Morales J, Espinos J P, Caballero A, Gonzalez-Elipe A R, Mejias Jose Antonio
Instituto de Ciencia de Materiales de Sevilla (CSIC-University Sevilla) and Dpt. Q. Inorganica, Avda. Americo Vespucio s/n, 41092 Sevilla, Spain.
J Phys Chem B. 2005 Apr 28;109(16):7758-65. doi: 10.1021/jp0453055.
This paper reports an analysis of the changes in the photoemission parameters of copper in small particles of copper oxides deposited on silicon dioxide. This study is of relevance for investigations in the fields of heterogeneous catalysis and coordination chemistry. Copper oxides (Cu2O and CuO) have been deposited on the surface of a flat SiO2 substrate by evaporation of copper and subsequent oxidization of the deposited particles. XPS has been used to analyze the chemical and coordination state of copper. Large variations in the Cu 2p(3/2) binding energy (BE) and Auger parameter (alpha') have been found as a function of the type and amount of deposited copper oxide. The differences in BE calculated from the values of the lowest amount of deposited material and those of the bulk compounds were -0.4 eV (Cu2O) and -1.9 eV (CuO), while those in alpha' amounted to 2.9 (Cu2O) and 1.6 eV (CuO). The observed changes have been described in terms of the chemical state vector (CSV) concept in a Wagner plot and rationalized by considering the characteristics of bonding and electronic interactions that occur at a given oxide/oxide interface. These interactions have been modeled by means of quantum mechanical calculations with cluster models simulating the Cu-O-Si bonding at the interface. The effect of the polarization of the surrounding media around the copper cations has been also estimated for both the dispersed clusters supported on the SiO2 substrate and for the copper oxide materials in bulk form. A change in the values of alpha' and BE of copper (ie., delta alpha' = 1.1 eV, deltaBE = 0.1 eV) upon adsorption on the Cu+ species of Cu2O moieties dispersed on SiO2 of a phenyl-acetylene molecule illustrates the use of XPS to study the formation of cation-ligand complexes in heterogeneous systems. A detailed description of the bonding interactions of these coordinated Cu+ species in terms of initial and final state effects of the photoemission process has been also carried out by means of quantum mechanical calculations and cluster models.
本文报道了对沉积在二氧化硅上的氧化铜小颗粒中铜的光发射参数变化的分析。该研究对于多相催化和配位化学领域的研究具有重要意义。通过蒸发铜并随后氧化沉积颗粒，将氧化铜（Cu2O和CuO）沉积在平坦的SiO2衬底表面上。X射线光电子能谱（XPS）已用于分析铜的化学和配位状态。已发现Cu 2p(3/2)结合能（BE）和俄歇参数（α'）随沉积氧化铜的类型和数量而有很大变化。根据沉积材料最低量的值和块状化合物的值计算出的BE差异分别为-0.4 eV（Cu2O）和-1.9 eV（CuO），而α'的差异分别为2.9（Cu2O）和1.6 eV（CuO）。在瓦格纳图中，根据化学状态向量（CSV）概念描述了观察到的变化，并通过考虑在给定氧化物/氧化物界面处发生的键合和电子相互作用的特征进行了合理化解释。这些相互作用已通过量子力学计算进行建模，使用簇模型模拟界面处的Cu-O-Si键合。对于负载在SiO2衬底上的分散簇以及块状形式的氧化铜材料，还估计了铜阳离子周围介质极化的影响。苯乙炔分子吸附在分散在SiO2上的Cu2O部分的Cu+物种上时，铜的α'和BE值发生变化（即，δα' = 1.1 eV，δBE = 0.1 eV），这说明了使用XPS研究多相系统中阳离子-配体络合物的形成。还通过量子力学计算和簇模型对这些配位Cu+物种的键合相互作用进行了详细描述，涉及光发射过程的初始和最终状态效应。
