Probing atomic ordering and multiple twinning in metal nanocrystals through their vibrations

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 105; no. 39; pp. 14784 - 14789
• Main Authors: Portales, H, Goubet, N, Saviot, L, Adichtchev, S, Murray, D.B, Mermet, A, Duval, E, Pileni, M.-P
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 30-09-2008; National Acad Sciences
• Subjects: Anisotropy; Condensed Matter; Crystallinity; Crystallography; Elastic anisotropy; Materials Science; Metals; Nanocrystals; Nanoparticles; Physical Sciences; Physics; Raman scattering; Silver; Size distribution; Spectral bands; Spectrum analysis; Vibration; Vibration mode
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0803748105

Control of nanocrystal (NC) crystallinity currently raises great interest because of its potential benefits in both physics modeling and technological applications. Advances in methods for synthesizing perfect single-crystalline NCs are recent, so that the effect of crystallinity on NC properties has received only limited study and still needs to be properly investigated. Here, we report that crystallinity of gold NCs dramatically modifies their vibrations. Using low-frequency Raman scattering, we clearly demonstrate that single-domain NCs vibrate differently than their multiply twinned counterparts, through the splitting of the quadrupolar vibrations, which is only observed for the former. Using the resonant ultrasound approach, we calculate the vibrational frequencies of a gold sphere and show that elastic anisotropy induces a lift of degeneracy of the quadrupolar mode in good agreement with our experimental measurements. These findings open up challenging perspectives on using Raman spectroscopy to characterize nanocrystallinity.