Unusually Large Lattice Mismatch-Induced Optical Behaviors of Au@Cu-Cu2O Core-Shell Nanocrystals with Noncentrally Located Cores

To extend the optical property characterization of metal-Cu2O polyhedra, 50 nm Au@Cu cubic cores are used to fabricate Au@Cu-Cu2O core-shell cubes, octahedra, and rhombic dodecahedra with tunable sizes. Despite the unusually large lattice mismatch of 15.1% between Cu and Cu2O, fine adjustment in the volumes of reagents introduced allows the formation of these heterostructures. To relieve the lattice strain, the metal cores are essentially never found to locate at the particle center, and slight lattice spacing shifts are recorded. Although efforts are made to reduce the heterostructure sizes, the Cu2O shells are generally too thick to reveal surface plasmon resonance (SPR) absorption band from the metal cores. Only the Au@Cu-Cu2O cubes with many cores located near the particle corners show observable SPR band red-shift, but UV-vis spectra of all particle shapes are still dominated by Cu2O absorption and light scattering bands. Au@Cu-Cu2O cubes consistently show the most red-shifted absorption bands than those of octahedra resulting from the optical facet effects.