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Augmented reality (AR) is rapidly emerging as an increasingly useful technology in educational settings. In the ARETE (Augmented Reality Interactive Educational System) H2020 project, consortium members designed and implemented an ecosystem aimed at supporting teachers in building a collaborative learning environment through the use of AR in order to improve educational experiences. In particular, one of the pilot projects aims to introduce AR into school behavior lessons for the first time, leveraging the Positive Behaviour Intervention and Support (PBIS) methodology. Specifically, in this paper we will discuss the proposed architecture within the ARETE project that incorporates AR technology into the learning process of behavior lessons to support the teaching, practice and reinforcement phases of expected behaviors. Through the combination of different technologies and systems, it is possible to create an example of a technological and innovative ecosystem designed for creating behavioral lessons in AR.

Aluminium (Al) batteries are a promising, next-generation technology and current research efforts are aimed at positioning this technology to compete with existing lithium-ion batteries (LIB). The development of non-aqueous electrolyte chemistries for Al battery systems has received renewed attention to address some of the shortcomings associated with LIB. Of particular importance in this development is the liquid electrolyte as its rheology governs the battery chemistry. The goals are to generate a liquid that is compatible with the other (solid) battery components, stable long-term with repeated use, and to optimise the rheology (i.e. target high conductivity and low viscosity). Chloroaluminate room temperature ionic liquid (RTIL) electrolytes made by mixing Lewis acidic aluminium chloride (AlCl3) salt with a (often chloride-containing) Lewis basic salt e.g. 1-ethyl-3-methylimidazolium chloride (EMIM-Cl) has been extensively studied. This tuneable electrolyte provides good thermal stability, good ionic conductivity, and a wide polarizable potential window. While these traits are advantageous these types of Lewis basic salt precursors are generally expensive, difficult to synthesize and in some instances can be toxic. Recently, ionic liquid analogues (ILA) that are made from abundant, inexpensive and often non-toxic materials have begun to be explored. To date the two most common Lewis basic salts examined have been urea and acetamide but their rheological and electrochemical properties need to be improved in order to complete with RTIL-based electrolytes. Our group have recently revealed that amidine-based chloroaluminate ILA electrolytes show promise over urea-, acetamide-, and pyrrolidinium-based electrolytes.[1] Specifically, guanidinium chloride (Guan-Cl) and acetamidinium chloride (Acet-Cl) based salts display reversible electrochemical plating/stripping of Al, good ionic conductivities (e.g. 10 mS cm-1), and moderate viscosities (e.g. 50 cP). Also, in this work we initially proposed a mathematical model to extract the conductivity from these electrolytes by fitting the voltammetric i-E curve (from Al deposition/dissolution) to a linear, modified Butler-Volmer formalism. The characteristic, anodic i-E trace shows a striking linearity often over very large potential ranges (e.g. >2 V), and this response is used to extract ionic conductivity. This represents a novel, electroanalytical method to obtain this important rheological metric. As such, in this contribution we will highlight our latest efforts to expand, benchmark (to common methods for measuring conductivity), and determine the limits of our i-E curve fitting method to measure ionic conductivity.[2] Specifically, we have examined the AlCl3:Acet-Cl electrolyte in depth by looking at the potential scanning rate, potential range probed, and the compositional (mole ratio Lewis acid : Lewis base) effect on the conductivity extracted from our fitting method. We have also studied a range of other common chloroaluminate electrolytes to compare with published literature. All of these values are then benchmarked to conductivity data measured both from a traditional impedance-based method and that from a commercial conductivity probe. Lastly, we also have examined temperature-dependent conductivities from all three of these methods. Overall, we find good agreement between values measured from our in situ i-E curve fitting method to those from more traditional conductivity measurement methods. This electroanalytical work serves to deepen our understanding of the conductivity of chloroaluminate ILAs for Al battery applications. References: [1] A.J. Lucio, I. Efimov, O.N. Efimov, C.J. Zaleski, S. Viles, B.B. Ignatiuk, A.P. Abbott, A.R. Hillman, K.S. Ryder. Chem. Commun., 2021, 57, 9834-9837. [2] A.J. Lucio, E. Bulmer, I. Sumarlan, A.R. Hillman, K.S. Ryder. 2022 in preparation. Figure 1

Covid-19 and the associated restrictions on interaction have led to an unprecedented shock to activity and firms’ balance sheets. To assess the impact, this paper applies a new large-scale firm-level simulation model calibrated to the United Kingdom (UK). The paper specifically examines the Coronavirus Job Retention Scheme (CJRS) furlough program and a credit guarantee. The Corporate Sector Agent-Based (CAB) Model (Hillman, Barnes, Wharf and MacDonald, 2021) takes into account: heterogeneity across firms; interactions between firms across a realistic customer-supplier network; and rule-of-thumb behaviour by firms and bankruptcy constraints. The model amplifies the effect of shocks and generates substantial persistence and overshooting, as well as displaying a number of non-linearities. The CAB uses a data-rich approach based on ORBIS firm-level data and the OECD Input-Output tables. Simulations in this paper are calibrated to the observed path of UK output in 2020.

This paper develops a new large-scale firm-level simulation model, the Corporate Sector Agent-Based (CAB) Model, which is applied to analyse the COVID-19 shock and policy options in Barnes, Hillman, MacDonald and Wharf (2021). Agent-based models (ABMs) simulate the interaction of autonomous agents to generate emergent aggregate behaviours. The CAB model takes into account: heterogeneity across firms; a realistic customer-supplier network; interactions between firms; rule-of-thumb behaviour by firms and bankruptcy constraints.

Sustainable access to safe drinking water is a global societal goal [1]. Accordingly, much attention has been given to the development of technologies for remediation of the unintended effects of agricultural practices and industrial processes. The case of fluoride in water is an interesting case in two respects: its desirability up to a point and its natural origins. The beneficial effects of fluoride on dental health are recognized: in some countries drinking water is routinely fluoridated. However, high levels of fluoride can have detrimental effects on teeth, bones and internal organs; the recommended upper limit is 1.5 mg/L. The fluoride concentration in natural waters - the source of most drinking water - is dictated by the presence of calcium ions, through the solubility product of calcium fluoride. Dependent on the local geology, the calcium ion concentration may be relatively low or high, such that either the beneficial effects of fluoride may not be realized or its injurious effects may dominate. Determination of fluoride concentration using ion selective electrodes is well-established. The question then is how to remedy high fluoride levels. Existing methods for removal of excess fluoride from drinking water and wastewater include precipitation (as Ca or Al salts), membrane technologies and adsorption. Each of these has limitations, e.g. high costs, toxic by-products and slow or complex processes. Here we explore electrochemically controlled fluoride ion extraction by electroactive polymer films. This approach has been studied for water softening (using polypyrrole [2]) and perchlorate removal (using polypyrrole composites [3] and polyaniline-based copolymers [4]). Here we explore the feasibility of using a range of polyaniline-based materials in an electrochemically switched ion exchange system for fluoride removal from water [5]. The concept is based on F- ion uptake as counter ions in the oxidation (p-doping) of the conducting polymer film. Upon oxidation, the film will “capture” F- ions from solution. After separation of the purified water, the F- ions would then be ejected into a concentrated waste stream by reduction (un-doping) of the oxidized polymer. In this presentation we compare the characteristics and performance of polyaniline, poly(o-aminophenol) and poly(o-toluidine) homopolymer films with each other and with those of their copolymers of various composition. Film deposition is controlled electrochemically and monitored nanogravimetrically using the EQCM. Acoustic impedance enables distinction between gravimetric and viscoelastic interpretation of the response [8]. The extent of redox-driven fluoride uptake is then determined upon exposure to solutions of varying fluoride (and in some cases chloride) concentration. Correlation of EQCM-derived film mass and charge responses is used to assay fluoride and solvent uptake during film oxidation and reduction. Comparison with the total redox site population (from the response in fluoride-free media) yields the efficiency. Observations for these aniline-based homopolymers and copolymers reveal behavior that is quite different to that seen for typical small anionic dopants, such as chloride, nitrate and perchlorate. Further, there are surprisingly diverse responses to fluoride for these relatively similar polymeric materials, notably the extent of film solvation change during fluoride uptake. Use of different electrochemical control functions and timescales reveals differences in fluoride ion uptake and release rates. The relevance of these data to defluoridation will be discussed. References [1] https://sdgs.un.org/goals/goal6 [2] C. Weidlich, K. Mangold, K. Jüttner, Electrochim. Acta 50 (2005) 1547-1552. [3] S. Zhang, Y. Shao, J. Liu, I. A. Aksay, Y. Lin, ACS Appl. Mater. Interf. 3 (2011) 3633-3637. [4] Y. Zhang, S. Mu, B. Deng, J. Zheng, J. Electroanal. Chem. 641 (2010) 1-6. [5] H. Cui, Y. Qian, H. An, C. Sun, J. Zhai, Q. Li, Water Res. 46 (2012) 3943-3950. [6] A. Unal, A.R. Hillman, K.S. Ryder, S. Cihangir, J. Electrochem. Soc. 168 (2021) 022502. [7] A. Unal, A.R. Hillman, K.S. Ryder, S. Cihangir, J. Electroanal. Chem. 895 (2021) 115519. [8] A.R. Hillman, M.A. Mohamoud, I. Efimov, Anal. Chem. 83 (2011) 5696.

