'Ex-Situ' Annealing and Structural Transformations in Gold Nanoparticles

The atomic structure and morphology of gold nanoparticles have been studied using High-Resolution Transmission Electron Microscopy (HRTEM). The structural transformations of these particles have been probed through ex-situ annealing experiments, yielding population statistics on structure as a function of particle size and annealing temperature. The results show that for an original structurally heterogeneous particle population, there is a rise in the percentage of particles with the decahedral morphology as annealing temperature is increased. This can be correlated with a reduction in the number of icosahedral particles as a function of annealing temperature. HRTEM imaging following low temperature annealing reveals a range of modified and distorted decahedral particles, giving insight into the temperature threshold of the solid state transformation and the microstructural processes occurring.