Aqueous Phase Synthesis of Au-Cu Core-Shell Nanocubes and Octahedra with Tunable Sizes and Noncentrally Located Cores

Copper nanocubes with tunable edge lengths over the range from 49 to 136 nm and ultrasmall octahedra with opposite corner distances of 45, 51, and 58 nm have been synthesized in aqueous solutions by reducing CuCl, or copper acetate with ascorbic acid in the presence of octahedral gold nanocrystal cores and hexadecylamine (HDA) at 100 degrees C for 45 min to 1.5 h. Addition of HDA increases the sohition pH and acts as a coordinating ligand to the copper ions to facilitate controlled copper shell growth. Due to ultralarge lattice mismatch between Au and Cu, nonuniform copper deposition yields cubes and octahedra with noncentrally located gold cores. The Au Cu octahedra show little shift in the plasmonic band with increasing particle size. For Au Cu nanocubes, the degree of absorption band red-shift gets smaller as cube size increases. The Au Cu nanocubes have shown reasonable reactivity toward 4-nitrophenol reduction at 40 degrees C.