Colloidal crystals as photonic crystals

Colloidal crystals (CC) are closely related to photonic crystals (PC) as both of them can be considered as composite materials with a spatial periodic distribution of building blocks. In the case of CC those building blocks are submicrometric particles. Here we will report on recent advances made in our laboratory to fabricate new colloidal crystals with the aim to find new optical properties in relation to PC. We will focus on the following novel topics: (1) Non-close packed face centred cubic (FCC) structures by chemical etching techniques. Most results on solid colloidal crystals concern close packed systems. However, theory predicts that a non-close packed crystal structure presents stronger light scattering properties as compared to the close packed one. Here we shall show results on the fabrication method and optical characterization of non-close packed FCC colloidal crystals. (2) Diamond structures made from nanorobotics. This technique helps to build up complicate 3D crystal structures not achievable, so far, from colloidal self-assembly methods. We will report on the construction method of a crystal aggregate with diamond symmetry. (c) 2005 Elsevier B.V. All rights reserved.