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In Situ Observation of Multiple Phase Transitions in Low-Melting Ionic Liquid [BMIM][BF4] under High Pressure up to 30 GPa.
MedLine Citation:
PMID:  22239600     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
In situ characterization of phase transitions and direct microscopic observations of a low-melting ionic liquid, 1-butyl-3-methyl imidazolium tetrafluoroborate ([BMIM][BF4]), has been performed in details by Raman spectroscopy. Compression of [BMIM][BF4] was measured under hydrostatic pressure up to about 30.0 GPa at room temperature by using a high pressure diamond anvil cell (DAC). With pressure increasing, the characteristic bands of [BMIM][BF4] displayed nonmonotonic pressure-induced frequency shifts, and it is found to undergo four successive phase transitions at around 2.25 GPa, 6.10 GPa, 14.00 GPa, and 21.26 GPa. Especially, above the pressure of 21.26 GPa, the luminescence of the sample occurs, which is connected with a most significant phase transition at around this pressure. It was indicated that the structure change under high pressure might be associated with conformational change in the butyl chain. Upon releasing pressure, the spectrum was not recovered under the pressure up to 1.16 GPa, thereby indicating that this high pressure phase remains stable over a large pressure range between 30-1.16 GPa in low-melting ionic liquid [BMIM][BF4]. While the sample was kept under the normal pressure for 24 hours, the spectrum was recovered and it showed that the phase transition of [BMIM][BF4] was reversible. In other words, such kind of low-melting ionic liquid [BMIM][BF4] still remains stable even after treated under so high pressure up to 30 GPa.
Authors:
Lei Su; Xiang Zhu; Zheng Wang; Xuerui Cheng; Yongqiang Wang; Chaosheng Yuan; Zhenping Chen; Chunli Ma; Fangfei Li; Qiang Zhou; Qiliang Cui
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-1-12
Journal Detail:
Title:  The journal of physical chemistry. B     Volume:  -     ISSN:  1520-5207     ISO Abbreviation:  -     Publication Date:  2012 Jan 
Date Detail:
Created Date:  2012-1-13     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101157530     Medline TA:  J Phys Chem B     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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