Criminal investigations require establishment of the identities of suspects, victims and witnesses. The most common physical evidence that accomplishes this is a fingermark: it is unique to an individual and time-invariant. Its presence can establish contact between an individual and an object or place the individual at a crime scene. In practice, most such marks are latent (non-visible) fingermarks: these require chemical or physical treatment to render a visible image. Typical chemical treatments involve interaction of a reagent (powder, cyanoacrylate, dye) with the fingerprint residue. Deterioration or loss of residue due to environmental exposure limits the efficacy of these treatments. The success rate for developing a latent mark to a standard permitting a legally acceptable identification is only ca. 10%; this motivates new chemical approaches. In a complementary strategy, we have used the fingerprint residue as a template (“mask”) to direct electrochemically generated reagent to the bare surface between the deposited ridges, thereby creating a negative image of the fingerprint. On metallic substrates the deposition and viewing processes may be controlled electrochemically. This offers the promise of application to a range of objects forensically relevant to both violent crime (knives, guns, bullet casings) and volume crime (tools, handles at points of entry and metal theft). This templating concept was originally demonstrated using electrodeposited polyaniline [1] and PEDOT [2] films, whose electrochromic properties were used to optimize the visual contrast within the fingerprint image. We subsequently extended this concept through the use of electrodeposited poly(pyrrole-co-3,4-ethylenedioxythiophene) copolymers of varying composition to provide wider and more subtle variation of optical properties (simplistically, colour) [3]. Through deliberate selection of co-monomer feedstock, polymer deposition potential and subsequent “viewing” potential, one could then pre-select bespoke material characteristics optimized to a specific substrate. Here we further extend the concept by the inclusion of the dyes Methyl Red (MR), Methyl Orange (MO), Indigo Carmine (IC) or Basic Yellow 40 (BY) into electrodeposited polypyrrole (PPy) films by a combination of electrostatic and/or physical entrapment. The substrates were stainless steel electrodes, upon which a latent fingerprint had been deposited. The deposition medium was an aqueous pyrrole (0.05 mol L-1) / dye (0.005 mol L-1) solution. In the case of MR, sodium dodecylsulphate (0.005 mol L-1) was employed to improve dye solubility. We compare the effectiveness of potentiostatic (0.90 – 1.00 V vs. Ag/AgCl) and galvanostatic (2.5 – 5.0 mA cm-2) deposition control functions. The extent of polymer deposition was varied via deposition time (60 to 300 s) and coulometrically assayed. Dye encapsulation was qualitatively apparent as the polypyrrole films presented the colour of the dye used as dopant: PPy/MR and PPy/MO films were reddish-brown, and PPy/IC was blue. Complementary to these colours seen via absorbance, the emission properties of BY (widely used in conjunction with cyanoacrylate) are also apparent via fluorescence when irradiated with UV light. We will present and interpret images demonstrating how these all these composite electroactive materials yield excellent colour contrast between the surface and the fingerprint. Specifically, one can readily identify the so-called second level features that, in conjunction with dactyloscopy images, unambiguously identify individuals or establish connections between crime scenes. The advantages of this approach, alone and in combination with conventional visualization techniques, will be discussed.

The Physical Developer solution currently recommended for use in the United Kingdom for fingermark visualisation uses two surfactants: n-dodecylamine acetate (nDDAA) and Synperonic® N. Synperonic® N is covered by the EU directive 82/242/EEC, which sought to phase out chemicals with degradation products more harmful than their precursor. This study explores the replacement of Synperonic® N with alternative detergents and examines their ability to produce clear, stable solutions that are effective at developing fingermarks. The critical properties of the detergents were investigated, such as the critical micelle concentration and the hydrophilic-lipophilic balance, and planted mark comparisons were performed on promising formulations. Tween® 20 was deemed unsuitable due to the production of cloudy solutions and the requirement to age the formulation to improve effectiveness. Brij® C10 produced clear formulations; however, these were too stable causing unacceptably long exhibit processing times, and an additional preparation stage was necessary. Brij® L23, Brij® S10, Igepal® CO-630, Polyoxyethylene (10) tridecyl ether and Tergitol™ 15-S-9 also proved to be unsuccessful alternatives. Decaethylene glycol monododecyl ether (DGME) was found to be a suitable alternative to Synperonic® N and depletion series experiments suggested that a range of DGME and nDDAA detergent quantities were effective at developing marks. The processing time using DGME was similar to Synperonic® N and the most favourable ratio of reagents is proposed in this paper as a reformulated Physical Developer solution.

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link. 10.1016/j.scijus.2020.08.002. Bladed weapons are frequently encountered in violent crime offences including street based and armed robberies, murder, sexual assaults and terrorism. A study was conducted involving four frequently encountered clothing fabrics: t-shirt (knitted cotton), denim jeans (twill woven cotton), long sleeved top (knitted synthetic blend), and skirt (non-woven faux leather) and five knives to investigate any damage resulting from a downward stabbing motion, with 300 stabs in total. Any resultant penetrating severance damage was then photographed, measured and analysed. Statistical analysis revealed significant differences between the stab hole size and shape, as a consequence of the design of a bladed weapon (in particular, the tip shape) that caused it. There is a notable correlation between the Assure knife (rounded tip) and no resulting severance damage, as the fabric surfaces were not breached with this knife. This suggests a clear alternative to pointed tip knife blades. These findings will be of interest to investigators of knife crime offences, crime-reduction units, knife manufacturers and practitioners, who share the goal of identifying a safer alternative to conventional knife blade design.

Electrodeposited conducting polymer films derived from aromatic monomers are known to possess properties that depend significantly on the deposition protocol, particularly the electrochemical control function employed. This study explores the underlying reasons for this common observation for the specific case of polypyrrole films deposited from aqueous media onto gold electrodes under potentiostatic, potentiodynamic and galvanostatic control. Although the control functions impose different conditions, the control parameters (potential, potential range and scan rate, and current) were selected so as generate films at comparable rates; this avoids inappropriate attribution of structural and compositional variations to different thickness regimes, irrespective of how they were generated. In each case, film deposition was periodically interrupted and the film characterised by specular neutron reflectivity measurements. By using d4-pyrrole monomer in H2O solvent, the isotopic selectivity of neutron reflectivity was used to extract polymer and solvent concentration profiles as a function of distance from the electrode/film interface. Spatial integration of these profiles was used to quantify total film solvent populations; these are expressed as solvent volume fractions. Films grown under the three different control regimes have measurably distinct solvent volume fraction profiles and there is evolution of these profiles with increasing thickness. Ultimately, for the conditions employed, the order of increasing porosity (i.e. solvent content) by control function was potentiostatic

