High-speed electrodeposition of copper-tin-zinc stacks from liquid metal salts for Cu2ZnSnSe4 solar cells.

Cu2ZnSnSe4-based solar cells with 5.5% power conversion efficiency were fabricated from Cu/Sn/Zn stacks electrodeposited from liquid metal salts. These electrolytes allow metal deposition rates one order of magnitude higher than those of other deposition methods.

Curing characteristics of flowable and sculptable bulk-fill composites.

OBJECTIVES: The aim of this study was to determine and correlate the degree of conversion (DC) with Vickers hardness (VH) and translucency parameter (TP) with the depth of cure (DoC) of five bulk-fill composites. MATERIALS AND METHODS: Six specimens per group, consisting of Tetric EvoCeram Bulk Fill ("TEC Bulk," Ivoclar Vivadent), SonicFill (Kerr), SDR Smart Dentin Replacement ("SDR," Dentsply), Xenius base ("Xenius," StickTech; commercialized as EverX Posterior, GC), Filtek Bulk Fill flowable ("Filtek Bulk," 3M ESPE), and Tetric EvoCeram ("TEC," control), were prepared for DC and VH: two 2-mm-thick layers, each light-cured for 10 s; one 4-mm bulk-fill, light-cured for 10 or 20 s; and one 6-mm bulk-fill, cured for 20 s. DC was measured using a Fourier-transform infrared spectrometer, VH using a Vickers hardness tester. DoC and TP were measured using an acetone-shaking test and a spectrophotometer, respectively. Data were analyzed using ANOVA and Pearson's correlation (α = 0.05). RESULTS: DC and VH ranged between 40-70 % and 30-80 VHN, respectively. TEC Bulk, Xenius, and SonicFill, bulk-filled as 4-mm-thick specimens, showed bottom-to-top hardness ratios above 80 % after 20 s curing. A positive linear correlation was found for bottom DC and VH. An average DC ratio of 0.9 corresponded to a bottom-to-top VH ratio of 0.8. CONCLUSIONS: Sculptable bulk-fills require 20 s, whereas 10 s curing time was sufficient for flowable bulk-fills using a high-intensity LED unit. CLINICAL RELEVANCE: Clinicians should be aware that longer curing times may be required for sculptable than flowable bulk-fill composites in order to achieve optimal curing characteristics.

Crystal structure of apatite type Ca2.49Nd7.51(SiO4)6O1.75.

The title compound, Ca2+x Nd8-x (SiO4)6O2-0.5x (x = 0.49), was synthesized at 1873 K and rapidly quenched to room temperature. Its structure has been determined using single-crystal X-ray diffraction and compared with results reported using neutron and X-ray powder diffraction from samples prepared by slow cooling. The single-crystal structure from room temperature data was found to belong to the space group P63/m and has the composition Ca2.49Nd7.51(SiO4)6O1.75 [dicalcium octa-neodymium hexa-kis-(ortho-silicate) dioxide], being isotypic with natural apatite and the previously reported Ca2Nd8(SiO4)6O2 and Ca2.2Nd7.8(SiO4)6O1.9. The solubility limit of calcium in the equilibrium state at 1873 K was found to occur at a composition of Ca2+x Nd8-x (SiO4)6O2-0.5x , where x = 0.49.

Towards an all-copper redox flow battery based on a copper-containing ionic liquid.

The first redox flow battery (RFB), based on the all-copper liquid metal salt [Cu(MeCN)4][Tf2N], is presented. Liquid metal salts (LMS) are a new type of ionic liquid that functions both as solvent and electrolyte. Non-aqueous electrolytes have advantages over water-based solutions, such as a larger electrochemical window and large thermal stability. The proof-of-concept is given that LMSs can be used as the electrolyte in RFBs. The main advantage of [Cu(MeCN)4][Tf2N] is the high copper concentration, and thus high charge and energy densities of 300 kC l(-1) and 75 W h l(-1) respectively, since the copper(i) ions form an integral part of the electrolyte. A Coulombic efficiency up to 85% could be reached.

