Specialist Periodical Reports Edited by R G Compton and J D Wadhawan Electrochemistry Volume 11 Nanosystems Electrochemistry Electrochemistry Volume 11: Nanosystems Electrochemistry A Specialist Periodical Report Electrochemistry Volume 11: Nanosystems Electrochemistry A Review of Recent Literature Editors Richard G Compton, University of Oxford, UK Jay D Wadhawan, University of Hull, UK Authors Mathieu Etienne, Universite´ de Lorraine (UHP Nancy I), France Jonathan E Halls, University of Bath, UK Alexander Kuhn, Universite´ de Bordeaux, France Gabriel Loget, Universite´ de Bordeaux, France Emmanuel Maisonhaute, Laboratoire Interfaces et Syste`mes Electrochimiques, UPMC Univ Paris 06, CNRS, France Vicente Montiel, Instituto Universitario de Electroquı´mica, Universidad de Alicante, Spain Martin Pumera, Nanyang Technological University, Singapore Carlos M Sa´nchez-Sa´nchez, Instituto Universitario de Electroquı´mica, Universidad de Alicante, Spain Jose´ Solla-Gullo´n, Instituto Universitario de Electroquı´mica, Universidad de Alicante, Spain Alain Walcarius, Universite´ de Lorraine (UHP Nancy I), France Xiao-Shun Zhou, Institute of Physical Chemistry, Zhejiang Normal University, China If you buy this title on standing order, you will be given FREE access to the chapters online Please contact sales@rsc.org with proof of purchase to arrange access to be set up Thank you ISBN: 978-1-84973-401-1 DOI: 10.1039/9781849734820 ISSN: 0305-9979 A catalogue record for this book is available from the British Library & The Royal Society of Chemistry 2013 All rights reserved Apart from any fair dealing for the purpose of research or private study for non-commercial purposes, or criticism or review, as permitted under the terms of the UK Copyright, Designs and Patents Act, 1988 and the Copyright and Related Rights Regulations 2003, this publication may not be reproduced, stored or transmitted, in any form or by any means, without the prior permission in writing of The Royal Society of Chemistry, or in the case of reprographic reproduction only in accordance with the terms of the licences issued by the Copyright Licensing Agency in the UK, or in accordance with the terms of the licences issued by the appropriate Reproduction Rights Organization outside the UK Enquiries concerning reproduction outside the terms stated here should be sent to The Royal Society of Chemistry at the address printed on this page Published by The Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge CB4 0WF, UK Registered Charity Number 207890 For further information see our web site at www.rsc.org Preface DOI: 10.1039/9781849734820-FP005 We are delighted to introduce this re-launched series of Specialist Periodical Reports in Electrochemistry, to serve the global community with topical, critical and tutorial reviews covering the breadth of Electrochemical Science, Technology and Engineering Electrochemistry is the study of charge transfer across an interface, and finds application and relevance to a plurality of subfields and disciplines such as energy and environmental science, materials science, physical, organic, inorganic and analytical chemistries, engineering, earth sciences, biology and medicine It is a subject that empowers the engineering of devices for monitoring the state of our health, for converting the ‘‘free’’ energy from the Sun to workable power that we may consume, and for large scale systems, for extracting materials we require on a day-to-day basis from their naturally occurring inorganic minerals There is even common ground between stock markets, particularly those dealing with Futures and Options, with electrochemical systems, notably those involving ‘‘diffusionwith-drift’’ – hydrodynamic electrodes It is a diverse and engaging subject that is of major significance in the present world of the ever-increasing electrification; we have endeavoured to embrace and encompass this cultural and technological expansivity of our subject through this book series, and capture the essence of this big picture through the artwork that forms the front cover image of this series – it is Migration