Assembly and interaction of Au/C core-shell nanostructures: In situ observation in the transmission electron microscope

Using transmission electron microscopy, we identify the temperature-dependent interaction pathway of carbon-supported Au nanoparticles. At low temperature (room temp. to 400 degrees C) Au nanoparticles predominantly interact by coalescence initiated by an atomic Au bridge. At high temperature (400-800 degrees C), the particles assemble into Au/C core-shell nanostructures. C-shells around individual nanoparticles; passivate their surface and prevent coalescence. Ultimately coalescence does occur via rupture of the passivating shells, which invariably follows the assembly of C sheets enveloping and compressing multiple closely spaced Au/C nanoparticles.