Roger J. Mortimer

Loughborough University, Loughborough, England, United Kingdom

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Publications (68)204.5 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Aerosol-assisted chemical vapor deposition (AACVD) was used for the first time in the preparation of thin-film electrochromic nickel(II) oxide (NiO). The as-deposited films were cubic NiO, with an octahedral-like grain structure, and an optical band gap that decreased from 3.61 to 3.48 eV on increase in film thickness (in the range 500-1000 nm). On oxidative voltammetric cycling in aqueous KOH (0.1 mol dm(-3)) electrolyte, the morphology gradually changed to an open porous NiO structure. The electrochromic properties of the films were investigated as a function of film thickness, following 50, 100, and 500 conditioning oxidative voltammetric cycles in aqueous KOH (0.1 mol dm(-3)). Light modulation of the films increased with the number of conditioning cycles. The maximum coloration efficiency (CE) for the NiO (transmissive light green, the "bleached" state) to NiOOH (deep brown, the colored state) electrochromic process was found to be 56.3 cm(2) C(-1) (at 450 nm) for films prepared by AACVD for 15 min followed by 100 "bleached"-to-colored conditioning oxidative voltammetric cycles. Electrochromic response times were <10 s and generally longer for the coloration than the bleaching process. The films showed good stability when tested for up to 10 000 color/bleach cycles. Using the CIE (Commission Internationale de l'Eclairage) system of colorimetry the color stimuli of the electrochromic NiO films and the changes that take place on reversibly oxidatively switching to the NiOOH form were calculated from in situ visible spectra recorded under electrochemical control. Reversible changes in the hue and saturation occur on oxidation of the NiO (transmissive light green) form to the NiOOH (deep brown) form, as shown by the track of the CIE 1931 xy chromaticity coordinates. As the NiO film is oxidized, a sharp decrease in luminance was observed. CIELAB L*a*b* coordinates were also used to quantify the electrochromic color states. A combination of a low L* and positive a* and b* values quantified the perceived deep brown colored state.
    ACS Applied Materials & Interfaces 06/2013; · 5.90 Impact Factor
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    ABSTRACT: Prussian-blue (PB) film for electro-chromism can be electro-deposited on to an electrode (usually tin-doped indium oxide/glass) either directly from a PB colloid or from ferric ferricyanide in a two-electrode electro-chemical cell by applying a reductive potential. Alternatively, a “sacrificial” electron-producing silver flag electrode in the solution, when connected to the PB-receiving electrode, can effect the required reductive deposition. A silver spot, here innovatively applied as silver paint directly onto the deposition electrode, produces PB film on immersion in the iron(III)(III) solution, obviating the separate counter-electrode method.
    Journal of Solid State Electrochemistry 12/2012; 16(12). · 2.28 Impact Factor
  • Roger J. Mortimer, Thomas S. Varley
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    ABSTRACT: A novel color-reinforcing electrochromic device (ECD) is described in which the anode and cathode reactions simultaneously exhibit reversible colorless to intense purple changes. Under coloration, the mixed-valence iron(III) hexacyanoruthenate(II) chromophore is formed on oxidation of iron(II) hexacyanoruthenate(II), with simultaneous reduction of the methyl viologen dication to form a mixture of the radical cation monomer/dimer. Using the CIE (Commission Internationale de l’Eclairage) system of colorimetry, the color stimulus of such ECDs and the changes that take place on reversibly switching between the colored and colorless states have been calculated from in situ visible spectra recorded under electrochemical control. On ECD color switching, with the excellent color-matching between the two purple states, sharp and reversible changes in the hue and saturation occur, as shown by the minimal hysteresis of the track of the CIE 1931 xy chromaticity coordinates. Extrapolation of the xy track to the color locus gave a complementary wavelength (λc) of 565 (±5) nm in close agreement with values obtained for the individual electrochromic materials. The concentration of the solution-phase methyl viologen and its diffusion to the cathode controlled both the proportion of surface-confined Ruthenium purple (RP) that is switched to the intense purple form and the overall ECD changes. For the ECDs’ “on” states, the CIELAB 1976 color space coordinates were L* = 86, a* = 9, and b* = −15, and L* = 79, a* = 15, and b* = −22, respectively, for 5 and 10 mmol dm–3 methyl viologen solution concentrations. CIELAB 1976 color space coordinates showed that the ECDs were fully transparent and colorless in the “off” states, with L* = 100, a* = 0, and b* = 0. Switching times, as estimated for 95% of the total absorbance change, were 4 and 10 s respectively, for coloration and bleaching for the 5 mmol dm–3 methyl viologen ECD, and 8 and 16 s for the 10 mmol dm–3 methyl viologen ECD.Keywords: electrochromic; electrochromism; ruthenium purple; methyl viologen; CIE chromaticity coordinates; colorimetry
    Chemistry of Materials. 08/2011; 23(17).
