Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, 30-239 Krakow, Poland.
Phys Chem Chem Phys. 2018 Jun 6;20(22):15368-15379. doi: 10.1039/c8cp01049h.
Quantitative studies on self-assembled hematite/silica nanoparticle (NP) bilayers on mica were performed by applying scanning electron microscopy (SEM), atomic force microscopy (AFM), and streaming potential measurements. The coverage of the supporting hematite layers was adjusted by changing the bulk concentration of the suspension and the deposition time. The coverage was determined by direct enumeration of deposited particles from AFM images and SEM micrographs. Afterward, silica nanoparticle monolayers were assembled under diffusion-controlled transport. A unique functional relationship was derived connecting the silica coverage with the hematite precursor layer coverage. The formation of the hematite monolayer and the hematite/silica bilayer was also monitored in situ by streaming potential measurements. It was confirmed that the zeta potential of the bilayers was independent of the supporting layer coverage, exceeding 0.15. These measurements were theoretically interpreted in terms of the general electrokinetic model that allowed for deriving a formula for calculating nanoparticle coverage in the bilayers. Additionally, from desorption experiments, the interactions among hematite/silica particles in the bilayers were determined using DLVO theory. These results facilitate the development of a robust method of preparing nanoparticle bilayers with controlled properties, with potential applications in catalytic processes.
通过扫描电子显微镜（SEM）、原子力显微镜（AFM）和流动电势测量，对云母上自组装的赤铁矿/二氧化硅纳米粒子（NP）双层进行了定量研究。通过改变悬浮液的体相浓度和沉积时间来调整支撑赤铁矿层的覆盖率。通过从 AFM 图像和 SEM 显微照片中直接计数沉积的颗粒来确定覆盖率。然后，在扩散控制的传输下组装二氧化硅纳米粒子单层。推导出了一个连接二氧化硅覆盖率与赤铁矿前体层覆盖率的独特功能关系。通过流动电势测量还原位监测了赤铁矿单层和赤铁矿/二氧化硅双层的形成。证实双层的 ζ 电位与支撑层覆盖率无关，超过 0.15。根据允许推导出计算双层中纳米粒子覆盖率的公式的一般电动模型，对这些测量进行了理论解释。此外，通过解吸实验，使用 DLVO 理论确定了双层中赤铁矿/二氧化硅颗粒之间的相互作用。这些结果有助于开发一种具有可控性质的制备纳米粒子双层的稳健方法，在催化过程中有潜在的应用。
