Competitive Seeded Growth: An Original Tool to Investigate Anisotropic Gold Nanoparticle Growth Mechanism

The influence of the initial seed structure on final nanoparticle geometry has been investigated by an original “competitive approach” using small-angle X-ray scattering, UV–vis spectroscopy, and transmission electronmicroscopy analysis. Herein, by using the seed-mediated gold nanoparticle growth, seeds with different sizes and crystalline structures were synthesized and injected into the same growth media. The seeds were chosen because of their different growth evolution into two different morphologies. Cetyltrimethylammonium bromide-coated single-crystalline seeds grow into rodlike shapes, whereas citrate-coated multicrystalline seeds mainly grow into wheat-shape polycrystalline particles with small elongation called nanobeans in coexistence with a large quantity of spheres. When seeds are added into the same growth media for competition, a mixture of different morphologies is obtained. By controlling the number of added competing seeds in the solution, it was found that the multicrystalline seeds have a higher growth rate than the single-crystalline seeds. This has direct impact on the final distribution of the size and morphology of the nanoparticles. The consequence is a large tendency toward nanobean and sphere structure formation even when a small number of multitwinned seeds is added in the solution. This method demonstrates the importance of the nature of defects hidden in the initial seed and proves that these defaults are inherited to the final nanocrystal throughout the growth stage from the beginning of the growth. This competitive seeded growth approach is an easy way to identify the influence of seed morphologies in the synthetic pathway of nanoparticle formation.