Ionic Liquid Mediated Graphene-based Pd Nanocomposites for Coupling Reactions

Review: ca. 100 refs.

Luminescence study of europium(III) ion has been carried out in a completely incenerable (CHON based) ionic liquid system. The ionic liquid used in the study was trioctylmethylammonium nitrate ([N 1888 ][NO 3 ] while the extractant used was N,N‐dioctyl‐2‐hydroxyacetamide (DOHyA). The complexation of europium(III) in such type of ionic liquid system and its elaboration by luminescence study is highlighted for the first time in this paper. The luminescence behaviour of europium(III) was ascertained as a function of various parameters, such as aqueous phase acidity, extractant concentration, initial metal ion concentration, types of ionic liquid diluents etc. The luminescence intensity of Eu(III) was remarkably high in the ionic liquid medium at all aqueous phase acidity (0.1 M to 5 M HNO3) as compared to that of in aqueous phase. The luminescence lifetime of Eu(III) in this complex is in the range of 360 μs – 550 μs which is quite higher than that of aqueous phase (107 μs ‐ 130 μs), suggesting the luminescence enhancement is a result of reduction in non‐radiative decay channels in ionic liquid medium. The emission peak of Eu(III) in DOHyA was compared with that of DOMeA (N,N‐dioctyl‐2‐methoxyacetamide) in ionic liquid medium in order to highlight the presence of –OH group in DOHyA. The luminescence spectra of Eu(III) was also investigated by changing the type of aqueous phase acidity from nitrate ion to chloride ion and the results are detailed in the paper.

An easy ionothermal method is proposed to deoxygenate graphene oxide (GO) for preparation of graphene by using a choline chloride (ChCl)/urea mixture-based ionic liquid. In the synthesis process, the urea portion in the ionic liquid breaks up to release NH3 at around 100 °C. This reacts with the oxygen functional groups of the GO sheets, leading to the formation of graphene. The ionothermal method is an environmentally-friendly and attractive strategy for reducing GO because both ChCl and urea are naturally biocompatible compounds. X-Ray photoelectron spectroscopy indicates that nitrogen atoms can be doped into the graphene skeleton accompanied by the reduction of GO. As an electrode for an electrochemical double layer capacitor in aqueous KOH, the ionothermally reduced GO exhibits a gravimetric capacitance of 155 F g−1 at a current density of 0.2 A g−1 and good cycling performance, which is comparable to the hydrazine reduced GO. We expect that the ionothermal method will have implications for the use of ionic liquids in the large-scale synthesis of graphene-based materials.

The first example of an efficient one-pot reductive sulfenylation and thiocyanation of carbonyl compounds in environmentally benign ionic liquid (IL) media is reported. The process involves reduction of carbonyl compounds with NaBH4 in the IL [bmim]BF4 followed by I2-catalyzed reaction of the resulting alcohols with aromatic / aliphatic thiols or ammonium thiocyanate in the same vessel to afford sulfides or thiocyanates, respectively, in excellent yields (78–93%). Notably, the protocol precludes the necessity to prepare and isolate the intermediate alcohols in a separate step as they are formed in situ, and the IL used can be recycled easily for further use without any loss of efficiency.

Ionic liquid/reduced graphene oxide/nickel-palladium nanoparticle hybrid synthesized for non-enzymatic electrochemical glucose sensing

Physicochemical and radiolytic degradation properties of dihexyloctanmide-imidazolium ionic liquid