We present a detailed mechanistic study of the PD process, focused on the nucleation and growth dynamics of silver particles on fingermarks deposited on a paper surface, from macroscopic (whole fingermark) and microscopic (particle level) perspectives. Conceptually, we separate the outcomes into aspects that precede exposure of the exhibit (relating to the reagent formulation), that relate to the development of the fingermark during immersion in the PD formulation, and that characterise the fully developed mark subsequent to immersion. Initially, dynamic light scattering shows the silver particles in solution to be relatively monodisperse, with a peak particle size of 880 nm. In the second instance, the issue is whether the particles grow to final size in solution then deposit on the surface or deposit as relatively small particles then grow on the surface. To the naked eye, silver deposition is evident after 2 min; corresponding optical profilometry images show evidence of surface-bound particles (mean diameter 2.13 µm) after 30 s. Across the development time (15 min) the particle population density (2.36 ( ± 0.52) x 10

Funding: Marine Scotland Science (MSS). Wild Atlantic salmon Salmo salar stocks have globally declined over recent decades. On their migratory return to coastal waters, individuals typically are infested by ectoparasitic caligid sea lice (Lepeophtheirus salmonis Krøyer, Caligus elongatus Nordmann). Infestation in laboratory trials can exert non-lethal impacts on the host fish, including increased stress levels and reduced growth, physical condition and swimming performance. However, to date no evidence exists for non-lethal effects of sea lice on wild adult Atlantic salmon. Using observations for > 6000 return-migrant adult salmon captured from the coastline at Strathy Point (SP), North Scotland, in the estuary of the River North Esk (NE), East Scotland, and the lower reach of the River Tamar (TA), Southwest England, we show that the somatic condition (weight at length) of wild salmon is associated with mobile sea lice density. This putative sea lice-mediated reduction of condition varied with year and seasonal date of freshwater return, and increased with the proportion of adult female parasites on a given fish. Influence of host sex, sea-age and smolt age was negligible. The estimated impact differed between the 3 sampling sites likely due to underestimation of infestation levels at NE and TA — largely attributable to negative influences of reduced salinity on parasite retention prior to sampling. Caligid infestation in the present samples explained a small, but discernible, proportion of the variation in host condition. Reductions in somatic condition of Atlantic salmon are associated with disproportionate declines in accreted lipid reserves, which are critical to up-river migration and ultimately the provisioning of eggs. Postprint Postprint

Here, we describe new developments in the study of electrodeposition processes with time-resolved dynamic neutron reflectivity (NR) methods to achieve insights into the differences between growth of metal films using a range of electrochemical control functions. We show that the temporal resolution has increased from 1 to 2 h per data set (in our previous studies) to approximately 8 min. We have studied the electrochemical deposition of copper and silver as thin-film metals onto a gold electrode substrate from a deep eutectic solvent using potentiodynamic (PD), potentiostatic (PS) and galvanostatic (GS) electrochemical control functions. In particular, we have utilised novel developments in neutron reflectivity methods to acquire real-time data for the growing metal films. Event mode capture of neutron scattering events, as a function of momentum transfer vector, Q, during electrochemical growth has enabled time-resolved measurement of the neutron reflectivity, R(Q), profiles of the growing metal films. Subsequent fitting and iterative optimisation of the R(Q,t) data reveals the thickness, roughness and relative density (spatially resolved solvent content) of the metal film during growth. These data show that the different electrochemical growth methodologies exhibit different trends in thickness, roughness and solvation. Silver films show an increasing roughness trend with time but these trends are largely independent of growth method. In contrast, the roughness of copper films, grown under similar conditions, shows a strong dependency on growth method with PS methods producing smoothest films. These conclusions are confirmed by ex-situ AFM measurements. The fitted NR data show that the Cu and Ag films contain between 5 and 10% volume fraction solvent. Furthermore, we have explored different NR data fitting methodologies in order to process the large numbers of data sets produced. Gratifyingly, the different methodologies and starting conditions yield a very consistent picture of metal film growth.

We report the electrochromic properties of a polymeric nanocomposite prepared by potentiodynamic deposition of transition-metal complex [Ni(3-Mesalen)], designated as [1], in the presence of TiO2 nanoparticles (NPs) with an average size of 9.7 ± 1.1 nm. Entrapment of TiO2 NPs in the poly[1] matrix was confirmed by several techniques. The nanocomposite TiO2@poly[1] films showed similar electrochemical responses to the original (nanoparticle-free) poly[1] films, but with higher electroactive surface coverages (Γ), showing the advantage of the nanocomposite preparation. The results indicated that the electronic structure of poly[1] was retained in the nanocomposite; nonetheless, a lower e value was obtained for the charge-transfer band of the former, revealing superior stability of the nanocomposite for ligand high oxidation states. The TiO2@poly[1] nanocomposite showed interesting color changes, from yellow (reduced state) to green and russet (oxidized states), with enhanced electrochemical stability, demon...

The strategy of combining electroactive polymers and inorganic nanomaterials has been widely explored in recent years in order to improve some of their properties, namely electrocatalysis and electrochromism. This report focuses on a new composite prepared through the electropolymerization of the transition metal complex [Ni(3-Mesalen)], designated as [1] in the presence of WO3 nanoparticles (NPs) and its electrochromic (EC) performance. The WO3 NPs were prepared using tungsten metal powder; their characterization indicated quasi-spherical morphology, high crystallinity and particle sizes in the range 30–40 nm. The nanocomposite WO3@poly[1] films displayed similar electrochemical responses to those of pristine poly[1] films in LiClO4/CH3CN, but higher electroactive surface coverages, an advantage of NPs incorporation in the nanocomposite. The presence of the WO3 NPs in the poly[1] matrix was assessed by X-ray photoelectron spectroscopy and scanning electronic microscopy. The nanocomposite presented similar electronic spectra to those of poly[1], indicating that the electronic structure of the pristine film is maintained in the nanocomposite, but exhibited lower e-values for bands associated with charge transfer transitions for high oxidised states, revealing an enhanced stability towards ligand over-oxidation. The WO3@poly[1] nanocomposite showed more favourable EC properties in LiClO4/CH3CN than the pristine film. For typical coverages (Γ = 0.06-0.10 μmol cm−2) the composite showed lower switching times (τ = 1.3 − 3.6 s), higher optical contrast (ΔT ≈ 31%, an improvement of ca. 40%) and better colouration efficiencies (in the range η = 104 − 115 cm2C−1, improvement of ca. 13 − 22%).

Innumerable technological devices and applications utilise metals and metal ions that ultimately find their way into the environment. While many metals are required at trace level for good health, their presence at higher levels is generally detrimental to human health and to the environment at large. For example, higher levels of copper are associated with liver and kidney disease; of nickel with cancer, cardiovascular disease, neurological conditions and infant developmental disorders; and of cobalt with respiratory conditions. This motivates the need to detect and determine these species at trace level; a related goal (not addressed directly here) is their extraction for the purposes of remediation. Although numerous analytical techniques exist for the determination of metal ions, electrochemically-based devices have a number of advantages, including portability for remote application. This work explores underpinning fundamental electrochemistry and interfacial characterisation associated with the fabrication and performance of carboxylate ligand-functionalised conducting polymer films as metal ion sensing moieties immobilised on electrode surfaces. Typical chelating ligands for metal ions are relatively bulky compared to the electropolymerizable monomer units, for example based on pyrrole or thiophene, commonly used to generate electroactive polymer films. As a consequence, electropolymerization of ligand-functionalised monomers is not generally effective: steric hindrance simply impedes coupling of the monomer units. We therefore adopt the alternative approach of electropolymerizing monomers functionalised with relatively small labile groups, followed by hydrolysis of the labile groups and re-functionalisation with the desired ligand. Here we explore this strategy for pyrrole-, thiophene- and aniline-based monomers functionalised with 9-fluorenylmethoxycarbonyl (fmoc) or pentafluorophenyl groups via ester linkages. Following electrochemically controlled polymerization, the resulting polymer films were treated with base to remove the labile groups, then with Nα,Nα-bis-(carboxymethyl)-L-lysine to couple N-nitrilotriacetic acid functionalities via amide formation. The polymerization process and the subsequent electroactivity of each of the parent films were studied using voltammetric and nanogravimetric (QCM) techniques. The ultimate effectiveness of the surface synthetic sequence, effected by post-deposition functionalisation with the ligand species, was validated using FTIR spectroscopy. This was accomplished by monitoring the bands associated with the carbonyl functionality: this is initially part of an ester, then an acid and finally an amide, each of which has a characteristic frequency. In the case of initially pentafluorophenyl-functionalised monomers, the hydrolysis of this group is associated with the loss of the C-F functionality. Measurements as a function of time permit the dynamics of these processes to be followed. Additionally, nanogravimetric measurements allow the time course of as-deposited polymer hydrolysis and subsequent functionalisation to be followed and quantitatively compared with the reaction stoichiometry. The effectiveness of these ligand-functionalised films was explored in terms of their ability to take up nickel, cobalt and copper ions from aqueous solution. Coulometric and gravimetric (QCM) data at various points in the process and as a function of solution metal ion concentration permit the acquisition of isotherms for metal ion uptake. At high metal ion concentration, the ligand sites are saturated; this permits metal:ligand stoichiometry to be evaluated. The relative merits of Langmuir, Frumkin, Temkin and Freundlich isotherms are discussed and the viability of the films for metal ion sensing evaluated. Unsurprisingly, the Langmuir isotherm provides a relatively poor description of the variation of metal ion uptake with concentration; this is attributed to the rather simplistic assumptions of this model. Of the remaining models, the Frumkin isotherm provides the best description of metal ion uptake for all systems considered. The binding constants evaluated from the polymer isotherms are significantly smaller than for the same ligand in solution; this is presumably a consequence of steric effects in the surface-confined polymer environment. Of relevance to potential applications, the films can be regenerated, i.e. restored to metal-free state, by exposure to EDTA solution.

