Water Stable Ionic Liquid Research Articles

Electrodeposition of nanocrystalline silver films and nanowires from the ionic liquid 1-ethyl-3-methylimidazolium trifluoromethylsulfonate

We report in this paper on the electrodeposition of nanocrystalline silver films and nanowires in the air and water stable ionic liquid 1-ethyl-3-methylimidazolium trifluoromethylsulfonate [EMIm]TfO containing Ag(TfO) as a source of silver. The study was performed by means of cyclic voltammetry and chronoamperometry, and the electrodeposits were characterized by SEM-EDX and XRD. The cyclic voltammetry behaviour showed typical reduction and oxidation peaks corresponding to the deposition and stripping of silver in the employed electrolyte. XRD patterns of the electrodeposited silver layers revealed the characteristic peaks of crystalline silver with crystallites in the nanosize regime. Silver nanowires with average diameters and lengths of about 200 nm and 3 μm, respectively, were prepared by potentiostatic deposition within a commercial nuclear track-etched polycarbonate template.

Reactivity of Brönsted acid ionic liquids as dual solvent and catalyst for Fischer esterifications

Several water-stable ionic liquids with different acidity and affinity were synthesized and applied as both solvents and acid catalysts for Fischer esterification of ethanol reacting with four aliphatic carboxylic acids (acetic acid, n-hexanoic acid, lauric acid, and stearic acid). Among the studied ionic liquids, ((n-bu-SO3H) MIM)(HSO4) (3-butyl- 1-(butyl-4-sulfonyl) imidazolium sulfate) and ((n-bu-SO3H) MIM)(p-TSO) (3-butyl-1-(butyl-4-sulfonyl) imidazolium toluenesulfonate) show higher reactivity for the production of ethyl esters. The catalytic activities of these ionic liquids are strongly dependent on the acidity of their anions and cations, as well as their hydrophilicity and affinity with the reactants. Water refluxing through the condenser may be another important reason for obtaining high conversion of esterification, indicating a water-sequester process is still needed in order to obtain a higher yield of ester in the ionic liquid catalyzed esterification system. Kinetics studies show the conversions of the acids increase with reaction tem- perature and time, and reach equilibrium within about two hours. The apparent activation energies are 39.1±2.0, 49.7± 2.5, 51.4±2.5 and 59.3±3.0 kJ·mol −1 for the formation of ethyl acetate, ethyl n-hexanoate, ethyl laurate and ethyl stearate, respectively.

Sol–gel synthesis of vanadium pentoxide nanoparticles in air- and water-stable ionic liquids

Vanadium pentoxide (V2O5) nanoparticles were synthesized at moderate reaction temperatures by hydrolysis of VO[OCH(CH3)2]3 in two different air- and water-stable ionic liquids with the same anion: 1-butyl-1-methyl pyrrolidinium bis(trifluoromethylsulfonyl)amide ([Py1,4]Tf2N) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([EMIM]Tf2N) via the sol–gel method using acetone and isopropanol either as refluxing solvents or as co-solvents. The cation type of the ionic liquid affects the crystallinity, morphology, and surface area of the produced nanoparticles: [Py1,4]Tf2N gave products with higher crystallinity especially with acetone as a refluxing and co-solvent, while [EMIM]Tf2N gave a clear mesoporous morphology with isopropanol as a refluxing solvent. Ionic liquids affect the key factors (morphology and surface area) that make V2O5 an attractive material as catalyst and/or cathodic material for lithium ion batteries.

In situ STM investigation of the lithium underpotential deposition on Au(111) in the air- and water-stable ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide

In the present paper the underpotential deposition (UPD) of lithium on Au(111) from 0.5 mol L(-1) LiTFSA in the air- and water stable ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide, [Py(1,4)]TFSA, has been investigated by cyclic voltammetry (CV) and in situ scanning tunneling microscopy (STM). The pure [Py(1,4)]TFSA was found to be inert in the potential regime investigated. The results show that the lithium UPD on Au(111) in [Py(1,4)]TFSA begins at potentials considerably positive to the electrode potential of bulk deposition and follows a layer-by-layer mechanism with the formation of at least two monolayers. A large number of monoatomically deep pits appear when the potential reaches positive values, which is an indication that a Li-Au alloy was formed.

