Douglas R. MacFarlane

University of Vic, Vic, Catalonia, Spain

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Publications (580)2456.54 Total impact

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    ABSTRACT: Ambient temperature sodium batteries hold the promise of a new generation of high energy density, low-cost energy storage technologies. Particularly challenging in sodium electrochemistry is achieving high stability at high charge/discharge rates. We report here mixtures of inorganic/organic cation fluorosulfonamide (FSI) ionic liquids that exhibit unexpectedly high Na+ transference numbers due to a structural diffusion mechanism not previously observed in this type of electrolyte. The electrolyte can therefore support high current density cycling of sodium. We investigate the effect of NaFSI salt concentration in methylpropylpyrrolidinium (C3mpyr) FSI ionic liquid (IL) on the reversible plating and dissolution of sodium metal, both on a copper electrode and in a symmetric Na/Na metal cell. NaFSI is highly soluble in the IL allowing the preparation of mixtures that contain very high Na contents, greater than 3.2 mol/kg (50 mol%) at room temperature. Despite the fact that overall ion diffusivity decreases substantially with increasing alkali salt concentration, we have found that these high Na+ content electrolytes can support higher current densities (1mA/cm2) and greater stability upon continued cycling. EIS measurements indicate that the interfacial impedance is decreased in the high concentration systems, which provides for a particularly low-resistance solid-electrolyte interphase (SEI), resulting in faster charge transfer at the interface. Na+ transference numbers determined by the Bruce-Vincent method increased substantially with increasing NaFSI content, approaching > 0.3 at the saturation concentration limit which may explain the improved performance. NMR spectroscopy, PFG diffusion measurements and molecular dynamics simulations reveal a changeover to a facile structural diffusion mechanism for sodium ion transport at high concentrations in these electrolytes.
    No preview · Article · Feb 2016 · The Journal of Physical Chemistry C

  • No preview · Article · Jan 2016 · ACS Sustainable Chemistry & Engineering
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    Full-text · Article · Jan 2016
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    ABSTRACT: Carbon dioxide (CO2) chemical absorption and regeneration was investigated in two diamino carboxylate protic ionic liquids (PILs), dimethylethylenediamine formate (DMEDAH formate) and dimethylpropylenediamine acetate (DMPDAH acetate), using novel calorimetric techniques. The PILs under study have previously been shown to possess a CO2 absorption capacity similar to the industrial standard, 30% aqueous MEA, while requiring much lower temperatures to release the captured CO2. We show that this is in part due to the fact that the PILs exhibit enthalpies of CO2 desorption as low as 40 kJ mol(-1), significantly lower than the 85 kJ mol(-1) required for 30% aqueous MEA. Computational and spectroscopic analyses were used to probe the mechanism of CO2 capture, which was found to proceed via the formation of carbamate moieties on the primary amine of both DMEDAH and DMPDAH. Evidence was also found that weakly acidic counter-ions such as formate and acetate provide, unexpectedly, an additional proton acceptor site in the traditional carbamate mechanism, revealing opportunities to increase CO2 uptake capacity in the future through careful design of the anion and cation used in the PIL capture agent.
