发表机构
Aarhus University; MAX IV Laboratory, Lund University; Friedrich Schiller University Jena（奥胡斯大学; 隆德大学马克四实验室; 耶拿弗里德里希·席勒大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过光电效应和电子显微镜表征实验室生长的硅酸镁纳米颗粒薄膜，发现Mg/Si比例和退火影响组成与形貌，为星际硅酸镁尘埃催化研究提供二维模型。
AI 中文摘要
星际硅酸盐尘埃颗粒表面的原子结构可能在星际介质（ISM）恒星和行星形成区域发生的多种化学过程中发挥关键作用。在此，我们利用光电效应原位表征了硅酸镁纳米颗粒薄膜的局部化学结构，并利用非原位电子显微镜追踪了不同起始组成所导致的形貌变化。纳米颗粒薄膜通过在超高真空（UHV）条件下将Si、Mg和O原子共沉积到石墨基底上制备，并使用X射线光电子能谱和近边X射线吸收精细结构测量进行表征。结合密度泛函理论计算的分析表明，将Mg与Si的比例从3.5调整到1.8，会使颗粒组成从MgO和硅酸镁的混合物转变为以硅酸镁为主。在UHV中退火也会使组成向硅酸镁方向推进，然而，始终观察到非化学计量比的化学基序，呈现出潜在催化活性位点的分布。电子显微镜图像显示，组成依赖的薄膜形貌在热退火后会发生不同的重构。本文介绍的硅酸镁纳米颗粒薄膜被表征为通过激光烧蚀制备的ISM类似物尘埃颗粒的二维版本，因此更适合作为表面科学研究星际硅酸镁尘埃催化性质的研究模型。
英文摘要
The atomic structure at the surface of interstellar silicate dust particles likely plays a key role in a variety of chemical processes occurring in star- and planet-forming regions of the interstellar medium (ISM). Here, we use the photoelectric effect to characterize, in situ, the local chemical structure of Mg-silicate nanoparticulate films, and ex situ electron microscopy to trace changes to morphology resulting from different starting compositions. Nanoparticulate films are prepared via co-deposition of Si, Mg and O atoms on a graphitic substrate under ultra-high vacuum (UHV) and are characterised with X-ray photoelectron spectroscopy and near edge X-ray absorption fine structure measurements. Analysis, supported by density functional theory calculations, shows that adjusting the Mg-to-Si ratio from 3.5 to 1.8 changes particle composition from a mixture of MgO and Mg-silicate towards predominantly Mg-silicate. Annealing in UHV also pushes the composition towards Mg-silicate, however, non-stoichiometric chemical motifs are always observed, presenting a distribution of potentially catalytically active sites. Electron microscopy images show composition-dependent film morphologies that restructure differently upon thermal annealing. The Mg-silicate nanoparticulate films presented here are characterised as a 2D version of ISM analogue dust particles prepared via laser ablation and are therefore a more readily suitable model for surface science investigations into the catalytic properties of interstellar Mg-silicate dust.
Comments25 pages, 9 figures. Planned for submission to ACS Earth Space Chem
