The main aim of the work reported is the design of proof-of-concept of at point-of-use hydrogen peroxide electrogeneration from air. The experimental work discussed within this thesis explores five major areas: the kinetics of electrocatalysis, ion-pairing, change of solvent media, the electrode surface modication by a redox mediator, and the electrochemical reduction of oxygen within enhanced mass transport systems. The electrocatalytic rates and mass transport of two oxygen reduction redox meditors, viz. anthraquinone and methyl viologen, are studied in aqueous solutions. The investigation is facilitated through the use of a boron-doped diamond electrode, allowing the catalytic response to be clearly delineated from that of the direct oxygen reduction process. The use of simulation software is highlighted in combination with experimental voltammograms to extract kinetic data. Specifically, the voltammetric features, such as the `reverse' peak and the `split waves', are given particular attention. Consequently, it is possible to deconvolute the electrocatalytic reaction mechanisms. The reactivity of the viologen radical cation is comparable to the semiquinone radical anion in aqueous solution ((4.8~6)x10^9 M^-1 s^-1), but over a far wider pH range (pH 2.5 - pH 8.5). The change of local proton concentration, and sequential electron transfers play key roles here. Moreover, the reduced reactivity of semiquinone is observed upon formation of ion-pairs with tetrabutylammonium cations in alkaline solutions. The electro-reduction of oxygen and its mediated pathways are also investigated in non-aqueous media; in particular the thermodynamics, the kinetics, and mass transport involved in these processes. Through a variable temperature study in electrolytic acetonitrile solution, the oxygen dissolution is quantitatively shown to be an endothermic process. Moreover, the diffusion coeficients and concentration of oxygen upon change of acetonitrile mole fraction is also explored in water-acetonitrile mixtures. The rates of bimolecular reactions are extracted from simulation programs, involving semiquinone in anhydrous acetonitrile and viologen radical cation in ethanol, and show a 3 - 4 orders of magnitude reduction compared to that in aqueous solution. Although the solubility of oxygen is ca. 6 - 8 times larger in non-aqueous solvents, the much reduced homogeneous rates limit the electrogeneration of hydrogen peroxide in pure organic media. Novel surface modification methodologies for graphitic surfaces with covalently attached anthraquinonyl groups are studied and characterised. The anthraquinonyl-modified carbon surfaces show much reduced overpotentials required for oxygen reduction. In the final chapter, utilising the new surface modification methodology and novel designs, two gravity-feed flow cells for electrochemical reduction of oxygen in aqueous solutions are proposed and characterised, one based upon the tubular electrode geometry. The other exhibits much enhanced current conversion by using a porous reticulated vitreous carbon electrode. The latter may provide a prototype hydrodynamic system to produce dilute hydrogen peroxide solution at point-of-use.

The work of this thesis comprises extensive Noncontact Atomic Force Microscopy (NC-AFM) characterization of clean metal-oxide (YSZ(100)/(111) and MgO(100)) and graphitic (HOPG) supports as templates for the novel, photochemically induced nucleation of cobalt oxide nanostructures, particularly Cobalt (III) Oxide. The nanostructure-support surfaces were also studied by X-ray Photoelectron Spectroscopy (XPS) to verify the nature of the supported cobalt oxide and to corroborate the surface topographic and phase NC-AFM data. Heteroepitaxial growth of Co2O3 nanostructures proves to exhibit a variety of different growth modes based on the structure of the support surface. On this basis, single-crystal support surfaces ranging from nonpolar to polar and atomically flat to highly defective and reactive were chosen, again, yielding numerous substrate-nanostructure interactions that could be probed by high-performance surface science techniques.

