Until now it hasn’t been possible to thoroughly check the three-dimensional distribution of the different types of atoms in the nanoparticles after they’ve been made. This limits the information available to the researchers who need to be able to correlate the nanoparticles’ performance with the detailed atomic structure.
Dr Peter Felfer, working with A/Prof. Julie Cairney and Prof. Thomas Maschmeyer at the University of Sydney (USyd) has used atom probe microscopy in the AMMRF (now Microscopy Australia) at USyd to manipulate the 15 nanometre-wide nanoparticles so they can be analysed in the atom probe, something not successfully done before.
The results showed that the particles did consist of a gold core inside a silver shell but there were many gaps in the coating and even some unexpected chemical traces left behind from the manufacturing process. These residual atoms were not evenly distributed and seem to have prevented the particles from being properly coated with silver. A good coating of the reactive silver on the particle surface is crucial for its performance, so gaps would be having a significant impact on the final function.
This atom probe evidence is now enabling the researchers to fine-tune the synthesis of their nanoparticles, which should lead to optimised performance. This, in turn, will lead to greater efficiencies in a whole host of emerging applications.
Felfer et al., 2014, Angewandte Chemie, 126 (42)
October 24, 2014