Electrochemical cycling of Ag surfaces under basic conditions has led to the discovery of a new, simple, rapid and cost effective method for the preparation of nano-structured Ag surfaces with features ranging from 30–150 nm in diameter. Our results indicated that during cyclic voltammetry, the surface was oxidized, resulting in the formation of soluble Ag complexes which were re-deposited as elemental Ag nanostructures (NSs) on the cathodic scan. The electrochemical properties of the Ag NSs were greatly affected by the presence of organophosphonates and other additives (vide infra), which also influenced the growth of nanostructures. The interaction of these Ag NSs with malathion and paraoxon were explored in more detail using Surface Enhanced Raman Spectroscopy. Results showed that generally smaller nanosized features resulted in high quality surface Raman enhancement. Next, Ag NSs’ properties in the presence of organophosphonates was investigated in tap water and apple juice in order to address issues related to matrix effects and potential interference from constituents in solution. Electrochemical and localized surface plasmon resonance results demonstrated the ability to detect organophosphonates in real samples, albeit at a lower limit of detections and without any selectivity to any particular organophosphonate. Next, the morphology and corrosion behaviour of Ag surfaces was explored in the absence and presence of surfactants and capping agents. Results demonstrated the protection of Ag surfaces against corrosion in the presence of Tween-20, while potassium citrate presence enhanceed corrosion of silver surfaces, resulting in the formation of a pitted surface with smaller Ag NSs. Lastly, the interactions of 2-cyano-3-(2′-(5′,10′,15′,20-tetraphenyl porphyrinato zinc-(II))yl) acrylic acid-modified Ag NSs with biomolecules were explored using spectro-electrochemical techniques. The photocurrent response of porphyrin-modified Ag NSs was quenched by the addition of adenosine-5’-monophosphate (AMP), guanosine-5’-monophosphate (GMP) and cytidine5’-monophosphate (CMP), with a quenching efficiency of 80%, 68% and 48% for AMP, CMP and GMP, respectively.

Projections of the World Energy Council indicate a significant increase in global energy consumption in the medium and long term due to a growing world population and rising prosperity whilst global fossil fuel reserves are in decline. Eighty percent of the world’s energy consumption is generated from fossil fuels and this is unlikely to change in the short and medium term inevitably leading to energy shortfalls. The CO2-less energy of nuclear fuel shows strong potential to meet the future energy demands. However economic, politic and environmental requirements mean that the nuclear industry must adapt its current technology and present fuel usage. A pyroelectrochemical reprocessing system utilising liquid cathode technology could provide an efficient and secure reprocessing cycle essential for reduction in volume and toxicity of nuclear waste and extension of natural nuclear resources. The electrochemistry of aqueous copper(II) and zinc(II) chloride was studied upon a liquid mercury cathode using cyclic voltammetry. Bulk deposition of the Cu upon the liquid mercury cathode was studied using both amperometry and Electrochemical Impedance Spectroscopy. The surface deposits formed by copper deposition upon the mercury liquid cathode were analysed using x-ray powder diffraction and determined to be the rare naturally occurring mineral Belendorffite, Cu7Hg6. Electrochemical diagnostics for surface deposition upon the mercury liquid cathode surface were investigated as a potential analogue system for high temperature liquid cathode systems. Bulk deposition investigation of lanthanum upon the high temperature bismuth system demonstrated transfer of EIS diagnostics for surface growth, with the system demonstrating a similarity to the zinc-mercury ambient system. An electrochemical technique for purifying LiCl/KCl molten salt using an electrolysis technique was demonstrated. The electrochemical cleaning method forgoes the standard chemical treatments that can leave contaminants within the treated salt and results in a cleaner less oxidising molten salt eutectic.