Biomass is one of the most promising replacements for fossil fuels as a feedstock for chemical and transportation fuel production. The combination of low vapor pressure and high polarity of most biomass derived molecules makes water the ideal solvent for biomass upgrading reaction schemes. Metal oxide and metal oxide supported catalysts are heavily used in oil refining and petrochemical production, and are capable of upgrading biomass molecules as well. However, the surface chemistries that dictate the behavior of aqueous phase biomass upgrading reactions over metal oxide catalysts are not nearly as well understood as in the case of gas phase hydrocarbon refining systems. This dissertation aims to investigate the surface chemistries of biomass derived oxygenate molecules on metal oxide and metal oxide supported metal catalysts. There are three main objectives in this dissertation: to understand how two and three carbon polyols interact with metal oxide surfaces, to elucidate the role of various surface sites on polyol-metal oxide interactions, and to discover the surface species of kinetic importance in aqueous phase reforming reactions of biomass molecules. Transmission infrared spectroscopy and density functional theory modeling were the major techniques used to demonstrate that polyols with alcohol groups on the first and third carbons, 1,3-propanediol and glycerol, form a multidentate surface species with a bridging alkoxide bond and an acid/base interaction through their two primary alcohol groups with Lewis acid sites of g-Al₂O₃. These interactions occur in the presence of bulk water. Polyols with alcohol groups only on the first and second carbons, ethylene glycol and 1,2-propanediol, only formed alkoxy bonds with the g-Al₂O₃ surface when bulk water was not coadsorbed, and these bonds were removed by re-adsorbing water. Glycerol also forms the same surface species on other metal oxides with strong Lewis acidic character: TiO₂ anatase, ZrO₂, and CeO₂. Glycerol only forms hydrogen bonds with MgO, which lacks strongly Lewis acidic sites. Basic surface hydroxyls and surface oxygen atoms of the metal oxides only played a minor role in interacting with the adsorbed glycerol. In-situ attenuated total reflectance infrared spectroscopy demonstrated that the aqueous phase reforming of glycerol over a 5 wt% Pt on g-Al₂O₃ catalyst is hindered by residual platinum bound hydrogen or oxygen atoms from commonly utilized catalyst reduction or cleaning procedures, respectively. A pretreatment consisting of multiple iterations of dissolved oxygen, dissolved hydrogen, and dissolved helium in water flow periods provides the cleanest Pt surface for monitoring carbon monoxide formation dynamics, and allows for observing the rate limiting step of the aqueous phase reforming reactions water-gas shift removal of Pt bound carbon monoxide. The bridging bound carbon monoxide is preferentially removed over the linearly bound species via water gas shift reactions even at room temperature.

Room-temperature chemisorption of hexacyclic aromatic hydrocarbons on the 2x1, sputtered, oxidized and H-terminated Si(100) surfaces, as well as those upon post treatments of hydrogenation, oxidization and electron irradiation have been investigated by using thermal desorption spectrometry (TDS), Auger electron spectroscopy (AES) and low energy electron diffraction (LEED). This work focuses on the effects of the functional groups (phenyl, methyl, vinyl, heteroatom, and H atom) in the chemisorbed aromatic hydrocarbons (benzene, toluene, xylene isomers, styrene and pyridine) on organic functionalization of the Si(100) surface, particularly on such surface processes as cycloaddition, dative adsorption, hydrogen abstraction, desorption, dissociation, diffusion, and condensation polymerization. Unlike the earlier notion that hydrogen evolution in the hydrocarbon/Si(100) systems is the result of hydrocarbon dissociation (into smaller hydrocarbon fragments and H atoms) on the surface, condensation polymerization of the adsorbed aromatic hydrocarbons is proposed in the present work, in order to explain the higher-temperature hydrogen evolution feature in the toluene/Si(100) system. This hypothesis is supported by our TDS results for other hydrocarbon adsorbates, especially in the pyridine/Si(100) system where electron-induced condensation polymerization has been observed at room temperature. The improved techniques in the TDS experiments developed in the present work have enabled us to observe condensation polymerization and the effect of H on the surface processes (via surface reconstruction) on Si(100) for the first time. New analysis methods have also been developed to determine the adsorption coverage from the AES data, and this work has not only improved the accuracy of the elemental-coverage evaluation, but also provided a means to estimate the rate and the order of chemisorption. By using the density functional theory with the Gaussian 98 program, the adsorption geometries and the corresponding adsorption energies of various adsorption phases have been calculated. These computational results have provided useful insights into the chemisorption structures on the Si(100) surface. The present work also presents the development of three kinetics models for hydrogen evolution in the aforementioned aromatic-hydrocarbon systems on Si(100). Based on a modified collision theory with consideration of diffusion, these theoretical models have proven to be quite successful in simulating the observed TDS profiles and in estimating the kinetic parameters for the analysis of condensation polymerization in 2-dimensional diffusion systems. The present work illustrates that TDS experiments can be used effectively with quantum computation and theoretical kinetics modelling to elucidate the intricate nature of organosilicon surface chemistry.

