Functionalization of TiO2 and Janus-TiO2 Nanoparticles with Organosilanes for Tunable Pickering Emulsification and Photocatalytic Wastewater Treatment

Abstract

This study examines the use of organosilanes to functionalize titanium dioxide (TiO₂) and Janus-TiO₂ nanoparticles, enabling precise control of surface chemistry for stabilizing Pickering emulsions. Organosilanes with varying hydrophobic chain lengths─3-aminopropyltrimethoxysilane (APS), octyltrichlorosilane (OTS), and trichloro(octadecyl)silane (ODTS)─were employed to modify TiO₂ surfaces, creating nanoparticles with tailored wettability. Comprehensive characterization, including contact angle measurements, FT-IR, TGA, and zeta potential analysis, confirmed successful modification and demonstrated the correlation between nanoparticle surface properties and emulsification efficiency. APS-functionalized particles exhibited enhanced emulsion stability, achieving prolonged stability through droplet flocculation and reduced mobility. An optimal contact angle window (∼10°–40°) was identified for effective emulsification, providing a framework for designing robust Pickering emulsifiers. Comparative analysis revealed ODTS’s superior performance over OTS, attributed to its longer alkyl chain imparting steric hindrance, which was insufficient in OTS-modified particles. Photodegradation studies of a model naphthenic acid revealed enhanced emulsion stability for Janus-TiO₂ and TiO₂-APS emulsions, enabling easy photocatalyst reuse and recovery. These findings offer valuable insights for the development of versatile, surface-engineered Pickering emulsifiers with potential applications in photocatalytic wastewater treatment applications and beyond.