Electroactive films based on conducting polymers have numerous potential applications, but practical devices frequently require a combination of properties not met by a single component. This has prompted an extension to composite materials, notably those in which particulates are immobilised within a polymer film. Irrespective of the polymer and the intended application, film wetting is important: by various means, it facilitates transport processes – of electronic charge, charge-balancing counter ions (“dopant”) and analyte/reactant molecules – and motion of polymer segments. While film solvent content and transfer have been widely studied for pristine polymer films exposed to molecular solvents, extension to non-conventional solvents (such as ionic liquids) or to composite films has been given much less attention. Here we consider such cases based on polyaniline films. We explore two factors, the nature of the electrolyte (solvent and film-permeating ions) and the effect of introducing particulate species into the film. In the first instance, we compare film behaviours when exposed to a conventional protic solvent (water) with an aprotic ionic liquid (Ethaline) and the intermediate case of a protic ionic liquid (Oxaline). Secondly, we explore the effect of inclusion of physically diverse particulates: multi-walled carbon nanotubes, graphite or molybdenum dioxide. We use electrochemistry to control and monitor the film redox state and change therein, and acoustic wave measurements to diagnose rheologicallyvs.gravimetrically determined response. The outcomes provide insights of relevance to future practical applications, including charge/discharge rates and cycle life for energy storage devices, “salt” transfer in water purification technologies, and the extent of film “memory” of previous environments when sequentially exposed to different media.

Electroactive polymer films derived from aniline and substituted derivatives have attracted huge interest, as a consequence of their electronic, optical, chemical and charge storage properties. Surprisingly, there has been limited translation of these characteristics into practical devices. Two factors that have impeded progress here are an inability to deliver and optimise multiple characteristics in a single material and the absence of control of internal film structure. The latter is particularly difficult to maintain for soft matter, whose molecular geometry and spatial disposition at the mesoscopic scale necessarily changes in response to solvent influx/efflux during redox switching. These solvation phenomena have been variously described in terms of activity (thermodynamic) effects, volume constraints (polymer mechanical properties) and mobility (kinetic) effects. Quite generally, the dominant factor depends on the timescale, a feature of the experiments reported here. In this presentation, we explore strategies aimed at understanding and controlling internal film structure and solvation for polymer films based on aniline-type monomers. From a chemical perspective, we explore the effects of three factors: the nature of the solvent / electrolyte, extension from homopolymers to co-polymers, and the inclusion of geometrically distinct particulate species to generate hybrid organic/inorganic materials. In the first instance, we compare film deposition and subsequent redox chemistry when exposed to a conventional protic solvent (water) or to the aprotic ionic liquid Ethaline (a mixture of choline chloride and ethylene glycol). As an intermediate case, we consider film deposition and redox chemistry in the protic ionic liquid Oxaline (a mixture of choline chloride and oxalic acid). Quantitative nanogravimetric (QCM) measurements during deposition from ionic liquid reveal that the polymer film has substantially greater solvent content than if deposited from aqueous medium. A recognised phenomenon for electroactive polymer films is an anomalous response for the first redox cycle; this is generally attributed to solvation effects. This phenomenon is manifested quite differently for polyaniline films in water and Ethaline. In water, film evolution occurs over a number of cycles, while in Ethaline (in which the film is more highly solvated) the transition is complete with a single cycle. In the second instance, we consider copolymerization of aniline with o-toluidine or with o-aminophenol. Counter ion coordination by the hydrogen bond donors results in substantive differences in the effectively transferred entity. In the cases of Ethaline and Oxaline, the counter ion is no longer a small, mobile chloride ion, but rather a large hydrogen bond donor-coordinated species. In pursuit of possible environmental applications, we consider the extreme case of fluoride as a counter ion. Surprisingly, the relatively small changes in polymer composition effected by co-polymerisation with o-toluidine or o-aminophenol result in substantial changes in fluoride uptake. Finally, we explore the effect of inclusion of particulates, chosen so as to influence different aspects of film behaviour. Specifically, we chose multi-walled carbon nanotubes (MWCNT), graphite flakes and molybdenum oxide particles as examples of 1D, 2D and 3D entities, respectively. Electrochemical and imaging data will be presented to demonstrate their substantive effects on film structure and dynamics. The outcomes of these studies provide insights relevant to practical applications. A particular case is that of medium transfer experiments, in which a film is deposited from one medium (aqueous or ionic liquid), redox cycled in the second and then returned to the first. We discuss the responses in terms of a “nature vs nurture” competition, in which the “nature” of a film is dictated by the conditions (medium) of deposition, and “nurture” is represented by the conditions to which it is exposed. Nanogravimetric (EQCM) responses of films subjected to water / ionic liquid / water and ionic liquid / water / ionic liquid transfer experiments reveal that films do retain some memory of their deposition conditions, but that extended redox cycling results in slow evolution that reflects the immediate medium of exposure. We discuss this in terms of slow polymer structural relaxation.

Exquisite control of the electrodeposition of metal films and coatings is critical to a number of high technology and manufacturing industries, delivering functionality as\ud diverse as anti-corrosion and anti-wear coatings, electronic device interconnects and energy storage. The frequent involvement of more than one metal motivates the\ud capability to control, maintain and monitor spatial disposition of the component metals, whether as multilayers, alloys or composites. Here we investigate the deposition, evolution and dissolution of single and two-component metal layers involving Ag, Cu, and Sn on Au substrates immersed in the deep eutectic solvent (DES) Ethaline. During galvanostatically controlled stripping of the metals from two-component systems the potential signature in simultaneous thickness electrochemical potential (STEP) measurements provides identification of the dissolving metal; coulometric assay of deposition efficiency is an additional outcome. When combined with quartz crystal microbalance (QCM) frequency responses, the mass change : charge ratio provides oxidation state data; this is significant for Cu in the high chloride environment provided by Ethaline. The spatial distribution (solvent penetration and external roughness) of multiple components in bilayer systems is provided by specular neutron reflectivity (NR). Significantly, the use of the recently established event mode capability shortens the\ud observational timescale of the NR measurements by an order of magnitude, permitting dynamic in situ observations on practically useful timescales. Ag,Cu bilayers of both\ud spatial configurations give identical STEP signatures indicating that, despite theextremely low layer porosity, thermodynamic constraints (rather than spatial accessibility) dictate reactivity; thus, surprisingly, Cu dissolves first in both instances. Sn penetrates the Au electrode on the timescale of deposition; this can be prevented by interposing a layer of either Ag or Cu.

