Interactions between Silica Colloids with Magnetite Cores: Diffusion, Sedimentation and Light Scattering

• Published in: Journal of colloid and interface science Vol. 212; no. 1; pp. 14 - 23
• Main Authors: Donselaar, Liesbeth N., Philipse, Albert P.
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 01.04.1999; Elsevier
• Subjects: Chemistry; Colloidal gels. Colloidal sols; Colloidal state and disperse state; diffusion; dynamic light scattering; Exact sciences and technology; General and physical chemistry; magnetic colloids; sedimentation; static light scattering; magnetic colloids; dynamic light scattering; diffusion; sedimentation; static light scattering; Magnetite; Sedimentation rate; Cyclohexane; Van der Waals interaction; Magnetic force; Diffusion coefficient; Colloidal dispersion; Experimental study; Silica
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1006/jcis.1998.5931

The magnetic and Van der Waals attraction between uncharged silica spheres with a magnetic core has been studied using sedimentation and static and dynamic light scattering techniques. Specifically the effect of the interactions on the concentration dependence of the sedimentation velocity, diffusion, and the apparent radius of gyration was investigated. It was found experimentally that the concentration dependence is decreased significantly as a result of the Van der Waals and magnetic attractions and even may change sign in comparison to the hard-sphere case. Calculations of the (linear) concentration dependence for weak interactions predict this decrease and also indicate that for the silica-magnetite particles the second virial coefficient passes a maximum with increasing silica layer thickness.