The interactions which occur between both polar and non-polar fluid phases and surfaces of various carbon materials: Activated Carbon (AC), non-porous Carbon Black (CB) and Multiwall Carbon Nanotubes (MWCNTs)with different surface chemistry have been studied. These are currently of great interest as they govern the interfacial behaviour of carbons in a wide range of applications; separation adn composite technologies being two prime examples. Consequently, techniques for chemical modification of carbon surfaces ar also of interest. Surface oxygen functional groups have been introduced, or modified, using the following oxidation techniques: liquid-phase oxidation (both AC and CB), Fenton and Birch reduction treatment (MWCNTs) and in a more controlled manner using gas-phase ozone treatment (CB). The chemistry of all the resulting carbon surfaces were characterised using X-ray Photoelectron Spectroscopy (XPS), which gives a quick and direct quantitative measure of the external surface composition. This technique, which has not yet been extensively employed in detailed adsorption studies, is a promising alternative to Temperature Programmed Desorption (TPD) and Boehm titration method in the determination of oxygen and other surface groups. Physical effects of the various surface modifications have been studied using a variety of techniques appropriate for the material in question. Scanning Electron Microscopy (SEM) images show some deteriorating effects of the liquid-phase oxidations on the structure of both activated carbon and carbon black materials. Conversely, surface areas from nitrogen adsorption at 77oK, coupled witj immersion calorimetry data for toluene, show thet the physical structure of the carbon blacks is not modified by ozone treatment. This has allowed a detailed study of the effects of surface oxygen level (i.e. polarity) on vapour adsorption. Regarding the MWCNT materials, detailed High-Resolution Electron Microscopy (HRTEM) photographs show that the multi-wall structure of the nanotubes in not significantly disrupted during the introduction of active functional groups by the Fenton or Birch treatment and therefore keeping intact their mechanical properties which augurs well for their use as reinforcement in composite structures whilst also improving their dispersion properties in polar fluids. A systematic shift to higher adsorption values, due to the increasing specific interactions between the alcohol -OH groups and the surface oxygen groups, is observed in all the isotherms of alcohols from the CB series as the total surface oxygen concentration ([O]T) increases. Moreover, this effect was observed to be most significant for methanol confirming that the mechanism of adsorption is dominated by hydrogen bonding and therefore dependant on the surface concentration of oxygen sites; whereas it becomes less marked in the case of ethanol and isopropanol respectively due to the increasing non-specific, dispersion, interactions of the alkyl chain with the non-polar carbon surface. Overall correlations were observed between the surface oxygen concentration [O]T, the resulting enthalpy of immersion -^Hi values and the characteristic energy E of the Dubinin-Radushkevich-Kaganer (DRK) equation obtained for toluene and these alcohols and the influence of the carbon surface chemistry on the character of the adsorption isotherms is also discussed. This behaviour is also observed and much more pronounced in the case of water adsorption on other oxidised carbon materials (AC, CB and MWCNT) due to the higher polarity of water molecules. The water adsorption data were analysed using in particular the Dubinin-Serpinsky (DS) equation and also some of its recent variations such as Barton and D'Arcy & Watt equations. The DS2 and various Barton equations were found to fit best the AC and CB materials modified by liquid-phase oxidations and also for the CB 03 series with increasing level of oxidation while both D'Arcy & Watt equations gave the best fittings for the MWCNTs materials. It was also shown that the resulting parameters ao (for the DS equation) describing the surface concentration of primary polar adsorption sites and as the limiting water adsorption value were both linked to the surface oxygen level [O]T. Regarding interfacial bonding, the oxidised CB and MWCNT materials are expected to show an improved physicochemical wetting of their surfaces by various resin compunds

Surface chemical gradients are materials that exhibit continuous, gradually varying chemical or physical properties along and across the length of a substrate. As a result, each point on the gradient surface can represent an individual sample. They are broadly classified as chemical and physical gradients depending upon the properties that the gradient exhibits. A physical gradient involves a continuous variation of physical properties such as surface roughness and film porosity on the micrometer scale. Chemical gradients involve a gradual variation of chemical properties such as polarity, acidity and basicity, etc. Such gradients have found various applications in cell adhesion, nanoparticle absorption, etc. Because of the multitude of potential applications of acid-base gradient materials in separation science and biological applications, the