A two-step approach to realize size- and shape-selective separation of crude gold nanotriangles with high purification

Abstract

In this work, a facile and effective two-step separation strategy that combined both CTAB and CTAC has been proposed that enables the purification of gold nanotriangles on a large scale. The resulting nanotriangles exhibit straight edges and sharp corners, with a narrower size distribution. The separation of size or morphology could be achieved by utilizing different surfactants. It was found that CTAB served as a size separation agent and CTAC served as a shape separation agent in the separation process. The optimum concentrations were found to be 0.167 M CTAB for size separation and 0.222 M CTAC for shape separation respectively. By simply adjusting the concentration and the sequence of CTAB and CTAC, we were able to exquisitely separate nanotriangles from the crude gold nanoparticles. Furthermore, the separation mechanism has also been discussed based on surfactant depletion-induced aggregation on different contact areas of the nanoparticles. The proposed two-step separation strategy holds great potential to be extended to the separation of other nanoparticles with anisotropic shapes and different sizes, improving the high yield of anisotropy with great uniformity, which will eventually facilitate SERS-based applications.