CHARACTERIZATION OF TITANIA GELS BY O-17 NUCLEAR-MAGNETIC-RESONANCE AND ELECTRON-DIFFRACTION

The reaction of O-17-labelled water with titanium n-propoxide [Ti(OPrn )4] proceeds rapidly to produce OTi3 and OTi4 environments that can be clearly identified from O-17 magic-angle spinning NMR spectra. The ge l structure is highly disordered but the quadrupolar interaction is sh own to be small throughout (quadrupolar coupling constant, C(q) < 1.5 MHz). Organic fragments, which can be monitored by C-13 NMR, remain ri ght up until crystallisation of anatase at 300-degrees-C.Crystallisati on is confirmed by electron diffraction, and electron microscopy deter mines the crystallite size to be ca. 3 nm. O-17 NMR and electron diffr action are also used to follow the conversion of anatase to rutile.