Mass synthesis of large, single-crystal gold nanoplates using a pyridinium-based ionic liquid

Single-crystal gold nanoplates, with triangular, hexagonal, or truncated triangular shapes, have been successfully synthesized in high yield via microwave heating of HAuCl₄-4H₂O in an ionic liquid (N-butyl-pyridinium tetrafluoroborate, [BuPy][BF₄]) without any extra capping agents and reducing agents. The gold nanoplates are single crystals bound primarily by (111) lattice planes, as revealed by both selected area electron diffraction and powder X-ray diffraction. These large gold nanoplates have intense absorption in the near infrared region. The reaction temperature plays important role in the formation of final products. This facile approach may be extended to the synthesis of other metal nanomaterials of different size.