Liquid Nickel Salts: Synthesis, Crystal Structure Determination, and Electrochemical Synthesis of Nickel Nanoparticles.

New nickel-containing ionic liquids were synthesized, characterized and their electrochemistry was investigated. In addition, a mechanism for the electrochemical synthesis of nanoparticles from these compounds is proposed. In these so-called liquid metal salts, the nickel(II) cation is octahedrally coordinated by six N-alkylimidazole ligands. The different counter anions that were used are bis(trifluoromethanesulfonyl)imide (Tf2 N(-) ), trifluoromethanesulfonate (OTf(-) ) and methanesulfonate (OMs(-) ). Several different N-alkylimidazoles were considered, with the alkyl sidechain ranging in length from methyl to dodecyl. The newly synthesized liquid metal salts were characterized by CHN analysis, FTIR, DSC, TGA and viscosity measurements. An odd-even effect was observed for the melting temperatures and viscosities of the ionic liquids, with the complexes with an even number of carbon atoms in the alkyl chain of the imidazole having a higher melting temperature and a lower viscosity than the complexes with an odd number of carbons. The crystal structures of several of the nickel(II) complexes that are not liquid at room temperature were determined. The electrochemistry of the compounds with the lowest viscosities was investigated. The nickel(II) cation could be reduced but surprisingly no nickel deposits were obtained on the electrode. Instead, nickel nanoparticles were formed at 100 % selectivity, as confirmed by TEM. The magnetic properties of these nanoparticles were investigated by SQUID measurements.

Electrodeposition of germanium at elevated temperatures and pressures from ionic liquids.

The electrodeposition of germanium at elevated temperatures up to 180 °C and pressures was studied from the ionic liquids 1-butyl-1-methylpyrrolidinium dicyanamide and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide containing [GeCl4(BuIm)2] (where BuIm = 1-butylimidazole) or GeCl4. Cyclic voltammetry (CV), electrochemical quartz crystal microbalance (EQCM), rotating ring-disk electrode (RRDE), scanning electron microscope (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), electron backscatter diffraction (EBSD) and Auger electron spectroscopy (AES) were used to investigate the electrochemical behavior and the properties of the electrodeposited germanium. Electrodeposition at elevated temperatures leads to higher deposition rates due to: (1) increase in the diffusion rate of the electroactive germanium compounds; (2) faster electrochemical kinetics in the electrolyte; and (3) higher electrical conductivity of the electrodeposited germanium film. Moreover, the morphology of the germanium film is also of a better quality at higher electrodeposition temperatures due to an increase in adatom mobility.

Homoleptic and heteroleptic N-alkylimidazole zinc(ii)-containing ionic liquids for high current density electrodeposition.

New homoleptic and heteroleptic zinc(ii)-containing liquid metal salts with N-alkylimidazole (AlkIm) ligands and bis(trifluoromethylsulfonyl)imide (Tf2N(-)) anions are described. The general formulae of the complexes are [Zn(AlkIm)6][Tf2N]2 and [Zn(AlkIm)6-x(AlkIm')x][Tf2N]2. Single-crystal X-ray diffraction revealed that, in the solid state, the cations consist of octahedral zinc(ii) centres. The heteroleptic complexes contain two different N-alkylimidazole ligands. The melting points of the liquid metal salts are below or slightly above room temperature. The dependence of the melting points, viscosity and crystal structure on the alkyl chain length of the N-alkylimidazole ligand for the homoleptic complexes and on the ratio of the two N-alkylimidazole ligands AlkIm and AlkIm' for the heteroleptic compounds is discussed. The possibility of incongruent melting and the presence of a mixture of the four-coordinate zinc(ii) centre and neutral ligands is discussed. The new zinc(ii)-containing liquid metal salts have been used as non-aqueous electrolytes for electrodeposition of zinc. A highly reversible deposition-stripping behaviour was found. Zinc electroplating was possible at very high current densities of more than -200 mA cm(-2) in unstirred solutions. Compact and highly crystalline zinc deposits were obtained.

Electrodeposition of thick palladium coatings from a palladium(II)-containing ionic liquid.

