The Effect of Water on the Functionalization of Mesoporous Silica with 3-Aminopropyltriethoxysilane

Abstract

The effect of water on the reaction of 3-aminopropyltriethoxysilane (APTES) with mesoporous silica is investigated on two model systems. A MCM-41type material with a well-defined pore size is used to investigate changes in the pore size distribution upon reaction with APTES in toluene containing various amounts of water. It is found that, with increasing amount of water, clustering of APTES occurs, leading to a nonuniform distribution of the grafted amino groups and a scarcely functionalized pore body. A second model system with defined particle morphology and one-dimensional channels is employed to visualize the distribution of the grafted amino groups by fluorescent labeling and confocal laser scanning microscopy. The combination of nitrogen sorption and confocal laser scanning microscopy provides valuable insights concerning the role of trace water in the functionalization of mesoporous silica with alkoxysilanes. SECTION Nanoparticles and Nanostructures

Tuning the aspect ratio of arrays of silica nanochannels

“…1). [19][20][21][22][23][24] ASNCs can thus be considered as the mesoporous analogue to hexagonal zeolites with one-dimensional channel systems that have for example been used as host materials for the supramolecular organization of guest molecules. 25,26 With their larger pore size, ASNCs extend the possibilities of the zeolite-based host-guest concept by allowing the introduction of guest species that are larger than the pore size range covered by zeolites.…”

“…In analogy to MCM-41, ASNCs possess abundant silanol groups that allow for surface functionalization. 21,22 The morphogenesis of mesoporous silica fibers was first proposed by Ozin and co-workers. 27 Liquidcrystal embryos with hexagonal cross-sections start the growth after the silane addition.…”

Postsynthetic functionalization of mesoporous silica

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Postsynthetic functionalization of mesoporous silicaBrühwiler, D Brühwiler, D (2010) methods to control and to analyze the distribution of the grafted functional groups are discussed, with particular emphasis on concepts that allow the placement of the groups at specific distances from each other, as well as on approaches towards the selective functionalization of the external particle surface.3

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Functional Group Distributions on Mesoporous Silica

“…[11] Particularly in the case of amino-functionalized silanes, it is reasonable to assume that polar solvents lead to increased mobility of the molecules on the mesoporous silica surface. This concept can for example be applied to control the site isolation of amino groups on mesoporous silica.…”

“…[8,9] The use of fluorescent labels opens further possibilities for characterizing the functional group distributions by confocal laser scanning microscopy (CLSM). [10][11][12] However, CLSM requires relatively large mesoporous silica particles with defined morphology. Most procedures for the synthesis of mesoporous silica yield materials with irregular morphology but often extremely narrow pore size distributions (Figure 1).…”