Shape matters : Anisotropy of the morphology of inorganic colloidal particles - synthesis and function

Abstract

The shape of a crystalline particle can be defined by a characteristic set and abundance of surfaces corresponding to the lattice planes [hkl] of the crystal. The structure, the density, the electronic system, and the energy of each [hkl]-surface is different from the others. Consequently, every morphology is also characterized by a unique free energy compared to alternative shapes at a constant surface-to-volume ratio. Using tools from geometrical crystallography, an attempt is made to describe the systems in terms of morphology energy landscapes. It is obvious that, similar to surface phenomena, shape-related properties are also apparent, in particular at the nanometer-scale. However, morphology effects go much beyond surface effects. It will be shown that not only catalytic properties differ with particle shape, but also magnetic, optical, electronic, mechanical, and self-assembly properties are influenced. In addition, analytical methods are highlighted that are suitable for the determination of the shape of the particles. Different methods are discussed that can be found for the synthesis of anisotropic metal and metal-oxide nanoparticles.