    No preview · Article · Jan 2016 · Physical Chemistry Chemical Physics
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    ABSTRACT: High-energy density Zinc-air batteries are currently of interest since they could play a key role in emerging large-scale energy storage applications. However, achieving good rechargeability of such metal-air batteries requires significant further research and development effort. Room Temperature Ionic liquids (RTILs) offer a number of ideal thermal and physical properties as potential electrolytes for large-scale energy storage applications and thus, can help increase the practicality of such electrochemical devices. This paper reports the synthesis and application of three novel quaternary alkoxy ammonium bis(trifluoromethylsulfonyl)amide based RTILs, with two or more ether functional groups designed to interact and solubilize zinc ions, in order to aid in the electrochemical reversibility of the metal. The anion is successfully reduced from, and re-oxidized into, the three alkoxy ammonium RTILs suggesting that they are potential candidates as electrolytes for use in zinc-air batteries. Cyclic voltammetry reveals that the presence of water reduces the activation barrier required to deposit zinc and assists stable charge/discharge cycling in an electrolyte consisting of 0.1 M Zn(NTf2)2 in the tri-alkoxy ammonium chain RTIL, [N2(20201)(20201)(20201)] [NTf2], with 2.5 wt.% H2O. Further experiments demonstrate that with such electrolyte a Zn electrode can complete at least 750 cycles at a current density of 0.1 mA/cm2 at room temperature. Crown
    No preview · Article · Dec 2015
  • Raimund Koerver · Douglas R. MacFarlane · Jennifer M. Pringle
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    ABSTRACT: Recent advances in thermoelectrochemical cells, which are being developed for harvesting low grade waste heat, have shown the promise of cobalt bipyridyl salts as the active redox couple. The Seebeck coefficient, Se, of a redox couple determines the open circuit voltage achievable, for a given temperature gradient, across the thermoelectrochemical cell. Thus, the accurate determination of this thermodynamic parameter is key to the development and study of new redox electrolytes. Further, techniques for accurate determination of Se using only one half of the redox couple reduces the synthetic requirements. Here, we compare three different experimental techniques for measuring Se of a cobalt tris(bipyridyl) redox couple in ionic liquid electrolytes. The use of temperature dependent cyclic voltammetry (CV) in isothermal and non-isothermal cells was investigated in depth, and the Se values compared to those from thermo-electromotive force measurements. Within experimental error, the Se values derived from CV methods were found to be in accordance with those obtained from electromotive force (emf) measurements. The applicability of cyclic voltammetry techniques for determining Se when employing only one part of the redox couple was demonstrated.
    No preview · Article · Dec 2015
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    ABSTRACT: Cholinium-based ionic liquids made of aminoate anions ([Ch][AA] ILs) have been proven to have low toxicity and to be readily biodegradable. This class of ILs has great potential as a novel phase-forming component for aqueous two-phase system (ATPS) used in protein separation. In this study, environmentally benign ATPSs were prepared by using a series of [Ch][AA] ILs (where [AA] = lysinate, β-alaninate, glycinate, serinate) with a thermo-separable polypropylene glycol 400 (PPG 400). These [AA] anion components differ in both hydrophobicity and acid/base behavior, allowing a tunable response to the pH of the ATPS. By using the effective excluded volume theory, the phase-separation abilities of the different [Ch][AA]-based ATPSs were determined, and the trends showed good agreement with the [AA] anion hydration capacities. The partition behavior of a model protein, i.e., bovine serum albumin (BSA), was investigated by measuring the IL-rich (bottom) phase extraction efficiency and partition coefficient. The results showed that the partition behavior of the protein was governed by the hydrophobicity of the [AA] anion, whereby the BSA showed a greater affinity toward the IL-rich phase comprising a less hydrophobic [AA] anion. Furthermore, the effect of pH on the partition behavior of model proteins (i.e., BSA and trypsin) was investigated. When the pH of the system is greater than the isoelectric point pI of the model proteins and the [AA] anion, the model proteins are found to be mainly partitioned to the bottom phase. However, at a pH below the pI of the model proteins and the pI of the [AA] anion, the partitioning of model proteins favored the polymer-rich top phase. Overall, our findings demonstrate the flexibility possible in directing the target protein to a desired phase in ATPS through a proper selection of the IL's hydrophobicity and [AA] anion.
