Silica silane-functionalised

For APTES-MCF-A it appears as if two additional overlapping peaks are present at —61 and -69 ppm. An organotrialkoxy silane such as APTES can condense forming multiple Si -O - Si bonds [21 ] (Figure 4). In this case the resonances can be assigned as being due to two Si - O - Si bonds (-61 ppm) and three Si - O - Si bonds (-69 ppm), based on previously reported data for a porous silica gel functionalised with APTES in a similar manner [21]. 

Even on the relatively simple surface provided by silica, several reaction types can occur with these bifunctional reagents. Nevertheless, the majority of the functionalising groups provide the intended ligand sites even though there may be a distribution of binding modes of the silane centre to the silica surface. Similar studies to these on oxides with different chemical reactivity would be seem to be potentially fruitful. 

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