Template-assisted electrodeposition of SixGe1−x nanowires with varying length and composition from two different ionic liquids

We have recently reported that “luminescent” SixGe1−x can be electrodeposited from 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([Py1,4]Tf2N) at room temperature. Interestingly, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([EMIm]Tf2N) ionic liquid delivers a germanium-rich SixGe1−x showing also a quantum-size effect, as revealed in the present study. These results led us to evaluate the possibility of obtaining high quality SixGe1−xnanowires from two different ionic liquids by the simple and inexpensive template-assisted electrochemical pathway. Herein, we report for the first time on the room temperature template synthesis of SixGe1−xnanowires by potentiostatic electrochemical deposition from the air- and water-stable ionic liquids [Py1,4]Tf2N and [EMIm]Tf2N containing (each) GeCl4 and SiCl4 as precursors. As a first step, a commercially available track-etched polycarbonate membrane (PC) with an average nominal pore diameter of 90 nm was used as template. SixGe1−xnanowires with an average diameter corresponding to the nanopores' diameter and lengths of 1 to 2.5 µm were reproducibly obtained. [EMIm]Tf2N delivers longer SixGe1−xnanowires than [Py1,4]Tf2N under the same parameters and reaction conditions. Characterization of the nanowires was performed by EDX and HR-SEM.

Electrodeposition of Ferromagnetic Materials from Air and Water Stable Ionic Liquids

This paper describes recent results from the authors' labs dealing with the electrodeposition of thin cobalt layers from 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([Py1,4] ¬TFSA) ionic liquid with tailor-made metal salts. We applied the electrochemical quartz crystal microbalance (EQCM) with damping monitoring for the in-situ determination of the mass-charge balance and of the current efficiency of the deposition process. Higher temperatures improved the quality of the deposited layers. Thus uniform deposits with a grain size of some tens of nm were obtained at 120 degrees Celsius whereas no Co layers could be electrodeposited at room temperature from the [Py1,4] ¬TFSA either by potentiostatic or galvanostatic control.

Electrodeposition of Nanoscale SixGe1-x from an Air- and Water Stable Ionic Liquid

We report for the first successful electrodeposition of highly pure SixGe1-x from the air- and water stable ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([Py1,4]Tf2N) containing GeCl4 and SiCl4 as precursors. The electrodeposition is investigated by cyclic voltammetry and high resolution scanning electron microscopy. SixGe1-x can be deposited reproducibly and easily in this ionic liquid. Interestingly, the SixGe1-x deposit showed a strong colour change (from red to blue) at room temperature during electrodeposition. The observed colours are strong hints for band gaps between at least 1.5 and 3.2 eV, which are indicative of a quantum size effect. This proves the potential of ionic liquids in the electrodeposition of high quality SixGe1-x.

In situ STM and EQCM studies of tantalum electrodeposition from TaF 5 in the air- and water-stable ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide

The electroreduction of 0.5 M TaF 5 on Au(1 1 1) and on polycrystalline gold substrates was investigated at room temperature in the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide, [Py 1,4]TFSA, by cyclic voltammetry, in situ scanning tunneling microscopy (STM) and electrochemical quartz crystal microbalance (EQCM). The electrochemical reduction of TaF 5 in the employed ionic liquid occurs in several steps. The first redox process is attributed to the reduction of TaF 5 to TaF 3, which likely occurs in the solution, as EQCM indicates no mass change. The electrodeposition of tantalum occurs only in a very narrow potential window and is preceded by the formation of various non-stoichiometric tantalum subhalides. Attempts to deposit micrometer thick tantalum layers at room temperature fail, presumably because of kinetic reasons.

