Preparation, purification, and characterization of aminopropyl-functionalized silica sol

• Published in: Journal of colloid and interface science Vol. 390; no. 1; pp. 34 - 40
• Main Authors: Pálmai, Marcell, Nagy, Lívia Naszályi, Mihály, Judith, Varga, Zoltán, Tárkányi, Gábor, Mizsei, Réka, Szigyártó, Imola Csilla, Kiss, Teréz, Kremmer, Tibor, Bóta, Attila
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 15.01.2013; Elsevier
• Subjects: 3-Aminopropyl(diethoxy)methylsilane; acetic acid; Acetic Acid - chemistry; adsorption; Amines - chemistry; Aminopropyl silica nanoparticles; centrifugation; Chemistry; Colloidal state and disperse state; Colloids; dialysis; ethanol; Ethanol - chemistry; Exact sciences and technology; Fourier transform infrared spectroscopy; General and physical chemistry; light scattering; nanoparticles; nuclear magnetic resonance spectroscopy; Particle Size; Physical and chemical studies. Granulometry. Electrokinetic phenomena; purification methods; Silanes - chemistry; silica; Silicon Dioxide - chemistry; Silylation in sol; solvents; stable isotopes; Surface modification; transmission electron microscopy; ultrafiltration; X-radiation; zeta potential; Surface modification; Aminopropyl silica nanoparticles; Silylation in sol; 3-Aminopropyl(diethoxy)methylsilane; Characterization; Modification; Binary compound; Purification; Nanoparticle; Preparation; Silylation; Silica
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2012.09.025

[Display omitted] ► New synthesis procedure for the aminopropyl-modification of 20nm diameter silica nanoparticles. ► Purification conditions were optimized to maximize stability. ► The mean particle diameter did not change during the surface modification reaction. ► A covalent submonolayer functionalization of the silica surface was achieved. A new, simple, and “green” method was developed for the surface modification of 20nm 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.