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Magnetite nanorod thermotropic liquid crystal colloids: synthesis, optics and theory

Magnetite nanorod thermotropic liquid crystal colloids: synthesis, optics and theory
Magnetite nanorod thermotropic liquid crystal colloids: synthesis, optics and theory
We have developed a facile method for preparing magnetic nanoparticles which couple strongly with a liquid crystal (LC) matrix, with the aim of preparing ferronematic liquid crystal colloids for use in magneto-optical devices. Magnetite nanoparticles were prepared by oxidizing colloidal Fe(OH)2 with air in aqueous media, and were then subject to alkaline hydrothermal treatment with 10 mol dm-3 NaOH at 100 ºC, transforming them into a polydisperse set of domain magnetite nanorods with maximal length ~500 nm and typical diameter ~20 nm. The nanorods were coated with 4-n-octyloxybiphenyl-4-carboxylic acid (OBPh) and suspended in nematic liquid crystal E7. As compared to the conventional oleic acid coating, this coating stabilizes LC-magnetic nanorod suspensions. The suspension acts as a ferronematic system, using the colloidal particles as intermediaries to amplify magnetic field– LC director interactions. The effective Frederiks magnetic threshold field of the magnetite nanorod–liquid crystal composite is reduced by 20% as compared to the undoped liquid crystal. In contrast with some previous work in this field, the magneto-optical effects are reproducible on time scales of months. Prospects for magnetically switched liquid crystal devices using these materials are good, but a method is required to synthesize single magnetic domain nanorods.
Liquid crystals, Fe3O4, Nanorods, Nanostructures, Ferronematics
0021-9797
158-166
Podoliak, Nina
0908b951-00a7-48a5-bc82-631640910b9c
Buchnev, Oleksandr
60cdb0d2-3388-47be-a066-61b3b396f69d
Bavykin, Dmitry V.
1e9fabfc-d078-4585-876f-85ff33b7eed5
Kulak, Alexander N.
7dc57b4f-aae0-42a4-ae15-fd50ab6521c2
Kaczmarek, Malgosia
408ec59b-8dba-41c1-89d0-af846d1bf327
Sluckin, Timothy J.
8dbb6b08-7034-4ae2-aa65-6b80072202f6
Podoliak, Nina
0908b951-00a7-48a5-bc82-631640910b9c
Buchnev, Oleksandr
60cdb0d2-3388-47be-a066-61b3b396f69d
Bavykin, Dmitry V.
1e9fabfc-d078-4585-876f-85ff33b7eed5
Kulak, Alexander N.
7dc57b4f-aae0-42a4-ae15-fd50ab6521c2
Kaczmarek, Malgosia
408ec59b-8dba-41c1-89d0-af846d1bf327
Sluckin, Timothy J.
8dbb6b08-7034-4ae2-aa65-6b80072202f6

Podoliak, Nina, Buchnev, Oleksandr, Bavykin, Dmitry V., Kulak, Alexander N., Kaczmarek, Malgosia and Sluckin, Timothy J. (2012) Magnetite nanorod thermotropic liquid crystal colloids: synthesis, optics and theory. Journal of Colloid and Interface Science, 386 (1), 158-166. (doi:10.1016/j.jcis.2012.07.082).

Record type: Article

Abstract

We have developed a facile method for preparing magnetic nanoparticles which couple strongly with a liquid crystal (LC) matrix, with the aim of preparing ferronematic liquid crystal colloids for use in magneto-optical devices. Magnetite nanoparticles were prepared by oxidizing colloidal Fe(OH)2 with air in aqueous media, and were then subject to alkaline hydrothermal treatment with 10 mol dm-3 NaOH at 100 ºC, transforming them into a polydisperse set of domain magnetite nanorods with maximal length ~500 nm and typical diameter ~20 nm. The nanorods were coated with 4-n-octyloxybiphenyl-4-carboxylic acid (OBPh) and suspended in nematic liquid crystal E7. As compared to the conventional oleic acid coating, this coating stabilizes LC-magnetic nanorod suspensions. The suspension acts as a ferronematic system, using the colloidal particles as intermediaries to amplify magnetic field– LC director interactions. The effective Frederiks magnetic threshold field of the magnetite nanorod–liquid crystal composite is reduced by 20% as compared to the undoped liquid crystal. In contrast with some previous work in this field, the magneto-optical effects are reproducible on time scales of months. Prospects for magnetically switched liquid crystal devices using these materials are good, but a method is required to synthesize single magnetic domain nanorods.

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Published date: 15 November 2012
Keywords: Liquid crystals, Fe3O4, Nanorods, Nanostructures, Ferronematics
Organisations: Optoelectronics Research Centre, Mathematical Sciences, Physics & Astronomy, Engineering Science Unit, Quantum, Light & Matter Group

Identifiers

Local EPrints ID: 345427
URI: https://eprints.soton.ac.uk/id/eprint/345427
ISSN: 0021-9797
PURE UUID: f6656862-378f-46c4-8777-c95526bd68c7
ORCID for Nina Podoliak: ORCID iD orcid.org/0000-0002-3146-0355
ORCID for Timothy J. Sluckin: ORCID iD orcid.org/0000-0002-9163-0061

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Date deposited: 20 Nov 2012 16:02
Last modified: 06 Jun 2018 13:20

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Contributors

Author: Nina Podoliak ORCID iD
Author: Oleksandr Buchnev
Author: Alexander N. Kulak

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