Freddie Rabouw: Emission dynamics of single nanoparticles

The most interesting aspect of colloidal semiconductor nanocrystals is the tunability of optical properties by size, shape and composition. However, this same aspect complicates the characterization of nanocrystals. A typical nanocrystal consists of thousands of atoms of semiconductor material, and again thousands of atoms in the ligand molecules (e.g. oleic acid). (Slight) variations in size and structure among nanocrystals in a synthesis batch result in differences in optical properties. Moreover, dynamic fluctuations in structure (e.g. ligand configuration) and charge state even cause the emission properties of an individual nanocrystal to vary in time. Eventually, these variations determine the ensemble properties of a batch of nanocrystals. Single-nanocrystal experiments are necessary to measure and understand the variations. In this presentation I will (1) start with a basic explanation of single-nanocrystal luminescence experiments and their analysis and then (2) show recent unpublished data on single CuInS2 nanocrystals, resolving open questions about their unconventional luminescence mechanism.