| a. Objectives: This programme aims at a bottom-up approach to nano-structured metamaterials based on combinations of a variety of colloidal nanoparticle (NP) building blocks (semiconductor/-metal/magnetic) and control over the self-assembly and structures by external fields. We propose a general research line leading to a fundamental understanding of nanocolloid self-organization. The role of interparticle interactions (including shape) and external fields on self-organization will be studied with the aim to quantitatively understand and thus manipulate binary nanocolloid crystallization. b. Background, relevance and implementation: Control over the placement of matter in three dimensions (3D) in combination with external fields leads to unprecedented possibilities to design, fabricate and control materials with new or enhanced properties. The dimensions of the colloidal nanocrystalline building blocks are in the 1-100 nm range in which size matters dramatically for their properties; in addition, collective quantum mechanical and electrodynamic interactions will be tuned by the inter-particle distances, the overall 3D geometry and by electric or magnetic fields. By self-assembly that is guided by structured surfaces, shear, electric or magnetic fields, ordered binary NP solids will be prepared. The collective electrical, optical, and magnetic functions and the control over them with external fields that we envisage go, for such binary metamaterials, far beyond those of the single components. The proposed research line will find practice in the fabrication of three types of functional meta-materials each with unique properties, all having a semiconductor NP as one of the components, but with three different second components: Binary NP solids in which spontaneous electron-hole generation occurs, leading to systems with spatially ordered charge carriers, form the first objective. We want the charge separated excitons to be either optically generated or in electronic equilibrium. Secondly, we aim at systems where spin-polarization control is an additional meta-function originating from the second type of NPs having magnetic properties. The third type of meta-materials focus deals with semiconductor NPs combined with metallic NPs. Here the property we want to focus on is 2-photon excitation by local field enhancement due to a collective plasmonic response. Besides fundamental knowledge on (NP) self-organization, the results of this program are expected to find applications in displays, lighting, (optical) storage, (bio)sensing, catalysis, spintronics, photonic crystals, and the opto-electronics field in general. |
