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Electrochemical techniques are used to investigate the physical and chemical properties for different forms of cellulose materials and processes within functionalized cellulose materials. Thin films on electrodes are formed and processes are monitored using voltammetry and impedance methods. In the first part of this thesis, ferrocene is used to covalently functionalise natural cellulose nano-whiskers which allows stable electrochemical responses to be observed consistent with Fe(IIIIII) redox switching in thin films at the electrode surface. Next, electrostatic layer-by- layer methods are used for making films of nano-cellulose-polyanilline and poly-(acrylamide- co-acrylamide-phenylboronic acid) with poly-diallyldimethylammonium or P(A-APBA)- PDDA on electrode surfaces. These films are investigated as a function of pH and thickness and proposed for sensor applications. In the second part of the thesis, natural cotton is used as a sampling substrate for the detection of heavy metals with a new reagent-less voltammetric cell design using a "dry stripping voltammetry" method, and demonstrating extremely low detection limits under optimised conditions.

Electrochemistry is crucial in many areas of technology and has many applications, with the potential for even broader use, hindered only by the current limitations of the technology. A good example is the low uptake and slow development of novel fuel cells, due to the less than promised performance in comparison to combustion engines. One way of improving the performance of electrochemical processes is to redesign the electrode, in particular by taking advantage of the recent advances in nano-carbon technology. The aim of this study is to investigate novel electrode designs using nano-carbon to improve electrochemical processes Presented are different applications of nano-carbons including nitrate reduction for water treatment and sensing, oxidation of ammonia and oxalate.

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Multifunctional composites have attracted a great deal of attention as they offer a way to cut down the parasitic weight in vehicles which not only reduces the operational costs but also reduces the fuel consumption in vehicles. Current engineering design is increasingly sophisticated, requiring more efficient material utilisation; sub-system mass and volume are crucial application determinants. This dissertation contributes to the fabrication of composites that can store electrical energy and are known as structural supercapacitors. The key in the fabrication of structural supercapacitors was not simply to bind two disparate components together, but to produce a single coherent material that inherently performed both roles of a structural composite and a supercapacitor. This design approach is at a relatively early stage, and faces significant design and material synthesis challenges. Disparate material requirements, such as structural and electrochemical properties, have to be engineered and optimised simultaneously. This study investigates on structural supercapacitors fabricated by using as-received as well as activated carbon fibre cloths as reinforcement and electrodes; multifunctional resin as electrolyte and matrix; and glass fibre cloths, filter papers or polymer membranes as insulators. Such a system should deliver electrical energy storage capacity as well as bear mechanical loads. Different liquid electrolytes, such as ionic liquids and salts based on Li+ and NH4+, were studied in order to optimise the multifunctionality of polymer electrolyte. Mesoporous silica particles were also introduced into polymer electrolytes in order to enhance the mechanical and electrochemical performance of polymer electrolytes. Nanostructured/ multifunctional resin blends were cured in cylindrical form and were examined by compression testing as well as impedance spectroscopy. An ionic conductivity of 0.8 mS/cm and a compression modulus of 62 MPa have been synthesised for the polymer electrolyte in the current study. By varying the separators, multifunctional resins and the electrodes, different structural supercapacitor configurations were manufactured using a resin infusion under flexible tooling (RIFT) method and were characterised to study the electrochemical performance by using charge/discharge method and mechanical performance by using ±45° laminate shear testing. The improved structural supercapacitors showed an energy density of 0.1 Wh/kg, a power density of 36 W/kg and a shear modulus of 1.7 GPa.

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Electroanalytical chemistry provides an elegant technique by which to explore, amongst others, various biological and environmental applications. To this end, four areas of electroanalytical chemistry are investigated in order to develop biologically- and environmentally-relevant sensors, together with exploring the electro-generation of a biologically important molecule and the diffusional factors that may affect this generation.The first study involves the dynamics of the bond cleavage involved in the electro-generation of nitric oxide from a range of N-nitrosoamines. Adsorption phenomena is found to be of pivotal significance in the release of nitric oxide from two of the compounds explored, namely cupferron and N-itrosodiphenylamine, whilst bis(nitroso)phenylenediamine released, as hoped, two moles of nitric oxide in a single step. The challenge is to isolate the product, and to determine which form of nitric oxide was generated, i.e. the cation, NO+ or nitric oxide, NO. Isolation remains a challenge, however analysis of the reaction mechanism does allow a prediction of the product, be it NO+ or NO. NO+ is a highly oxidising species and hence is difficult to isolate, therefore it is far more preferable to electro-generate NO, which cupferron was the only compound investigated that achieved this.The second study involved the investigation of axiosymmetric anisotropic diffusion to disc shaped microelectrodes, with theoretical expressions examined with experimental data in order to examine the factors. A ferrocene/PEG in acetonitrile system was examined in order to test this theory and to determine the effect of viscosity on the diffusion coefficients, and also if it was possible to investigate the anisotropy by effectively "blocking" either Dr or Dz. Excellent symmetry between theory and experiment was found, hence the focus turned to a ferricyanide in caesium pentadecafluorooctanoate/D2O system where once again the calculated value of root(Dr.Dz) affords a theoretical waveshape with reasonable agreement between theory and experiment. Potential step chronoamperometry then determined separate values for Dr and Dz, with the resulting values affording an anisotropic ratio of 1.7, suggesting radial diffusion dominance over planar diffusion.Third, the modification of electrodes is explored in order to develop biologically and environmentally relevant sensors. In a first strand, two liquid crystal ferrocene compounds are examined, immobilised on the surface of a glassy carbon electrode simply via solvent evaporation. Both compounds demonstrated typical ion transfer processes across the liquid | liquid interface, with both anion insertion and cation expulsion processes demonstrated. The differing voltammetry observed in the presence of different anions formed the basis of the anion sensor.In a second avenue in this modified electrode work a cation sensor is developed, working on the basis of a biofilm, i.e. developing a modification of the electrode surface to mimic the action of a biofilm in chelating with cations. With this in mind, a basal plane graphite electrode was modified with a diazonium salt and polyphenol, and through the introduction of alginic acid into the polyphenol layer a degree of selectivity between the Group 2 cations was demonstrated, although quantitative properties eluded the work.Last, an environmental sensor for cyanide was developed using an electrochemical probe, tetramethylphenylenediamine (TMPD). The reaction between the electro-generated TMPD.+ and cyanide is successfully followed colorimetrically, before product characterisation studies help to determine the reaction mechanism. Voltammetric studies form the basis of a sensor, with square wave voltammetry achieving a detection limit of 4.4 microM. The reaction between TMPD and cyanide allowed remediation studies to be undertaken, with river freshwater samples from North Yorkshire (54deg 15' 19.19" N, 1deg 46' 13.49" W) and the Rodalquilar mine, Spain, (36deg 50' 52.9" N, 2deg 02' 36.87" W) demonstrating the removal of cyanide by an impressive three orders of magnitude.