The first palladium-containing Liquid Metal Salts (LMS) are presented and shown to be suitable electrolytes for the electrodeposition of palladium. The homoleptic LMS of formula [Pd(MeIm)4][Tf2N]2 or [Pd(EtIm)4][Tf2N]2 (MeIm = N-methylimidazole, EtIm = N-ethylimidazole) have higher melting points than the heteroleptic [Pd(MeIm)2(EtIm)2][Tf2N]2, which is proved to be the most promising electrolyte. The deposition reaction in these LMS was found to be irreversible but smooth and dense palladium layers can be deposited that are crack-free up to a thickness of 10 microns.

Gallium oxide nanorods: novel, template-free synthesis and high catalytic activity in epoxidation reactions.

Gallium oxide nanorods with unprecedented small dimensions (20-80 nm length and 3-5 nm width) were prepared using a novel, template-free synthesis method. This nanomaterial is an excellent heterogeneous catalyst for the sustainable epoxidation of alkenes with H2 O2 , rivaling the industrial benchmark microporous titanosilicate TS-1 with linear alkenes and being much superior with bulkier substrates. A thorough characterization study elucidated the correlation between the physicochemical properties of the gallium oxide nanorods and their catalytic performance, and underlined the importance of the nanorod morphology for generating a material with high specific surface area and a high number of accessible acid sites.

Carbene formation upon reactive dissolution of metal oxides in imidazolium ionic liquids.

Metal oxides were found to dissolve in different imidazolium ionic liquids with a hydrogen atom in the C2 position of the imidazolium ring, but not if a methyl substituent was present in the C2 position. The crystal structure of the product that crystallised from an ionic liquid containing dissolved silver(i) oxide showed that this was a silver(i) carbene complex. The presence of carbenes in solution was proven by (13)C NMR spectroscopy and the reactions were also monitored by Raman spectroscopy. The dissolution of other metal oxides, namely copper(ii) oxide, zinc(ii) oxide and nickel(ii) oxide, was also studied in imidazolium ionic liquids and it was found that stable zinc(ii) carbenes were formed in solution, but these did not crystallise under the given experimental conditions. A crystalline nickel(ii) carbene complex could be obtained from a solution of nickel(ii) chloride dissolved in a mixture of 1-butyl-3-methylimidazolium and 1-ethyl-3-methylimidazolium acetate.

High current density electrodeposition of silver from silver-containing liquid metal salts with pyridine-N-oxide ligands.

New cationic silver-containing ionic liquids were synthesized and used as non-aqueous electrolytes for the electrodeposition of silver layers. In the liquid state of these ionic liquids, a silver (i) cation is coordinated by pyridine-N-oxide (py-O) ligands in a 1 : 3 metal-to-ligand ratio, although in some cases a different stoichiometry of the silver center crystallized out. As anions, bis(trifluoromethanesulfonyl)imide (Tf2N), trifluoromethanesulfonate (OTf), methanesulfonate (OMs) and nitrate were used, yielding compounds with the formulae [Ag(py-O)3][Tf2N], [Ag(py-O)3][OTf], [Ag(py-O)3][OMs] and [Ag(py-O)3][NO3], respectively. The compounds were characterized by CHN analysis, FTIR, NMR, DSC, TGA and the electrodeposition of silver was investigated by cyclic voltammetry, linear potential scans, scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDX). With the exception of [Ag(py-O)3][Tf2N], which melts at 108 °C, all the silver(i) compounds have a melting point below 80 °C and were tested as electrolytes for silver electrodeposition. Interestingly, very high current densities were observed at a potential of -0.5 V vs. Ag/Ag(+) for the compounds with fluorine-free anions, i.e. [Ag(py-O)3][NO3] (current density of -10 A dm(-2)) and [Ag(py-O)3][OMs] (-6.5 A dm(-2)). The maximum current density of the compound with the fluorinated anion trifluoromethanesulfonate, [Ag(py-O)3][OTf], was much lower: -2.5 A dm(-2) at -0.5 V vs. Ag/Ag(+). Addition of an excess of ligand to [Ag(py-O)3][OTf] resulted in the formation of the room-temperature ionic liquid [Ag(py-O)6][OTf]. A current density of -5 A dm(-2) was observed at -0.5 V vs. Ag/Ag(+) for this low viscous silver salt. The crystal structures of several silver complexes could be determined by X-ray diffraction, and it was found that several of them had a stoichiometry different from the 1 : 3 metal-to-ligand ratio used in their synthesis. This indicates that the compounds form crystals with a composition different from that of the molten state. The electrochemical properties were measured in the liquid state, where the metal-to-ligand ratio was 1 : 3. Single crystal X-ray diffraction measurements showed that silver(i) is six coordinate in [Ag(py-O)3][Tf2N] and [Ag(py-O)3][OTf], while it is five coordinate in the other complexes. In [Ag3(py-O)8][OTf]3, there are two different coordination environments for silver ions: six coordinate central silver ions and five coordinate for the outer silver ions. In some of the silver(i) complexes, silver-silver interactions were observed in the solid state.

