Surfactant-free synthesis and magnetic property evaluation of air-stable cobalt oxide nanostructures
We report the synthesis of metastable cobalt oxide (CoO) nanostructures via the low-temperature microwave-assisted solvothermal (MAS) process. An alcoholic solution of cobalt (II) acetylacetonate in a sealed vessel was irradiated with microwaves at a temperature <150 °C and a pressure below 100 p...
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| Format: | Article |
| Language: | English |
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IOP Publishing
2023-01-01
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| Series: | Nano Express |
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| Online Access: | https://doi.org/10.1088/2632-959X/acf4ae |
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| author | Naveen Joshi S A Shivashankar Roger Narayan |
| author_facet | Naveen Joshi S A Shivashankar Roger Narayan |
| author_sort | Naveen Joshi |
| collection | DOAJ |
| description | We report the synthesis of metastable cobalt oxide (CoO) nanostructures via the low-temperature microwave-assisted solvothermal (MAS) process. An alcoholic solution of cobalt (II) acetylacetonate in a sealed vessel was irradiated with microwaves at a temperature <150 °C and a pressure below 100 psi. As-synthesized powder material was characterized in terms of its structure and morphology. X-ray diffractometry (XRD) indicates the formation of well-crystallized CoO nanoparticles without the need for post-synthesis annealing. The mean crystallite size of the nanoparticles was estimated to be 41 nm. The morphology of the as-prepared powder sample was evaluated by field-emission scanning electron microscopy (FESEM), which revealed the formation of densely packed nanospheres of diameter <100 nm. The CoO nanospheres were obtained without the need for any surfactants or capping agents; they were found to be quite resistant to oxidation in ambient air over several months. We attribute the stability of CoO nanospheres to their dense packing, the driving force being the minimization of surface energy and surface area. Fourier-transform infrared (FT-IR) spectroscopy and Raman spectroscopy confirm the formation of phase-pure CoO nanostructures. The deconvolution of the active modes in Raman spectra obtained at room temperature reveals the O _h symmetry in rock-salt CoO produced by the MAS route. We have analyzed its effect on the magnetic characteristics of the CoO nanostructures. Isothermal field-dependent magnetization (MH) and inverse magnetic susceptibility measurements show a phase transition from antiferromagnetic to ferromagnetic interactions in the CoO nanostructures at around 10 K. The results indicate that the phenomenon of magnetic phase transition as a function of temperature is unique to CoO nanoparticles. This finding reveals the magnetic behavior of CoO nanostructures and presents opportunities for its possible application as an anisotropy source for magnetic recording. |
| first_indexed | 2024-03-12T01:28:45Z |
| format | Article |
| id | doaj.art-daa1e8682ae54001b4c7f0f4fd116b25 |
| institution | Directory Open Access Journal |
| issn | 2632-959X |
| language | English |
| last_indexed | 2024-03-12T01:28:45Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | Nano Express |
| spelling | doaj.art-daa1e8682ae54001b4c7f0f4fd116b252023-09-12T09:46:43ZengIOP PublishingNano Express2632-959X2023-01-014303500910.1088/2632-959X/acf4aeSurfactant-free synthesis and magnetic property evaluation of air-stable cobalt oxide nanostructuresNaveen Joshi0https://orcid.org/0000-0002-1371-3291S A Shivashankar1Roger Narayan2https://orcid.org/0000-0002-4876-9869Centre for Nano Science and Engineering, Indian Institute of Science, Bengaluru- 560012, India; Department of Materials Science and Engineering, Centennial Campus, North Carolina State University , Raleigh, NC, 27695-7907, United States of AmericaCentre for Nano Science and Engineering, Indian Institute of Science, Bengaluru- 560012, IndiaDepartment of Materials Science and Engineering, Centennial Campus, North Carolina State University , Raleigh, NC, 27695-7907, United States of America; Joint Department of Biomedical Engineering, Centennial Campus, North Carolina State University , Raleigh, NC, 27695-7115, United States of AmericaWe report the synthesis of metastable cobalt oxide (CoO) nanostructures via the low-temperature microwave-assisted solvothermal (MAS) process. An alcoholic solution of cobalt (II) acetylacetonate in a sealed vessel was irradiated with microwaves at a temperature <150 °C and a pressure below 100 psi. As-synthesized powder material was characterized in terms of its structure and morphology. X-ray diffractometry (XRD) indicates the formation of well-crystallized CoO nanoparticles without the need for post-synthesis annealing. The mean crystallite size of the nanoparticles was estimated to be 41 nm. The morphology of the as-prepared powder sample was evaluated by field-emission scanning electron microscopy (FESEM), which revealed the formation of densely packed nanospheres of diameter <100 nm. The CoO nanospheres were obtained without the need for any surfactants or capping agents; they were found to be quite resistant to oxidation in ambient air over several months. We attribute the stability of CoO nanospheres to their dense packing, the driving force being the minimization of surface energy and surface area. Fourier-transform infrared (FT-IR) spectroscopy and Raman spectroscopy confirm the formation of phase-pure CoO nanostructures. The deconvolution of the active modes in Raman spectra obtained at room temperature reveals the O _h symmetry in rock-salt CoO produced by the MAS route. We have analyzed its effect on the magnetic characteristics of the CoO nanostructures. Isothermal field-dependent magnetization (MH) and inverse magnetic susceptibility measurements show a phase transition from antiferromagnetic to ferromagnetic interactions in the CoO nanostructures at around 10 K. The results indicate that the phenomenon of magnetic phase transition as a function of temperature is unique to CoO nanoparticles. This finding reveals the magnetic behavior of CoO nanostructures and presents opportunities for its possible application as an anisotropy source for magnetic recording.https://doi.org/10.1088/2632-959X/acf4aesurfactantsfreesynthesismagneticpropertyevaluation |
| spellingShingle | Naveen Joshi S A Shivashankar Roger Narayan Surfactant-free synthesis and magnetic property evaluation of air-stable cobalt oxide nanostructures Nano Express surfactants free synthesis magnetic property evaluation |
| title | Surfactant-free synthesis and magnetic property evaluation of air-stable cobalt oxide nanostructures |
| title_full | Surfactant-free synthesis and magnetic property evaluation of air-stable cobalt oxide nanostructures |
| title_fullStr | Surfactant-free synthesis and magnetic property evaluation of air-stable cobalt oxide nanostructures |
| title_full_unstemmed | Surfactant-free synthesis and magnetic property evaluation of air-stable cobalt oxide nanostructures |
| title_short | Surfactant-free synthesis and magnetic property evaluation of air-stable cobalt oxide nanostructures |
| title_sort | surfactant free synthesis and magnetic property evaluation of air stable cobalt oxide nanostructures |
| topic | surfactants free synthesis magnetic property evaluation |
| url | https://doi.org/10.1088/2632-959X/acf4ae |
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