Hydrogenases catalyse the reversible oxidation and production of H₂. They have been the subject of intense interest in recent years since these enzymes, or catalysts inspired by them, may greatly enhance our exploitation of H₂ as an energy carrier in a future ‘green’ H₂-based economy. However, a major challenge to the future use of these catalysts is their reactions with small molecule inhibitors, such as O₂ or CO. This thesis presents studies using Protein Film Electrochemistry, in which an enzyme is adsorbed onto an electrode to give an electroactive film. Although most hydrogenases are inhibited or irreversibly damaged by even trace O₂, certain O₂-tolerant hydrogenases are unusual in that they are able to sustain H₂ oxidation activity in the presence of O₂. Results outlined in this thesis suggest that the O₂ tolerance of the membrane-bound [NiFe]-hydrogenase from Ralstonia eutropha relies upon O₂ attack generating exclusively the ‘Ready’ inactive state (formed by complete, four-electron reduction of O₂), which subsequently reactivates both rapidly and at high potential. The results contributed to a new explanation for how hydrogenases in certain microbes survive O₂. Electrochemical studies performed on a variant enzyme suggest that a modified proximal FeS cluster plays a role in conferring this O₂ tolerance. Studies of an enzymatic H₂/O₂ fuel cell employing the O₂-tolerant [NiFe]-hydrogenase Hyd1 from Escherichia coli as the anodic catalyst highlight the subtle influence of the reactions of the hydrogenase with O₂ on the power characteristics of the fuel cell under various operating conditions. This research also identifies straight-chain aldehydes as unprecedented inhibitors of H₂ production by the [FeFe]-hydrogenases. However, some of these results cannot currently be made freely available as they are to be published at a later date in academic journals.

Directed evolution studies by Whitehouse et al. identified several variants of P450BM3 (CYP102A1) with enhanced substrate oxidation rates across a range of substrates. This thesis describes the use of these ‘generic accelerator’ variants, in combination with selectivity altering mutations to engineer P450BM3¬ for the oxidation of pharmaceuticals. Using engineered variants the non-steroidal anti-inflammatory drug diclofenac was metabolised to the primary human metabolites 4′- and 5-hydroxydiclofenac, with total conversion of 2 mM substrate by 5 μM enzyme. The local-anaesthetic lidocaine and the steroid testosterone were similarly metabolised to human metabolites. This is the first report of a drug compound being totally converted to the human metabolites by a P450BM3 variant, and is also the first report of lidocaine metabolism by a P450¬BM3 variant. The engineered variants are akin to CYP3A4, the primary human drug metabolising enzyme, as they show activity towards a range of compounds including anionic, cationic and neutral drugs. This range of activity is at the expense of NADPH coupling, which remains low with these substrates. In order to more fully understand the origin of the rate enhancing properties of the generic accelerator variants, spectroelectrochemical, stopped-flow and kinetic studies were performed. A custom optically transparent thin layer electrode system was designed and fabricated for use in spectroelectrochemical titrations. A spectroelectrochemical cell and gold mesh electrode were designed and used in spectroelectrochemical investigations of P450BM3 variants, as well as other P450s and their redox partners. These spectroelectrochemical, stopped-flow and kinetic studies, in combination with X-ray crystal structures provided insight into the origin of the rate enhancing properties of these enzymes and supplied the first example of the complete characterization of the thermodynamic and kinetic properties of WT and mutant P450BM3 for the oxidation of a non-natural substrate. The generic accelerator variants are, in the resting state, in a more catalytically ready conformation than the WT enzyme, and reorganization energy barriers appear to be lowered, so that fewer substrate-induced structural changes are required to promote electron transfer and initiate the catalytic cycle.