by Pia de Richemont/ www.piaderichemont.com; we thank Pia for allowing us to use her work This first volume under our editorship, and Volume 12, are concerned with Nanosystems Electrochemistry – the study of interfacial charge transport when the materials or interfaces are spatially confined to submicron levels The use of small electrodes is highly advantageous since the electrical time constant decreases as the electrode size reduces, allowing for ultrafast measurements (timescale on the order of ten nanoseconds) to occur In the first chapter, Emmanuel Maisonhaute and Xiao-Shun Zhou provide an overview of Electrochemistry to Record Single Events, introducing the reader to nanoelectrodes, nanopores, nanogaps, nanoparticle detection, molecular electronics using single molecules, and the impact of tiny, fast moving acoustic cavities on electrified interfaces Carlos Sa´nchez-Sa´nchez, Jose Solla-Gullo´n and Vincent Montiel take this further in their chapter on Electrocatalysis at Nanoparticles, where they examine the functional competency of nanoparticle index plane on the electrocatalysis of nanoparticles with low-co-ordinated surface atoms – an area of immense importance for fuel cell material science, and move to the study of single nanoparticles on nanoelectrodes, where they detail the effects of single nanoparticle collisions through the amplification of electrocatalysis In moving to apply these principles to develop innovative devices for the nanoworld, Gabriel Loget and Alexander Kuhn review the fascinating field of Biopolar Electrochemistry in the Nanosciences, where control of the electrical field between two electrodes is employed to induce motion and transformation of Electrochemistry, 2013, 11, v–vi | v  c The Royal Society of Chemistry 2013 particles contained therein without direct mechanical contact of a material with an electrode The nanostructuring of an electrode is considered in the chapters by Martin Pumera, and Mathieu Etienne and Alain Walcarius Pumera reviews Nanocarbon Electrochemistry, covering graphene, carbon nanotubes and doped nanodiamond; Etienne and Walcarius provide a pedagogic account on Electrochemistry within Templated Nanosystems covering the preparation, electrochemistry and applications of metallic nanostructured electrodes, metal oxide and sol-gel derived nanomaterials, and ordered macro- and mesoporous carbons Last, Jonathan Halls and Jay Wadhawan provide a tutorial overview on Electrochemistry within Liquid Nanosystems, where they examine the effect when the solvent into which an electrode is immersed contains some form of long-range order – ‘‘liquid nanotechnology’’, with particular emphasis on the electrochemistry within lyotropic liquid crystals – quasi-biphasic nanosystems where water may not exist in a bulk state, so that macroscopic properties such as pH become essentially meaningless concepts We hope you enjoy this volume It remains for us to thank Merlin Fox, Alice Toby-Brant, Leanne Marle, Katrina Harding and the rest of the RSC Publishing team for all their diligent work, and Bruce Gilbert and the Specialist Periodical Reports Editorial Board for enabling the resurrection of this book series Richard Compton Oxford University Jay Wadhawan University of Hull vi | Electrochemistry, 2013, 11, v–vi CONTENTS Cover Migration by Pia de Richemont (www.piaderichemont.com) Preface Richard Compton and Jay Wadhawan v Electrochemistry to record single events Xiao-Shun Zhou and Emmanuel Maisonhaute Introduction Individual systems explored with nanoelectrodes Single molecules for molecular electronics A fast moving nanometric interface: the example of acoustic cavitation Conclusions Acknowledgements References Electrocatalysis at nanoparticles Carlos M Sa´nchez-Sa´nchez, Jose Solla-Gullo´n and Vicente Montiel Introduction Electrocatalysis at nanoparticles with low-coordinated surface atoms Electrocatalytic reactions studied at single nanoparticles Summary Acknowledgements References 21 26 27 27 34 34 35 59 65 66 66 Electrochemistry, 2013, 11, vii–viii | vii  c The Royal Society of Chemistry 2013 Bipolar Gabriel electrochemistry