Synthesis and properties of alkoxy- and alkenyl-substituted peralkylated imidazolium ionic liquids.

Novel peralkylated imidazolium ionic liquids bearing alkoxy and/or alkenyl side chains have been synthesized and studied. Different synthetic routes towards the imidazoles and the ionic liquids comprising bromide, iodide, methanesulfonate, bis(trifluoromethylsulfonyl)imide ([NTf2](-)), and dicyanamide {[N(CN)2](-)} as the anion were evaluated, and this led to a library of analogues, for which the melting points, viscosities, and electrochemical windows were determined. Incorporation of alkenyl moieties hindered solidification, except for cations with high symmetry. The alkoxy-derivatized ionic liquids are often crystalline; however, room-temperature ionic liquids (RTILs) were obtained with the weakly coordinating anions [NTf2](-) and [N(CN)2](-). For the viscosities of the peralkylated RTILs, an opposite trend was found, that is, the alkoxy derivatives are less viscous than their alkenyl-substituted analogues. Of the crystalline compounds, X-ray diffraction data were recorded and related to their molecular properties. Upon alkoxy substitution, the electrochemical cathodic limit potential was found to be more positive, whereas the complete electrochemical window of the alkenyl-substituted imidazolium salts was shifted to somewhat more positive potentials.

Room-temperature silver-containing liquid metal salts with nitrate anions.

The synthesis, structural, thermal and electrochemical properties of fluorine-free silver-containing ionic liquids are presented. The ionic liquid cations are formed by a silver(i) ion surrounded by two 1-alkylimidazole ligands, with the counter anions being nitrate ions. Depending on the alkyl chain length, the complexes were found to be liquids at room temperature or melting slightly above this. For the solid compounds it was possible to elucidate the structure by single crystal X-ray analysis. The ionic liquids are electroactive, have good mass transport properties and can be used for the electrodeposition of silver at high current densities. The thermal properties and stability of these compounds were tested by differential scanning calorimetry and thermogravimetric analysis. The viscosity of the ionic liquids follows a Vogel-Tamman-Fulcher relationship as a function of temperature. The electrochemical properties of the complexes were tested by cyclic voltammetry and the resulting electrodeposits were examined using scanning electron microscopy and atomic force microscopy.

Bis(ethyl-eneglycolato-κ(2) O,O')tellurium(IV).

The title compound, C4H8O4Te, crystallized from a solution of Te(4+) in ethyl-ene glycol. The Te(IV) atom is in a distorted seesaw coordination defined by four O atoms from two different ethyl-eneglycate ligands. The C atoms of the ethyl-eneglycate ligands are disorderd over two positions, with population parameters of 50.3 (6) and 49.7 (6)% indicating a statistical distribution. Due to the possibility to transform the primitive monoclinic unit cell into a metrically ortho-rhom-bic C unit cell, the data are twinned and were refined with the twin law -100/0-10/101 with the relative scale factor refining to 1.82 (4)% for the minor component.

Monomer-to-polymer conversion and micro-tensile bond strength to dentine of experimental and commercial adhesives containing diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide or a camphorquinone/amine photo-initiator system.