    No preview · Article · Oct 2015 · ACS Sustainable Chemistry & Engineering
  • Sowmiya Theivaprakasam · Douglas R MacFarlane · Sagar Mitra
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    ABSTRACT: The electrochemistry of the electrolyte plays a significant role in the performance of lithium ion batteries. In order to further investigate the effect of combining an ionic liquid with a conventional electrolyte, a hybrid electrolyte (HE) based on a mixture of 38% N-methyl-N-propyl-pyrrolidinium bis(trifluromethanesulfonyl) imide in an electrolyte consisting of LiPF6 in Ethylene Carbonate: Diethyl Carbonate (1:1) was studied and compared with the properties of a standard organic electrolyte in this work. Thermal measurements reveal that the addition of the ionic liquid improves the thermal stability of the hybrid electrolyte. The interfacial behavior was studied in lithium symmetric cells and it was found that the combined effects of the ionic liquid and the conventional electrolyte results in lower interfacial resistance. The charge-discharge behaviour of LiFePO4 / Li cells was investigated; at the end of 100 cycles, the discharge capacity of the cell with LP30, HE and [C3mpyr][TFSI] was 141 mAh/g, 148 mAh/g and 45mAh/g, respectively. Analysis of the separator recovered from Li/LiFePO4 cells that had been stored for 30 days at 20°C shows iron dissolution from the cathode into the LP30 electrolyte, but not into the hybrid electrolyte. Posthumous studies of the cycled electrodes were carried out using FTIR, XRD, FEG-SEM and HR-TEM analyses, show that the HE forms a permeable interface on the cathode material which prevents metal dissolution from the cathode structure, leading to better cyclic performance.
    No preview · Article · Oct 2015 · Electrochimica Acta
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    ABSTRACT: Coal solubilisation is often a necessary step for the alternative utilisation of the cheap and abundant brown coal resources in the State of Victoria, Australia, such as producing high quality fuel or chemicals. A series of ionic liquids (ILs), ammonium carbamates, formed by the association of carbon dioxide (CO2) with low molecular weight secondary amines, were investigated as solvents for the solubilisation of Victorian brown coal. The ionic liquid was mixed with a Loy Yang coal at a mass ratio of 20 to 1 (dry basis) for 24 h at ambient temperature. The solubilisation yields of the coal using three such ILs from dimethyl-, diallyl- and dipropyl-amines, respectively, were between 18% and 23%. Repeated solubilisation of the coal with fresh solvent achieved higher yields, with the highest at 66% by the carbamate formed from dimethylamine (DIMCARB). The variations in chemical structure between the products were compared by elemental analysis and a variety of spectroscopic techniques (FTIR, Solid State 13C NMR and Py-GC-MS). The soluble products of the initial solubilisation were more aliphatic than their parent coal. The less polar ILs formed from diallyl- and dipropyl-amines (DACARB and DPCARB) appeared to be more selective for high molecular weight triterpenoids than DIMCARB. Subsequent treatment tended to dissolve more aromatic components.
    No preview · Article · Oct 2015 · Fuel
  • Manoj A Lazar · Danah Al-Masri · Douglas R MacFarlane · Jennifer M Pringle
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    ABSTRACT: Thermoelectrochemical cells are increasingly promising devices for harvesting waste heat, offering an alternative to the traditional semiconductor-based design. Advancement of these devices relies on new redox couple/electrolyte systems and an understanding of the interplay between the different factors that dictate device performance. The Seebeck coefficient (Se) of the redox couple in the electrolyte gives the potential difference achievable for a given temperature gradient across the device. Prior work has shown that a cobalt bipyridyl redox couple in ionic liquids (ILs) displays high Seebeck coefficients, but the thermoelectrochemical cell performance was limited by mass transport. Here we present the Se and thermoelectrochemical power generation performance of the cobalt couple in novel mixed IL/molecular solvent electrolyte systems. The highest power density of 880 mW m(-2), at a ΔT of 70 °C, was achieved with a 3 : 1 (v/v) MPN-[C2mim][B(CN)4] electrolyte combination. The significant power enhancement compared to the single solvent or IL systems results from a combination of superior ionic conductivity and higher diffusion coefficients, shown by electrochemical analysis of the different electrolytes. This is the highest power output achieved to-date for a thermoelectrochemical cell utilising a high boiling point redox electrolyte.
