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Study of paramagnetic defect centers in as-grown and annealed TiO2 anatase and rutile nanoparticles by a variable-temperature X-band and high-frequency (236 GHz) EPR.

Author(s): Misra SK, Andronenko SI, Tipikin D, Freed JH, Somani V, Prakash O

J Magn Magn Mater. 2016 Mar 01;401:495-505 Authors: Misra SK, Andronenko SI, Tipikin D, Freed JH, Somani V, Prakash O

Article GUID: 27041794
Title:Study of paramagnetic defect centers in as-grown and annealed TiO2 anatase and rutile nanoparticles by a variable-temperature X-band and high-frequency (236 GHz) EPR.
Authors:Misra SK,  Andronenko SI,  Tipikin D,  Freed JH,  Somani V,  Prakash O
Link:https://www.ncbi.nlm.nih.gov/pubmed/27041794?dopt=Abstract
Category:J Magn Magn Mater
PMID:27041794
Dept Affiliation: PHYSICS
1 Physics Department, Concordia University, 1455 de Maisonneuve Blvd West, Montreal, QC H3G 1M8, Canada.
2 ACERT Biomedical Center, Baker Laboratory, Cornell University, Ithaca, NY 14853-1301, USA.
3 Department of Metallurgical Engineering and Material Science, Indian Institute of Technology, Bombay, Powai, Mumbai 400076, India.

Description:

Study of paramagnetic defect centers in as-grown and annealed TiO2 anatase and rutile nanoparticles by a variable-temperature X-band and high-frequency (236 GHz) EPR.

J Magn Magn Mater. 2016 Mar 01;401:495-505

Authors: Misra SK, Andronenko SI, Tipikin D, Freed JH, Somani V, Prakash O

Abstract

Detailed EPR investigations on as-grown and annealed TiO2 nanoparticles in the anatase and rutile phases were carried out at X-band (9.6 GHz) at 77, 120-300 K and at 236 GHz at 292 K. The analysis of EPR data for as-grown and annealed anatase and rutile samples revealed the presence of several paramagnetic centers: Ti3+, O-, adsorbed oxygen (O2-) and oxygen vacancies. On the other hand, in as-grown rutile samples, there were observed EPR lines due to adsorbed oxygen (O2-) and the Fe3+ ions in both Ti4+ substitutional positions, with and without coupling to an oxygen vacancy in the near neighborhood. Anatase nanoparticles were completely converted to rutile phase when annealed at 1000° C, exhibiting EPR spectra similar to those exhibited by the as-grown rutile nanoparticles. The high-frequency (236 GHz) EPR data on anatase and rutile samples, recorded in the region about g = 2.0 exhibit resolved EPR lines, due to O- and O2- ions enabling determination of their g-values with higher precision, as well as observation of hyperfine sextets due to Mn2+ and Mn4+ ions in anatase.

PMID: 27041794 [PubMed - as supplied by publisher]