Amine Capped Gold Colloids at Oxidic Supports: Their Electronic Interactions
Amine Capped Gold Colloids at Oxidic Supports: Their Electronic Interactions
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DOI：
10.1515/zpch-2018-0004
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发表时间：
2018-04
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影响因子：
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通讯作者：
Michael Siemer;Lars Mohrhusen;Maximilian Grebien;K. Al‐Shamery
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文献类型：
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作者：
Michael Siemer;Lars Mohrhusen;Maximilian Grebien;K. Al‐Shamery
在氧化物载体上胶体沉积贵金属纳米颗粒是制备非均相催化剂材料的一种新方法。我们使用x射线光电子和俄歇光谱以及高分辨率透射电子显微镜，研究了不同胺配体与金纳米颗粒在几种氧化载体（二氧化钛、二氧化硅、氧化铝、氧化镁或氧化锌）沉积前后的相互作用。胺在金薄膜和纳米粒子上的吸附导致金属光电子结合能的降低。通常，这是通过胺基供体-受体相互作用来解释的。通过对俄歇信号的额外分析，它对氧化态的变化比光电子能谱更敏感，我们证明了这些变化是由于最终态效应，即在胺吸附物存在下增加的光电子空穴筛选。结果表明，这种效应对纳米颗粒大小和盖顶胺的空间性质都不敏感。在氧化载体上沉积后，光电子结合能进一步降低。所提出的研究结果表明，必须注意简单地解释带电时的结合能转移，这对理解金属负载氧化物表面的局部电子状况有影响，这对多相催化至关重要。
Abstract Colloidal deposition of noble metal nanoparticles on oxidic supports is a recent approach for the fabrication of heterogeneous catalyst materials. We present studies on the interaction of different amine ligands with gold nanoparticles before and after deposition on several oxidic supports (titania, silica, alumina, magnesia or zinc oxide), using X-ray photoelectron and Auger spectroscopy, and high-resolution transmission electron microscopy. The adsorption of amines on thin gold films as well as on nanoparticles leads to a decrease in metal photoelectron binding energies. Usually, this is explained by donor-acceptor interactions via the amine group. By additional analysis of Auger signals, which are more sensitive to changes in the oxidation state than photoelectron spectra, we demonstrate that these shifts are due to a final state effect, namely, the increased photoelectron hole screening in presence of amine adsorbates. It will be shown, that this effect is not sensitive neither to the nanoparticle size nor the sterical properties of the capping amine. After deposition on oxide supports, the photoelectron binding energies are even further decreased. The presented findings exhibit that care has to be taken to interpret binding energy shifts simply with charging, which has impact on understanding the local electronic situation on the surface of metal-loaded oxides, crucial for heterogeneous catalysis.