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Here we demonstrate the generation of novel ionic liquid analogue (ILA) electrolytes for aluminium (Al) electrodeposition that are based on salts of amidine Lewis bases. The electrolytes exhibit reversible voltammetric plating/stripping of Al, good ionic conductivities (10-14 mS cm

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.

Sea lice are amongst the most ecologically and economically damaging parasites of farmed salmonids globally. Spill-over from aquaculture can increase parasite pressure on wild fish populations, but quantifying this effect is challenging due to the relative paucity of data available on ‘natural’ salmonid louse burdens in the absence of aquaculture, particularly for Atlantic salmon Salmo salar. Here, wild Atlantic salmon and sea trout S. trutta were screened at the tidal limit of the River Tamar (UK) for the presence of sea lice. During 2013 and 2015, the prevalence of sea lice ranged from 41 (n = 361) to 60% (n = 275) and 55 (n = 882) to 58% (n = 800) in Atlantic salmon and sea trout, respectively. All sea lice collected were identified as Lepeophtheirus salmonis. Mean L. salmonis infection intensity across the study period was 5.84 (range: 1-66) in Atlantic salmon and 6.45 (range: 1-37) in sea trout. Infection intensity was positively correlated with the amount of external damage present for both fish species. Given that the fish were examined when returning to freshwater, the lice burdens obtained may represent an underestimate. Nevertheless, these data provide important baseline information on ‘natural’ sea louse infections in South West England, which has been proposed as a potential region for aquaculture development.

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%).

Polyaniline itself can be converted to its conductive form from its insulating form by applying an oxidising potential in which polyaniline is converted to its positive charge state. Anions in the target solution are driven into the positively charged polymer film by electrostatic force, and this process is reversed when a reduction potential is applied. Consequently, interfacial processes of polyaniline modified electrode make it viable to remove undesirable ions from the target solution. During this process, polyaniline operates as an ion-exchanger by directing specific ions at definite potentials, which is the principle of the electrochemically switched ion-exchange technique. Therefore, polyaniline can be employed as a convenient material to perform as a new ion-exchanger modified film in an acidic environment. On the other hand, an abrupt decrease in the electroactivity of polyaniline at elevated pH values restricts its use in such practical applications. To overcome this problem, copolymerization of aniline and o-toluidine is expedient as it will be able to enhance the electrochemical properties of polyaniline. Hence, several copolymers were synthesised in the presence of different aniline and o-toluidine feedstock ratios. It was found that the surface coverage value of a representative poly(aniline-co-o-toluidine) copolymer film was 139.7 nmol cm−2 compared with 76 nmol cm−2 for pure Pani under identical conditions. In addition, the redox cycling in monomer-free NaF solutions showed that the poly(aniline-co-o-toluidine) film exhibited excellent reversibility between redox reactions at pH 6.60. These outcomes clearly illustrate the contribution of o-toluidine to the electrochemical properties of polyaniline at raised pH medium.

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.

Although the World Health Organization (WHO) recommends a limit of 1.5 mg l−1 fluoride ions in drinking water, this is not satisfied in many parts of the world. When this limit is exceeded, the electrochemically switched ion-exchange (ESIX) technique (mainly based on conductive polymers) has been identified as a promising method for removing the excess fluoride ions. The present study aimed to develop an efficient method based on the ESIX technique by using poly(aniline-co-o-aminophenol) copolymer to extract fluoride ions. Electrochemical quartz crystal microbalance (EQCM) and acoustic admittance data were utilized to assay the synthetic efficiency of copolymer deposition, and to evaluate the dependence of the defluoridation process on the proportions of the monomers in the copolymer matrix and on film thickness. The resulting films were characterised by Fourier transform infrared spectroscopy (FTIR) and scanning electrochemical microscopy (SEM) techniques. For optimized co-monomer ratio in the feedstock, poly(aniline-co-o-aminophenol) at an applied potential of 0.30 V showed excellent performance for fluoride removal from water at pH 6.6, to the extent of 20 (mg F−) (g polymer)−1. Comparison of the performance of ESIX using poly(aniline-co-o-aminophenol) with that of other techniques and materials reveal that it has significant potential for water defluoridation.

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.

International audience

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.

International audience

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 TiO

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.

The electrochemical quartz crystal microbalance (EQCM) and probe beam deflection (PBD) have been widely used to study interfacial processes in molecular solvent-based electrolytes. However, there has been limited use of the EQCM and none of PBD in room temperature ionic liquids, including deep eutectic solvents (DES). Here we explore the use of the combined EQCM/PBD technique to the study of Ag and Sn electrodeposition from a DES comprising a 1:2 mixture of choline chloride and ethylene glycol. While overcoming the effect of viscous loss in the acoustic wave (EQCM) part of the experiment is understood, the optical (PBD) technique fails to provide a meaningful response in slow scan rate voltammetric experiments; this contrasts sharply with the straightforward behaviour seen in aqueous media. Solution transport considerations reveal this to be a consequence of long surface-to-beam transit times in the viscous DES. The problem can be overcome by operating at scan rates 1-2 orders of magnitude slower, permitting application of this powerful technique to novel media of technological interest. The PBD responses reveal unanticipated chemical effects: multiple complexes in the Ag system and solubility limitations in the Sn system, neither of which is evident from the electrochemical or QCM responses.

Mechanistic studies are reported for redox switching (doping/undoping) of Au-supported poly(3,4-ethylenedioxythiophene) (PEDOT) films exposed to LiClO 4 /CH 3 CN (a conventional electrolyte based on a molecular solvent) and to Ethaline and Propaline (two choline chloride-based deep eutectic solvent (DES) media). A combination of electrochemical, acoustic (quartz crystal microbalance, QCM) and optical (probe beam deflection, PBD) methods was used to monitor the exchange of mobile species between the film and the bathing electrolyte. Qualitatively, film responses to a potentiodynamic control function showed that the redox switching mechanisms are quite different in all three media. When exposed to acetonitrile, anion transfer is dominant, with some accompanying solvent transfer but negligible cation transfer; application of the convolution protocol allowed these transfers to be quantified. Analogous observations in the DES media could be interpreted qualitatively in terms of dominant cation transfer, but the convolution protocol could not be used to quantify the contributions of individual species; in these viscous media, this is a consequence of the long transit times from the film/solution interface to the optical detection zone. Chronoamperometric experiments, in which the measurement time was an order of magnitude (or more) longer permitted the diffusional processes driven by the polymer/DES interfacial population changes to reach the optical detection zone.