Synthesis and Characterization of Monodisperse Colloidal Silica with Tailored Optical
and Surface Properties
Katie Pickrahn
Mentor: Ali Mohraz
Colloids are solid particles with at least one characteristic dimension between a few
nanometers and a few micrometers. Silica is one material that has repeatedly been used to
create colloidal particles, owing to the ease by which large quantities of silica particles of
the same size may be produced. The goal of this project is to systematically synthesize
monodisperse, core-shell colloidal silica with tailored surface chemistries and optical
properties. The core-shell architecture consists of a fluorescent core surrounded by a nonfluorescent layer, allowing for the imaging of these particles using confocal laser
scanning microscopy. These particles are used as model materials for fundamental
research in colloid science and soft matter physics. The results of digital image
processing of the core-shell particles and particles that are fluorescent throughout are
discussed. Colloidal silica may also be used as scattering agents in light guides, requiring
dispersion of the particles in an organic monomer solution. The effects of particle surface
chemistry on suspension stability in an organic solvent are discussed. By controlling the
size and surface chemistry of colloidal silica and understanding the effects of the coreshell architecture on digital imaging, we can better tailor the production of particles that
enhance research in colloid science.