  • Roger J. Mortimer
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    ABSTRACT: Electrochromic materials have the property of a change, evocation, or bleaching of color as effected either by an electron-transfer (redox) process or by a sufficient electrochemical potential. The main classes of electrochromic materials are surveyed here, with descriptions of representative examples from the metal oxides, viologens (in solution and as adsorbed or polymeric films), conjugated conducting polymers, metal coordination complexes (as polymeric, evaporated, or sublimed films), and metal hexacyanometallates. Examples of the applications of such electrochromic materials are included. Other materials aspects important for the construction of electrochromic devices include optically transparent electrodes, electrolyte layers, and device encapsulation. Commercial successes, current trends, and future challenges in electrochromic materials research and development are summarized.
    Chemical Society Reviews 07/2011; 41:241-268. · 24.89 Impact Factor
  • Roger J. Mortimer, Thomas S. Varley
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    ABSTRACT: The development of a Microsoft® Excel® spreadsheet is described, for the accurate calculation of CIE (Commission Internationale de l’Eclairage) 1931 xy chromaticity coordinates and luminance data from visible region absorption spectra recorded in transmission mode. Using firmly established CIE principles, absorbance-wavelength data from visible spectra recorded using a Hewlett Packard 8452A diode array spectrophotometer are taken as input, with chromaticity coordinates being generated as output. The colorimetric transformations described are well known to colour scientists, with the methodology and background now being made accessible to the electrochromic materials community. Colour stimulus measurement example calculation results are firstly presented for aqueous solutions of the dyes, Erythrosin B (red), Acid Green 25 and Remaxol Brilliant Blue R, and then for tracking electrochromic in situ colour stimulus changes in the methyl viologen and n-heptyl viologen systems. The quantification of colour during each viologen dication to cation radical reduction process, and each reverse (oxidation) process, showed that subtle changes in both hue and luminance could be detected, with evidence of colour contributions from both the cation radical and the cation radical dimer.Research highlights► Chromaticity coordinates are calculated from visible region absorption spectra. ► The calculations are based on firmly established CIE principles. ► In situ colorimetry of electrochromic changes is demonstrated. ► Dynamic colour switching in electrochromic viologens is quantified. ► Viologen radical cation dimerisation is important for colour change quantification.
    Displays 01/2011; 32(1):35-44. · 1.10 Impact Factor
  • Roger J. Mortimer, Thomas S. Varley
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    ABSTRACT: Ruthenium purple (RP) films on transmissive tin-doped indium oxide (ITO)/glass substrates have been synthesised by an electrochemical coagulation technique using an aqueous RP colloidal suspension prepared from separate very dilute aqueous solutions of iron(III) chloride and potassium hexacyanoruthenate(II), with dilute potassium chloride as supporting electrolyte solution. To aid stability of the RP films, ruthenium(III) chloride was added to the RP colloidal suspension. Using the CIE (Commission Internationale de l’Eclairage) system of colorimetry, the colour stimulus of the electrochromic RP films and the changes that take place on reversibly switching to the colourless form have been calculated from in situ visible spectra recorded under electrochemical control. On electrochemical reduction, the intensely absorbing bright purple mixed-valence iron(III) hexacyanoruthenate(II) chromophore is reduced to the colourless iron(II) hexacyanoruthenate(II) form. Sharp and reversible changes in the hue and saturation occur, as shown by the track of the CIE 1931 xy chromaticity coordinates. Concurrently, as the purple chromophore is bleached, a large increase in the relative luminance of the electrochromic film is observed. For the purple state, the CIELAB 1976 colour space coordinates were L* = 64, a* = 27 and b* = −36, with a complementary wavelength (λc) calculated as 555 nm, in excellent agreement with the absorption maximum (λmax) of 550 nm for the intervalence charge-transfer (IVCT) band.