Orientador: Assis Vicente Benedetti / Coorientador: Patrícia Hatsue Suegama / Banca: Hercílio Gomes de Melo / Banca: Isolda Costa / Banca: Adalgisa Rodrigues de Andrade / Banca: Roberto Zenhei Nakazato / Resumo: Este trabalho descreve a preparação e utilização de revestimento híbrido composto por TEOS (tetraethoxysilane), MPTS (3-Methacryloxypropyl trimethoxysilane) e MMA (methil methacrylate) depositados sobre chapas de aço estanhado como proteção temporária à corrosão. A utilização de aço estanhado em latas de conservas alimentícias teve seu inicio no século XVIII, porém se tornou popular após a Guerra Civil Norte Americana, 1861 - 1865. Esse material quando em contado direto com a solução de conserva pode se deteriorar gerando produtos que contaminam o alimento diminuindo sua validade. Diante desse fato camadas de verniz do tipo epóxi são comercialmente aplicadas no interior das embalagens para impedir sua corrosão. Outra forma de proteção temporária seria a utilização dos revestimentos híbridos que além de aumentarem resistência a corrosão podem ser utilizados em conjunto com verniz e tintas, funcíonando como um pré tratamento da superfície. Preparou-se revestimentos híbridos com a adição de inibidores de corrosão nas concentrações de 300, 500, 700 e 900 ppm do íon Ce(III) ou Ce(IV). Avaliou-se a influência do iniciador de polimerização, peróxido de benzoila, quando adicíonado em conjunto com os íons, do número de imersões e da velocidade de retirada do substrato da solução do híbrido. Como caracterização utilizou-se medidas de impedância eletroquímica (EIS), de potencial de circuito aberto (OCP), curvas de polarização, microscopias: eletrônica de varredura (SEM), de forcas atômicas (AFM) e emissão ótica de descarga luminescente (GDOES) e espectroscopia vibracíonal de absorção na região do infravermelho (IV). Através do conjunto de caracterizações utilizadas concluiu-se que a presença do BPO no sol dos revestimentos é importante uma vez que os revestimentos formados nessa condição foram mais protetores e mostraram... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work describes the preparatíon and use of hybrid coatings comprising TEOS (Tetraethoxysilane), MPTS (3-Methacryloxypropyl trimethoxysilane) and MMA (Methil methacrylate) deposited on Sn-coated steel plates as temporary protectíon against corrosíon. The use of Sn-coated steel in canned food began in the 18th century; however it became more popular after the American Civil War, 1861-1865. This material when in direct contact with the solutíon of preserving foods may deteriorate generating corrosíon products that contaminate the food and consequently decrease its validity. In light of this fact, varnish coatings of epoxy-type are commercially applied inside the packages to prevent corrosíon. Another way of temporary protectíon is the use of hybrid coatings that increase the corrosíon resistance and may be utilized in conjunctíon with paint and varnish, acting as a surface pretreatment. In this context, hybrid coatings were prepared with the additíon of corrosíon inhibitors using concentratíons of 300, 500, 700 and 900 ppm Ce(III) or Ce(IV) íons. Also, the influence of a polymerizatíon initiator, benzoyl peroxide when added together with the íons, the number of immersíons, and the withdraw rate of the substrate the hybrid solutíon was evaluated. The electrochemical and physical characterizatíon of coatings were performed using the following techniques: electrochemical impedance measurements (EIS), open circuit potential measurements (OCP), polarizatíon curves, scanning electron microscopy (SEM), infrared spectroscopy (IR), atomic force microscopy (AFM) and glow discharge optical emissíon spectroscopy (GDOES). In general, the characterizatíon results showed that the presence of BPO in the sol plays an important role since in this conditíon the coatings formed were more protective and showed the Ce(III) íons acting only as inhibitors... (Complete abstract click electronic access below) / Doutor

Carbon nanoparticles constitute a class of important materials that have uses in many different fields. This thesis focuses on the synthesis and surface modification of different carbon nanoparticles and each novel nanomaterial is demonstrated to have a specific sensing application. Carbon blacks play a significant role in the research that is presented herein. Emperor 2000, a commercial bulk-produced carbon black available from Cabot Corporation, is the starting material for many of the investigations. The surface of Emperor 2000 is shown to be susceptible to physisorption, through π-π stacking. These interactions are exploited to append pyrene-based compounds onto the surface of the carbon nanoparticles. This methodology results in carbon nanoparticles with surface boronic acid functionality that is demonstrated to be affective in the electrochemical detection of catecholic caffeic acid. Emperor 2000 carbon nanoparticles are commercially produced with phenylsulphonic acid functional groups on the surface. This functionality is subjected to synthetic methods to obtain carbon nanoparticles with extremely hydrohphobic character, which are demonstrated as important substrates for probing lipophilic redox systems and lipid character under different experimental conditions. Fluorescent carbon nanodots (C-dots) are another important form of carbon nanoparticle. Herein, the facile synthesis of C-dots that possess intrinsic pyridine functionality is described. These nanodots exhibit two-photon fluorescence that is exhibited both in solution and in HeLa cells. The nanodots are demonstrated to have the potential to be developed into nanomedicines and biocompatible scaffolds for new drug delivery mechanisms. These straightforward synthesis, modification, and application methods demonstrate the effectiveness and the versatility of carbon nanoparticles. This class of nanomaterial is generally outclassed by modern and more fashionable carbon nanotubes and graphene-based systems. However, carbon nanoparticles are more cost effective and readily available carbon-based nanomaterials that can be used for a wide range of applications.

