Preparation of amino-functionalized silica in aqueous conditions

Silica particle surfaces were modified with 3-aminopropyltriethoxysilane (APTES) for the fabrication under mild conditions of amino-functionalized silica particles which can be applied in a number of processes, e.g. chromatography. Surface activation was carried out in water at natural pH and in toluene on non-preheated silica in order to compare the grafting efficiency in these two solvents. No successive thermal treatments were carried out after grafting. Grafting extents were then calculated using solid state TOC measurements. Grafting extents of APTES in water and anhydrous solvent were surprisingly found to be the same after a simple rinsing step (i.e. 2.10 ± 0.09 μmol/m2). Thus, in our case, the use of anhydrous solvent is an unnecessary precaution if the silica is further used in water since equivalent grafting extents of APTES are obtained with a simple and eco-friendly grafting process.

► Grafting of silane in water is as efficient as grafting in toluene after rinsing. ► A partial mono-layer system is reached with water grafting. ► A 3D network system is reached with toluene grafting before rinsing. ► Reactivity of amino-groups of grafted silane was easily proved with salicylaldehyde.