    Dyes and Pigments 01/2011; 89(2):169-176. · 3.53 Impact Factor
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    ABSTRACT: The new tris(ferrocenylamine) ditertiary phosphine 1,1′-{FcCH2N(CH2PPh2)CH2(η5-C5H4)}2Fe [Fc=(η5-C5H5)Fe(η5-C5H4)] has been prepared along with two coordination complexes. All compounds have been characterised by a combination of spectroscopic and analytical methods. The single crystal X-ray structure of the pentametallic Ru2Fe3 complex 5 has been determined.
    Journal of Organometallic Chemistry 06/2010; 695(14):1838-1842. · 2.00 Impact Factor
  • David R. Rosseinsky, Roger J. Mortimer
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 01/2010; 32(32).
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    ABSTRACT: Variation of the colorimetric properties as a function of the film thickness and morphology has been investigated for two spray-coated electrochromic disubstituted 3,4-propylenedioxythiophene polymers. Changes in the luminance, hue, and saturation have been tracked using CIE 1931 Lxy chromaticity coordinates, with CIELAB 1976 color space coordinates, L*, a*, and b*, being used to quantify the colors. For (precycled) neutral PProDOT-(Hx)(2) films, with an increase in the thickness, L* is seen to decrease, with a* and b* coordinates moving in positive and negative directions, respectively, with quantification of the pink/purple (magenta) color as the summation of red and blue. For all thicknesses, L* is comparable, pre- and postcycling, with a* decreasing (less red) and b* becoming more negative (more blue) and the film now appearing as purple in the neutral state. Color coordinates for the reverse (reduction) direction exhibited hysteresis in comparison with the initial oxidation, with the specific choice of perceived color values depending not only on the film thickness but also on both the potential applied and from which direction the potential is changed. Neutral PProDOT-(2-MeBu)(2) films appear blue/purple to the eye both as-deposited and after potential cycling to the transparent oxidized state. For the neutral, colored state, with an increase in the thickness, L* is seen to decrease, with a* and b* coordinates moving in positive and negative directions, respectively. For PProDOT-(2-MeBu)(2) films, the a* coordinates are lower positive values and the b* coordinates are higher negative values, thus quantifying the high dominance of the blue color in the blue/purple films compared to the pink/purple PProDOT-(Hx)(2) films. As for the PProDOT-(Hx)(2) films, the tracks of the color coordinates show that the specific choice of perceived color values depends on the film thickness. Unlike the PProDOT-(Hx)(2) films, hysteresis is absent in the oxidation/reduction track of the x-y coordinates for the PProDOT-(2-MeBu)(2) films, although slight hysteresis is present in the luminance. Characterization of the film morphologies through atomic force microscopy reveals a much rougher, higher surface area morphology for the PProDOT-(2-MeBu)(2) films versus the PProDOT-(Hx)(2) films. The branched repeat unit in the PProDOT-(2-MeBu)(2) films provides a structure that allows ions to ingress/egress more effectively, thus removing hysteresis from the optical response.
    ACS Applied Materials & Interfaces 10/2009; 1(10):2269-76. · 5.90 Impact Factor
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    ABSTRACT: Polymerization of the volatile sulfur nitride S2N2 can be brought about by interaction with latent fingerprint residues, with the resulting dark blue black polymer (SN)x visually developing the prints on a large range of media. Consideration of the technical and safety requirements of the technique allows an effective apparatus to be built and utilized with minimal risk. Observations on the diversity of media involved highlights the power of the technique, though results also indicate that no simple mechanism can account for all aspects of the interactions between the nitride, the prints and the media surfaces. This is especially apparent when prints on paper or plastic can still be imaged after washing with either water or organic solvents; likewise prints on aluminium foil can be imaged even after being heated to 500°C overnight.
