Abstract
The interaction between SBA-15 mesoporous silica, alkane solvents, and water was studied to understand the mechanism of the so-called double solvent technique. This method facilitates the loading of the pores of SBA-15 with a metal oxide precursor soln., by prewetting the SBA-15 with an alkane. In a previous study on cobalt oxide, differences in particle size, shape, and dispersion were obtained as a function of the solvent used (n-pentane, n-hexane, n-heptane, and cyclohexane). To understand this phenomenon and to explain the differences between the effects that the alkane solvents exert, a combined FTIR spectroscopy, solid state NMR spectroscopy, and microcalorimetry study was carried out. Though subtle, interactions between alkanes and the silica surface are different, indicating a more pronounced modification of the surface, i.e., rehydroxylation, in the presence of pentane. Probably this leads to a better wettability and therefore increases the introduction of aq. solns. into the pores. Also, the lower vapor pressure of this component, its lower interaction energy with the surface, and its lower interfacial tension toward water enhance the dispersion of the metal oxide precursor inside the pore network. [on SciFinder(R)]