Effects of base catalyst on the physicochemical properties and surface reactivity of silica nanoparticles

The surface reactivity of silica particles is a key property that enhances their versatility in various industries. Therefore, it is imperative to investigate the effects of different base catalysts on the surface reactivity of silica nanoparticles. Silica nanoparticles were synthesised using potassium hydroxide (KOH) and sodium hydroxide (NaOH) as strong base catalysts, as well as ammonia (NH₃) and lysine amino acid as weak base catalysts. The particle size was observed to increase with the pH of the reaction mixture. Additionally, X-ray photoelectron spectroscopy (XPS) revealed that the catalyst molecules adsorb onto the particle surface, thereby enhancing their surface reactivity. Sodium and potassium ions were found to significantly improve surface reactivity during silanisation, with KOH- and NaOH-sil-C8 samples exhibiting high silane grafting density (> 2.58 alkyl chains/nm²). These findings indicate that the type of base catalyst plays a crucial role in tailoring the properties and surface reactivity of silica nanoparticles.