main work of this dissertation work is focused on the preparation and fundamental, molecular level investigation of acid-base gradients on siloxane surfaces. In this work, we focused on the preparation and characterization of surface charge gradients. Charged gradients are gradients that contain charged functional groups that are spatially distributed along the length of the substrate. They can interact with each other or with other species in solution by electrostatic interactions. They can also play a key role in governing the interaction of macromolecules and bacteria on surfaces, the wetting of surfaces, the layer-by-layer (LBL) assembly of thin films, reactions in catalysis, and the separation of charged species in chromatography. Therefore, understanding localized interactions between surface functional groups and charged species in solution are particularly relevant to the development of surfaces resistant to biofouling, antimicrobial surfaces, catalytic surfaces, multi-layered composite thin films, and imprinted surfaces for chemical sensing and separations. Thus, it is of great of interest to develop methodologies to create and study heterogeneous and homogeneous charged surfaces with well-defined properties. There have been several different methods developed for the preparation of charged gradients. First a chemical gradient is prepared and then the chemical gradient is converted to charged gradient by a chemical approach. Silane-based methods for the preparation of chemical gradients are among those that are widely used because of the straightforwardness of the chemistry involved and also the availability of silanes with various chemical functionalities. A few of these silane based approaches such as the vapor-diffusion method and liquid diffusion method have been used for various applications so far. Most of these methods are only able to prepare surface chemical gradients for a specific application mainly because of their limitations in terms of gradient-length scale and chemistry involved. In this work, we used a procedure already developed in our lab to prepare chemical gradients from different functionalized alkoxysilanes; we call this procedure the ‘controlled-rate infusion method (CRI)’. This method can be adapted to different substrates and can form gradients at various length-scales, such as few hundred microns to tens of centimeters. The CRI method involves the infusion of an organoalkoxysilane solution into a container with a substrate mounted vertically so that time-dependent exposure along the substrate forms a gradient in chemical functionality from bottom to the top. The most important attribute of this method is that the local steepness of the gradient can be systematically controlled by simply changing the rate of infusion. The steepness of the gradient can also be changed at predefined positions along its length by programming the rate of infusion. CRI can also be used to prepare gradients containing multiple functionalities, termed multicomponent chemical gradients. The different chemical functionalities can be oriented in different directions to produce gradients where functionalities can be oriented along the same or opposed directions producing aligned and opposed multicomponent chemical gradients, respectively. In this work, the multicomponent gradients were converted to charge gradients via chemical reaction with 30% H2O2. Using controlled rate infusion and this technique, aligned or opposed multicomponent charge gradients containing NH3+, SO3- and SiO- groups were prepared. By infusing 3-aminopropyltriethoxysilane (APTEOS) and 3-mercaptopropyltriethoxysilane (MPTMOS) in the same or opposed direction, gradients containing charged species in different locations relative to each other along the length of the substrate were made. The gradient properties in each case were different and correlated to the way they were prepared i.e., where the gradients were oriented in an aligned or opposed fashion. Surface wettability and local surface charge, etc were found to be entirely different depending on the type of charge gradients (aligned and opposed). In another example, SiO- and NH3+ opposed gradients were prepared by infusing APTEOS on different base layers prepared from tetramethoxysilane (TMOS), phenyltrimethoxysilane (PTMOS), dimethyldimethoxysilane (DMDMOS) or octyltrimethoxysilane (OTMOS) followed by protonation of the surface amines. The gradient profiles and surface wettability were found to be independent of each other and dependent of the type of the base layer. In summary, this dissertation work focuses mainly on the preparation of multicomponent charge gradients and their molecular level characterization by a multitude of different analytical methods including XPS spectroscopy, tapping mode atomic force microscopy (TM-AFM), zeta potential measurement, and SCA and DCA measurements. CRI has incredible flexibility and adaptability, which was confirmed by extending it to different siloxane base films and creating gradients with different functionalities. Multicomponent charge gradients containing acid and base functionalities can be prepared and optimized for and acid base catalysis reactions such Michael addition as well as aldol, Henry, and Knoevenagel condensations.