An electrochromic nanocomposite based on a nickel-salen polymeric film – poly[Ni(3-Mesalen)], Mesalen = N,N’-bis(3-methylsalicylideneiminate) – and graphene nanoplatelets (GFNPs) with enhanced electrochromic stability was successfully prepared by anodic electropolymerization. Although the electrochemical processes typical of the polymer film were not changed by the presence of graphene, higher electroactive surface coverages could be obtained for nanocomposite films, which suggest the incorporation of GFNPs into the polymeric network. The nanocomposite showed multi-electrochromic behavior, with color changes between yellow (reduced state) and green (oxidized state). The inclusion of GFNPs into the poly[Ni(3-Mesalen)] structure accelerates the switching process, with the response time for green coloration decreasing by 50.7% and for yellow coloration by 60.0%, for films prepared with 30 electropolymerization cycles. In terms of electrochemical stability, after 10,000 electrochemical cycles the loss of charge was 7% for the graphene nanocomposite. The nanocomposite film was used as electrochromic material to assemble a flexible solid-state electrochromic device (ECD), which exhibited an outstanding electrochemical stability - only 3% of charge loss after 15 days of continuous activity.

A new nanocomposite was obtained through the incorporation of N-doped few-layered graphene (N-FLG) into films of the electroactive polymer poly[Ni(3-Mesalen)] (poly[1]). The nanocomposite, N-FLG@poly[1], prepared by in situ electropolymerization, showed similar electrochemical responses to pristine poly[1], but with more well-defined redox peaks and higher current intensities, in compliance with larger electroactive surface coverage. N-FLG incorporation did not affect the electronic structure of poly[1], but decreased in 12% the molar extinction coefficient of the charge transfer band between metal and oxidized ligand, which is a promising advantage since this band is related to polymer degradation. The N-FLG@poly[1] showed multi-electrochromic behaviour (yellow in reduced state and green/russet in oxidized states) and revealed excellent improvement in electrochromic performance compared to original poly[1], specifically an increase of 71% in electrochemical stability (loss of 2.7% in charge after 10 000 switching cycles). Furthermore, nanocomposite formation decreased the switching time for oxidation (reduction) τ = 9 s (11 s) and improved the optical contrast (Δ T = 35.9%; increase of 38%) and colouration efficiency ( η = 108.9 cm 2 C −1 ; increase of 12%), for a representative film of coverage Γ = 296 nmol cm −2 . The excellent electrochromic performance improvements are attributed to the alternative conducting pathways and to morphological modifications induced by N-FLG.

The successful operation of a photogalvanic cell for solar energy conversion requires that the illuminated electrode should discriminate between the two redox couples in solution. In the iron–thionine system the electrode must oxidise photogenerated leucothionine but not reduce the photo-generated Fe(III). Modified electrodes with coatings of thionine of up to 20 monolayers can be prepared on Pt and SnO2. Electrode kinetic results for the Fe(III) and thionine systems show that this modified electrode is suitable for the iron–thionine photogalvanic cell.

By using contour integration to invert the Laplace transforms, an analytical expression for the first order kinetic collection efficiency for a ring-disc electrode can be obtained for values of κ > 3. One can then obtain analytical results for the phase shift and amplitude of the ring current with respect to the disc current when an alternating current is passed through the disc. Hence, theoretical results for the complete frequency range can now be obtained. Theory and experiment are found to be in good agreement.

We report the application of two poly[Ni(salen)]-type electroactive polymer films as new electrochromic materials. The two films, poly[Ni(3-Mesalen)] (poly[1]) and poly[Ni(3-MesaltMe)] (poly[2]), were successfully electrodeposited onto ITO/PET flexible substrates, and their voltammetric characterization revealed that poly[1] showed similar redox profiles in LiClO4/CH3CN and LiClO4/propylene carbonate (PC), while poly[2] showed solvent-dependent electrochemical responses. Both films showed multielectrochromic behavior, exhibiting yellow, green, and russet colors according to their oxidation state, and promising electrochromic properties with high electrochemical stability in LiClO4/PC supporting electrolyte. In particular, poly[1] exhibited a very good electrochemical stability, changing color between yellow and green (λ = 750 nm) during 9000 redox cycles, with a charge loss of 34.3%, an optical contrast of ΔT = 26.2%, and an optical density of ΔOD = 0.49, with a coloration efficiency of η = 75.55 cm(2) C(-1). On the other hand, poly[2] showed good optical contrast for the color change from green to russet (ΔT = 58.5%), although with moderate electrochemical stability. Finally, poly[1] was used to fabricate a solid-state electrochromic device using lateral configuration with two figures of merit: a simple shape (typology 1) and a butterfly shape (typology 2); typology 1 showed the best performance with optical contrast ΔT = 88.7% (at λ = 750 nm), coloration efficiency η = 130.4 cm(2) C(-1), and charge loss of 37.0% upon 3000 redox cycles.

Acoustic admittance measurements at thickness shear mode resonators were used to determine shear moduli for polyaniline films during their potentiodynamic electrodeposition and subsequent redox cycling in aqueous background electrolyte. Data were acquired for films doped with perchlorate, sulphate or chloride anion. For all media, film shear moduli increased progressively with film thickness, from values consistent with a diffuse fluid-like layer to values typical of a viscoelastic material. At any given thickness, both the storage and loss moduli were largest in perchlorate medium; values in chloride and sulphate media were similar to each other, but smaller than in perchlorate. These measures of polymer dynamics are consistent with a previous classification of polyaniline film behaviour, in which perchlorate-doped films are viewed as compact while chloride- and sulphate-doped films are viewed as more open. In monomer-free background electrolyte solution, both film shear modulus components for all anions increased modestly upon film oxidation. Despite some hysteresis on the timescale of slow scan voltammetry, these variations were chemically reversible. Based on measurements involving deposition from chloride medium and transfer to sulphate medium, film shear moduli respond promptly to changes in dopant identity; this is consistent with rapid redox-driven exchange of anions with the bathing electrolyte.

EQCM experiments were made on PEDOT films exposed to LiClO4/CH3CN under permselective conditions and subjected to cyclic voltammetry in the potential range corresponding to p-doping. Current and frequency responses were used to generate time-resolved ion and solvent flux data as functions of potential. These fluxes normalize with respect to scan rate during p-doping and undoping, but the responses in the two directions are not mirror images. The results lead to the following mechanistic conclusions. Coupled electron/anion transfer is the first, and non-rate limiting, step in both redox switching directions, but involves differently solvated and configured polymer in the two directions. Solvent transfer and polymer reconfiguration follow the charge transfer steps, but are kinetically inseparable on the timescales accessed. This mechanism can be visualized by a scheme-of-squares representation whose two coordinates are “coupled electron/anion transfer” and “coupled solvent transfer/polymer reconfiguration”. The data analysis protocol provides a powerful approach to identifying mechanistic pathways, particularly in situations corresponding to partial film redox conversion. Keywords: PEDOT, Conducting polymer, Cyclic voltammetry, EQCM, Doping mechanism, Solvent transfer, Polymer dynamics

This paper describes studies of a combined electrochemical/acoustic wave sensor for detection of metal ions in aqueous solutions. The sensor is based upon surface complexation of the metal ions at thiodisuccinic acid (TDS) functionalised self-assembled monolayer (SAM) modified electrodes on 10 MHz AT-cut quartz resonators, functioning as a quartz crystal microbalance (QCM). The SAM-modified electrodes were employed for the detection of Cd(II) ions in single and mixed metal ion solutions, with Pb(II) or Cu(II) as the interferants. Acoustic determination was based on the QCM frequency change associated with the binding to the surface-immobilised ligand of metal ions as a function of their concentration. Frequency response data were acquired under emersed and immersed conditions for ligand binding to the Au electrode and, subsequently, metal ion binding to the ligand. In the latter case, the data were interpreted according to a range of isotherms, of which the Temkin isotherm was found empirically best to describe the concentration dependence. The acoustic wave data yielded information on equilibrium binding stoichiometry and energetics. The extent of metal ion binding was also determined by coulometric assay (upon reduction to the zero-valent metal) after transfer to metal ion-free electrolyte solution. XPS studies of surface-bound metal-TDS ligand complexes confirmed the binding stoichiometry obtained from the electrochemical and acoustic wave responses, and provided information on the ligand–substrate binding and bound analyte oxidation state.