Microporous materials have received much attention and offer new opportunities in electrochemistry because of their interesting properties. Compared with the corresponding nonporous materials, the highly porous structure may facilitate internal mass transport process, provide accessibility to binding sites and provide size selectivity. A new class of microporous materials, polymers of intrinsic microporosity (PIMs) emerged about ten years ago. They combine the microporosity generated from the rigid and contorted backbones and the processibility of linear molecular polymers, which make them particularly attractive for the applications in gas storage, membrane separations and also in electrochemistry. PIM-EA-TB containing ethanoanthracene (EA) and Tröger’s base (TB) is one of the most interesting PIMs and has a high BET surface area around 1000 m2 g-1. Most of the work in this thesis are based on PIM-EA-TB. Results chapters focus on catalysis in PIM films, ion flux in free-standing PIM membranes and carbonization of PIM-EA-TB. Electrochemical oxidation of glucose is important due to the practical applications in glucose sensing and in biological fuel cells. However, the practical application of many catalysts is limited by the poisoning by interferences such as proteins and chloride. Here, PIM-EA-TB was spin-coated onto the surface of supported gold nanoparticles to protect the catalysts from poisoning. It was demonstrated that the PIM-EA-TB film would not negatively affect the catalytic performance of gold nanoparticles for glucose oxidation. Also, it provided effective protection against protein poisoning because of its rigid backbone and rigid molecular structure preventing protein access. Chloride poisoning was reduced but not surpressed. In addition to nanoparticle catalysts, water-insoluble molecular catalysts were investigated. PIM-EA-TB was used as a rigid host for model catalyst, tetraphenylporphyrin (FeTPP). FeTPP was immobilised in the PIM-EA-TB film and then deposited on the electrode to create a high density heterogenised catalysts. Different compositions of PIM and FeTPP and different scanrates were investigated to reveal the catalytic mechanism. The PIM hosted FeTPP catalysts showed facile electron transfer and effective electrocatalytic reduction of oxygen and peroxide. The 4-(3-phenyl-propyl)-pyridine was applied to the PIM-FeTPP film to give an organogel in 12 order to investigate the liquid-liquid interface. The PIM immobilisation method could offer a new opportunity to the immobilisation of a wide range of the molecular catalysts. The understanding of transport processes in PIM-EA-TB membranes is important for the development of further applications in the electrochemistry. Different types of anions were investigated to see the anion uptake and charge transport in PIM-EA-TB films. Three cases were investigated, including the oxidation of ferrocene, the reduction of protons and the transport of anions and protons in the PIM-EA-TB thick films. In all three cases, the diameter and hydrophobicity of anions are important in the competing effects. The pKa of PIM-EA-TB was determined and novel ionic diode effects were observed. Nanofluidic devices are used to regulate the flow of ions to one preferential direction and they have great importance because of the similarity to biological ion channels and the application in biochemical fields. PIMs were explored to the possibility to establish an artificial ion channel with the gate function. A thin film preparative method was introduced to produce thin free-standing polymer films. The 300 nm PIM-EA-TB films supported on a poly-ethylene-terephthalate (PET) film with a 20 m diameter microhole exhibited ionic diode behaviour. Only when the cation and anion had different mobility, the current rectification effects were observed. Different pH values of the electrolyte were also investigated and resulted in a gradual change in rectification effects. Porous carbon materials have wide applications in different fields such as gas separation, water purification, catalyst supports, and fuel cells. One of the common methods to produce the porous carbon is the carbonization of polymers. However, the challenge is that it is difficult to control the pore size and pore distribution. PIM-EA-TB was carbonized at 500 °C in vacuum to produce a novel type of microporous carbon. The microporosity and morphology of the PIM precursor remained after carbonization. The new material exhibited relatively low electrical conductivity and low activity in the electrochemical oxygen reduction. The capacitance of the new carbon material was investigated and found to vary with pH depending on the protonation status of micropores. 13 Finally, the carbonized PIM films were used to control the formation of platinum nanoparticles. Platinum nanoparticles are important catalysts in many areas but may suffer from high costs and lack of reproducibility. Therefore, it is important to reduce the amount of platinum, increase the utilization of platinum as well as control the particle size. The carbonized PIM films still have the microporosity and offer an ideal substrate for platinum nanoparticles. The platinum nanoparticles were formed at the same time with the carbonization of PIM, which helped to control the size of platinum nanoparticles. Compared with bare platinum, the platinum nanoparticles produced by PIM-EA-TB showed a high electrochemically active surface area and good catalytic performances for oxygen reduction, methanol oxidation and glucose oxidation. Much less platinum (1μg per cm2) was needed to achieve the same catalytic performance compared to the bulk platinum.

