Kang Joo H, Menard Laurent D, Nuzzo Ralph G, Frenkel Anatoly I
School of Chemical Sciences and Frederick-Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA.
J Am Chem Soc. 2006 Sep 20;128(37):12068-9. doi: 10.1021/ja064207p.
Variable-temperature X-ray absorption spectroscopy measurements of sub-nanometer Pt nanoparticles on a high-surface-area gamma-alumina support reveal that the Pt-Pt bonds exhibit contraction upon heating [i.e., negative thermal expansion (NTE)]. Bare clusters under a He environment show an average linear expansion coefficient of -2.5 x 10-5 K-1 over the temperature range studied. Adsorption of hydrogen results in an overall bond relaxation and less dramatic Pt-Pt thermal bond-length contraction. From the temperature effect on bond length, disorder parameters, and the X-ray absorption near edge structure (XANES) spectra, temperature-dependent charge transfer between the support and the Pt clusters was concluded to be responsible for the observed behavior.
对高比表面积γ-氧化铝载体上亚纳米级铂纳米颗粒进行的变温X射线吸收光谱测量表明，铂-铂键在加热时会收缩[即负热膨胀（NTE）]。在氦气环境下的裸簇在研究的温度范围内显示出平均线性膨胀系数为-2.5×10⁻⁵ K⁻¹。氢气的吸附导致整体键松弛以及铂-铂热键长度收缩不那么明显。从温度对键长、无序参数和X射线吸收近边结构（XANES）光谱的影响来看，载体与铂簇之间随温度变化的电荷转移被认为是导致观察到的行为的原因。