in the nanosciences Loget and Alexander Kuhn Introduction Well-established and macroscopic applications of bipolar electrochemistry Novel micro- and nano applications of bipolar electrochemistry Conclusion References 71 71 82 86 99 99 Nanocarbon electrochemistry Martin Pumera Introduction Graphene Carbon nanotubes Doped nanodiamonds Concluding remarks References 104 Electrochemistry within template nanosystems 124 Mathieu Etienne and Alain Walcarius Introduction Metallic nanostructured electrodes Metal oxide and sol-gel-derived nanomaterials on/as electrodes Ordered macro- and mesoporous carbons Conclusion References 104 107 114 120 121 122 124 126 141 166 181 182 Electrochemistry within liquid nanosystems 198 Jonathan E Halls and Jay D Wadhawan Introduction Assembly of liquid nanosystems Consequences of restricted media Electrical circuit equivalent of lyotropic liquid crystals Electron transfer kinetics within liquid nanosystems Transport within liquid crystal media Applications Conclusions Acknowledgements References 198 199 204 207 208 211 227 231 232 232 viii | Electrochemistry, 2013, 11, vii–viii About the Editors Richard G Compton is Professor of Chemistry and Aldrichian Praelector at Oxford University, United Kingdom where he is also Tutor in Chemistry at St John’s College Compton has broad interests in both fundamental and applied electrochemistry and electroanalysis including nanochemical aspects He has published more than 1100 papers (h = 67; Web of Science, July 2012), books and numerous patents The 2nd edition of his graduate textbook Understanding Voltammetry (with C E Banks) was published in late 2010 by Imperial College Press He is CAS Visiting Professor at the Institute of Physical Sciences, Hefei and a Lifelong Honorary Professor at Sichuan University He holds Honorary Doctorates from the Estonian Agricultural University and Kharkov National University of Radioelectronics (Ukraine) and is a Fellow of the RSC and of the ISE He is the Founding Editor and Editor-in-Chief of the journal Electrochemistry Communications (current IF=4.86) published by Elsevier Scientist ranking (Essential Science Indicators, ISI, June, 2012): # 120 of 7849 top 1% Scientists in Chemistry; #133 of 7180 top 1% Scientists in Engineering; 1444 of 70037 top 1% Scientists (all fields) Jay D Wadhawan (age 34) is Senior Lecturer in Electrochemical Science, Technology & Engineering at University of Hull, where he represents the Faculty of Science at Senate He is Vice-Chair in Molecular Electrochemistry at the International Society of Electrochemistry and Research CoChampion in Electrocatalysis for Carbon Capture and Utilisation for the CO2CHEM EPSRC Grand Challenge Network He has acted as a Tutorial Lecturer at Universidade Federale de Alagoas, Brazil, Visiting Professor at Universite´ de Bordeaux 1, France, and Visiting Professor at Universite´ Paris Diderot, France He is an Associate Member of University of York Electrochemistry, 2013, 11, ix–ix | ix  c The Royal Society of Chemistry 2013 illustrated Fig 13, where low concentrations (2 mM) afford signals that correspond to semi-infinite diffusion, whilst higher concentrations (10 mM) give rise to exclusively radial diffusion regimes, consistent with an interphase reaction becoming more significant as the dopant concentration increases: strikingly, the radial diffusion coefficient changes its variation with loading, moving from a quadratic relationship to one of direct proportionality, q.v Fig 13 Such quantifications were able to empower the determination of the partition coefficient of TMPD between the surfactant and aqueous pseudophases as being lg Kp=2.33 Ỉ 0.51, in agreement with that calculated for the n-octanol H2O interface Diffusion anisotropy has also been assessed for the voltammetric oxidation of crystals of N,N,N ,N -tetraphenyl-para-pheneylenediamine (TPPD) embedded within the La phase of Brij 30/water/toluene, Fig 14.36 Here, the oxidation of the solid particles has been suggested to be due to the electron hopping between individual TPPD sites within crystals which impact on the electrode surface, affording