Diffusion doping of cobalt in rod-shape anatase TiO2 nanocrystals leads to antiferromagnetism

Shahzahan Mia; Shelton J. P. Varapragasam; Aravind Baride; Choumini Balasanthiran; Balamurugan Balasubramanian; Robert M. Rioux; James D. Hoefelmeyer

doi:10.1039/D0NA00640H

Diffusion doping of cobalt in rod-shape anatase TiO₂ nanocrystals leads to antiferromagnetism†

Shahzahan Mia,

^a Shelton J. P. Varapragasam,

^a Aravind Baride,

^a Choumini Balasanthiran,

^b Balamurugan Balasubramanian,

^d Robert M. Rioux

^bc and James D. Hoefelmeyer

*^a

Author affiliations

* Corresponding authors

^a Department of Chemistry, University of South Dakota, 414 E. Clark St., Vermillion, SD 57069, USA
E-mail: james.hoefelmeyer@usd.edu

^b Department of Chemical Engineering, The Pennsylvania State University, 22 Chemical Biomedical Engineering Building, University Park, Pennsylvania, USA

^c Department of Chemistry, The Pennsylvania State University, 22 Chemical Biomedical Engineering Building, University Park, Pennsylvania, USA

^d Nebraska Center for Materials and Nanoscience, Department of Physics and Astronomy, University of Nebraska, Lincoln, NE 68588-0299, USA

Abstract

Cobalt(II) ions were adsorbed to the surface of rod-shape anatase TiO₂ nanocrystals and subsequently heated to promote ion diffusion into the nanocrystal. After removal of any remaining surface bound cobalt, a sample consisting of strictly cobalt-doped TiO₂ was obtained and characterized with powder X-ray diffraction, transmission electron microscopy, UV-visible spectroscopy, fluorescence spectroscopy, X-ray photoelectron spectroscopy, SQUID magnetometry, and inductively-coupled plasma atomic emission spectroscopy. The nanocrystal morphology was unchanged in the process and no new crystal phases were detected. The concentration of cobalt in the doped samples linearly correlates with the initial loading of cobalt(II) ions on the nanocrystal surface. Thin films of the cobalt doped TiO₂ nanocrystals were prepared on indium-tin oxide coated glass substrate, and the electrical conductivity increased with the concentration of doped cobalt. Magnetic measurements of the cobalt-doped TiO₂ nanocrystals reveal paramagnetic behavior at room temperature, and antiferromagnetic interactions between Co ions at low temperatures. Antiferromagnetism is atypical for cobalt-doped TiO₂ nanocrystals, and is proposed to arise from interstitial doping that may be favored by the diffusional doping mechanism.

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Article information

DOI: https://doi.org/10.1039/D0NA00640H
Article type: Paper
Submitted: 31 May 2020
Accepted: 31 Aug 2020
First published: 09 Sep 2020
This article is Open Access

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Nanoscale Adv., 2020,2, 4853-4862

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Diffusion doping of cobalt in rod-shape anatase TiO₂ nanocrystals leads to antiferromagnetism

S. Mia, S. J. P. Varapragasam, A. Baride, C. Balasanthiran, B. Balasubramanian, R. M. Rioux and J. D. Hoefelmeyer, Nanoscale Adv., 2020, 2, 4853 DOI: 10.1039/D0NA00640H

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