A comprehensive thermodynamic model for solvent and salt transfer accompanying a partial redox conversion, i.e., conversion between any two oxidation levels, of an electroactive polymer (EAP) film is presented. We discuss two possible cases, namely, one-phase and two-phase behavior of an EAP film. An expression describing the extent of solvent transfer in these situations is presented. Salt transfer is characterized by the difference in permselectivity indices (Delta R(b,a)) between two oxidation levels of the EAP film. Delta R(b,a) represents the difference in co-ion (salt) exclusion properties of the EAP in the two different oxidation levels. Delta R(b,a) is expressed in terms of the EAP's charge, number of electrons transferred in the redox reaction of an electroactive unit, concentration of the supporting electrolyte, salt partition coefficient between solvent and EAP phases, and salt activity coefficients in both phases. Plots of Delta R(b,a) as a function of the electrolyte concentration allow determining the EAP's phase behavior, ratio of salt partition coefficients, and number of electrons exchanged in the redox process. Delta R(b,a) is an experimentally accessible quantity; it can be obtained from electrochemical quartz crystal microbalance (EQCM) experiments. Delta R(b,a) values can be used as a diagnostic tool to characterize an EAP film.

The fabrication and assembly of printed circuit boards (PCBs) involves the layering of metals onto an insulating substrate prior to the addition of electronic components. The interfaces between these metal layers are often subject to metal-metal interdiffusion, formation of brittle intermetallics and corrosion, compromising the integrity of the PCB-component solder joints. We have recently developed environmentally sustainable, non-toxic methodologies for application of metal PCB finishes using Deep Eutectic Solvents (DESs) as a novel solvent medium.1-3 Here we focus on the characterisation of metal-metal interfaces in DES media quantifying interfacial structure, layer thickness and morphology using a range of electrochemical and microscopy techniques, including chronoamperometry, cyclic voltammetry (CV) and novel simultaneous thickness electrochemical potential (STEP) measurements coupled with neutron reflectivity (NR.) We have developed the STEP methodology to ascertain some, if not all, of the same information that NR provides. Deposition of Ag and Cu layers has been carried out in different configurations onto Au substrates and characteristic STEP traces are presented for each upon galvanostatic stripping. The STEP methodology facilitates the identification and quantification of each metal layer by galvanostatic dissolution, which is comparable with time resolved NR measurements. The characteristic features of the STEP measurements are discussed including the shape and potential of the dissolution trace. The degree of mixing between the layers is qualitatively determined from E vs. t traces, along with the layer composition and thickness for systems in which layers remain discrete. In summary, we present a new, accessible and inexpensive technique, which probes the thickness, composition and interfacial mixing between layers in PCB metal systems using DES electrolytes and galvanostatic stripping methodologies. [1] A. D. Ballantyne, G. Forrest, M. Goosey, A. Griguceviciene, J. Juodkazyte, R. Kellner, A. Kosenko, R. Ramanauskas, K. S. Ryder, A. Selskis, R. Tarozaite and E. Veninga, Circuit World, 2012, 38(1), 21-29. [2] K. S. Ryder, A. D. Ballantyne, D. Price and T. Perrett, The PCB Magazine, February 2012, 22-30. [3] A. P. Abbott, S. Nandhra, S. Postlethwaite, E. L. Smith, and K. S. Ryder, Phys. Chem. Chem. Phys., 2007, 9, 3735–3743. Figure 1

Electrolytic coatings of metals such as nickel, chromium, zinc, silver and gold are commonly applied as decorative and/or functional coatings. Some of the functional benefits which metal coatings provide are corrosion resistance, wear resistance, electrocatalysis and use in magnetic applications. A range of strategic manufacturing industries are dependent on such electrolytic coatings including electronics, aerospace, automotive and energy. The vast majority of electrolytic coatings are plated from aqueous solutions but stringent health and safety legislation governing transport, use and disposal of feedstock chemicals has driven the challenge for innovation in electrolyte technology that facilitates coatings from less toxic materials and in a manner that is more efficient and more consistent with environmental and process sustainability. We have been motivated by this challenge and have developed a range of novel solvent systems for deposition of metal coatings as alternatives to existing process (e.g. Ni, Zn, Cu, Ag, Ag) as well as novel electrolytes for deposition of reactive metals such as Al. These electrolytes have become known as Deep Eutectic Solvents and have shown utility and promise in a range of metal finishing processes. [1] Whilst the thermodynamics, kinetics, metal ion speciation and growth processes of electrolytic coatings from aqueous solutions have been studied for more than one hundred years, little is currently known about these fundamental aspects of electrochemical deposition from DES media. [2] Here we describe our studies into the electrochemical characterisation of a range of metals in DES electrolytes. In particular, we will focus on aspects of growth and dissolution processes and how these effect the morphology and composition of metal films. We will describe the characterisation of thin metal films in DES media using a range of time resolved techniques including cyclic voltammetry, chronopotentiometry, chronoampertometry, gravimetry (QCM), neutron reflectometry (NR) and surface metrology. The use of in-situ electrochemical NR methods is novel and we will present new data on the growth and dissolution of single metal and bi-layer metals films. The Figure shows time resolved NR data for the electrochemical dissolution of a Cu/Ag bi-layer on a Au substrate. We will also present complimentary data on the characterisation of the same systems using so-called Simultaneous Thickness Electrochemical Potential (STEP) chronopotentiometric methods. We will consider the effect of small-molecule additives on surface morphology and finish (roughness) of electrolytic coatings. [3] Organic and inorganic additives are often added to electroplating solutions to improve surface finish, reduce roughness and promote uniform surface morphology of the coatings. Such additives are usually small molecules and often referred to as brighteners or levellers. However, there have been limited investigations into the effect of such additives on electrodeposition from ionic liquids (ILs) and deep eutectic solvents (DESs). Here we will describe the effect of four additives on electrolytic plating of exemplar metals, nickel and zinc, from an ethyleneglycol based DES; these are nicotinic acid (NA), methylnicotinate (MN), 5,5-dimethyl- hydantoin (DMH) and boric acid (BA). The additives show limited influence on the bulk speciation but have significant influence on the electrochemical behaviour of metal deposition. Small concentrations (ca. 15 mM) of NA and MN show inhibition of metal ion reduction whereas high concentrations of DMH and BA are required for a modest difference in behaviour from the additive free system. NA and MN also show that they significantly alter the nucleation and growth mechanism when compared to the additive free system and those with DMH and BA. Each of the additive systems had the effect of producing brighter and flatter bulk electrodeposits and with increased coating hardness. “Deep Eutectic Solvents (DESs) and their Applications”, Emma L. Smith, Karl S. Ryder and Andrew P. Abbott, Chem. Rev., 2014, 114, 11060. “EXAFS Study into the Speciation of Metal Salts Dissolved in Ionic Liquids and Deep Eutectic Solvents”, Jennifer M. Hartley, Chung-Man Ip, Gregory C.H. Forrest, Kuldip Singh, Stephen J. Gurman, Karl S. Ryder, Andrew P. Abbott and Gero Frisch, Inorg. Chem., 2014, 53(12), 6280. “Bright Metal Coatings from Sustainable Electrolytes: The Effect of Molecular Additives on Electrodeposition of Nickel from a Deep Eutectic Solvent”, Andrew P. Abbott, Andrew Ballantyne, Robert C. Harris, Jamil A. Juma and Karl S. Ryder, Phys. Chem. Chem. Phys., 2017, 19. 3219. Figure 1

We derive a lumped-element, equivalent-circuit model for the thickness-shear mode (TSM) resonator with a viscoelastic film. This modified Butterworth-Van Dyke model includes in the motional branch a series LCR resonator, representing the quartz resonance, and a parallel LCR resonator, representing the film resonance. This model is valid in the vicinity of film resonance, which occurs when the acoustic phase shift across the film is an odd multiple of pi/2 rad. For low-loss films, this model accurately predicts the frequency changes and damping that arise at resonance and is a reasonable approximation away from resonance. Elements of the parallel LCR resonator are explicitly related to film properties and can be interpreted in terms of elastic energy storage and viscous power dissipation. The model leads to a simple graphical interpretation of the coupling between the quartz and film resonances and facilitates understanding of the resulting responses. These responses are compared with predictions from the transmission-line and Sauerbrey models.

