(232f) Growth Mechanisms and Properties of Metal/semiconductor Hybrid Nanocrystals

The combination of different material domains into a single ?hybrid? colloidal nanocrystal offers an interesting material platform, both for studying the fundamental behavior of coupled nanocrystal systems, as well as for creating particles with multiple functionalities. Inorganic colloidal nanocrystals with both metallic and semiconducting domains make up an interesting subset of the general class of hybrid nanocrystals; when metallic and semiconducting domains of similar size are joined on the nanometer scale, the resulting hybrid nanoparticles exhibit overall optical properties which are not simply linear combinations of the optical properties of the individual components. Other properties of the resulting hybrid nanocrystals make them intriguing possibilities for use in directed assembly techniques, or as components in catalytic and photovoltaic devices.

In our work on binary metal/semiconductor nanocrystal systems, we have identified three dominant growth mechanisms: (1) surface growth of material B onto preformed nanocrystals of material A (e.g. Au onto CdS), (2) surface growth of B followed by diffusion into material A (e.g. Au onto InAs), and (3) simultaneous nucleation and growth of both components A and B (e.g. Ag and AgBr). Different material combinations which highlight each of these mechanisms will be discussed, as well as the results of optical and structural characterization. Understanding the underlying mechanisms of nanocrystal growth may allow for further tuning of the morphology and functionality of hybrid nanocrystals.