A green approach to mesoporous silica particles synthesis by sol-gel chemistry

Mesoporous silica materials have a wide variety of applications in different sectors depending on their characteristic porosity, particle dimensions and functionalization. They are used as heterogeneous catalyst agents in industrial synthesis, stationary phase in chromatography or in biomedical applications as drug delivery systems. Consequently a significant number of studies have focused on the development of preparation methods that allow the regulation of the pore size and pore morphology of the silica. This thesis work, conducted at UCC (University College Cork, Ireland), aims to find a “greener” path than the one traditionally used to synthesize good quality mesoporous silica particles. It is a preliminary work whose purpose is to determine if it can be considered viable to start further systematic research in this direction. Nowadays it is impossible to ignore the need of an environmentally sustainable approach towards chemical synthesis and processes design. Green Chemistry and its Twelve Principles are central to the development of the mesoporous silica material preparation procedure utilized within this research. A modified Stöber sol-gel method of synthesis was chosen for its intrinsically green features: it is a batch process, the reaction takes place at room temperature and one of the main solvents is water. This study focuses on changing those aspects of the “standard” procedure which are not so environmentally friendly: the second solvent (alcohol), the surfactant (most commonly CTAB) and the post synthesis hydrothermal treatment. In particular Sodium Alginate, a polysaccharide extracted from the cell wall of brown seaweed, is the surfactant of choice. Until now no works have been reported on the use of alginate as a direct anionic surfactant template. Characterization of obtained silica particles was performed employing N2 sorption for information about porosity and SEM and TEM imaging to evaluate particles aggregation, aspect and size.