Monodispersed Au nanoparticles are synthesized on the surface of exfoliated graphene nanoplatelets (GNP) in the presence of polyethyleneimine (PEI) with microwave assisted heating. A highly structured layered Au/GNP "paper" with good flexibility and mechanical robustness is prepared by vacuum assisted self-assembly. The thermal and electrical conductivity of the hybrid paper with and without the Au nanoparticles are investigated after different experimental processing conditions including thermal annealing and cold compaction. Annealing effectively decomposes and removes the adsorbed PEI molecules and improves thermal contact between Au/GNP particles, whereas cold compaction reduces porosity and induces stronger alignment of the Au/GNP within the hybrid paper. Both approaches lead to improvement in electrical and thermal conductivity. It is also found that adjacent GNP particles are electrically connected by the Au nanoparticles but thermally disconnected. It is believed that phonons are scattered at the Au/GNP interfaces, whereas electrons can tunnel across this interface, resulting in a separation of electron and phonon transport within this hybrid paper.
© 2011 American Chemical Society