diffusional signals which fit to afford a high anisotropic ratio, viz., Dr=10 À12 cm2 sÀ1 and Dz=3.2 Â 10À9 cm2 s À1, q.v Fig 14.36 6.2.3 Orientational effects in liquid crystal electrochemistry Effects due to the orientation of the liquid crystal versus the electrode surface have been explored In perhaps the first report on electrochemistry within undoped liquid crystals, we recently reported our work on the voltammetry within chromonic liquid crystals formed through aggregation of metal-ligated tetrasulfonated phthalocyanine species in water – liquid metal organic frameworks.37 These molecules assemble isodesmically to afford p-stacked H-aggregates which exhibit orientational order in the N phase, or orientational and positional order in the M phase, as illustrated in Fig 15 Small angle X-ray scattering indicates that the aggregates formed hold on average between 9–13 monomers, spaced by ca 3.4 A˚, with Bragg diffraction peaks as expected, q.v Fig 15 and Table The voltammetry for both phases examined, see Fig 16, is complicated, as expected for the mesogens, with chronoamperometric traces that suggest two dimensional diffusion can occur within columunar systems, previously thought to exhibit merely one-dimensional transport effects, and that the electric field may play an orientational roˆle within these systems,37 in a manner similar to that observed in thermotropic liquid crystals.38 Orientational order for thermotropic liquid crystals can be effected through the use of surfactant-coated plates opposite the electrode to align the mesogens in the homogeneous (parallel to the surface) or homeotropic (perpendicular to the surface) orientations, as used by Abrun˜a39 for the technologically important 5-cyanobiphenyl (formerly named K-15) liquid crystal first developed at University of Hull, UK Such media also have to be doped to elicit good Faradaic responses,39 and allow for a direct comparison between the room temperature nematic phase and the isotropic liquid formed at higher temperatures; Fig 17 illustrates the voltammetry of TCNQ which illustrates diffusion-controlled waves for both anodic and cathodic processes in the isotropic liquid, but diffusion-controlled signals 220 | Electrochemistry, 2013, 11, 198–234 Fig 14 Polarising microscope images of TPPD crystals within a La phase (a), the associated voltammetry under a variety of different scan rates (b), illustrating the electrochemical reversibility of the voltammograms (c) and the fit between experiment and anisotropic theory (d) Reproduced with Blackwell-Wiley permission from Ref 36 for the cathodic process and adsorption controlled responses for the anodic sweep in the nematic phase Abrun˜a assumed an inverse proportionality dependence of the diffusion coefficient on the sample viscosity in both isotropic and nematic phases, affording experimental viscosities for K-15 of Electrochemistry, 2013, 11, 198–234 | 221 Fig 15 Order within chromonic liquid crystals Reproduced with Elseveir permission from Ref 37 39 cP for the viscosity perpendicular to the director, with a viscosity of 28 cP for that parallel to the director.39 An alternative route to ordering liquid crystal systems is through magnetic field.40 This relies on the anisotropy of the diamagnetic susceptibility of the monomers, and allows for probing the transport within the liquid system either through the use of two macroscopic electrodes in orthogonal directions,34,41 or through positioning the magnetic field in orthogonal directions.17 The advantage with this method is that the size of the surfactant and aqueous subphases can be controlled, allowing for alterations in the apparent diffusion coefficient, which depends on both the aqueous (DA) and surfactant (DS) diffusion coefficients for systems involving partitiondiffusion:17,33,41 Dap ¼ & KP dw KP  d DA DS '&  ' ds þ ds DS þ dw DA KP where d is the fundamental repeat distance, ds is the surfactant bilayer thickness and dw is that corresponding to the water layer, for a La system Thus, assuming ideal swelling behaviour, ds and dw can be controlled merely 222 | Electrochemistry, 2013, 