Electrodeposition from Air and Water Stable Ionic Liquids: Prospects and Challenges

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Electrodeposition of Ferromagnetic Materials from Air and Water Stable Ionic Liquids

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Electrochemical Study of Copper in the 1-Ethyl-3-Methylimidazolium Dicyanamide Room Temperature Ionic Liquid

The potential utility of the air- and water-stable ionic liquid 1-ethyl-3-methylimidazolium dicyanamide (EMI–DCA) for electrochemical application was evaluated with copper(I) chloride. The temperature dependency of the density and absolute viscosity of EMI–DCA were measured over a temperature range from 297 to 343 K, and equations describing the dependencies are presented. Due to the ligand property of the DCA anion, both CuCl and are soluble in EMI–DCA. Cyclic voltammograms of Cu(I) in EMI–DCA and other two ionic liquids were compared. Cu(I) can be oxidized to Cu(II) or reduced to Cu metal in these solutions. The electrodeposition of Cu on glassy carbon and nickel electrodes involves a three-dimensional progressive nucleation and growth process. Scanning electron microscopy and X-ray diffraction results indicate that the morphology of the copper electrodeposits is dependent on the deposition potential, and compact coatings containing nanocrystalline copper could be obtained by potentiostatic electrolysis at low overpotentials. The low viscosity of EMI–DCA and the high solubility of metal chlorides in it would facilitate the electrodeposition of metals using this ionic liquid.

Electrosynthesis of Poly(para)phenylene in an Ionic Liquid: Cyclic Voltammetry and in Situ STM/Tunnelling Spectroscopy Studies

The electropolymerization of benzene in the air and water-stable ionic liquid 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate (HMIm)FAP is investigated. The study comprises cyclic voltammetry, IR and in situ STM/tunnelling spectroscopy measurements. The IR results indicate that poly(para)phenylene is the end product of the electropolymerization of benzene in the employed ionic liquid. The resulting conjugation lengths of the product fall between 19 and 21. A polymer reference electrode is used successfully for the electrochemical polymerization of benzene. The first in situ STM results show that the electropolymerization of benzene in the ionic liquid can be probed on the nanoscale and the band gap of the prepared polymer can be determined. The electrodeposited polymer film obtained at a constant potential of 1.0 V vs PPP (polyparaphenylene) exhibits a band gap of 2.9+/-0.2 eV.

Studies on the synthesis of nano-alumina in air and water stable ionic liquids

In this paper we report on the synthesis of aluminium oxide nanoparticles in two different air and water stable ionic liquids namely, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl) amide [BMP]TFSA and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) amide [EMIm]TFSA. The ionic liquids [BMP]TFSA and [EMIm]TFSA exhibit biphasic behaviour beginning with an AlCl3 concentration of 1.6 mol L–1 and 2.5 mol L–1, respectively. Different aluminium oxides were prepared by the hydrolysis of AlCl3 dissolved in the employed ionic liquids, followed by calcinations. AlCl3·6H2O was found to be the main hydrolysis product of the AlCl3 containing ionic liquids. The as-prepared AlCl3·6H2O is subject to thermal decomposition producing different forms of transition oxides, depending on the original liquid composition. Alumina was also obtained by hydrolysis of as-prepared AlCl3·6H2O by NH4OH solution. Hydrolysis of the upper phase of the biphasic mixture of 3 M AlCl3–[EMIm]TFSA with NH4OH produces transparent alumina which is converted into α-Al2O3 with a low amount of δ-Al2O3 after calcinations at 1000 °C. The formation of pseudoboehmite and γ-Al2O3 as intermediates are observed at 200 °C and 550 °C, respectively. The obtained pseudoboehmite is mesoporous with an average pore diameter of 3.8 nm and a high surface area of 226 m2 g–1. The chloroaluminite obtained by hydrolysis of the homogenous mixture of 1 M AlCl3–[BMP]TFSA undergoes thermal decomposition yielding amorphous alumina at 200 °C, which transforms completely to well crystallized α-Al2O3 at 1000 °C. The obtained α-alumina is porous with an average pore size of about 10 nm. This suggests that the ionic liquid [BMP]TFSA acts as a template and that it decomposes thermally at elevated temperature producing pores.