    No preview · Article · Sep 2015 · Physical Chemistry Chemical Physics
  • Jiaye Li · Haijin Zhu · Xiaoen Wang · Douglas R. MacFarlane · Michel Armand · Maria Forsyth
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    ABSTRACT: Solid-state polymer electrolytes, as an alternative to traditional liquid electrolytes, have been intensively investigated for energy conversion and storage devices. The transport rate of single ions is the key to their high performance. For application in emerging sodium batteries, we have developed three dual-cation polymeric ionomers, which contain bulky tetraalkylammonium ions in addition to the sodium ion. The sizes and relative contents of the ammonium ions vary relative to the sodium ion contents. Comparative studies of ion dynamics, thermal properties, phase behaviours and ionic conductivities were carried out, taking advantage of various spectroscopic and thermal chemistry methods. The ion conductivities of the ionomers are greatly enhanced by the introduction of bulky counterions, as a result of the additional free volume and decreased sodium ion association. Raman spectroscopy and thermal analysis as well as the solid-state nuclear magnetic resonance studies are used to probe the conductivity behaviour. This journal is
    No preview · Article · Aug 2015 · Journal of Materials Chemistry A
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    ABSTRACT: The physical absorption of CO2 by protic and aprotic ionic liquids such as 1-ethyl-3-methyl-imidazolium tetrafluoroborate was examined at the molecular level using symmetry adapted perturbation theory (SAPT) and density functional techniques through comparison of interaction energies of non-covalently bound complexes between the CO2 molecule and a series of ionic liquid ions and ion pairs. These energies were contrasted to complexes with model amines such as methylamine, dimethylamine and trimethylamine. Detailed analysis of the five fundamental forces that are responsible for stabilization of the complexes is discussed. It was confirmed that the nature of the anion had a greater effect upon the physical interaction energy in non functionalised ionic liquids, with dispersion forces playing an important role in CO2 solubility. Hydrogen bonding with protic cations was shown to impart additional stability to the non-covalently bound CO2···IL complex through inductive forces. Two solvation models, the Conductor-like Polarisable Continuum Model (CPCM) and the Universal Solvation Model (SMD), were used to estimate the impact of solvent effects on the CO2 binding. Both solvent models reduced interaction energies for all types of ions. These interaction energies appeared to favour imidazolium cations and carboxylic and sulfonic groups as well as bulky groups (e.g. NTf2) in anions for the physical absorption of CO2. The structure-reactivity relationships determined in this study may help in the optimization of the physical absorption process by means of ionic liquids.
    No preview · Article · Aug 2015 · The Journal of Physical Chemistry B
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    Tristan J. Simons · Andrew K. Pearson · Steven J. Pas · Douglas R. MacFarlane
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    ABSTRACT: The electrochemical behavior and deposition morphology of Pb2+ was investigated in the Room Temperature Ionic Liquid (RTIL) 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide ([C2mim][NTf2]) containing the salt Pb(NTf2)2. Cyclic Voltammetry (CV) experiments were found to result in a range of electrochemical responses depending on the working electrode material being used, with both Pt and Pb based electrodes showing the highest current and lowest overpotential for deposition, respectively. Pb was found to undergo a single diffusion controlled reduction process at a coulombic efficiency of 95 % on a Pt working electrode. The deposition of Pb was found to follow a 3 dimensional progressive nucleation mechanism, regardless of the substrate material or the temperature during the experiment. During the deposition, the diffusion coefficient of Pb2+ was found to be 1.3 × 10−7 cm2.s−1 by chronoamperometric analysis. Finally, the resulting morphologies of the Pb metal deposits were found to be heavily dependent on the deposition substrate, ranging from pyramids of 3 μm in diameter on Pt, to fine sub-micron interwoven needles on glassy carbon. Interestingly, the potential of deposition appeared to make little difference to the resulting morphology on Cu substrates. Finally, to demonstrate the cycling ability of the Pb metal surfaces, Pb was cycled on Pb electrodes 200 times, showing that the resulting Pb films were compact and non-dendritic in nature. It is concluded that [C2mim][NTf2] containing Pb(NTf2)2 shows many favourable cycling characteristics.