Supercapacitors, also known as electric double-layer capacitors (EDLCs), are able to store energy rapidly and reversibly through the formation of a double-layer of electronic and ionic charge, closely spaced, at the electrode/electrolyte interface.[1-2] Due to the combination of various advantageous properties, such as efficient operation at high power density, long cycle life and improved safety compared to Li-ion batteries,[3,4] supercapacitors are being increasingly used as alternative power sources to rechargeable batteries. However, the implementation of supercapacitors in practical application is still restricted by the limited energy density, typically 5-8 Wh/L,[5] which is much lower than that of lead-acid batteries which can achieve ~50-90 Wh/L.[6] Considering a symmetric configuration, the volumetric energy density (E V) of a supercapacitor is directly proportional to the volumetric capacitance (C V) of a single electrode and the square of operating voltage (U) following the equation, Ev = 1/8(C V·U 2). Therefore, in such a system, there are two ways to improve energy density: boosting capacitance and extending cell voltage window. The operating voltage of EDLCs is typically limited by the stability of electrolyte and thus room temperature ionic liquids (ILs) with large electrochemical stability windows (> 3-4 V) have become promising next-generation electrolytes. However, the relatively high viscosity of ILs results in lower ionic conductivity compared to traditional aqueous or organic electrolytes and also leads to challenges with pore wetting. On the electrode side, materials with a high intrinsic capacitance (C DL) per area and a large ion-accessible surface area (SSA) are needed to achieve high gravimetric capacitance (C G) since C G = C DL·SSA. The potentially high electrical conductivity, surface area, and chemical stability of graphene-based materials make them promising candidate electrode.[7,8] Theoretically, single layer graphene can exhibit SSA as high as 2675 m2/g. While pristine graphene is limited by its low quantum capacitance leading to C DL ~3-4 mF/cm2, more defective and functionalized graphene produced by the chemical or thermal reduction of graphene oxide (GO) have been shown to exhibit C DL > 17 mF/cm2 in non-aqueous electrolyte leading to theoretical gravimetric capacitance, C G,theoretical > 450 F/g if all of graphene’s surface area could be made ion-accessible. To prevent aggregation and restacking of graphene-based materials into lower SSA structures, we demonstrated an IL microemulsion system (Figure 1) that spontaneously assembles on the surface of GO, placing nanometer-sized droplets of a high-performance, hydrophobic IL 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMImTFSI) directly onto the available surface of well-dispersed single GO layers. We first demonstrate that a common non-ionic surfactant, Tween 20 is capable of forming a stable microemulsion with EMImTFSI with a particle size on the order of several nanometers. These surfactant stabilized nano-droplets (microemulsion particles) spontaneously adsorb to GO sheets yielding a dispersion which can be cast directly onto current collectors leading to a dense nanocomposite of GO/IL/Tween 20. Tween 20 is then removed by evaporation, while the GO is thermally reduced leading to what we refer to as layered IL-mediated reduced GO (IM-rGO) electrodes. The approach is found to yield high ion-accessible SSA as evidenced by one of the highest C G ever reported (302 F/g) when the composite contains 80 wt% IL. These results indicate that the microemulsion particles formed were better able to deploy IL as a spacer to prevent rGO sheets from restacking. Reducing the IL content to 60 wt%, resulted in dense electrodes that exhibited a C V = 218 F/cm3, which is the highest value reported to date among all graphene-based supercapacitors leading to exceptional volumetric energy density. Reference (1) Conway, B. E. Electrochemical Supercapacitors: Scientific Fundamentals and Technological Applications. Springer Science & Business Media 2013. (2) Miller, J. R.; Simon, P. Electrochemical capacitors for energy management. Science 2008, 321, 651. (3) Du Pasquier, A.; Plitz, I.; Menocal, S.; Amatucci, G. A comparative study of Li-ion battery, supercapacitor and nonaqueous asymmetric hybrid devices for automotive applications. J. Power Sources 2003, 115, 171. (4) Khaligh, A.; Li, Z. Battery, ultracapacitor, fuel cell, and hybrid energy storage systems for electric, hybrid electric, fuel cell, and plug-in hybrid electric vehicles: State of the art. IEEE transactions on Vehicular Technology 2010, 59, 2806. (5) Burke, A. R&D considerations for the performance and application of electrochemical capacitors. Electrochim. Acta 2007, 53, 1083. (6) Linden, D. Handbook of batteries. Fuel and Energy s 1995, 265. (7) Pope, M. A.; Aksay, I. A. Four-Fold Increase in the Intrinsic Capacitance of Graphene through Functionalization and Lattice Disorder. J. Phys. Chem. C 2015, 119, 20369. (8) Stoller, M. D.; Park, S.; Ruoff, R. S. Graphene-based ultracapacitors. Nano Lett. 2008, 8, 3498. Figure 1

Unveiling a novel mechanism: Reduction of graphene oxide by Lysinibacillus sp. through secretion of l-ascorbic acid

Effect of the alkyl group on the synthesis and the electrochemical properties of N-alkyl- N-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquids

Controllable synthesis of palladium nanoparticles and their catalytic abilities in Heck and Suzuki reactions

Electrodeposition (ED) from ionic liquid (IL) medium is of much importance due to a variety of architectures can be synthesized by IL assisted growth. However, these liquids are relatively new for the fabrication of compounds and alloys with a great control over the stoichiometry and thickness. In this article, we have discussed the prerequisites and a detailed methodology to develop stoichiometric CdTe thin films from IL medium with required thicknesses in a controlled way. We have found that the required precursor ratio of Te:Cd can be lower down to 1:10 for 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) IL which is usually 1:1000 for the aqueous electrolytes. Moreover, the aspect ratio of nanostructures can be tuned by changing the precursors’ ratio in IL bath. Nevertheless, IL can be reused multiple times to develop identical thin films which guarantee green and low cost pathway.