Synthesis and Characterization of Rutile and Anatase in Air- and Water-Stable Ionic Liquids with and without Isopropanol as a Cosolvent

Nanocrystalline TiO2 with pure rutile and pure anatase phases was prepared at moderate reaction temperatures by hydrolysis of TiCl4 in different air- and water-stable ionic liquids with the same anion ([Py1,4]Tf2N, [EMIM]Tf2N, and [P14,6,6,6]Tf2N), in isopropanol and in cosolvent of ionic liquid/isopropanol under different reaction conditions. The type of cation in the ionic liquid influences the morphology of the rutile phase: cone-like morphology was obtained in the case of [Py1,4]+ and [P14,6,6,6]+ ions and wormhole-like in the case of [EMIM]+. In the case of anatase, no significant effect was found. The influence of various reaction conditions like acidity of solution, solvent type, precursor type, and precursor concentration on the phase formation and morphology of titania were investigated.

Electrodeposition of Ge, Si and SixGe1−x from an air- and water-stable ionic liquid

The electrodeposition of Ge, Si and, for the first time, of Si(x)Ge(1-x) from the air- and water-stable ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([Py(1,4)]Tf(2)N) containing GeCl(4) and/or SiCl(4) as precursors is investigated by cyclic voltammetry and high-resolution scanning electron microscopy. GeCl(2) in [Py(1,4)]Tf(2)N is electrochemically prepared in a two-compartment cell to be used as Ge precursor instead of GeCl(4) in order to avoid the chemical attack of Ge(iv) on deposited Ge. Silicon, germanium and Si(x)Ge(1-x) can be deposited reproducibly and easily in this ionic liquid. Interestingly, the Si(x)Ge(1-x) deposit showed a strong colour change (from red to blue) at room temperature during electrodeposition, which is likely to be due to a quantum size effect. The observed colours are indicative of band gaps between at least 1.5 and 3.2 eV. The potential of ionic liquids in Si(x)Ge(1-x) electrodeposition is demonstrated.

Electrodeposition onto magnesium in air and water stable ionic liquids: From corrosion to successful plating

Magnesium is very reactive and therefore magnesium electroplating in aqueous solutions is hazardous. Mg is classified as a water sensitive substrate from the electrodeposition point of view. Therefore, it was suggested that ionic liquids be used as electrolytic solvents for electrodeposition onto Mg and its alloys. Five air and water stable ionic liquids based on choline chloride (ChCl) were investigated to deposit Zn onto several Mg alloys in air. The ChCl/urea mixture was found to be the most feasible liquid for successful electrodeposition. Other liquids produced powdery deposits or resulted in corrosion of Mg substrate. Application of a pulsed current was superior to a constant current in producing smooth, sealed and more corrosion-resistant Zn layers.

Silver electrodeposition from air and water-stable ionic liquid: An environmentally friendly alternative to cyanide baths

The influence of temperature on the kinetics and the morphology of silver deposits obtained from an air and water-stable ionic liquid (the 1-butyl-3-methyl imidazolium tetrafluoroborate) was studied by means of cyclic voltammetry and chronoamperometry. The nucleation and growth mechanisms have been investigated and the effect of temperature evaluated up to 200 °C. Dense, pure and very thin (about 0.3 μm) silver coatings, with decorative properties, have been obtained on commercial copper electrodes at different temperatures. The characterization of the deposits morphology has been performed by visual investigation and SEM microscopy. Data about thickness were acquired by Calotest® measurements. The deposits result constituted by pure silver as determined by combination of EDX microanalysis and Auger Electron Spectroscopy (AES). The deposition method promises to be a new, environmentally friendly, method for silver electrodeposition which is the reason for the absence of cyanide and volatile toxic solvents in the electroplating bath.

