Sol–Gel Synthesis and Microstructure Analysis of Amino‐Modified Hybrid Silica Nanoparticles from Aminopropyltriethoxysilane and Tetraethoxysilane

Agglomerated amino‐modified silica nanoparticles were prepared from a novel Stöber‐like precursor system consisting of aminopropyltriethoxysilane (APTES), tetraethoxysilane (TEOS), ethanol, and water where the molar ratio APTES/TEOS was 0, 0.1, 1.0, and 2.0, and the molar ratio H 2 O/‐SiOC 2 H 5 was about 20 to 60, or great excess amounts of H 2 O were employed. APTES catalyzed the hydrolysis and condensation of both silanes. 29 Si magic angle spinning nuclear magnetic resonance spectra confirmed that the particles consisted of Q n species (Si(OSi) n (OH) 4− n ; n =2, 3, 4) and T n species (NH 2 (CH 2 ) 3 –Si(OSi) n (OH) 3− n ; n =2, 3). The APTES content in the precursor solutions controlled the agglomerating spherical particle size and morphology: 0.1 in the ratio APTES/TEOS led to almost independent spheres of 300–400 nm, while the larger ratios 1 and 2 led to ∼250 and ∼150 nm spheres, respectively, that were largely agglomerated and some were fused to look like peanut‐shells. When soaked in Kokubo's simulated body fluid, those amino‐modified particles deposited apatite. The mechanisms of particle formation and apatite deposition were discussed in terms of an intraparticle hydrated layer.