SBA-15:TiO2 nanocomposites. I. Synthesis with ionic liquids and properties

Abstract

Nanosized titanium dioxide (TiO2) has been extensively studied due to its unique properties and broad applicability. However, to our knowledge, the assessment on how reaction media and synthesis routes affect TiO2 properties synthesized with SBA-15 type mesoporous silica is unprecedented. In this work, SBA-15/TiO2 nanocomposites were prepared in different reaction media, varying ionic liquids (CMITf2N and CMIBF4) with and without isopropyl alcohol. X-ray diffraction results showed that CMIBF4 greatly favors TiO2 anatase crystalline phase, and a single phase material was obtained using 0.032 of CMIBF4 without alcohol. On the other hand, the presence of CMITf2N slightly favored TiO2 rutile crystalline phase. Small Angle X-ray diffraction patterns revealed that ordered mesoporous SBA-15/TiO2 nanocomposites were obtained with lower ionic liquid concentration, whilst materials prepared with higher concentration lost their ordered mesoporous structure. Scanning electron microscopy images showed that materials prepared with ionic liquid and isopropyl alcohol displayed much smaller SBA-15 particle size: around 0.1 μm, instead of the standard 1 μm. Nitrogen adsorption–desorption analysis showed that the nanocomposites exhibited a narrow pore size distribution with high surface areas of up to 680 m2/g, pore volumes of up to 1.8 cm3/g and mean pore diameter of up to 10.4 nm, thus being very promising for application in photocatalysis and photoprotection.