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

chemisorbed precursor molecules remained on the surface. No further heat-treatment after the
deposition process was performed. Modified samples were taken from the surface and bottom
of the silica bed under ambient conditions and were stored in a desiccator to avoid hydrolysis
of the alkoxy groups due to air humidity.
Liquid precursor
Exhaust
N2 carrier gas
Solid (or liquid) precursor
Increasing temperature gradient
Figure 6. Flow-type ALD reactor used for deposition after Haukka 38 .
Sequential reactions of trifunctional γ-aminopropylalkoxysilanes and water for the deposition
of a high-density aminopropylsiloxane network on silica were applied. The pretreatment
temperature of silica (10 g) was 450 °C and the reaction temperature was 150 °C. During the
first reaction sequence, silica was treated with the silane precursor and during the second
reaction sequence aminosilylated silica was treated with water vapor to hydrolyze the free
alkoxy groups. These two sequences, referred to here as one cycle, were repeated from one to
five times (six times for AAPS). Both the aminosilane precursor and water were vaporized in
crucibles one at a time. For the removal of unreacted reactants, each reaction sequence was
followed by a nitrogen purge at the reaction temperature. For APTMS, the first hydrolysis
sequence was performed with deuterium oxide at 150 °C in order to detect unreacted silanol
groups on silica pretreated at 600 °C by DRIFTS.
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Porous oxide
particles