Understanding the factors influencing the ET characteristics of redox proteins confined at an electrochemical interface is of fundamental importance from both pure (fundamental science) and applied (biosensory) perspectives. This thesis reports on progress made in the emerging field of coupled electrochemical characterization and optical imaging in moving the analysis of redox-active films to molecular scales. More specifically the combination of cyclic voltammetry and wide-field Total Internal Reflection (TIRF) microscopy, here named ‘Fluorescent Cyclic Voltammetry’ (FCV), was applied to monitoring the response of surface-confined redox active proteins at submonolayer concentrations. The combined submicrometre spatial resolution and photon capture efficiency of an inverted TIRF configuration enabled the redox reactions of localized populations of proteins to be directly imaged at scales down to a few hundreds of molecules. This represents a 6-9 orders of magnitude enhancement in sensitivity with respect to classical current signals observed in bioelectrochemical analysis. Importantly, measurements of redox potentials at this scale could be achieved from both natural and artificially designed bioelectrochemical fluorescent switches and shed fundamental light on the thermodynamic and kinetic dispersion within a population of surface confined metalloproteins. The first three chapters of this thesis provide an overview of the relevant literature and a theoretical background to both the rapidly expanding fields of electroactive monolayers bioelectrochemistry and TIRF imaging. The initial design and construction of a robust electrochemically and optically addressable fluorescent switch, crucial to the applicability of FCV is reported in chapter 5. The generation of optically transparent, and chemically modifiable electrode surfaces suitable for FCV are also described. Chapter 6 describes the response of the surface confined azurin-based switch. Analysis of the spatially-resolved redox reaction of zeptomole samples in various conditions enables the mapping of thermodynamic dispersion across the sampled areas. In chapter 7 the newly developed FCV detection method was extended to investigate more complex bioelectrochemical systems containing multiple electron transferring redox centres and responding optically at different wavelengths. This approach provides a platform for spectral resolution of different electrochemical processes on the same sample. Finally in chapter 8 an electrochemical procedure is proposed for investigating the kinetic response of redox proteins using a fundamentally new methodology based on interfacial capacitance. In using variations in the surface chemistry to tune the rate of electron transfer, the approach was shown to be a robust and facile means of characterising redox active films in considerably more detail than possible through standard electrochemical methodologies. Ultimately, it can be applied to probe dispersion within protein populations and represents a powerful means of analysing molecular films more generally.