Electrodeposition of Al in 1-Butyl-1-methylpyrrolidinium Bis(trifluoromethylsulfonyl)amide and 1-Ethyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)amide Ionic Liquids: In Situ STM and EQCM Studies

In the present paper, the electrodeposition of Al on flame-annealed Au(111) and polycrystalline Au substrates in two air- and water-stable ionic liquids namely, 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)amide, [Py(1,4)]Tf(2)N, and 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)amide, [EMIm]Tf(2)N, has been investigated by in situ scanning tunneling microscopy (STM), electrochemical quartz crystal microbalance (EQCM), and cyclic voltammetry. The cyclic voltammogram of aluminum deposition and stripping on Au(111) in the upper phase of the biphasic mixture of AlCl(3)/[EMIm]Tf(2)N at room temperature (25 degrees C) shows that the electrodeposition process is completely reversible as also evidenced by in situ STM and EQCM studies. Additionally, a cathodic peak at an electrode potential of about 0.55 V vs Al/Al(III) is correlated to the aluminum UPD process that was evidenced by in situ STM. A surface alloying of Al with Au at the early stage of deposition occurs. It has been found that the Au(111) surface is subject to a restructuring/reconstruction in the upper phase of the biphasic mixture of AlCl(3)/[Py(1,4)]Tf(2)N at room temperature (25 degrees C) and that the deposition is not fully reversible. Furthermore, the underpotential deposition of Al in [Py(1,4)]Tf(2)N is not as clear as in [EMIm]Tf(2)N. The frequency shift in the EQCM experiments in [Py(1,4)]Tf(2)N shows a surprising result as an increase in frequency and a decrease in damping with bulk aluminum deposition at potentials more negative than -1.8 V was observed at room temperature. However, at 100 degrees C there is a frequency decrease with ongoing Al deposition. At -2.0 V vs Al/Al(III), a bulk aluminum deposition sets in.

Ionic liquids as green electrolytes for the electrodeposition of nanomaterials

Ionic liquids, especially air and water stable ones, experience much attention, since they have attractive physical properties. We exemplify in this paper the potential of ionic liquids in the electrodeposition of nanocrystalline metals without additives. The results show that nanocrystalline copper and aluminium can be electrodeposited in the air and water stable ionic liquids 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate ([BMP]TFO) and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([BMP]Tf2N), respectively, on conventional solid electrodes with sufficient electronic conductivity. Generally, the obtained Al or Cu deposits are shiny, dense and adherent with very fine crystallites with average sizes of about 30 and 40 nm, respectively. The [BMP]+ cation might act as a grain refiner, leading to nanosized deposits. The results of first attempts to use plasmas as mechanically contact-free electrodes for the cathodic deposition of nanoscaled metals (glow discharge electrodeposition) are also presented. The relevance of our results for the development of a green process to make nanomaterials as catalysts for fuel processing is briefly discussed.

Electrodeposition of selenium, indium and copper in an air- and water-stable ionic liquid at variable temperatures

The electrochemical behaviour of Au(1 1 1) and highly oriented pyrolytic graphite (HOPG) substrates in the air- and water-stable ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([BMP]Tf 2N) was investigated using in situ scanning tunneling microscopy (STM). Furthermore, the electrodeposition of Se, In and Cu in the same ionic liquid was investigated. The high thermal stability as well as the large electrochemical window of this ionic liquid compared with aqueous electrolytes allow the direct electrodeposition of grey selenium, indium and copper at variable temperatures, as the first step in making CIS solar cells electrochemically, in a one pot reaction. The results show that grey selenium can be obtained at temperatures ≥100 °C. XRD patterns of the electrodeposit obtained at 100 °C show the characteristic peaks of crystalline grey selenium. Nanocrystalline indium with grain sizes between 100 and 200 nm was formed in the employed ionic liquid, containing 0.1 M InCl 3, at room temperature. It was also found that copper(I) species can be introduced into the ionic liquid [BMP]Tf 2N by anodic dissolution of a copper electrode and nanocrystalline copper with an average crystallite size of about 50 nm was obtained without additives in the resulting electrolyte.