Bayle Maxime, Combe Nicolas, Sangeetha Neralagatta M, Viau Guillaume, Carles Robert
Université de Toulouse, CEMES CNRS, 29 rue Jeanne Marvig, BP 94347, 31055 Toulouse Cedex 4, France.
Nanoscale. 2014 Aug 7;6(15):9157-65. doi: 10.1039/c4nr02185a.
An experimental analysis of all elementary excitations--phonons and electron-holes--in gold nanocrystals has been performed using plasmon resonance Raman scattering. Assemblies of monodisperse, single-crystalline gold nanoparticles, specific substrates and specific experimental configurations have been used. Three types of excitations are successively analyzed: collective quasi-acoustical vibrations of the particles (Lamb's modes), electron-hole excitations (creating the so-called "background" in surface-enhanced Raman scattering) and ensembles of atomic vibrations ("bulk" phonons). The experimental vibrational density of states extracted from the latter contribution is successfully compared with theoretical estimations performed using atomic simulations. The dominant role of surface atoms over the core ones on lattice dynamics is clearly demonstrated. Consequences on the thermodynamic properties of nanocrystals such as the decrease of the characteristic Debye temperature are also considered.
利用等离子体共振拉曼散射对金纳米晶体中的所有基本激发——声子和电子空穴进行了实验分析。使用了单分散、单晶金纳米颗粒的组装体、特定的基底和特定的实验配置。依次分析了三种类型的激发：颗粒的集体准声学振动（兰姆模）、电子空穴激发（在表面增强拉曼散射中产生所谓的“背景”）以及原子振动集合（“体”声子）。从后一种贡献中提取的实验振动态密度成功地与使用原子模拟进行的理论估计进行了比较。清楚地证明了表面原子在晶格动力学方面相对于核心原子的主导作用。还考虑了对纳米晶体热力学性质的影响，例如特征德拜温度的降低。