This thesis presents an investigation of the dynamic properties of wide range of interfacial systems, from colloidal particles in solution, through the realm of aerosols and onto studies of molecular adsorption at an interface. The primary experimental technique utilized is optical tweezers. An exploration of the history of the use of radiation pressure to manipulate matter is presented, followed by an introduction to how optical tweezers work. Some of the more advanced methods of tweezing are discussed, with an emphasis on the use of spatial light modulators (SLMs) to realise dynamic holographic optical tweezers (DHOTs), an example of which has been constructed within our laboratory using off-the-shelf optical components, and combined with a spectrometer to facilitate high resolution spectroscopic studies of microscopic systems. The spectroscopic analysis of microparticles is greatly enhanced by optical feedback generated when the wavelength of light utilized is an integer number of wavelengths around the circumference of the microsphere. Enhanced signal occurs at these wavelengths, termed whispering gallery modes (WGMs). The absolute position of these resonances depends strongly upon the shape, size and refractive index of the particle, and is predicted by Mie theory. A discussion of the concepts behind Mie theory, as well as how to use an experimental WGM spectrum to deduce the size and composition of a microparticle, is provided. This technique is then put to use in a detailed study on the properties of single aerosols, comprised of sodium chloride solution, and generated using a handheld medical nebulizer. Studies have been carried out on both evaporating and growing droplets trapped with a Gaussian beam; in the latter case, periods of size stability are observed, owing to resonant absorption of radiation at the trapping laser wavelength. The SLM can be used to change the trapping laser to a Laguerre-Gaussian (LG) mode, and an investigation of how this affects the dynamics of the droplet is presented. It is found that the use of LG modes with $ellgeq10$ produced Raman spectra with significantly more intense WGMs, and also suppressed droplet evaporation. Through observations made with fluorescent polystyrene microspheres, it is argued that the LG modes are more efficient at coupling into WGMs of the droplets. Leading on from these experiments on salt water droplets, experiments have been conducted using ionic liquids (ILs). These fluids have many fascinating properties and potential applications. The optical trapping of droplets comprised of aqueous solutions of the ionic liquid ethylammonium nitrate (EAN) and water has been demonstrated for the first time. These droplets are analysed spectroscopically by illuminating them with the output from a broadband LED; WGMs that are observed in the backscattered light are used to determine their size and composition. The response of the droplets to conditions of varying relative humidity has also been investigated. In order to characterise the relative humidity experienced by both the salt water and IL droplets, the concentration of water vapour within the trapping cells has been measured using diode laser absorption spectroscopy. The spatially modulated laser beam is then utilized in a different fashion; instead of optically tweezing a sample, a low numerical aperture objective lens is utilized to focus the laser onto the surface of a gold coated microscope slide. When a colloidal sample is placed on this surface, the thermal gradients cause the particles to form two dimensional crystals. The SLM is utilized to form multiple nucleation sites, and the dynamics of the crystals are directly observed in real time using video microscopy. It is found that grain rotation-induced grain coalescence (GRIGC) occurs, with the rotation of both crystals before coalescence. Control over the grain size is achieved by altering the separation of the laser spots, and shows that the time scale for grain boundary annealing in our system is in good agreement with theoretical expressions formulated for nanocrystal growth. Finally, as a complimentary technique to the microparticle spectroscopy previously discussed, a bulk interface is probed by using evanescent wave broadband cavity enhanced absorption spectroscopy (EW-BBCEAS) specifically to study the adsorption of cytochrome c (cyt c) to a fused silica surface. Visible radiation from a supercontinuum source is coupled into an optical cavity consisting of a pair of broadband high reflectivity mirrors, and a total internal reflection (TIR) event at the prism/water interface. Aqueous solutions of cyt c are placed onto the TIR footprint on the prism surface and the subsequent protein adsorption is probed by the resulting evanescent wave. The time integrated cavity output is directed into a spectrometer, where it is dispersed and analysed. The broadband nature of the source allows observation of a wide spectral range (ca 250 nm in the visible). The system is calibrated by measuring the absorption spectra of dyes of a known absorbance. Absorption spectra of cyt c are obtained for both S and P polarized radiation, allowing information about the orientation of the adsorbed protein to be extracted.

