can overcome the role of a directing agent for anisotropic growth as blocking species on certain {111} crystal facets of the gold nanoparticles.…”

“…Therefore, the growth can be directed in lateral direction and flat nanoplates or truncated bitetrahedra are formed. [8,11] The kinetically controlled growth of the nanoparticles opens a way to come to anisotropic gold crystallites, i.e., rods, cubes, discs, cages, pyramids, or triangles. [7,16,17] In our previous work, we were able to show that triangular gold nanoplatelets are formed in a vesicular template phase in the presence of a strongly alternating polyampholyte, i.e., poly(N,N′-diallyl-N,N′-dimethylammonium-alt-3,5-bis(carboxyphenyl)maleamic carboxylate (PalPhBisCarb).…”

Controlled Crystallization of Gold Nanocrystals

“…The activation energy (Ea) for anisotropic structures is much higher than the activation energy for isotropic structures and, as Figure 2 demonstrates, the change in the Gibbs free energy of anisotropic Au NPs is lower than the change in that of isotropic Au NPs. Consequently, isotropic structures are thermodynamically favoured and have a lower and more stable energy profile [25]. Control of the addition rate of ascorbic acid into the growth solution changes the reaction rate and adjusts the product because, when ascorbic acid is added, the solution is supersaturated and has high Gibbs free energy.…”

“…Different reaction components have a strong influence on the product and have been widely investigated [19][20][21][22][23][24][25][26]. The significant parameters that affect the yield are concluded below:…”