OBJECTIVES: To compare the degree of conversion (DC) of adhesives initiated by diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) or a camphorquinone/tertiary amine system (CQ/Amine) as well as their 'immediate' micro-tensile bond strength (µTBS) to bur-cut dentine. METHODS: DC of Scotchbond Universal ('SBU'; 3M ESPE), its experimental counterpart containing TPO as photo-initiator system, an experimental G-aenial Bond ('Ga-B'; GC) adhesive formulation, and an experimental LUB-102 adhesive formulation ('LUB', Kuraray Noritake), containing as photo-initiatior system either 2wt% CQ along with 2wt% tertiary amine ('SBU_CQ/Amine'; 'Ga-B_CQ/Amine'; 'LUB_CQ/Amine'), or 2wt% TPO ('SBU_TPO'; 'Ga-B_TPO'; 'LUB_TPO'), was determined using Fourier-transform infrared spectroscopy (FTIR), after being cured with a dual-wavelength light-curing unit (bluephase 20i, Ivoclar Vivadent). The same adhesive formulations were applied to bur-cut mid-coronal dentine of intact human molars, and subjected to a µTBS test after 1-week water storage. Besides being applied following a self-etch (SE) application mode, the adhesive formulations SBU_CQ/Amine and SBU_TPO were also applied following an etch-and-rinse (E&R) mode, this both for DS and µTBS measurement. RESULTS: No significant difference in DC was found for any of the adhesive formulations, except for SBU_CQ/Amine_SE and SBU_TPO_SE. For both SBU formulations, a significantly higher DC was reached for the E&R than the SE approach. Regarding µTBS, no significant differences were recorded, except for the significantly higher µTBS measured for SBU_CQ/Amine_E&R and SBU_TPO_E&R. CONCLUSIONS: In self-etch adhesives, the photo-initiator TPO may be used instead of CQ/Amine. The curing and 'immediate' bonding efficiency depended on the application protocol (E&R versus SE), but not on the photo-initiator system. CLINICAL SIGNIFICANCE: The photo-initiator TPO may be used in self-etch adhesives instead of CQ/Amine with similar curing and 'immediate' bonding efficiency.

Electrodeposition of germanium from the ionic liquid 1-butyl-1-methylpyrrolidinium dicyanamide.

The electrodeposition of germanium from the ionic liquid 1-butyl-1-methylpyrrolidinium dicyanamide ([BMP][DCA]) and a mixture of [BMP][DCA] and 1-butyl-1-methylpyrrolidinium chloride ([BMP]Cl) was studied using cyclic voltammetry and using an electrochemical quartz crystal microbalance (EQCM). [GeCl4(BuIm)2] (BuIm = N-butylimidazole) was used as germanium source as it has a solubility of 0.47 M, up to 13 times the solubility of GeCl4 in [BMP][DCA]. Cyclic voltammograms show an irreversible electrochemical behavior and two reduction waves were observed. The wave at the more positive potential was assigned to the reduction of Ge(4+) to Ge(2+). The wave at the more negative potential was attributed to the formation of Ge(0). The diffusion coefficient of Ge(4+) in [BMP][DCA] containing 0.1 M [GeCl4(BuIm)2] is 1.1 × 10(-12) m(2) s(-1), and the exchange current density is 2 × 10(-4) A m(-2) at 50 °C. Polymerization of dicyanamide anions took place at the anode in the solution of [BMP][DCA]. The polymerization reaction could be avoided by using an equimolar [BMP]Cl-[BMP][DCA] mixture as electrolyte. Smooth, porous germanium films were electrodeposited on both copper and silicon substrates.

Continuous synthesis of peralkylated imidazoles and their transformation into ionic liquids with improved (electro)chemical stabilities.