Surface catalysed reactions play an important role in chemical productions. Developments of catalyst requiring high activity whilst improving on product selectivity can potentially have a profound effect in the chemical industry. Traditional catalyst modifications were focused on tuning the size, shape and foreign metal doping to form well defined metal nanoparticles of unique functionalities. Here, we show new approach to engineering of metal nanocatalysts via a subsurface approach can modify the chemisorption strength of adsorbates on the surface. Carbon modified nanoparticles were synthesised using glucose to stabilise Pd nanoparticles at a molecular level. Upon heat treatment, the carbonised glucose encapsulated the Pd nanoparticles with carbon atoms take residence in the octahedral holes (15 at.%). These materials were tested in liquid phase stereoselective hydrogenations of 3-hexyn-1-ol and 4-octyne. The former has importance in the fragrance industry towards the production of leaf fragrance alcohol. It was shown for the first time that the geometrically and electronically modified Pd with interstitial carbon atoms reduced the adsorption energy of alkenes, ultimately leading to higher reaction selectivity. Boron modified Pd nanoparticles was synthesised using BH₃.THF in the liquid phase. The material possess high B interstitial saturation (20 at.%), which can be synthesised for the first time below 100°C. These materials were tested in the liquid phase selective hydrogenation of various alkynes and 2-chloronitrobenzene, of which the latter has importance in the pesticides industry. Kinetic modelling on the hydrogenation of 4-octyne suggests these subsurface occupied B does play a pivotal role on increasing the reaction selectivity, as removal of these species lead to decreased selectivity. Au nanoparticles were synthesised and characterised using H¹³COOH NMR. The new liquid NMR characterisation method is successfully applied to examine the chemisorption strength of metal nanoparticles. An attempt to synthesise PVP capped B modified Pd nanoparticles with the above NMR characterisation was investigated. It is believed the examples of subsurface atom modifications as shown here may offer future catalyst developments in this area.

Herein, the influence of protonation and adsorption upon the redox and electrocatalysis of quinone species - specifically anthraquinone derivatives – is investigated. Through the comparison of the measured rate constants of one-electron reductions of a family of quinones in acetonitrile at both graphite and gold electrodes, it was confirmed that the redox potential indirectly influences the rate of electron transfer in a manner consistent with the potential-dependence of the density of states. In aqueous media, the voltammetric response of both anthraquione-2-sulfonate (AQMS) and anthraquinone-2,6-disulfonate (AQDS) was measured over the full aqueous pH range. A model is provided which is able to describe not just the variation in the formal potential but also the peak height as a function of pH. Importantly, this model predicts that the formal potential for the first (Ef1) and second (Ef2) electron transfers are comparable in magnitude (E^θ _f2−E^_θf1 equals -15mV for AQMS and -36mV for AQDS). This quantitative model is then further extended to consider the situation in which the system is not fully buffered, giving insight into the change of pH at the electrode surface during experimentation. Adsorption to graphitic electrodes can impart a strong influence on the measured voltammetric response. It is demonstrated that through the pre-exposure of a newly prepared graphitic electrode to organic solvents, these adsorption processes can be predominantly blocked. Moreover, it is shown that the electroactivity of the electrode is not significantly altered. This thesis also highlights two cases in which adsorption of the electroactive species may be used to positive effect. First, the surface adsorption of anthraquinone-2-monosulfonate is studied on a graphite electrode, where it is demonstrated that the heterogeneity of the electrode surface may be probed through studying the electrochemical response of the adsorbed species. From this work it is concluded that the rate of electron transfer at the graphitic basal plane is 2-3 orders of magnitude lower than that observed on the edge plane sites. Second, the co-adsorption of DNA and anthraquinone-2-monosulfonate is used as an indirect method to measure the solution phase concentration of DNA (LOD = 8.8μM). The reduced form of anthraquinone is also known to readily reduce oxygen. Through the use of a boron-doped diamond electrode it was possible to directly study the anthraquinone mediated reduction mechanism. Significantly, the voltammetric response indicates the reduction of the oxygen via the semi-quinone intermediate (kf = 4.8 × 10⁹ mol⁻¹ dm³ s⁻¹) is over two orders of magnitude faster than the reaction involving the di-reduced form (kf = 1 × 10⁷ mol⁻¹ dm³ s⁻¹). More importantly, this work provides voltammetric evidence for the existence of the semi-quinone species. This work is subsequently extended through the investigation of the poorly soluble anthraquinone derivative quinizarin. Not only is it possible to detect voltammetrically this biologically relevant species to concentrations as low as 5nM (100ppt), but the methodology also allows the electrochemistry of the quinizarin species to be probed, something which was not previously possible.