Ultrasmall nanoparticles with sizes around 1 nm are also called nanoclusters. They have a “countable” number of atoms (anything from a couple to tens of atoms). Using appropriate ligands such as thiols, extremely stable gold and silver nanoclusters can be prepared in solution. It is even possible to prepare atomically monodisperse nanoclusters (for example [Au25(SR)18]-, where ‘SR’ is the thiolate ligand). In bulk gold the energy levels of the atoms overlap to form a continuous band, but this is not the case for gold nanoclusters. Due to their extremely small size, the latter have discrete energy levels. This gives rise to interesting optical properties such as sharp absorption transitions and luminescence. [1,2]
I am interested in the relationship between the structure of gold (and silver) nanoclusters and their optoelectronic properties. I will investigate the effect of dithiol vs monothiol ligands on cluster structure and the mechanism of nanocluster formation. In addition to optical spectroscopy I will use X-ray absorption spectroscopy (EXAFS to investigate nanocluster structure and size, XANES to determine oxidation state of gold and sulfur).
Finally, there have been many reports of magnetic properties of gold nanoparticles, although the origin of this magnetism remains unclear . When bulk techniques are used to characterize these magnetic properties, sample contamination (with for example iron) is an issue. This can be avoided by using the element- sensitive technique XMCD. With perfectly monodisperse gold nanoclusters, it should be possible to correlate magnetism (if any) with nanocluster size and structure.
1. Jin, R. (2010). Quantum sized, thiolate-protected gold nanoclusters. Nanoscale, 2(3), 343–62.
2. Lu, Y., & Chen, W. (2012). Sub-nanometre sized metal clusters: from synthetic challenges to the unique property discoveries. Chemical Society Reviews, 41(9), 3594–3623.
3. Nealon, G. L., Donnio, B., Greget, R., Kappler, J.-P., Terazzi, E., & Gallani, J.-L. (2012). Magnetism in gold nanoparticles. Nanoscale, 4(17), 5244–58.