    Proc SPIE 09/2009;
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    ABSTRACT: Empty glass: Subjecting ethylene glycol silica sodalite to heat (680 degrees C) under a nitrogen atmosphere (i) successfully removes the templating agent to give cubic silica sodalite, which, upon consequent heating under an oxygen atmosphere (ii), transforms into a rhombohedral form of the empty sodalite, in effect a novel polymorph of silica.
    Chemistry - A European Journal 05/2009; 15(22):5441-3. · 5.93 Impact Factor
  • Paul F Kelly, Roberto S P King, Roger J Mortimer
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    ABSTRACT: Exposure of fingerprints to S(2)N(2) vapour results in the prints being visually imaged by polymeric (SN)(x) on an unprecedented range of media; in addition, the polymer forms in response to the interaction of S(2)N(2) with traces of inkjet inks, for example the minute amounts left by the contact between printed paper and an envelope.
    Chemical Communications 01/2009; · 6.38 Impact Factor
  • 01/2009;
  • [Show abstract] [Hide abstract]
    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 01/2009; 40(32).
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    ABSTRACT: Here we have studied the electrocopolymerisation of binary mixtures of functionalised thiophenes in varying compositions and determined independently for each copolymer the spectroelectrochemical responses and the composition of the material using X-ray photoelectron spectroscopy. We have observed strong correlations between the composition of the copolymer material and the composition of the binary solution from which the polymer was grown. In addition, we have shown that the spectroelectrochemical properties of the copolymers indicate the presence of random copolymer material where the lambda(Max) values of the neutral, undoped, polymer scales with composition but also suggest that there may be small amounts of block copolymer or phase-separated mixtures of the homopolymer components.
    Physical Chemistry Chemical Physics 01/2008; 9(46):6098-105. · 4.20 Impact Factor
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    ABSTRACT: The electrocatalysis of dopamine has been studied using a cobalt hexacyanoferrate film (CoHCFe)-modified glassy carbon electrode. Using a rotating disk CoHCFe-modified electrode, the reaction rate constant for dopamine was found to be 3.5 × 105 cm3 mol-1 s-1 at a concentration of 5.0 × 10-5 mol L-1. When a Nafion® film is applied to the CoHCFe-modified electrode surface a high selectivity for the determination of dopamine over ascorbic acid was obtained. The analytical curve for dopamine presented linear dependence over the concentration range from 1.2 × 10-5 to 5.0 × 10-4 mol L-1 with a slope of 23.5 mA mol-1 L and a linear correlation coefficient of 0.999. The detection limit of this method was 8.9 × 10-6 mol L-1 and the relative standard deviation for five measurements of 2.5 × 10-4 mol L-1 dopamine was 0.58%.
    Sensors. 01/2008;
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    ABSTRACT: The formation of variable-thickness CeO2 nanoparticle mesoporous films from a colloidal nanoparticle solution (approximately 1–3-nm-diameter CeO2) is demonstrated using a layer-by-layer deposition process with small organic binder molecules such as cyclohexanehexacarboxylate and phytate. Film growth is characterised by scanning and transmission electron microscopies, X-ray scattering and quartz crystal microbalance techniques. The surface electrochemistry of CeO2 films before and after calcination at 500 °C in air is investigated. A well-defined Ce(IV/III) redox process confined to the oxide surface is observed. Beyond a threshold potential, a new phosphate phase, presumably CePO4, is formed during electrochemical reduction of CeO2 in aqueous phosphate buffer solution. The voltammetric signal is sensitive to (1) thermal pre-treatment, (2) film thickness, (3) phosphate concentration and (4) pH. The reversible ‘underpotential reduction’ of CeO2 is demonstrated at potentials positive of the threshold. A transition occurs from the reversible ‘underpotential region’ in which no phosphate phase is formed to the irreversible ‘overpotential region’ in which the formation of the cerium(III) phosphate phase is observed. The experimental results are rationalised based on surface reactivity and nucleation effects.
