Department of Inorganic and Analytical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, 1205 Geneva, Switzerland.
Department of Inorganic and Analytical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, 1205 Geneva, Switzerland.
J Colloid Interface Sci. 2014 Mar 1;417:346-55. doi: 10.1016/j.jcis.2013.11.060. Epub 2013 Dec 1.
Interaction forces and aggregation rates were determined in order to characterize colloid stability of negative carboxyl latex particles in the presence of oppositely charged poly(amido amine) (PAMAM) dendrimers of three different generations G4, G7 and G10. The force profiles were measured by the atomic force microscopy (AFM) based on multi-particle colloidal probe technique. Close to the isoelectric point, the measured force profiles were more attractive than the pure van der Waals interactions. This behavior was rationalized in term of an additional electrostatic patch-charge contribution whose magnitude increases by increasing the dendrimer generation. The aggregation rates were calculated from these results using the classical theory developed by Derjaguin, Landau, Verwey and Overbeek (DLVO) as well as including the additional attractive term and a radially symmetric force field. The calculated aggregation rates were compared to the ones obtained directly from time-resolved dynamic light scattering (DLS) measurements using exactly the same latex particles as in the AFM study. The results from these two methods were in good agreement in the case of dendrimers of lower generation, while at higher generation, significant differences were found. In the latter case, the stability ratio in the slow aggregation regime extracted from direct force measurements was much higher than the one measured experimentally by DLS. Despite the fact that the additional attractive term was included in the calculation, the discrepancy between the two different stability ratios suggests that the assumption of radial symmetric interaction is weak.
为了表征带负电羧基胶乳颗粒在带相反电荷的三代数聚酰胺-胺（PAMAM）树状大分子 G4、G7 和 G10 存在时的胶体稳定性，测定了相互作用力和聚集速率。通过基于多颗粒胶体探针技术的原子力显微镜（AFM）测量力曲线。在等电点附近，测量的力曲线比纯范德华相互作用更具吸引力。这种行为可以用额外的静电补丁电荷贡献来合理化，其大小随树状大分子代的增加而增加。从这些结果中使用由 Derjaguin、Landau、Verwey 和 Overbeek（DLVO）开发的经典理论以及包括额外的吸引力项和径向对称力场来计算聚集速率。将计算得到的聚集速率与直接从时间分辨动态光散射（DLS）测量得到的聚集速率进行了比较，使用的乳胶颗粒与 AFM 研究中完全相同。在较低代的树状大分子的情况下，这两种方法的结果非常吻合，而在较高代的情况下，则存在显著差异。在后一种情况下，从直接力测量中提取的缓慢聚集区的稳定性比 DLS 实验测量的稳定性高得多。尽管在计算中包含了额外的吸引力项，但两个不同稳定性比之间的差异表明径向对称相互作用的假设很弱。
