Preparation, purification and characterization of aminopropyl-functionalized silica sol

Pálmai, Marcell and Nagy Naszályi, Lívia and Mihály, Judith and Varga, Zoltán and Tárkányi, Gábor and Mizsei, Réka and Szigyártó, Imola Csilla and Kiss, Teréz and Kremmer, Tibor and Bóta, Attila (2013) Preparation, purification and characterization of aminopropyl-functionalized silica sol. Journal of Colloid and Interface Science, 390 (1). pp. 34-40. ISSN 0021-9797

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Abstract

A new, simple and “green” method was developed for the surface modification of 20 nm diameter Stöber silica particles with 3-aminopropyl(diethoxy)methylsilane in ethanol. The bulk polycondensation of the reagent was inhibited and the stability of the sol preserved by adding a small amount of glacial acetic acid after appropriate reaction time. Centrifugation, ultrafiltration and dialysis were compared in order to choose a convenient purification technique that allows the separation of unreacted silylating agent from the nanoparticles without destabilizing the sol. The exchange of the solvent to acidic water during the purification yielded a stable colloid, as well. Structural and morphological analysis of the obtained aminopropyl silica was performed using transmission electron microscopy (TEM), dynamic light scattering (DLS) and zeta potential measurements, Fourier-transform infrared (FTIR), 13C and 29Si MAS nuclear magnetic resonance (NMR) spectroscopies, as well as small angle X-ray scattering (SAXS). Our investigations revealed that the silica nanoparticle surfaces were partially covered with aminopropyl groups, and multilayer adsorption followed by polycondensation of the silylating reagent was successfully avoided. The resulting stable aminopropyl silica sol (ethanolic or aqueous) is suitable for biomedical uses due to its purity.

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