Synthesis and analysis of amino-functionalised mesoporous silica

Abstract

The regularly ordered pore arrangement and the narrow pore size distribution of mesoporous silica offer possibilities for several applications such as drug delivery and controlled release. A successful implementation requires methods that allow the selective functionalisation of external and internal surfaces. A convenient and scale-up friendly procedure for synthesising high quality mesoporous silica MCM-41 at room temperature was developed. Amino-functionalised samples were analysed using several methods to understand the grafting behaviour of aminopropylalkoxysilanes. The distribution of amino groups on mesoporous silica surfaces was evaluated by analysing textural properties and amino group loadings, as well as by labelling the amino groups with fluorescein isothiocyanate (FITC) for photoluminescence spectroscopy. A reliable method to determine the amount of grafted amino groups over a wide range of loadings was developed. The functionalisation of mesoporous silica by vapour phase deposition was studied as an alternative to the common solvent based techniques. The accessibility of amino groups anchored on selected mesoporous silicas was investigated by FITC coupling. Onedimensional channel systems with small pores (3.1 nm and 3.9 nm) and large pores (7.6 nm) as well as three-dimensional channel systems were compared to non-porous silica. Several methods for the selective functionalisation of the external surface of mesoporous silica were critically evaluated.