11, 198–234 Table Physical characteristics of the N and M phases illustrated in Fig 15 Reproduced with Elseveir permission from Ref 37 X-ray scattering data À1 qe =A˚ Electrochemistry, 2013, 11, 198–234 | 223 Phase r2 =O cm Rb =O Cdc =mFcm À2 2y/1 d d=A˚ N Nickel(II) Phthalocyanine Tetrasulfonic acid Tetrasodium salt 0.26 M in H2O pH M Copper(II) Phthalocyanine Tetrasulfonic acid Tetrasodium salt 0.88 M in H2O 12.70 5773 12.3 2.03 3.99 26.5 43.5 22.1 3.36 Aggregate length Aggregate width Aggregate spacing 9.17 4585 2.1 2.88 4.07 6.81 10.5 13.0 15.6 21.2 24.4 26.3 30.7 21.7 13.0 8.45 6.78 5.68 4.18 3.64 3.39 Aggregate length Aggregate width qo pffiffiffi qo 2qopffiffiffi qo 3qo pffiffiffi 2qo Aggregate spacing Isotropic solution 0.1 M aqueous KCl 11.29 0.485 0.744 0.926 1.11 1.50 1.73 f q=qo 1.00 1.53 1.91 2.28 3.10 3.56 Assignment (a) (i) (a) (ii) (a) (iii) (b) (i) (b) (ii) Fig 16 Voltammetry and chronoamperometric transients of the chromonic liquid crystals illustrated in Fig 15: blue signals [panels (a)(i), (iii) and (b)(i)] correspond to the N phase; red signals [panels (a)(ii) and (b)(ii)] correspond to the M phase Reproduced with Elseveir permission from Ref 37 by manipulating the volume fraction of each pseudophase This is also true for the diameter of the cylindrical micelles of the H1 phase.17 Figure 18 illustrates the voltammetry of ferrocyanide in a LaH phase with electrodes perpendicular and parallel to the director, where the effects of anisotropy are clearly evident through diminished signals.34 Similar effects are observed for both vitamin K1 and plant pigment (a mixture of chlorophyll a, chlorophyll b and their corresponding phæophytins) within the H1 phase that was oriented through rotating the direction of the applied magnetic field,17 Fig 19 Since chlorophyll a and vitamin K1 are both involved in the first few electron transfer processes of Photosystem I, orientation effects were 224 | Electrochemistry, 2013, 11, 198–234 Fig 17 Voltammetry of TCNQ within K-15 in the nematic (solid line) or isotropic (dashed line) phase Reproduced with Electrochemical Society permission from Ref 39a A B Fig 18 Voltammetry of ferricyanide at orthogonal electrodes immersed in isotropic solution or LaH phase Reproduced with ACS permission from Ref 34 investigated in the photoelectrochemistry of H1 phases doped with these (Fig 19); surprisingly, no currents were observed within the homeotropic system, whilst the homogeneous arrangement afforded small photo-reductive currents, consistent with the photo-induced electron Electrochemistry, 2013, 11, 198–234 | 225 (a) (b) (c) Fig 19 Voltammograms (scan rate 0.1 V sÀ1) corresponding to (a) the reduction of vitamin K1 and (b) the oxidation of plant pigment, when immobilised within the H1 phase of Triton X-100/aqueous 0.1 M HCl, in the homeotropic (red, inner voltammograms) or homogeneous (blue, outer voltammograms) alignment The arrows indicate the direction of the initial potential sweep Panel (c) illustrates typical photo-reductive currents observed on illumination of the homogeneously aligned sample with red light, holding the potential of the glassy carbon working electrode at 0.0 V vs Ag9AgCl9Cl À Reproduced with Elseveir permission from Ref 17 transfer from the excited state of phæophytin a to vitamin K1 in the presence of an acid electrolyte dopant, with the reduction of the oxidised form of phæophytin a providing the reduction current The contrast between the oridentations was suggested to stem from transport of hydrophobic reactants within the liquid nanoframework.17 226 | Electrochemistry, 2013, 11, 198–234 6.2.4 Other electrochemical work in lyotropic liquid crystals Several research groups have examined the voltammetry of model species within lyotropic liquid crystal frameworks Owen et al.,18 examined the oxidation of ferrocyanide and ferrocene in the H1 phase formed by doping 50:50 wt.