Thermal stability of mesoscopic compounds of cetyltrimethylammonium and Keggin metatungstates

Colusso, AC; Cortie, MB; Dowd, A; McDonagh, AM

Thermal stability of mesoscopic compounds of cetyltrimethylammonium and Keggin metatungstates

Colusso, AC Cortie, MB

Dowd, A

McDonagh, AM

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Publication Type:: Journal Article
Citation:: Dalton Transactions, 2017, 46 (33), pp. 11053 - 11062
Issue Date:: 2017-01-01

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Field	Value	Language
dc.contributor.author	Colusso, AC	en_US
dc.contributor.author	Cortie, MB https://orcid.org/0000-0003-3202-6398	en_US
dc.contributor.author	Dowd, A https://orcid.org/0000-0002-0500-3599	en_US
dc.contributor.author	McDonagh, AM https://orcid.org/0000-0002-9502-1175	en_US
dc.date.available	2020-05-25T19:03:12Z
dc.date.issued	2017-01-01	en_US
dc.identifier.citation	Dalton Transactions, 2017, 46 (33), pp. 11053 - 11062	en_US
dc.identifier.issn	1477-9226	en_US
dc.identifier.uri	http://hdl.handle.net/10453/124960
dc.description.abstract	© 2017 The Royal Society of Chemistry. A hybrid surfactant/polyoxometalate compound was synthesized by combining isopolytungstate anions with the cationic surfactant cetyltrimethylammonium bromide (CTA-Br) to produce a hierarchical compound that we identify as (CTA)7[H2W12O40]Cl·2H2O. At room temperature the compound consisted of hexagonally ordered sheets of Keggin ions, with an intervening gallery containing alkyl-chains of the organic cations. The synthesis was highly dependent on solution pH, reaction time and the order in which the reactants were added. We examined the effect of temperature on the stability of (CTA)7[H2W12O40]Cl·2H2O using thermal gravimetric analysis, differential scanning calorimetry, FT-IR spectroscopy and in situ synchrotron X-ray diffraction, and found a step-wise conversion to monoclinic WOxvia a series of intermediates. Heating under nitrogen atmospheres accelerated transition events by ∼100 °C when compared to heating in air. During heating, the interplanar gallery at first expanded in a series of steps starting at 90 °C as the CTA+ amphiphiles changed orientation, before collapsing rapidly at 240 °C, a temperature coinciding with the removal of about 40% of the organic material. Between 240 and 320 °C, the material consisted of fragments of the Keggin ion cores, arranged in 2D hexagonally-packed sheets. At ∼330 °C, the Keggin ions were completely destroyed and replaced by bulk W17O47 which, upon further heating, transformed to bulk WO2 or WO3 depending on the environment.	en_US
dc.relation.ispartof	Dalton Transactions	en_US
dc.relation.isbasedon	10.1039/c7dt02073b	en_US
dc.subject.classification	Inorganic & Nuclear Chemistry	en_US
dc.title	Thermal stability of mesoscopic compounds of cetyltrimethylammonium and Keggin metatungstates	en_US
dc.type	Journal Article
utslib.citation.volume	33	en_US
utslib.citation.volume	46	en_US
utslib.for	0302 Inorganic Chemistry	en_US
utslib.for	0307 Theoretical and Computational Chemistry	en_US
utslib.for	0399 Other Chemical Sciences	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Science
pubs.organisational-group	/University of Technology Sydney/Faculty of Science/School of Mathematical and Physical Sciences
pubs.organisational-group	/University of Technology Sydney/Strength - CCET - Centre for Clean Energy Technology
utslib.copyright.status	open_access
pubs.issue	33	en_US
pubs.publication-status	Published	en_US
pubs.volume	46	en_US

Abstract:

© 2017 The Royal Society of Chemistry. A hybrid surfactant/polyoxometalate compound was synthesized by combining isopolytungstate anions with the cationic surfactant cetyltrimethylammonium bromide (CTA-Br) to produce a hierarchical compound that we identify as (CTA)7[H2W12O40]Cl·2H2O. At room temperature the compound consisted of hexagonally ordered sheets of Keggin ions, with an intervening gallery containing alkyl-chains of the organic cations. The synthesis was highly dependent on solution pH, reaction time and the order in which the reactants were added. We examined the effect of temperature on the stability of (CTA)7[H2W12O40]Cl·2H2O using thermal gravimetric analysis, differential scanning calorimetry, FT-IR spectroscopy and in situ synchrotron X-ray diffraction, and found a step-wise conversion to monoclinic WOxvia a series of intermediates. Heating under nitrogen atmospheres accelerated transition events by ∼100 °C when compared to heating in air. During heating, the interplanar gallery at first expanded in a series of steps starting at 90 °C as the CTA+ amphiphiles changed orientation, before collapsing rapidly at 240 °C, a temperature coinciding with the removal of about 40% of the organic material. Between 240 and 320 °C, the material consisted of fragments of the Keggin ion cores, arranged in 2D hexagonally-packed sheets. At ∼330 °C, the Keggin ions were completely destroyed and replaced by bulk W17O47 which, upon further heating, transformed to bulk WO2 or WO3 depending on the environment.

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http://hdl.handle.net/10453/124960