A versatile and efficient method to synthesize tetrasubstituted imidazoles via a one-pot modified Debus-Radziszewski reaction and their subsequent transformation into the corresponding imidazolium ionic liquids is reported. The tetrasubstituted imidazoles were also synthesized by means of a continuous flow process. This straightforward synthetic procedure allows for a fast and selective synthesis of tetrasubstituted imidazoles on a large scale. The completely substituted imidazolium dicyanamide and bis(trifluoromethylsulfonyl)imide salts were obtained via a metathesis reaction of the imidazolium iodide salts. The melting points and viscosities are of the same order of magnitude as for their non-substituted analogues. In addition to the superior chemical stability of these novel ionic liquids, which allows them to be applied in strong alkaline media, the improved thermal and electrochemical stabilities of these compounds compared with conventional imidazolium ionic liquids is also demonstrated by thermogravimetrical analysis (TGA) and cyclic voltammetry (CV). Although increased substitution of the ionic liquids does not further increase thermal stability, a definite increase in cathodic stability is observable.

Heteroleptic silver-containing ionic liquids.

The first examples of structurally characterised mixed-ligand metal-containing ionic liquids (ILs) are presented, synthesised by the use of different N-alkylimidazoles. The cations consist of two-coordinate silver(i) centres ligated by two different N-alkylimidazole ligands. It is shown that the resulting ionic liquids have lower melting points than the single ligand ILs.

Speciation of copper(II) complexes in an ionic liquid based on choline chloride and in choline chloride/water mixtures.

A deep-eutectic solvent with the properties of an ionic liquid is formed when choline chloride is mixed with copper(II) chloride dihydrate in a 1:2 molar ratio. EXAFS and UV-vis-near-IR optical absorption spectroscopy have been used to compare the coordination sphere of the cupric ion in this ionic liquid with that of the cupric ion in solutions of 0.1 M of CuCl(2)·2H(2)O in solvents with varying molar ratios of choline chloride and water. The EXAFS data show that species with three chloride ions and one water molecule coordinated to the cupric ion as well as species with two chloride molecules and two water molecules coordinated to the cupric ion are present in the ionic liquid. On the other hand, a fully hydrated copper(II) ion is formed in an aqueous solution free of choline chloride, and the tetrachlorocuprate(II) complex forms in aqueous choline chloride solutions with more than 50 wt % of choline chloride. In solutions with between 0 and 50 wt % of choline chloride, mixed chloro-aquo complexes occur. Upon standing at room temperature, crystals of CuCl(2)·2H(2)O and of Cu(choline)Cl(3) formed in the ionic liquid. Cu(choline)Cl(3) is the first example of a choline cation coordinating to a transition-metal ion. Crystals of [choline](3)[CuCl(4)][Cl] and of [choline](4)[Cu(4)Cl(10)O] were also synthesized from molecular or ionic liquid solvents, and their crystal structures were determined.

High current density electrodeposition from silver complex ionic liquids.

Liquid metal salts are electrolytes with the highest possible metal concentration for electrodeposition, because the metal ion is an integral part of the solvent. This paper introduces the new ionic silver complexes [Ag(MeCN)(4)](2)[Ag(Tf(2)N)(3)], [Ag(MeCN)][Tf(2)N] and [Ag(EtIm)(2)][Tf(2)N], where MeCN stands for acetonitrile, EtIm for 1-ethylimidazole and Tf(2)N is bis(trifluoromethylsulfonyl)imide. These complexes have been characterized by differential scanning calorimetry, single crystal X-ray crystallography, thermogravimetrical analysis, Raman spectroscopy and cyclic voltammetry. [Ag(MeCN)(4)](2)[Ag(Tf(2)N)(3)] is a room temperature ionic liquid. Smooth silver layers of good quality could be deposited from it, at current densities of up to 25 A dm(-2) in unstirred solutions. [Ag(EtIm)(2)][Tf(2)N] melts at 65 °C and can be used as an electrolyte for silver deposition above this temperature. [Ag(MeCN)][Tf(2)N] has a melting point that is too high to be useful in electrodeposition. Addition of thiourea or 1H-benzotriazole to the electrolyte decreased the surface roughness of the silver coatings. The morphology of the metal layers was investigated by atomic force microscopy (AFM). Adsorption of 1H-benzotriazole on the silver metal surface has been proven by Raman spectroscopy. This work shows the usefulness of additives in improving the quality of metal films electrodeposited from ionic liquids.