Structural, optical and magnetic properties of Gd/TiO 2 -reduced graphene oxide nanocomposites
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Structural, optical and magnetic properties of Gd/TiO2‑reduced graphene oxide nanocomposites N. Nithyaa1 · M. Muralidharan2 · N. Victor Jaya1 Received: 12 April 2020 / Accepted: 22 July 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The focus of the present work is to study the effect of reduced graphene oxide (rGO) on morphology, crystal structure and magnetic properties of Gadolinium (Gd)-doped TiO2 nanoparticles. Gd/TiO2-rGO nanocomposites are synthesised in two steps: sol–gel and hydrothermal method. The prepared composites are studied with XRD, Raman, HRTEM, PL, EPR and VSM for further analysis. XRD and HRTEM studies elucidate the crystallinity of the nanocomposite decreases with increase in Gd concentration. Electron micrographs of the samples reveal that both pure T iO2 and Gd/TiO2 nanoparticles are evenly decorated on the graphene sheets. Raman and PL spectroscopic techniques confirm the presence of oxygen vacancies (Vo) and surface defects. Enhanced optical absorption shows the interaction between Ti–Gd with rGO composites. Decrease in bandgap values may be understood by quantum confinement effect. The presence of singly ionised Vo is confirmed from EPR spectra which is responsible for weak ferromagnetic behaviour at room temperature. Moreover, magnetic studies show the concurrency of ferromagnetic and antiferromagnetic interaction that originates from different defects present in the Gd/ TiO2-rGO nanocomposites.
1 Introduction Carbon materials are of special attraction because of its bonding nature, formation of large stable frameworks, different hybridisations and dimensions, etc. [1]. Graphite, a carbon allotrope with three dimensions consists of stacked graphene layers, whereas graphene is two-dimensional with a single layer of carbon atoms arranged in a honeycomb lattice order [2, 3]. Graphene, the thinnest and strongest material in the universe, also has exceptional properties such as high specific surface area (2630 m2 g−1)2 [4], superior carrier mobility at room temperature (10,000 c m2 V−1 s−1) [5], high thermal conductivity (3000–5000 Wm−1 K−1) [6], enhanced optical transparency [7]. In addition, intrinsic Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10854-020-04077-0) contains supplementary material, which is available to authorised users. * N. Nithyaa [email protected] 1
Department of Physics, Anna University, Chennai, Tamil Nadu 600025, India
Department of Material Science, University of Madras, Chennai, Tamil Nadu 600025, India
2
room temperature ferromagnetism occurs with various defects in graphene structures, such as edge defects, vacancy, topological changes, hydrogen chemisorptions, frustration [8]. Magnetic transitions among dia-, para-, antiferro- and superparamagnetism are also possible [9]. Recently, there are several reports on room temperature magnetic properties of wide bandgap metal oxides [10, 11]. Nanoparticulate of metal oxides exhibits room temperature ferromagnetism
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