This dissertation focuses on the synthesis and electrochemical testing of new electrolyte salts for rechargeable multivalent ion batteries. In chapters 2 and 3 the synthesis of Mg and Ca hexafluoropnictogenate salts as well as the electrochemical behaviour of Mg(PF6)2 is presented. Pure samples of Mg(EF6)2 (E = P, As, and Sb) can be synthesized using Mg metal and NOPF6/NOSbF6 in CH3CN or via a ammonium salt deprotonation route using Me3NHAsF6 and Bu2Mg. The NOPF6 method was extended to the Ca variant, but isolation of a pure Ca(PF6)2 material required the presence of a crown ether. Electrochemical and microscopy measurements of THF-CH3CN solutions of Mg(PF6)2 show that the electrolyte good electrochemical stability and can facilitate the plating/stripping of Mg. Further, this electrolyte system can be cycled in a full cell using the Chevrel phase Mo6S8 cathode. The electrochemical stability of the AsF6− and SbF6− salts is lower than that of the PF6− salt and electrolyte decomposition is observed when cycling on Mg electrodes. In chapter 4 the development of a series of Mg aluminates [Mg(AlOR4)2] using a general synthetic platform based on Mg(AlH4)2 and various alcohols is presented. Preliminary electrochemical studies performed on these aluminate salts in dimethoxyethane identify the phenoxy and perfluoro-tert-butoxy derivatives as promising electrolyte systems. Electrochemical cycling of these electrolytes using gold and Mg electrodes show that systems containing chloride, brought through to the product from the starting material in the form of NaCl, exhibit lower plating/stripping overpotentials and higher Coulombic efficiencies than systems from which chloride had been removed. Further, these two electrolytes can be used in Mg full cells containing the Chevrel phase cathode. Solid-state 23Na NMR analysis as well as DFT calculations show that chloride-containing electrolytes facilitate the co-insertion of Na into the cathode material. In chapter 5 the hydroboration of pyridines and CO2 in the presence of pinacolborane is presented. An optimized system employing NH4BPh4 and HBpin is developed and a mechanism of pyridine hydroboration is proposed based on multinuclear NMR spectroscopy. The catalytic reaction was found to be catalyzed by a boronium salt, which was structurally characterized in the solid-state by single crystal X-ray diffraction. This new catalytic method is shown to be tolerant to a number of functional groups in the 3-position on pyridine as well as quinoline, and CO2, producing the hydroboration products in good yields.

abstract: Buildings continue to take up a significant portion of the global energy consumption, meaning there are significant research opportunities in reducing the energy consumption of the building sector. One widely studied area is waste heat recovery. The purpose of this research is to test a prototype thermogalvanic cell in the form factor of a UK metric brick sized at 215 mm × 102.5 mm × 65 mm for the experimental power output using a copper/copper(II) (Cu/Cu2+) based aqueous electrode. In this study the thermogalvanic brick uses a 0.7 M CuSO4 + 0.1 M H2SO4 aqueous electrolyte with copper electrodes as two of the walls. The other walls of the thermogalvanic brick are made of 5.588 mm (0.22 in) thick acrylic sheet. Internal to the brick, a 0.2 volume fraction minimal surface Schwartz diamond (Schwartz D) structure made of ABS, Polycarbonate-ABS (PCABS), and Polycarbonate-Carbon Fiber (PCCF) was tested to see the effects on the power output of the thermogalvanic brick. By changing the size of the thermogalvanic cell into that of a brick will allow this thermogalvanic cell to become the literal building blocks of green buildings. The thermogalvanic brick was tested by applying a constant power to the strip heater attached to the hot side of the brick, resulting in various ∆T values between 8◦C and 15◦C depending on the material of Schwartz D inside. From this, it was found that a single Cu/Cu2+ thermogalvanic brick containing the PCCF or PCABS Schwartz D performed equivalently well at a 163.8% or 164.9%, respectively, higher normalized power density output than the control brick containing only electrolyte solution. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2018

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.