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Characterization of the Structures of Size-Selected TiO2 Nanoparticles Using X-ray Absorption Spectroscopy

Volume 58, Number 5 (May 2004) Page 598-602

Choi, Hyun Chul; Ahn, Hyo-Jin; Jung, Young Mee; Lee, Min Kyu; Shin, Hyun Joon; Kim, Seung Bin; Sung, Yung-Eun

To investigate the relationship between the size and structure of TiO2 nanoparticles, three size-selected samples of TiO2 nanoparticles were prepared via a hydrolysis method that uses Ti[OCH(CH3)2]4 as the starting material. The structures of the nanoparticles were characterized using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray absorption spectroscopy (XAS). Analysis of the XRD patterns and of the TEM images showed that the samples were dispersed, with an average particle size of ~30 nm (sample A), ~12 nm (sample B), and ~7 nm (sample C). Their X-ray absorption spectra indicate that samples A and B have an anatase structure, whereas sample C has a structure very similar to that of the TiO 2 II phase, which generally arises only under high-pressure conditions. This difference can be attributed to size-induced radial pressure within the smaller nanoparticles, which plays an important role in the phase of TiO2 nanoparticles in sample C.