Anisotropic and Janus Metal Nanoparticles

Metal nanoparticles display very interesting optical properties, related to the interaction of light with conduction electrons, resulting in coherent oscillations in resonance with certain frequencies, which are called localized surface plasmon resonances (LSPRs). Such LSPRs can be readily modulated through the size and morphology of the nanoparticles, so that the whole visible and near-IR ranges can be covered. Thus, it is extremely relevant to devise methods for the synthesis of particles with different non-spherical geometries. Additionally, geometrical anisotropy can lead to anisotropy of the optical response, which adds to the potential for light manipulation. Many different metal nanoparticles can be prepared by means of colloid chemistry methods, including nanorods and nanopolyhedra. However, recent efforts have gone into the growth of sharp branches on the nanoparticles, so that the electromagnetic field can be enhanced and concentrated at the tips. The so-called nanostars thus offer many advantages for applications related with surface enhanced spectroscopies. 

In this talk we shall present some ideas for the combination of anisotropy with sharp branches within metal nanoparticles, as well as for the preparation of particles containing patches with different properties (Janus particles). Growth mechanisms and thorough characterization will be presented for several recently developed systems.