气候变化领域集成服务门户(CCPortal): Spectroscopic studies of a phosphonium ionic liquid in supercritical CO2

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DOI	10.3390/chemengineering4020020
	Spectroscopic studies of a phosphonium ionic liquid in supercritical CO2
	Heitz M.P.; Putney Z.C.; Campaign J.
发表日期	2020
ISSN	23057084
起始页码	1
结束页码	19
卷号	4 期号:2
英文摘要	Fluorescence spectroscopy was used to study a solution comprised of coumarin 153 (C153)+ trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide ([P6,6,6,14]+ [Tf2N]−)+ supercritical CO2 (scCO2). We compare the spectroscopy of C153 in neat scCO2 to that of C153/scCO2 with the addition of ionic liquid (IL). Excitation and emission peak frequencies of C153 in scCO2 and in IL/scCO2 diverged at reduced densities (ρr = ρ/ρc) below the CO2 critical density. At low fluid density, spectral changes in the IL/scCO2 solutions showed evidence that C153 experiences a very different microenvironment—one that is unlike neat scCO2. The data show that the presence of IL clearly influences the C153 excitation and emission profiles. Excitation was broadened and red shifted by >2000 cm−1 and the presence of an additional low-energy emission component that was red shifted by ~3000 cm−1 was clearly visible and not observed in neat scCO2. The solution heterogeneity was controlled by changing the scCO2 density and at high fluid density, both the excitation and emission spectra were more similar to those in neat scCO2. Steady-state anisotropy also showed that at low fluid density, the C153 emission was significantly polarized. Aggregation of C153 has been reported in the literature and this led us to hypothesize the possibility that C153 dimer (aggregation) formation may be occurring in scCO2. Another possible explanation is that dye–IL aggregates may dissolve into the scCO2 phase due to C153 acting as a “co-solvent” for the IL. Time-resolved intensity decay measurements yielded only slightly non-exponential decays with accompanying time constants of ~3–4 ns that were significantly shorter than the 5–6 ns time constants in neat scCO2, which are suggestive of C153–IL interactions. However, these data did not conclusively support dimer formation. Pre-exponential factors of the time constants showed that almost all of the emission was due to monomeric C153. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
英文关键词	Carbon dioxide; Ionic liquid; Supercritical fluid; Time-resolved fluorescence; Trihexyltetradecylphosphonium bis (trifluoromethylsulfonyl) imide
来源期刊	ChemEngineering
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/176898
作者单位	Chemistry and Biochemistry Department, The College at Brockport, State University of New York, Brockport, New York, NY 14420, United States
推荐引用方式 GB/T 7714	Heitz M.P.,Putney Z.C.,Campaign J.. Spectroscopic studies of a phosphonium ionic liquid in supercritical CO2[J],2020,4(2).
APA	Heitz M.P.,Putney Z.C.,&Campaign J..(2020).Spectroscopic studies of a phosphonium ionic liquid in supercritical CO2.ChemEngineering,4(2).
MLA	Heitz M.P.,et al."Spectroscopic studies of a phosphonium ionic liquid in supercritical CO2".ChemEngineering 4.2(2020).