    Full-text · Article · Aug 2015 · Electrochimica Acta
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    ABSTRACT: The tris(2,2′-bipyridyl) complexes of cobalt(II) and (III) ([Co(bpy)3]2+/3+) produce a redox couple of great interest in thermoelectrochemical cells and dye sensitized solar cells including both types of devices based on ionic liquid electrolytes. We present a systematic study of the electrochemistry of [Co(bpy)3]2+ [NTf2]-2 in two ionic liquids (ILs) based on the 1-ethyl-3-methylimidazolium (C2mim) cation and two ILs based on the 1-butyl-1-methylpyrrolidinium cation (C4mpyr), as well as three aprotic molecular solvents. Platinum (Pt) and glassy carbon (GC) working electrodes were compared. In all solvents better electrochemical responses were observed on GC, which yielded higher currents in the cyclic voltammograms and lower rate constants for the redox reaction. The [Co(bpy)3]1+/2+ couple is also readily observed, but this redox reaction is chemically irreversible, possibly because the [Co(bpy)3]1+ complex dissociates. However, the [Co(bpy)3]1+/2+ reaction is chemically reversible in all of the solvents studied, except 3-methoxypropionitrile, if excess of 2,2′-bipyridyl is added to the solution.
    No preview · Article · Aug 2015 · Electrochimica Acta
  • Haitao Li · Chenghua Sun · Muataz Ali · Fengling Zhou · Xinyi Zhang · Douglas R. MacFarlane
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    ABSTRACT: Acid catalytic processes play a classic and important role in modern organic synthesis. How well the acid can be controlled often plays the key role in the controllable synthesis of the products with high conversion yield and selectivity. The preparation of a novel, photo-switchable solid-acid catalyst based on carbon quantum dots is described. The carbon quantum dots are decorated with small amounts of hydrogensulfate groups and thus exhibit a photogenerated acidity that produces a highly efficient acid catalysis of the ring opening of epoxides with methanol and other primary alcohols. This reversible, light-switchable acidity is shown to be due to photoexcitation and charge separation in the carbon quantum dots, which create an electron withdrawing effect from the acidic groups. The catalyst is easily separated by filtration, and we demonstrate multiple cycles of its recovery and reuse.
    No preview · Article · Jun 2015 · Angewandte Chemie
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    Haitao Li · Chenghua Sun · Muataz Ali · Fengling Zhou · Xinyi Zhang · Douglas R. MacFarlane
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    ABSTRACT: Acid catalytic processes play a classic and important role in modern organic synthesis. How well the acid can be controlled often plays the key role in the controllable synthesis of the products with high conversion yield and selectivity. The preparation of a novel, photo-switchable solid-acid catalyst based on carbon quantum dots is described. The carbon quantum dots are decorated with small amounts of hydrogensulfate groups and thus exhibit a photogenerated acidity that produces a highly efficient acid catalysis of the ring opening of epoxides with methanol and other primary alcohols. This reversible, light-switchable acidity is shown to be due to photoexcitation and charge separation in the carbon quantum dots, which create an electron withdrawing effect from the acidic groups. The catalyst is easily separated by filtration, and we demonstrate multiple cycles of its recovery and reuse. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Full-text · Article · Jun 2015 · Angewandte Chemie International Edition
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    ABSTRACT: Manganese oxides (MnOx ) are considered to be promising catalysts for water oxidation. Building on our previous studies showing that the catalytic activity of MnOx films electrodeposited from aqueous electrolytes is improved by a simple heat treatment, we have explored the origin of the catalytic enhancement at an electronic level by X-ray absorption spectroscopy (XAS). The Mn L-edge XA spectra measured at various heating stages were fitted by linear combinations of the spectra of the well-defined manganese oxides-MnO, Mn3 O4 , Mn2 O3 , MnO2 and birnessite. This analysis identified two major manganese oxides, Mn3 O4 and birnessite, that constitute 97 % of the MnOx films. Moreover, the catalytic improvement on heat treatment at 90 °C is related to the conversion of a small amount of birnessite to the Mn3 O4 phase, accompanied by an irreversible dehydration process. Further dehydration at higher temperature (120 °C), however, leads to a poorer catalytic performance. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Full-text · Article · May 2015 · ChemSusChem
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    ABSTRACT: Ionic liquids formed by association of carbon dioxide (CO2) with low molecular weight secondary amines to form carbamate salts (e.g. N,N-dimethylammonium N′,N′-dimethylcarbamates, or DIMCARB) as solvents have been identified as ‘distillable’ as they reform their volatile precursor components upon heating at relatively low temperature and, thus, can be recovered by condensation. DIMCARB was selected for the solubilisation of a number of Victorian brown coals including Loy Yang coal, a dark, a medium light and a light lithotype and a Yallourn woody coal. The coal was mixed with DIMCARB at a mass ratio of 1:20 for 24 h at room temperature. The soluble product was recovered by centrifugation followed by acid washing to remove residual DIMCARB. The solubilisation yields achieved were between 10% and 63% in the order of woody coal < dark lithotype < medium light lithotype < Loy Yang < light lithotype. The soluble and non-soluble products were characterised by FTIR, NMR and pyrolysis GC–MS. Results revealed a positive correlation between the solubility and aliphatic content in the coals. Polycyclic aliphatic and aromatic compounds, specifically the triterpenoid group, were selectively dissolved by DIMCARB.