% Brij 56/0.5 M aqueous KCl Whilst the ferrocyanide oxidation was observed to be electrochemically reversible, the ferrocene system was complicated by precipitation in the aqueous subphase of electrochemically-oxidised ferricinium during its reduction Diffusion coefficients, obtained in non-oriented samples were observed to be significantly smaller than in water Coupled with conductivity measurements, this was interpreted as being due to restricted motion within the channels afforded by the H1 phase.18 Similar interpretations were given in a series of papers by Kumar and Lakshminarayanan,42 who examined the Triton X 100 H1 phase, employing AC impedance spectroscopy (in addition to cyclic voltammetry) to extracting diffusion coefficients through the crude Randles circuit outlined in y4 As with the work by Owen,18 these authors also noted the significant shift in the half-wave potential of the redox species in the lyotropic medium compared with surfactant-free aqueous solution Moreover, the study of quinone systems, which were suggested to involve merely electron, rather than electron and proton transfers, provide additional complexity to these systems which require further characterisation Likewise, the multielectron-proton voltammetry of methylene blue within a sodium dodecylsulfate/n-C5H11OH/H2O lyotropic system was examined as a system where attractive electrostatic forces may exist between the analyte and the framework, to determine the dependence of the diffusion coefficient, extracted through microdisc voltammetry, under the assumption of isotropic diffusion!43 The authors suggested the diffusion coefficient of methylene blue increases with n-pentanol content.43 Applications Several applications employing liquid crystal electrochemistry have been proposed 7.1 Liquid nanosystems as templates for electrochemical deposition The basic idea is illustrated in Fig 20: the liquid nanosystem is employed as a template, with electroreducible metal cations44 or electrooxisiable (a) (b) Fig 20 Schematic illustration of the templating procecess Reproduced with Blackwell-Wiley permission from Ref 44d Electrochemistry, 2013, 11, 198–234 | 227 polymer45 acting as a dopant The orientation of the system at the electrode surface allows for electrodeposition around the surfactant micelles, so that after solubilisation of the surfactant in a suitable solvent, the porous film on the electrode remains This idea, pioneered by the Southampton Electrochemistry Group, UK, allows for high surface area films which may be useful as electrodes for a whole host of other applications, as noted in the chapter in this volume by Etienne and Walcarius.46 7.2 Liquid nanosystems as frameworks for sensing systems The presence of water in lyotropic systems, allows for these to be versatile frameworks for humidity sensors through changes in conductance Room temperature ionic liquid systems, which are highly sensitive to the concentration of water,47 are likewise versatile for this purpose, with many of them forming lyotropic systems.48 The quasi-biphasic nature of the surfactant/aqueous system also allow these to represent an excellent biominetic, and are highly useful as frameworks in which to immobilise enzymes for sensing49 or as enzymatic electrodes for biofuel cells.50 7.3 Liquid nanosystems for electrosynthesis Biphasic electrosynthesis is an attractive route for Kolbe dimerisation reactions under essentially ‘‘green’’ conditions.51 The same is true for lyotropic phases prepared using oleic acid with sodium hydroxide as electrolyte.52 Oxidation of the carboxylate within a mesophase, produces merely two products – the Kolbe dimer and the associated non-Kolbe product,52 as in the case of bulk biphasic electrolysis under galvanostatic control.52 The change in the applied current enabled the selective oxidation of the oleate to afford the non-Kolbe product in up to ca 70% yield.52 7.4 Lyotropic chromonic semiconductors for processable electronics Although the evaporation of water from chromonic liquid crystals is a hazard that is difficult to avoid, it can be employed for advantage in the deposition of highly aligned p-stacked molecules Lavrentovich and coworkers53 studied dried chromonic systems based on Violet 20 – an hydrophilic molecule with a perylene-based core – see Fig 21, as materials for organic field-effect