functionalized surfaces on porous silica by atomic layer ... - Aaltodoc

3. EXPERIMENTAL
The main features of the materials and ALD procedures used in the experiments are presented
in this section. The methods used to characterize the surface species on both the plain
substrate and deposited atomic layers are briefly introduced. The experimental details can be
found in the original publications I-VII.
3.1 Materials
Nine amorphous silicon dioxide samples of various types were used to test the
characterization methods applied in this study. I,II The silica samples for the DRIFTS and 1 H
MAS NMR measurements were pretreated in a muffle furnace in air at 105, 550, or 1000 °C
for 16 h. The most important physical properties of silica, i.e. specific surface area, pore
volume, and average pore diameter, were determined by nitrogen physisorption and laser
diffraction measurements.
EP 10x silica gel from Crosfield, UK, in the atomic layer depositions were used as the
support. The specific surface area (Brunauer-Emmett-Teller, BET), the pore volume, and the
average pore diameter of EP 10x as determined by a standard nitrogen physisorption
technique were 300 m 2 g -1 , 1.2 cm 3 g -1 , and 20 nm, respectively. The specific surface area of
EP 10x heat-treated at 800 °C was diminished to 280 m 2 /g and the pore volume to 1.0 cm 3 /g.
The average particle size of EP 10x was 100 µm, as reported by the manufacturer. Silica for
the deposition experiments was stabilized by pretreatment at 200, 450, 600, and 800 °C in the
manner described above. The numbers of silanol groups were determined by 1 H MAS NMR.
Commercial trifunctional γ-aminopropyltrimethoxysilane (APTMS), γ-aminopropyl-
triethoxysilane (APTS), and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AAPS);
bifunctional γ-aminopropyldiethoxymethylsilane (APDMS); and monofunctional γ-amino-
propyldimethylethoxysilane (APDMES) were used as precursors for the modification of
silica. AAPS, APDMS, and APDMES were obtained from ABCR, Germany; APTMS from
ABCR, Germany, and Aldrich, U.S.A.; and APTS from Merck, Germany. The source
materials in the preparation of imide structures on aminosilylated silica were pyromellitic
anhydride (PMDA) and 1,6-diaminohexane (DAH) obtained from Fluka Chemika, Germany.
The purity of the reagents was >95%. The schematic structures of the precursors are shown in
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