Quantitative analysis of nanoparticle interactions and their distributions

纳米粒子的相互作用对于理解所有胶体系统至关重要。然而，迄今为止，只有等温滴定量热法等几种方法可以测定它们，所得的结果都是平均值。然而，纳米颗粒通常不是单分散的，而是表现出性质的分布。该项目解决了这个基本的尚未解决的问题，并开发了新的方法来确定离解常数、化学计量学和聚集纳米粒子的协同性的大小和形状相关分布，使用分析超离心的联合沉降(s)和扩散系数(D)分布。这些分布可作为等高线图，并可获得不同纳米颗粒浓度的一组结合等温线。拟合合适的结合模型可以得到每条等温线的解离常数、化学计量和协同性，从而得到这些常数与s和d相关的分布。从s和d分布中，还可以得到大小、形状和粒子密度分布，并与相互作用常数分布相关联。该方法将首先用于单分散球形粒子。随后，将确定多分散球形纳米粒子的相互作用常数分布，随后也将确定纳米棒等各向异性纳米粒子的相互作用常数分布。对于各向异性的纳米粒子，晶面依赖的相互作用应在不同的浓度下进行表征。最后，研究不同形状和材料的纳米粒子聚集，揭示形状和材料对纳米粒子相互作用的影响。

Nanoparticle interactions are essential for the understanding of all colloidal systems. However, so far, only few methods exist for their determination like isothermal titration calorimetry, yielding average values. However, nanoparticles are usually not monodisperse and exhibit a distribution of properties. This project addresses this fundamental yet unsolved problem and develops new methodology to determine size- and shape-dependent distributions of dissociation constants, stoichiometry and cooperativity of aggregating nanoparticles using combined sedimentation (s)- and diffusion coefficient (D) distributions from Analytical Ultracentrifugation. These distributions are available as contour maps and a set of binding isotherms can be obtained for different nanoparticle concentrations. Fitting to an appropriate binding model yields the dissociation constant, stoichiometry and cooperativity for each isotherm resulting in a distribution of these constants in dependence of s and D. From the s- and D-distributions, the size, shape and particle density distributions can also be obtained and correlated to the interaction constant distributions. The methodology will first be established for monodisperse spherical particles. Later, interaction constant distributions will be determined for polydisperse spherical nanoparticles and subsequently also anisotropic nanoparticles like nanorods. For anisotropic nanoparticles, crystal face dependent interactions shall be characterized for different concentration regimes. Finally, aggregating nanoparticles with different shape and material will be investigated to reveal the influence of shape versus material onto the nanoparticle interactions.