transistors The electrical conductivity of the dried films were observed to exhibit strong anisotropy, with behaviour reminiscent of that corresponding to organic semiconductors, with field-effect carrier mobility along the dried film aggregates being53 B0.03 cm2 V À1 sÀ1, Fig 22 The advantage of this system is that the cost of processing the system to afford a well-aligned solid is low, whilst the electron mobility is high 7.5 Liquid nanosystems for energy harvesting We recently proposed the La phase as an inexpensive and convenient medium to act as a nano-confined system for performance optimisation of photogalvanic cells,13 Fig 23 In this system, the framework medium is doped with photoredox active species which may engage in electron transfer to a fuel present within the 228 | Electrochemistry, 2013, 11, 198–234 (a) (b) Fig 21 Violet 20 chromonic mesogen and an organic field effect transistor fabricated using dried films of the chromonic liquid crystal Reproduced with AIP permission from Ref 53 (a) (b) Fig 22 Current-voltage characteristics of the organic field effect transistor fabricated using dried films of Violet 20 chromonic liquid crystal Reproduced with AIP permission from Ref 53 aqueous subphase (such as protons), allowing a change in the concentration of oxidised and reduced forms of the photoactive species present at the illuminated electrode The short transport pathlengths afforded by this medium, coupled with the high reagent solubility and a sacrificial counter electrode empowered the construction of a photogalvanic device using Nmethylphenothiazine as the light-sensitive dye that exhibited ca 2% power conversion efficiency under violet light, Fig 24 The cell was additionally demonstrated13 to be useful as an electrochemical capacitor with specific pseduocapacitance B1–10 F gÀ1, Fig 25 Electrochemistry, 2013, 11, 198–234 | 229 Fig 23 Illustration of the cause of photogalvanic behaviour Taken from Ref 13 (a) (b) Fig 24 Performance of the device as a solar cell Taken from Ref 13 230 | Electrochemistry, 2013, 11, 198–234 (a) (b) (i) (b) (ii) Fig 25 Performance of the system as an electrochemical capacitor Taken from Ref 13 Conclusions Electrochemistry within liquid nanosystems involves a complex series of processes including multiple interface electron transfer affected by the multitude of dielectric constants and viscosities present, with many facets to the transport of species within the medium The exact location of reactant and product from a simple electron transfer can vary causing dramatic Electrochemistry, 2013, 11, 198–234 | 231 changes in the reaction mechanism through the occurrence of interphase electron exchange In addition to this, the occurrence of spatially constrained environments can add to the complexity of the systems Whilst some of these effects have been unravelled for the case of doped media, a complete understanding of the roˆle played by the solvent framework requires much more work, especially for the consideration of the coupled proton-electron transfers that occur within the biological systems that these systems, at best, 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and R Bilewicz, J Colloid Interfac Sci., 2012, 385, 130 51 J D Wadhawan, F Marken and R G Compton, Pure Appl Chem., 1947, 2001, 73 52 J E Halls, F da Silva, M O F Goulart and J D Wadhawan, in preparation 53 V G Nazarenko, O P Boiko, M I Anisimov, A K Kadashchuk, Y A Nastishin, A B Golovin and O D Lavrentovich, Appl Phys Lett., 2010, 97, 263305 234 | Electrochemistry, 2013, 11, 198–234 .. .Electrochemistry Volume 11: Nanosystems Electrochemistry A Specialist Periodical Report Electrochemistry Volume 11: Nanosystems Electrochemistry A Review of Recent... displacements (d) Current decay curves for a clean Au (111 ) substrate (A) and HS-6V6-SH on Au (111 ) in air (B) Reprinted with permission from Ref 117 displayed as peaks in the analysis A refinement... References 104 107 114 120 121 122 124 126 141 166 181 182 Electrochemistry within liquid nanosystems 198 Jonathan E Halls and Jay D Wadhawan Introduction Assembly of liquid nanosystems Consequences