A series of aminopropyl-silica-magnesia hybrid materials has been prepared by the sol–gel method from tetraethoxysilane (TEOS), magnesium chloride (MgCl2) and aminopropyltriethoxysilane (APTES) under acid conditions. The APTES:TEOS ratio was varied between 0:1 and 1:0. The aminopropyl coverage concentrations for APTES-silica-Mg samples were in the range of 0.3–2.3 mmol g−1. The hybrid materials were characterized by numerous techniques, including X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), Fourier transform Raman spectroscopy (FT-Raman), solid-state 13C and 29Si nuclear magnetic resonance (13C- and 29Si-NMR), thermogravimetry (TGA), N2 adsorption–desorption, small-angle X-ray scattering (SAXS), and scanning electron microscopy (SEM). The increase of APTES content in the silica network resulted in the increase of six-membered siloxane rings. The hybrid systems were shown to be formed from fully-condensed, trifunctional APTES species. The porosity and morphology of the hybrid materials were influenced by the initial TEOS/APTES ratio. The radius of gyration of the primary particles, determined by SAXS, was between 1.1 and 2.9 nm.
Sol–gel Hybrid material Aminopropyl Silica Silica-magnesia
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R. Brambilla thanks CNPq for a graduate fellowship. This work was financed by operating and travel grants from the CNPq (Brazil) and the NSERC (Canada). The authors are grateful to the LNLS for the SAXS measurements (Project SAXS1-8043).
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