Characterization of electroactive polymer films and their application in practical devices (electronic, chemical, sensing, energy storage, optical, actuator) tends to focus on the transfer of charged species (electrons and counter ions), since these are the entities most directly associated with the response to the electrochemical control function. However, transport rates of ions (“dopant”, in the context of conducting polymer systems) are dictated by solvent content of the film, which governs the local viscosity of the medium through which mobile species move. Further, the presence of solvent (and other small molecules) creates free volume that facilitates the dynamics of polymer motion, macroscopically seen as a plasticising effect on film viscoelasticity. In the light of the above, it is of value to determine the solvent content of electroactive polymer films; this is the focus of the present work. Experimentally, the challenge is that the solvent is (by choice) electrochemically “silent” and optically transparent, and its selective observation within a film exposed to a vast reservoir of bulk solution is not trivial. Nanogravimetric measurements made using the EQCM have provided innumerable insights into changes in film solvent population, e.g. in response to redox state changes, but the technique cannot provide absolute solvent population in the film. Spectroscopic techniques generally have difficulty in distinguishing solvent in a film from that in bulk solution, but reflectivity techniques do possess surface selectivity. Of these, ellipsometry has the advantage of rapid data acquisition, i.e. good time resolution, but modelling the data can present ambiguities. Here we use neutron reflectivity (NR) which, through the penetrating nature of neutrons, allows access to "buried" interfaces. Traditionally, the negative consequence of this weak interaction with matter is long data acquisition times; addressing this is the central feature of this presentation. Since neutrons interact with the nuclei in the system (cf. photons interacting with the electrons in ellipsometry), NR has the huge advantage of isotopic selectivity. This is commonly referred to as “contrast variation” and has the critical characteristic of allowing one to vary the visibility of a selected chemical component without (to a first approximation) altering the (electro)chemistry of the system. Most frequently, this is exploited by deuteration, since the neutron scattering lengths of H and D are very different. Correlation of the h- and d-system NR data sets removes ambiguities in modelling the data. We have previously used NR with solvent contrast variation to determine solvent volume fraction depth profiles, ΦS(z), in redox polymer films at equilibrium (fixed potential) and on long timescales during slow cycling. We now present data under dynamic conditions more relevant to fabrication or operation of a working device. This necessitates an order of magnitude improvement in time resolution. Instrumentally, the challenge can be met using more sophisticated detection systems, including event mode data capture, in which every incident/reflected neutron is detected individually. The dramatic increase in the size of data sets presents challenges in modelling the data, but the facility to (re-)select signal averaging time post experiment permits optimisation of competing aspirations of time resolution and signal-to-noise. This is key for single shot experiments, such as film deposition or evolution of film behaviour. Here we present neutron reflectivity data for aniline-, pyrrole- and thiophene-based polymer films. For these systems, we have the opportunity to exploit h- and d- variants of both solvent and monomer. Four significant insights are revealed. First, the data reveal that film deposition protocol (i.e. potentiostatic, potentiodynamic or galvanostatic control function) influences film solvation state and spatial distribution; while anecdotally suspected, this provides unambiguous quantitative evidence. Second, there are substantial spatial variations in film solvent content; this is a feature commonly not accommodated in models of modified electrodes. Third, for some systems, film solvent population and spatial disribution are "frozen" into the system during fabrication, so deposition protocol determines film characteristics in the longer term. Fourth, in selected cases the structure evolves with electrochemical manipulation, such that differently prepared films subsequently exposed to the same environment and history evolve to a common solvation profile. The implications of these phenomena for film design and handling are discussed for particular types of application.

The pressure release bubble nucleation technique was used to study the kinetics of bubble nucleation for the H2O/CO2/Pyrex system over the supersaturation range 1-7. Attempts to fit the experimental bubble evolution data to the nucleation equation of Wilt (J. Colloid Interface Sci. 112, 530 (1986)) reveal apparent anomalies between the dependence of the predicted and that of experimental rates on supersaturation. These differences are explained in terms of a distribution of active nucleation sites at which the bubbles nucleate on the Pyrex surface. Each site type displays its own rate kinetics, and the overall bubble nucleation rate is the sum of the rates from each site type. The concept of "nucleation rate dispersion" is introduced to the field of bubble nucleation kinetics.

A combination of XPS, reflectance infrared spectroscopy, and neutron reflectivity measurements has been used to probe the spatial and global extents to which carboxylic acid motifs in electrodeposited conducting polymer films can be functionalized by reaction with vapor phase reagents (a carbodiimide together with trifluoroethanol) with the goal of controlling hydrophobicity. Across a range of polymer deposition and reaction temperatures, neutron reflectivity showed that, surprisingly, functionalization of the polymer matrix at depths >5-10 nm into the polymer film was always significantly lower than at the exposed surface. The most efficient functionalization was found to occur when a low-density polymer matrix was prepared by elution of motifs cleaved from the polymer by base hydrolysis. Finally, when trifluoroethanol functionalization was performed, the macroscopic property of hydrophobicity was related to the surface, internal microstructure, and composition of the reacted films as elucidated by the above combination of probes.

We describe in situ neutron reflectivity (NR) and RAIRS studies of the chemical modification of films of a polypyrrole-based conducting polymer derived from the pentafluorophenyl ester of poly(pyrrole-N-propanoic acid) (PFP) electrodeposited on electrode surfaces. We explore the role of the solvent in controlling the rate of reaction with solution-based nucleophiles (amines, which react with the ester to form amides). By varying the identity of the solvent (water vs acetonitrile) and the neutron contrast (deuteration), we find that both the identity of the solvent and its population within the film are paramount in determining chemical reactivity and electroactivity. IR signatures allow monitoring of the reaction of solution-based amine-tagged species such as amino-terminated poly(propylene glycol), ferrocene ethylamine, and lysine with film-based ester functionalities: the carbonyl bands show ester/amide interconversion and some hydrolysis to acid. Time-dependent spectral analysis shows marked variations in reaction rate with (i) (co-)polymer composition (replacement of some fluorinated ester-functionalized pyrrole with unfunctionalized pyrrole), (ii) the solvent to which the polymer film is exposed, and (iii) the rate of polymer deposition. NR data provide solvent profiles as a function of distance perpendicular to the interface, the variations of which provide an explanation for film reactivity patterns. Homopolymer films are relatively hydrophobic, thus hindering reaction with species present in water solutions. Incorporating pyrrole groups raises the solvent population-dramatically for water-thereby facilitating entry and reaction of aqueous-based lysine. Changing film deposition rate yields films with different absolute levels of solvent and reactivity patterns that are dependent on the size of the reactant molecules: more rapid deposition of polymer gives films with a more open structure leading to a higher solvent content and thence increased reactivity. These results, supported by XPS and AFM data, allow assembly of composition-structure-reactivity correlations, in which the controlling feature is film solvation.

Electrogenerated polymers based on copper salen-type complexes were characterised electrochemically and by in situ UV–vis and ex situ EPR spectroscopy. The films, poly[Cu(salen)] and poly[Cu(saltMe)], exhibit reversible oxidative electrochemical behaviour in a wide potential range (0.0–1.5 V). Different regimes for charge transport behaviour are accessed by manipulation of film thickness and experimental time scale: thin films (surface concentration, Γ < ca. 80 nmol cm−2) show thin-layer/surface behaviour in the scan rate range used (0.020–2.0 V s−1), whereas thicker polymers (Γ > ca. 90 nmol cm−2) exhibit a changeover from thin-layer to diffusion control regime at a critical scan rate that depends on polymer and film thickness: 0.15–0.20 V s−1 for poly[Cu(salen)], 90 < Γ < 130 nmol cm−2 and 0.20–0.30 V s−1 for poly[Cu(saltMe)], 170 < Γ < 230 nmol cm−2. UV–vis and EPR spectroscopies have allowed the characterisation of electronic states in the reduced and oxidised forms. The role of the copper atom during film oxidation was probed by combining UV–vis data with EPR on copolymers of the copper and nickel complexes. Data from both techniques are consistent and indicate that polymerisation and redox switching are associated with ligand-based processes. EPR of Ni-doped Cu polymers provided evidence for the non-involvement of the metal centre in polymer oxidation; like the analogous nickel polymers, copper polymers behave like delocalised π-system (‘conducting’) rather than discrete site (‘redox’) polymers.

