Deposition Kinetics of Iron Oxide Nanoparticles on a Poly(diallyldimethylammonium Chloride)-Coated Silica Surface: Influences on the Formation of a Softer Particle-Polyelectrolyte Layer

作者：Che Hui Xin; Leong Sim Siong; Ng Wei Ming; Ahmad Abdul Latif; Lim Jitkang^*

来源：Journal of Physical Chemistry C, 2017, 121(38): 20777-20789.

DOI：10.1021/acs.jpcc.7b05358

Particle-polyelectrolyte layers with an open structure were constructed by using cationic poly(diallyldimethylammonium chloride) (PDDA) as a binder to promote the attachment of iron oxide nanoparticles (IONPs) onto silica colloids. The deposition kinetics of IONPs onto PDDA-coated silica surfaces were monitored by a quartz crystal microbalance with dissipation (QCM-D). Here, our experiments provide clear evidence of the direct influences of deposition kinetics on the structural properties of the formed PDDA/IONP layers. At low IONP deposition rates, softer particle-polyelectrolyte layers were formed with a great amount of IONPs attached to the outer compartment of these layers. This unique feature of the polymer-particle system can be further modulated by varying the ionic strength of the background medium, containing both PDDA and IONPs. As the ionic strength of the solution is increased, the PDDA/IONP assembled layers become more flexible, leading to a larger amount of deposited IONPs and reducing the characteristic rate constant of deposition kinetics. The ability to fine-tune the structural property of these layers by adjusting the ionic strength, however, is restricted by the critical coagulation concentration (CCC) of IONPs. To understand this threshold phenomenon, we employed dynamic light scattering (DLS) to determine the CCC value of IONPs as 50 mM. The result was further verified by extended Derjaguin-Landau-Verwey-Overbeek (DLVO) calculation. On the basis of our results, the adjustment of ionic strength below the CCC substantially influences the deposition kinetics of IONPs, where higher ionic strength gives faster deposition kinetics. Additionally, these PDDA/IONP assembled layers become rougher when a higher salt concentration is used, and this result was confirmed by a topography scan using atomic force microscopy (AFM).

• 出版日期2017-9-28