Second virial coefficient measurements of dilute gold nanocrystal dispersions us

2019-08-19 05:38:55

scattering ray dependent expected nanocrystal

责任者: Saunders, Aaron E.;Korgel, Brian A. 单位: Department of Chemical Engineering, Texas Materials Institute, University of Texas, Austin, TX 78712-1062, United States 来源出处: Journal of Physical Chemistry B,2004,108(43):16732-16738 摘要: Small-angle X-ray scattering (SAXS) was used to study the size-dependent two-body solvent-mediated interparticle interactions between dodecanethiol-coated gold nanocrystals (2-6 nm in diameter) in dilute toluene dispersions. Using a modified Zimm analysis of concentration-dependent X-ray scattering data, the second virial coefficient B2 was measured as a function of nanocrystal diameter and compared to theoretical predictions. The measured values of B2 are more negative than those expected for hard spheres, indicating that interparticle attractions are significant in this system, even though the particles are dispersed in good solvents for the ligands. The data can be fit using a square well potential to model the pair interactions with nanocrystal size-dependent well depths ranging between 0.1 and 0.4 kT and a range of interaction of 30 A. The interaction potentials between particles in the larger size range (i.e., >5 nm diameter) are close to those expected from a simple steric stabilization model accounting for the core-core van der Waals attraction modified by an osmotic repulsion between adsorbed chains. Smaller particles, however, exhibited significantly stronger attraction than expected from this simple model, which could possibly be due to decreased ligand surface coverage at the smaller nanocrystal sizes. 关键词: Gold;Nanostructured materials;Dispersions;Superlattices;Volume fraction;Solvents;Deposition;Macromolecules;X ray scattering;Particle assembly dynamics;Solvent evaporation;Nanocrystal surfaces