Surface Studies on the Ionic Liquid 1-Ethyl-3-Methylimidazolium Ethylsulfate Using X-Ray Photoelectron Spectroscopy (XPS)

Gottfried, J. Michael; Maier, Florian; Rossa, Jürgen; Gerhard, Dirk; Schulz, Peter S.; Wasserscheid, Peter; Steinrück, Hans‐Peter

doi:10.1524/zpch.2006.220.10.1439

Cited by 111 publications

(129 citation statements)

References 25 publications

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“…An increased signal at 80°(that is, in the surface sensitive geometry), indicates an enrichment of this element in the topmost layers as compared to the bulk; correspondingly, a decreased signal at 80°indicates a depletion of this element in the topmost layers. Deviations of the surface composition from that in the bulk can be due to a pronounced preferential orientation of cations or anions in the IL, due to surface enrichment or depletion of one component in a mixture or a solution of ILs, but also due to the surface enrichment of contaminations [142,147].…”

Section: Molecular Insights Into Il/gas and Il/support Interfacesmentioning

confidence: 99%

Ionic Liquids in Catalysis

2014

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Ionic liquids (ILs), salts with melting points below 100°C, represent a fascinating class of liquid materials typically characterized by an extremely low vapor pressure. Besides their application as new solvents or as electrolytes for electrochemical purposes, there are two important concepts of using ILs in catalysis: Liquid-liquid biphasic catalysis and IL thin film catalysis. Liquid-liquid biphasic catalysis enables either a very efficient manner to apply catalytic ILs, e.g. in Friedel-Crafts reactions, or to apply ionic transition metal catalyst solutions. In both cases, phase separation after reaction allows an easy separation of reaction products and catalyst re-use. One problem of liquidliquid biphasic catalysis is mass transfer limitation. If the chemical reaction is much faster than the liquid-liquid mass transfer the latter limits the overall reaction rate. This problem is overcome in IL thin film catalysis where diffusion pathways and thus the characteristic time of diffusion are short. Here, Supported Ionic Liquid Phase (SILP) and Solid Catalyst with Ionic Liquid Layer (SCILL) are the two most important concepts. In both, a high surface area solid substrate is covered with a thin IL film, which contains either a homogeneously dissolved transition metal complex for SILP, or which modifies catalytically active surface sites at the support for SCILL. In each concept, interface phenomena play a very important role: These may concern the interface of an IL phase with an organic phase in the case of liquidliquid biphasic catalysis. For IL thin film catalysis, the interfaces of the IL with the gas phase and with catalytic nanoparticles and/or support materials are of critical importance. It has recently been demonstrated that these interfaces and also the bulk of ILs can be investigated in great detail using surface science studies, which greatly contributed to the fundamental understanding of the catalytic properties of ILs and supported IL materials. Exemplary results concerning the IL/vacuum or IL/gas interface, the solubility and surface enrichment of dissolved metal complexes, the IL/support interface and the in situ monitoring of chemical reactions in ILs are presented.

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Section: Molecular Insights Into Il/gas and Il/support Interfacesmentioning

confidence: 99%

Ionic Liquids in Catalysis

2014

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“…In the fi rst XPS study of the surface of a commercially available IL a signifi cant Si contamination was found, [ 36 ] which was probably due to a silicon-containing grease used to seal the glassware applied during synthesis. [ 50 ] This contamination is obviously highly surface active, as it could not be detected using bulk sensitive methods with a detection limit in the ppm range. Furthermore, XPS measurements allowed to quantify other carbon and oxygen containing contaminations of imidazolium based ILs, which again were below the detection limit of bulk sensitive methods.…”

Section: Surface Contaminationsmentioning

confidence: 99%

Surface Science and Model Catalysis with Ionic Liquid‐Modified Materials

et al. 2011

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Materials making use of thin ionic liquid (IL) films as support-modifying functional layer open up a variety of new possibilities in heterogeneous catalysis, which range from the tailoring of gas-surface interactions to the immobilization of molecularly defined reactive sites. The present report reviews recent progress towards an understanding of "supported ionic liquid phase (SILP)" and "solid catalysts with ionic liquid layer (SCILL)" materials at the microscopic level, using a surface science and model catalysis type of approach. Thin film IL systems can be prepared not only ex-situ, but also in-situ under ultrahigh vacuum (UHV) conditions using atomically well-defined surfaces as substrates, for example by physical vapor deposition (PVD). Due to their low vapor pressure, these systems can be studied in UHV using the full spectrum of surface science techniques. We discuss general strategies and considerations of this approach and exemplify the information available from complementary methods, specifically photoelectron spectroscopy and surface vibrational spectroscopy.

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“…Clearly, the intensities of C and O are higher than the theoretical values, which may be caused by trace organic contaminations introduced during synthesis. In addition, the presence of Si-containing surface contaminants might also contribute to the excessive oxygen concentration, [43] although no Si signal was detected (possibly < 0.3 wt %). The enrichment of F in the IL surface can be explained by the facts that fluorine has a high relative sensitivity factor (RSF = 1), and that the atoms of fluorine-containing anions involved in emissive processes are not affected by shake-up/off events.…”

Section: Esi-msmentioning

confidence: 99%

“…[44] Figure 9 a gives the XPS spectra of [S2]DCA, which are free from O and F. Besides the IL-related signals (C, S, and N), we observed trace Si-containing contaminants, which might originate from the sealing of the storage container or the silicone grease introduced during synthesis. [43,44] The S 2p spectrum of [S2]DCA is shown in Figure 9 b. The B.E.…”

Section: Esi-msmentioning

confidence: 99%

Novel Cyclic Sulfonium‐Based Ionic Liquids: Synthesis, Characterization, and Physicochemical Properties

Zhang

Liu

et al. 2008

Chemistry A European J

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A new series of ionic liquids composed of three cyclic sulfonium cations and four anions has been synthesized and characterized. Their physicochemical properties, including their spectroscopic characteristics, ion cluster behavior, surface properties, phase transitions, thermal stability, density, viscosity, refractive index, tribological properties, ion conductivity, and electrochemical window have been comprehensively studied. Eight of these salts are liquids at room temperature, at which some salts based on [NO(3)](-) and [NTf(2)](-) ions exhibit organic plastic crystal behaviors, and all the saccharin-based salts display relatively high refractive indices (1.442-1.594). In addition, some ionic liquids with the [NTf(2)](-) ion exhibit peculiar spectroscopic characteristics in FTIR and UV/Vis regions, whilst those salts based on the [DCA](-) ion show lower viscosities (34.2-62.6 mPa s at 20 degrees C) and much higher conductivities (7.6-17.6 mS cm(-1) at 20 degrees C) than most traditional 1,3-dialkylimidazolium salts.

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Surface Studies on the Ionic Liquid 1-Ethyl-3-Methylimidazolium Ethylsulfate Using X-Ray Photoelectron Spectroscopy (XPS)

Cited by 111 publications

References 25 publications

Ionic Liquids in Catalysis

Ionic Liquids in Catalysis

Surface Science and Model Catalysis with Ionic Liquid‐Modified Materials

Novel Cyclic Sulfonium‐Based Ionic Liquids: Synthesis, Characterization, and Physicochemical Properties

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