Matter of age: growing anisotropic gold nanocrystals in organic media.

We investigated the influence of the reduction state of gold ions on the growth of gold nanocrystals in N,N-dimethyl formamide (DMF). While freshly prepared solutions of AuCl3 produce spherical nanocrystals, aged precursor solutions containing mainly Au+ ions and Au(0) atoms lead to various branched nanoparticles. Furthermore, we show that also the amount of the reducing and stabilisation agent tetra-n-octylammonium formate (TOAF) plays a decisive role on the shape of the nanocrystals, allowing us to grow triangular and cubic nanoparticles.