Spectroscopic studies of group IV metal/silica xerogels and zeolites

Metal/silica materials have been studied extensively, primarily due to the catalytic activity and the changes in their physical properties that occur with the introduction of a metal species to the silica matrix. There are various types of these materials which are either crystalline or amorphous and for each of these types, both dense and porous examples exist. Titania/silica materials are the most studied of the Group IV metal/silica materials. The zeolite, TS-1, has been known for many years and is commercially used as a catalyst for the conversion of phenol to catechol and hydroquinone. Porous, amorphous glasses, such as xerogels, have also been studied because of their unique optical properties. Additionally, commercially produced ULE ® (Ultra Low Expansion) glass, which has an extremely low coefficient of thermal expansion (CTE), has extensive optical uses because of its durability and near-zero CTE. While the physical properties of these materials are well known, the molecular structure and electronic properties have been less extensively studied. Our spectroscopic studies of these materials have brought into question longstanding arguments regarding the structure of the titania species in the silica matrix. We have also shown that while the morphology and physical attributes of these materials differ greatly, there are some significant similarities among their electronic and vibrational properties.; Additionally, we were able to synthesize zirconia/silica and hafnia/silica glasses, the latter of which had not been previously synthesized. Initial spectroscopic studies of these materials indicate that they differ from titania/silica materials due in part to their apparent lack of a luminescence outside of that of the silica background.