We describe the potentiodynamic preparation and subsequent characterization of poly[Ni(3-MeOsaltMe)] films (surface concentration, 3 < i/nmol cm -2 < 350) in acetonitrile media. Coulometric and gravimetric (electrochemical quartz crystal microbalance, EQCM) data allow one to monitor the deposition process and show that the resultant films are physically and chemically stable. Combined EQCM/probe beam deflection measurements were used to quantify the individual contributions (fluxes and population changes) of anions, cations, and solvent to the overall redox switching process. The first redox cycle for a film “rested” in the reduced state results in accumulation of anion (charge) and solvent in the film. The subsequent steadystate response is dominated by a combination of anion and solvent transfers; this takes place in two stages, the second of which involves significantly more solvent entry, to an extent dependent upon time scale. After a sequence of redox cycles, the initial thermodynamically “irreversible” behavior is restored by “resting” the film. Solvation effects are critical determinants of film redox chemistry and dynamics: in addition to controlling the feasibility and stability of deposition, they control film ion transport rate.

Poly(3,4-ethylenedioxythiophene) (PEDOT) is one of a range of conducting polymers based on aromatic heterocyclic monomers, typified by thiophene, pyrrole and their derivatives. The substitution pattern in PEDOT has the dual advantages of shifting the potentials for polymerization and redox switching into a more convenient range (as compared to the parent thiophene) and of blocking attack at the 3- and 4- positions of the aromatic ring. Both of these attributes enhance its practical application for energy storage applications, such as batteries and supercapacitors. Quite generally, the rates of doping and undoping (charging and discharging, in the context of energy storage) of conducting polymers are limited not by the rate of electron transport along the polymer backbone, but by the transport rate(s) of the charge balancing ion(s), i.e. dopant(s). The dynamics of these processes have been widely studied during redox switching of PEDOT films immersed in diverse electrolyte media based on molecular solvent systems. Although the quantitative details vary with the electrolyte selected, the qualitative outcome is that anion transfer is commonly the dominant process accompanying PEDOT oxidation (p-doping), but that cation transfer (in the opposite direction) can be appreciable, and in any case solvent transfer is significant; in the context of nanogravimetric measurements (using the EQCM), the ion and neutral molecule transfers can be distinguished according to their correlation with transferred charge. Measurements of the absolute solvent population (cf. changes measured in an EQCM experiment) in many conducting polymer films reveal that this may represent ca. 50% by volume of the film: this facilitates both ion transfers and polymer spinal motions. While such studies have revealed many interesting phenomena, notably solvation-controlled viscoelastic phenomena, a number of limitations make conventional solvent media unsuitable for practical applications; these may include available potential window, safety, toxicity or flammability. This motivates research on the redox chemistry of electroactive polymers in novel media, such as room temperature ionic liquids. Amongst these, we have been exploring the properties of deep eutectic solvent (DES) media based on various formulations of quaternary ammonium salts (QAS), hydrogen bond donors (HBD) and metal salts, in which complexation chemistry amongst the components generates fully ionic media. From a practical perspective, this provides an essentially unlimited source of ions (dopant). From a fundamental perspective, the dramatic difference is that these fully ionic media contain no solvent to plasticise the polymer; the more subtle difference is that the question of permselectivity that prevails (or fails) at low (or high) electrolyte concentration in a conventional solvent-based medium now becomes redundant. Here we describe nanogravimetric acoustic wave (EQCM) studies of redox driven ion transfers for PEDOT films exposed to three DES formulations variously involving choline chloride (Ch+Cl-) as the QAS, ethylene glycol (EG) as the HBD and ZnCl2 as the metal salt. Viscosity effects associated with the DES are significant but, via acoustic admittance measurements, one can obtain film ion population change data. These are presented as a function of timescale (potential scan rate in a voltammetric experiment) for potentiostatically- and potentiodynamically-grown PEDOT films subsequently exposed to ZnCl2/EG, ZnCl2/acetamide and ZnCl2/Ethaline (where Ethaline is a 1:2 stoichiometric mixture of Ch+Cl- and EG). Significantly, for thicker films (consistent with practical applications), there is incomplete charge recovery at faster scan rates, with accompanying failure to restore the initial film ion composition. In multi-cycling experiments this leads to evolution of response; we discuss re-equilibration when the film is subsequently held in a resting state. Cycling over prolonged time intervals also results in evolution of film responses. The fundamental interpretation and practical consequences of these observations will be discussed. We thank EU FP7 for financial support (NMP3-SL-2008-226655)

Latent fingerprints on metal surfaces may be visualized by exploiting the insulating characteristics of the fingerprint deposit as a “mask” to direct electrodeposition of an electroactive polymer to the bare metal between the fingerprint ridges. This approach is complementary to most latent fingerprint enhancement methods, which involve physical or chemical interaction with the fingerprint residue. It has the advantages of sensitivity (a nanoscale residue can block electron transfer) and, using a suitable polymer, optimization of visual contrast. This study extends the concept in two significant respects. First, it explores the feasibility of combining observation based on optical absorption with observation based on fluorescence. Second, it extends the methodology to materials (here, polypyrrole) that may undergo post-deposition substitution chemistry, here binding of a fluorophore whose size and geometry preclude direct polymerization of the functionalised monomer. The scenario involves a lateral spatial image (the whole fingerprint, first level detail) at the centimetre scale, with identification features (minutiae, second level detail) at the 100–200 μm scale and finer features (third level detail) at the 10–50 μm scale. However, the strategy used requires vertical spatial control of the (electro)chemistry at the 10–100 nm scale. We show that this can be accomplished by polymerization of pyrrole functionalised with a good leaving group, ester-bound FMOC, which can be hydrolysed and eluted from the deposited polymer to generate solvent “voids”. Overall the “void” volume and the resulting effect on polymer dynamics facilitate entry and amide bonding of Dylight 649 NHS ester, a large fluorophore. FTIR spectra demonstrate the spatially integrated compositional changes. Both the hydrolysis and fluorophore functionalization were followed using neutron reflectivity to determine vertical spatial composition variations, which control image development in the lateral direction.

Spatially selective electrodeposition of poly-3,4-ethylenedioxythiophene (PEDOT) thin films on metallic surfaces is shown to be an effective means of visualizing latent fingerprints. The technique exploits the fingerprint deposit as an insulating mask, such that electrochemical processes (here, polymer deposition) may only take place on deposit-free areas of the surface between the ridges of the fingerprint deposit; the end result is a negative image of the fingermark. Use of a surfactant (sodium dodecylsulphate, SDS) to solubilise the EDOT monomer allows the use of an aqueous electrolyte. Electrochemical (coulometric) data provide a total assay of deposited material, yielding spatially averaged film thicknesses, which are commensurate with substantive filling of the trenches between fingerprint deposit ridges, but not overfilling to the extent that the ridge detail is covered. This is confirmed by optical microscopy and AFM images, which show continuous polymer deposition within the trenches and good definition at the ridge edges. Stainless steel substrates treated in this manner and transferred to background electrolyte (aqueous sulphuric acid) showed enhanced fingerprints when the contrast between the polymer background and fingerprint deposit was optimised using the electrochromic properties of the PEDOT films. The facility of the method to reveal fingerprints of various ages and subjected to plausible environmental histories was demonstrated. Comparison of this enhancement methodology with commonly used fingerprint enhancement methods (dusting with powder, application of wet powder suspensions and cyanoacrylate fuming) showed promising performance in selected scenarios of practical interest.

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