Department of Materials Science and Engineering, Michigan Technological University, Houghton, 49931, USA.
Adv Colloid Interface Sci. 2011 Jul 11;165(2):91-101. doi: 10.1016/j.cis.2010.12.009. Epub 2011 Jan 15.
The DLVO theory treats the total interaction force between two surfaces in a liquid medium as an arithmetic sum of two components: Lifshitz-van der Waals and electric double layer forces. Despite the success of the DLVO model developed for homogeneous surfaces, a vast majority of surfaces of particles and materials in technological systems are of a heterogeneous nature with a mosaic structure composed of microscopic and sub-microscopic domains of different surface characteristics. In such systems, the heterogeneity of the surface can be more important than the average surface character. Attractions can be stronger, by orders of magnitude, than would be expected from the classical mean-field DLVO model when area-averaged surface charge or potential is employed. Heterogeneity also introduces anisotropy of interactions into colloidal systems, vastly ignored in the past. To detect surface heterogeneities, analytical tools which provide accurate and spatially resolved information about material surface chemistry and potential - particularly at microscopic and sub-microscopic resolutions - are needed. Atomic force microscopy (AFM) offers the opportunity to locally probe not only changes in material surface characteristic but also charges of heterogeneous surfaces through measurements of force-distance curves in electrolyte solutions. Both diffuse-layer charge densities and potentials can be calculated by fitting the experimental data with a DLVO theoretical model. The surface charge characteristics of the heterogeneous substrate as recorded by AFM allow the charge variation to be mapped. Based on the obtained information, computer modeling and simulation can be performed to study the interactions among an ensemble of heterogeneous particles and their collective motions. In this paper, the diffuse-layer charge mapping by the AFM technique is briefly reviewed, and a new Diffuse Interface Field Approach to colloid modeling and simulation is briefly discussed.
DLVO 理论将液体介质中两个表面之间的总相互作用力视为两个分量的算术和：Lifshitz-van der Waals 力和双电层力。尽管针对均匀表面开发的 DLVO 模型取得了成功，但在技术系统中的大多数颗粒和材料表面都是具有镶嵌结构的非均匀性质，由不同表面特性的微观和亚微观域组成。在这样的系统中，表面的非均匀性可能比平均表面特性更为重要。吸引力可能比采用面积平均表面电荷或电势的经典平均场 DLVO 模型所预期的要强几个数量级。非均匀性还将相互作用的各向异性引入胶体系统中，这在过去被严重忽视。为了检测表面不均匀性，需要使用能够提供有关材料表面化学和电势的准确且空间分辨信息的分析工具 - 特别是在微观和亚微观分辨率下 -。原子力显微镜 (AFM) 提供了通过在电解质溶液中测量力-距离曲线来局部探测不仅材料表面特性的变化而且还探测不均匀表面的电荷的机会。可以通过用 DLVO 理论模型拟合实验数据来计算扩散层电荷密度和电势。通过 AFM 记录的不均匀基底的表面电荷特性允许对电荷变化进行映射。基于获得的信息，可以进行计算机建模和模拟以研究不均匀颗粒的集合体之间的相互作用及其集体运动。本文简要回顾了 AFM 技术的扩散层电荷映射，并简要讨论了胶体建模和模拟的新的扩散界面场方法。