    Journal of Solid State Electrochemistry 01/2008; 12(12):1541-1548. · 2.28 Impact Factor
  • Ece Unur, June-Ho Jung, Roger J. Mortimer, John R Reynolds
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    ABSTRACT: This article is Closed Access. It was published in the journal, Chemistry of Materials [© ACS Publications] and is available from: http://pubs.acs.org/loi/cmatex We report an analytical method which allows the systematic variation of color states of pairs of electrochromic conjugated conducting polymers with simultaneous spectroelectrochemical and colorimetric characterization of the resulting color summation. This method measures colors by transmitting light through two polymer films stacked together in electrolyte and under separate potentiostatic control. The polymers that were used in this work are poly(3,4-ethylenedioxythiophene) (PEDOT), poly(3,4-propylenedioxypyrrole) (PProDOP), and dihexyl substituted poly(3,4-propylenedioxythiophene) (PProDOT-Hx2). These are all cathodically coloring polymers, PEDOT switching from a transmissive sky blue to a deep blue, PProDOP switching from a highly transmissive gray/blue to a brown and then to an orange, and PProDOT-Hx2 switching from a transmissive sky blue to a deep blue-purple color upon reduction. Coupling these polymers logically by the dual-polymer electrochromic film characterization technique led us to obtain new colors which were not observed when these polymers studied separately. For example; coupling PEDOT and PProDOP films in their neutral state resulted in a new red/brown color (L*=59 a*=25 b*=50) which is different from the original colors these polymers show in their neutral states, deep blue (L*=64 a*=-5 b*=-38) and orange (L*=76 a*=31 b*=75), respectively. A full palette of colors is accessible by coupling existing electrochromic polymers by this new bipotentiostatic technique. Closed access
    01/2008;
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    ABSTRACT: Reaction of S(2)N(2) vapour with Na-ZSM-5 results in rapid polymerisation and inclusion of the resulting (SN)(x) within the zeolite channels.
    Chemical Communications 01/2008; · 6.38 Impact Factor
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    ABSTRACT: The new ferrocenyl substituted ditertiary phosphine {FcCH2N(CH2PPh2)CH2}2 [Fc=(η5-C5H4)Fe(η5-C5H5)] (1) was prepared, in 72% yield, by Mannich based condensation of the known bis secondary amine {FcCH2N(H)CH2}2 with 2 equiv. of Ph2PCH2OH in CH3OH. Phosphine 1 readily coordinates to various transition-metal centres including Mo0, RuII, RhI, PdII, PtII and AuI to afford the heterometallic complexes {RuCl2(p-cym)}2(1) (2), (AuCl)2(1) (3), cis-PtCl2(1) (4), cis-PdCl2(1) (5), cis-Mo(CO)4(1) (6), trans,trans-{Pd(CH3)Cl(1)}2 (7) and trans,trans-{Rh(CO)Cl(1)}2 (8). In complexes 2, 3, 7 and 8 ligand 1 displays a P,P′-bridging mode whilst for 4–6 a P,P′-chelating mode is observed. All new compounds have been fully characterised by spectroscopic and analytical methods. Furthermore the structures of 1, 2·2CH2Cl2, 3·CH2Cl2, 4·CH2Cl2, 6·0.5CHCl3 and 8 have been elucidated by single crystal X-ray crystallography. Electrochemical measurements have been undertaken, and their redox chemistry discussed, on both noncomplexed ligand 1 and representative compounds containing this new ditertiary phosphine.
    Journal of Organometallic Chemistry - J ORGANOMET CHEM. 01/2008; 693(13):2317-2326.

Publication Stats

695 Citations
204.50 Total Impact Points

Institutions

  • 1991–2012
    • Loughborough University
      • Department of Chemistry
      Loughborough, England, United Kingdom
    • University of Oxford
      • Inorganic Chemistry Laboratory
      Oxford, England, United Kingdom
  • 2005–2009
    • University of Florida
      • Department of Chemistry
      Gainesville, FL, United States
  • 1990–2002
    • University of Birmingham
      • School of Chemistry
      Birmingham, England, United Kingdom
  • 2000
    • São Paulo State University
      • Departamento de Química Analítica
      Bauru, Estado de Sao Paulo, Brazil
  • 1992
    • University of Exeter
      Exeter, England, United Kingdom