A Study of Controllable Aggregation using Silane Treated Silica Nanoparticles
Open Access
- Author:
- Littles, Dionna J
- Area of Honors:
- Chemical Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Themis Matsoukas, Thesis Supervisor
Dr. Wayne Roger Curtis, Thesis Honors Advisor - Keywords:
- colloidal silica
silane surface treatment
controllable aggregation
pH - Abstract:
- Colloidal silica particles were surface-treated with the silane coupling agent N-[3-(Trimethoxysilyl)propyl]ethylenediamine (TMPE). The aggregation behavior of TMPE-treated silica was then characterized as a function of silica volume fraction, grams of TMPE, and pH of the solution; the goal being to successfully manipulate these variables to establish a system of controllable aggregation. After surface modification, size measurements were recorded using Dynamic Light Scattering (DLS). Size measurements indicated that increasing the amount of TMPE led to slower aggregation rates and smaller final aggregate sizes. These results can be explained by the presence of excess TMPE in solution, which has a stabilizing effect on colloidal silica and reduces their need to form clusters. Results also showed that pH can be used to control the final size of aggregates by changing the zeta potential of the silica surface, in which a high zeta potential (~ ˃ |20| mV) correlates to a stable colloidal dispersion. At high pH values (˃ 8.9), samples had low zeta potentials, formed unstable dispersions, and eventually aggregated to the point of complete gelation. At low pH values, the protonation of amino groups on silica surface created a high zeta potential and stabilized the silica particles in suspension through electrostatic repulsion. Results show that it is possible to control aggregation by manipulating the amount of TMPE used for surface treatment and the pH of the dispersion.