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We have evaluated the catalytic properties of Au-based nanostructures (including nanocages, nanoboxes, and solid nanoparticles) using a model reaction based on the reduction of p-nitrophenol by NaBH(4). From the average reaction rate constants at three different temperatures, we determined the activation energy, the entropy of activation, and the pre-exponential factor for each type of Au nanostructure. The kinetic data indicate that the Au-based nanocages are catalytically more active than both the nanoboxes and nanoparticles probably due to their extremely thin but electrically continuous walls, the high content of Au, and the accessibility of both inner and outer surfaces through the pores in the walls. In addition, a compensation effect was observed in this Au-based catalytic system, which can be primarily interpreted by a model based on kinetic regime switching.

Time-resolved spectroscopy has been used to investigate the vibrational properties of hollow cubic nanoparticles: Au-Ag nanoboxes and nanocages. In these experiments, laser-induced heating was used to coherently excite the breathing vibrational modes of the particle. The vibrational periods scale with the edge length of the particle and the nanocages and nanoboxes showing equivalent responses despite a large difference in their morphology. The measured vibrational periods are compared to finite element calculations, where the particles are modeled as a hollow cube, with the principle crystal axes parallel to the sides of the cube. Very good agreement is obtained between the calculations and the experimental data, with the experimental frequencies being slightly lower than the calculated values (by approximately 7%). These results demonstrate the importance of accurately modeling the particles in order to interpret experimental data.

Silver nanocubes dispersed in water were transformed into Pd-Ag or Pt-Ag nanoboxes by adding either Na(2)PdCl(4) or Na(2)PtCl(4). By controlling the amount of noble metal salt added, and therefore the molar ratio of Na(2)PdCl(4) or Na(2)PtCl(4) to Ag, we could tune the surface plasmon resonance peak of the nanostructures across the entire visible spectrum, from 440 to 730 nm. Replacement of Ag with Pd resulted in the formation of a nanobox composed of a Pd-Ag alloy single crystal, but the nanobox formed after replacement of Ag with Pt was instead composed of distinct Pt nanoparticles. DDA calculations suggest that both nanoboxes absorb light strongly, with Q(abs)/Q(sca) approximately 5. After galvanic replacement, Pd-Ag and Pt-Ag nanostructures remain SERS active, suggesting their use as a SERS probe for studying the dependence of interfacial chemistry on composition.