L-Arginine-Catalyzed Synthesis of Nanometric Organosilica Particles through a Waterborne Sol Gel Process and Their Porous Structure Analysis

We report an efficient and easy-to-implement waterborne sol gel process for the synthesis of nanometric organosilica particles. In this process, tetraethyl orthosilicate (TEOS) and 3-(methacryloxy)propyl trimethoxy silane (gamma-MPS), employed as silica sources, were heterogeneously delivered in an aqueous solution of L-arginine, a basic amino acid used as a catalyst, from a top organic layer. Co-condensation of TEOS with gamma-MPS led to the formation of organosilica particles with diameters between 30 and 230 nm when increasing the gamma-MPS content from 0 to 10.1 mol % in the silica source. Nitrogen sorption analyses confirmed the microporous nature of the obtained particles after calcination. The Brunauer-Emmett-Teller (BET) surface areas increased from 27 (before calcination) to 684 m(2) g(-1) (after calcination) for the organosilica particles containing 10.1 mol % of gamma-MPS. Fourier transform infrared spectroscopy and Si-29 NMR were employed to analyze the chemical structure of the organosilica spheres and provide insight into the mechanism of particle formation. In the second part, hybrid organosilica particles with a core-shell morphology were synthesized through the combination of Pickering emulsion and the sol-gel process. gamma-MPS emulsion droplets stabilized by tiny silica particles (formed in a separate step) were first generated and used as seeds to grow a silica shell on their surface through TEOS addition from the top organic layer. Transmission electron microscopy and pore size analyses of the resulting particles after calcination revealed a unique dual-porosity structure with a mesoporous inner core and a micro/mesoporous silica shell with ink-bottle-type pores.