Adsorption of silica colloids onto like-charged silica surfaces of different roughness

• Published in: Colloids and surfaces. A, Physicochemical and engineering aspects Vol. 520; no. C; pp. 85 - 96
• Main Authors: Dylla-Spears, R., Wong, L., Shen, N., Steele, W., Menapace, J., Miller, P., Feit, M., Suratwala, T.
• Format: Journal Article
• Language: English
• Published: United States Elsevier B.V 05.05.2017; Elsevier
• Subjects: Adsorption; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; Colloidal silica; DLVO theory; ENGINEERING; MATERIALS SCIENCE; Polishing; QCM; Surface roughness; Colloidal silica; Polishing; QCM; Surface roughness; Adsorption; DLVO theory
• ISSN: 0927-7757; 1873-4359
• DOI: 10.1016/j.colsurfa.2017.01.042

[Display omitted] •QCM-D sensors can successfully be roughened by optical finishing techniques.•Roughness increase from 1.3nm to 2.7nm boosts 50-nm SiO2 colloid adsorption by 3x.•Roughness scale relative to adsorbate size plays a role in adsorption outcome. Particle adsorption was explored in a model optical polishing system, consisting of silica colloids and like-charged silica surfaces. The adsorption was monitored in situ under various suspension conditions, in the absence of surfactants or organic modifiers, using a quartz crystal microbalance with dissipation monitoring (QCM-D). Changes in surface coverage with particle concentration, particle size, pH, ionic strength and ionic composition were quantified by QCM-D and further characterized ex situ by atomic force microscopy (AFM). A Monte Carlo model was used to describe the kinetics of particle deposition and provide insights on scaling with particle concentration. Transitions from near-zero adsorption to measurable adsorption were compared with equilibrium predictions made using the Deraguin-Verwey-Landau-Overbeek (DLVO) theory. In addition, the impact of silica surface roughness on the propensity for particle adsorption was studied on various spatial scale lengths by intentionally roughening the QCM sensor surface using polishing methods. It was found that a change in silica surface roughness at the AFM scale from 1.3nm root-mean-square (rms) to 2.7nmrms resulted in an increase in silica particle adsorption of 3-fold for 50-nm diameter particles and 1.3-fold for 100-nm diameter particles—far exceeding adsorption observed by altering suspension conditions alone, potentially because roughness at the proper scale reduces the total separation distance between particle and surface.