Synthesis of Silica Particles Victor Vazquez Sevilla Mentor: Ali Mohraz In 1967 Werner Stöber developed a process for the synthesis of monodisperse colloidal silica through precipitation by reacting Tetraethyl orthosilicate (TEOS) in an ethanol and ammonia solution. In the Stöber synthesis procedure particle size is typically varied by changing the initial reactant/reagent concentrations or reaction temperature. Colloidal silica has numerous applications in industry for pigments, catalysis, and chemical mechanical polishing where the quality and performance of these products depends on the monodispersity and size of the particles. Recently, a new seed growth method has been employed to achieve different size particles following the Stöber method with addition of TEOS. My project furthers the study of seeded growth technique by examining growth of (Fluorescein isothiocyanate or FITC) dyed silica particles. Fluorescent silica particles of variable sizes are desired for many studies that rely on fluorescent confocal microscopy imaging. My preliminary results show that the seeded growth technique can be used to grow FITC dyed particles up to 980nm from 300 nm seeds.