Anomalous lattice dynamics and thermal properties of supported size- and shape-selected Pt nanoparticles

作者：Beatriz Roldán Cuenya, Anatoly I. Frenkel, S. Mostafa, Farzad Behafarid, Jason R. Croy, Luis K. Ono, Qiang Wang · 发表于：Physical Review B · 年份：2010 · DOI：10.1103/physrevb.82.155450 · 被引用次数：54 · 研究领域：nanoparticles nucleation surface interactions、Quantum Dots Synthesis And Properties、Electrocatalysts for Energy Conversion

Anomalous lattice dynamics and thermal behavior have been observed for ligand-free, size-, and shape-selected Pt nanoparticles (NPs) supported on nanocrystalline $\ensuremath{\gamma}{\text{-Al}}_{2}{\text{O}}_{3}$ via extended x-ray absorption fine-structure spectroscopy. Several major differences were observed for the NPs with respect to bulk Pt: (i) a contraction in the interatomic distances, (ii) a reduction in the dynamic (temperature-dependent) bond-length disorder and associated increase in the Debye temperature $({\ensuremath{\theta}}_{D})$, and (iii) an overall decrease in the bond-length expansion coefficient coupled with NP stiffening. The increase in the Debye temperature is explained in terms of the NP size, shape, support interactions, and adsorbate effects. For a similar average size, we observe a striking correlation between the shapes of the NPs and their ${\ensuremath{\theta}}_{D}$ values.