Solid-State ^47,49Ti NMR Determination of the Phase Distribution of Titania Nanoparticles

Abstract

47,49Ti solid-state NMR spectra are reported from TiO2 nanoparticles. Particles heated below 700 °C are predominantly anatase. The corresponding 47,49Ti NMR spectra can be simulated by using the NMR interaction parameters determined from bulk polycrystalline TiO2 with an additional Lorentzian smoothing, which increases as the particle size, as determined by X-ray diffraction, decreases. Above 700 °C conversion to rutile increases with increasing calcination temperature. XRD and solid-state NMR provide complementary quantification of the phase distribution with very good agreement between the techniques when there are comparable quantities of rutile and anatase present. At low anatase content NMR is more sensitive to the phase distribution.