Vibrational Response of Au−Ag Nanoboxes and Nanocages to Ultrafast Laser-Induced Heating

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 ∼7%). These results demonstrate the importance of accurately modeling the particles in order to interpret experimental data.