    Full-text · Article · May 2015 · Fuel
  • Yogita V. Oza · Douglas R. MacFarlane · Maria Forsyth · Luke A. O’Dell
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    ABSTRACT: Two sulfonated ionomers based on poly(triethylmethyl ammonium 2-acrylamido-2-methyl-1-propane sulfonic acid) (PAMPS) and containing mixtures of Li+ and quaternary ammonium cations are characterised. The first system contains Li+ and the methyltriethyl ammonium cation (N1222) in a 1:9 molar ratio, and the 7Li NMR line widths showed that the Li+ ions are mobile in this system below the glass transition temperature (105 °C) and are therefore decoupled from the polymer segmental motion. The conductivity in this system was measured as 10−5 Scm−1 at 130 °C. A second PAMPS system containing Li+ and the dimethylbutylmethoxyethyl ammonium cation (N114(2O1)) in a 2:8 molar ratio showed much lower conductivities despite a significantly lower Tg (60 °C), possibly due to associations between the Li+ and the ether group on the ammonium cation, or between the latter cations and the sulfonate groups.
    No preview · Article · Apr 2015 · Electrochimica Acta
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    ABSTRACT: Efficient catalysis of water oxidation represents one of the major challenges en route to efficient sunlight-driven water splitting. Cobalt oxides (CoOx ) have been widely investigated as water oxidation catalysts, although the incorporation of these materials into photoelectrochemical devices has been hindered by a lack of transparency. Herein, the electrosynthesis of transparent CoOx catalyst films is described by utilizing cobalt(II) aminopolycarboxylate complexes as precursors to the oxide. These complexes allow control over the deposition rate and morphology to enable the production of thin, catalytic CoOx films on a conductive substrate, which can be exploited in integrated photoelectrochemical devices. Notably, under a bias of 1.0 V (vs. Ag/AgCl), the film deposited from [Co(NTA)(OH2 )2 ](-) (NTA=nitrilotriacetate) decreased the transmission by only 10 % at λ=500 nm, but still generated >80 % of the water oxidation current produced by a [Co(OH2 )6 ](2+) -derived oxide film whose transmission was only 40 % at λ=500 nm. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    No preview · Article · Mar 2015 · ChemSusChem

Publication Stats

20k Citations
2,456.54 Total Impact Points


  • 1988-2015
    • University of Vic
      Vic, Catalonia, Spain
  • 1986-2015
    • Monash University (Australia)
      • • Department of Materials Engineering, Clayton
      • • School of Chemistry, Clayton
      • • Centre for Green Chemistry
      • • Centre for Reproduction and Development
      Melbourne, Victoria, Australia
  • 2006-2014
    • University of Wollongong
      • ARC Centre of Excellence for Electromaterials Science
      City of Greater Wollongong, New South Wales, Australia
  • 2007
    • Sophia University
      • Division of Chemistry
      Edo, Tōkyō, Japan
  • 1989-2004
    • Monash University (Malaysia)
      Labuan, Labuan, Malaysia