Graphene oxide (GO) and reduced graphene oxide (rGO) synthesised from GO, has a promising future in fields ranging from electronics to energy technologies[1]. GO may be synthesized by the modified Hummer’s method[2], where a mixture of potassium permanganate and concentrated sulfuric acid forms the ground pillar for the oxidation of graphite to GO. rGO can be synthesized by a broad range of methods, with the chemical and the thermal reduction routes being very common[3]. The synthesis mechanism of GO by the modified Hummer’s method is still unknown, even though the active oxidizing species dimanganese heptoxide has been suggested as the main redox active specie[4]. The mechanism of the thermal reduction of GO to rGO is also unknown. We present results from i n situ synchrotron X-ray diffraction (XRD) experiments of syntheses and thermal reduction of GO. The in situ synthesis of GO was performed by placing a mixture of permanganate and sulphuric acid in a capillary next to graphite. The synthesis was then initiated by gently pushing the fluid mixture into the powder with N2 gas. The in situ XRD of the GO synthesis showed how the oxidation reaction proceeds in three separate stages, as seen in Figure 1. The first stage was the dissolution of potassium permanganate, followed by an intercalation stage and subsequent formation of crystalline material. The GO 001 diffraction peak was observed early during the synthesis, in the second stage, and the intensity of the 001 diffraction increased during the third stage. The in situ XRD results of the thermal reduction of GO to rGO showed a dependence on the temperature ramping and addition of diamond powder. Syntheses were measured at 1, 5, 10, 20 and 50 °/min temperature ramps. The syntheses were performed in a capillary with GO being heated by a hot air blower under constant N2 flow. Three stages were observed for the reduction process; a GO stage, an amorphous stage and a rGO stage. The change in stage was defined from the changing of the d-value of the initial 001 GO peak, see Figure 2. The initial GO diffraction pattern changed during the heating and more diffraction peaks were observed. The results showed that the nature of the rGO material depends heavily on both temperature and additives. These in situ XRD studies revealed the crystalline intermediates and final product of synthesis by a modified Hummer’s method and the diffractional change during the thermal reduction of GO. The stages observed for both syntheses illuminate how important it is to consider the experimental parameters dependent on the application; they might even have to be optimized separately. As the future use of GO and rGO is expanding and the commercialization of these products are enhanced, the syntheses mechanisms may be of increasing interest. [1] M. Segal, Nat Nano, 4 (2009) 612-614. [2] Hummer and Offeman, J. Am. Chem. Soc. (1958) 1339-1339 [3] Pei and Cheng, Carbon (2012) 3210-3228 [4] Dreyer, Park, Bielawski and Ruoff, Chem. Soc. Rev. (2010) 228-240 Figure 1

Graphene oxide – Ionic liquid composite electrolytes for safe and high-performance supercapacitors

a key to the development of innovative sustainable technology platforms is represented by the combination of different green strategies. The access to new synthetic processes deriving from the merging of heterogeneous catalysis with intrinsically safer solvents such as ionic liquids, and possibly using flow through techniques, is discussed in this chapter. Examples taken from the very recent literature are analysed and classified according to four different strategic approaches to generate catalysis in ionic liquid media; (i) the ionic liquid is the solvent for the catalytic reaction, (ii) the ionic liquid is both the solvent and the catalyst (or pre-catalyst), (iii) the ionic liquid is simply used as the catalyst, easily removable from the reaction mixture, (iv) the ionic liquid is supported in the form of a thin layer on a solid support. In the last case, the solid material is exploitable in fixed bed reactors, thus rendering possible the application of continuous flow technologies.

We present a facile and scalable method for the rapid production of reduced graphene oxide (RG–O) by ionic liquid-assisted microwave chemistry. Microwave irradiation of graphite oxide (GO) in an ionic liquid (IL) enables the rapid reduction of GO within 15 s, producing RG–O containing the IL within their porous structures. The reduced graphene oxide prepared by IL-assisted microwave irradiation (mRG–O) electrodes exhibited a high specific capacitance of ∼135 F g−1, which can be attributed to the open architecture of the mRG–O filled with IL moieties. A supercapacitor made with mRG–O in an IL electrolyte operated at a voltage of 3.5 V and showed a high energy density (∼58 W h kg−1) and power density (∼246 kW kg−1).