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Charge transfer efficiency at the organic/transparent conducting oxide (TCO) interface is one of the key parameters controlling the overall efficiency of organic photovoltaics (OPVs). Modification of this interface with a redox-active organic surface modifier may further enhance the charge transfer across the interface by providing a charge-transfer pathway between the electrode and the organic active layer. Functionalized perylene diimide molecules (PDI) are useful for modifying metal oxide/acceptor interfaces for inverted solar cell devices because their LUMO energy level is close to some commonly used acceptor molecules. The effects of PDI structural parameters on the interfacial charge transfer processes across the organic/ITO interface were investigated. Six different PDI monolayers with different structural parameters were deposited on ITO surfaces to investigate the relationship between molecular orientation, linker length, aggregation and charge transfer process. The PDI orientation, degree of PDI aggregation and charge transfer process acrosses PDI/ITO interfaces were characterized by polarized ATR spectroscopy, PM-ATR spectroscopy and photoelectrochemistry. Both linker length and orientation affected the tunneling distance between PDI and ITO, therefore affecting the charge transfer rate constant across the PDI/ITO interfaces. PDI aggregation forced a more out-of-plane orientation of PDI molecules and increased the overall measured charge transfer rate constant. However, PDI aggregation also increased the excited state recombination rate which ultimately led to decrease of the charge collection efficiency. The first application of a PM-TIRF platform to characterize the electron-transfer processes of PDI monomeric films across the organic/electrode interface is presented. The PM-TIRF technique provides higher sensitivity as well as the capability to measure very fast charge transfer events, compared to other commonly used potential-modulated spectroscopy techniques. PDI-phenyl-PA monomeric films exhibited a more in-plane orientation compared with aggregated films and showed a smaller charge transfer rate constant across the PDI/ITO interfaces compared with PDI films with higher degrees of aggregation after normalizing the tunneling distance contributions.

Electrochemical and spectroelectrochemical techniques were employed to investigate the redox characteristics of dyes for dye sensitized solar cells (DSCs) adsorbed at the surface of fluorine-doped tin oxide (FTO) and FTO TiO2 electrodes. In this work are studied Ru-based dyes such as cis-bis(isothiocyanato)-bis(2,2’-bipyridyl- 4,4’dicarboxylato)-ruthenium(II) (N719) and (cis-RuLL'(SCN)2 with L=4,4'- dicarboxylic acid-2,2'-bipyridine and L'=4,4'-dinonyl-2,2'-bipyridine) known as Z907, and indoline organic dyes coded as D102, D131, D149, and D205. The adsorption, diffusion and stability of adsorbed dyes were studied using cyclic voltammetry in acetonitrile and 0.1 M NBu4PF6. The adsorption technique at FTO electrodes was optimized in order to be reproducible so that electrochemical studies as a function of dye coverage were carried out. Langmuirian binding constants were approximately estimated for all dyes adsorbed at FTO electrodes. Rate constants for the chemical degradation of the oxidized dye were also obtained. Is shown that degradation of the dyes mainly occurs at the surface of FTO and only insignificant degradation is evident once the dyes are adsorbed on TiO2. The degradation of dye adsorbed on FTO is shown to affect charge transport from the nonporous TiO2 via electron hopping. Spectroelectrochemical studies of indoline dyes adsorbed on FTO/TiO2 electrodes revealed a red shift of absorption peaks after oxidation and the presence of a strong charge transfer band in the near IR that suggest delocalization of holes in the dye layer. This is consistent with observation that the diffusion coefficient for hole conduction in the adsorbed dye layer is several orders of magnitude higher for the organic dyes compared to the Ru-based dyes. DSCs fabricated using indoline dyes showed good performance. Incident photon-tocurrent conversion efficiency (IPCE) spectra and I-V characteristics are presented.

Pyroprocessing, via electrorefining in a molten salt bath, is a promising treatment route for spent nuclear fuel reprocessing. In order to implement such a technology and ensure its safe operation it is vital to develop on-line techniques to understand and monitor the molten salt and its contents. These tools are technically challenging because of the high temperatures and corrosive environment experienced in molten salt media. Electrochemical, spectroscopic and spectroelectrochemical methods were developed and used to study actinide and fission product behaviour in molten LiCl-KCl eutectic. A spectroscopic furnace was designed and supporting methodology developed in order to allow the acquisition of reproducible quantitative data. The apparatus monitored the precipitation of NdCl3 by the addition of Li2CO3 and PrCl3 by the addition of Li2O in LiCl-KCl eutectic. The precipitates formed were identified as the respective LnOCl. In order to probe actinide behaviour in this hygroscopic medium, dry actinides chlorides were synthesised. The oxidation of uranium metal by BiCl3 in LiCl-KCl eutectic yielded UCl3 while neptunium and plutonium were prepared as Cs2AnCl6 via precipitation in concentrated aqueous HCl by addition of CsCl. The molar extinction coefficients for U(III), U(IV), Np(IV) and Pu(III) were obtained in LiCl-KCl eutectic at 450 áμ’C. The study of the Np(IV)/Np(III) couple via spectroelectrochemical techniques, enabled the determination of the Np(III) molar extinction coefficients. Uranium was studied in LiCl-KCl eutectic using square wave voltammetry, cyclic voltammetry and chronoabsorptometry. The electrochemical techniques benchmarked the results obtained by spectroelectrochemistry. The results from the different techniques were compared to and explained by determining the Gibbs energy and activation energy of U(III) and U(IV). It was concluded that all the mentioned techniques are suitable for the study of high temperature molten chlorides. Because of its capacity to gather numerous data parameters while minimising the number of experiments required and the quantity of material needed, spectroelectrochemical methods were highlighted as the most promising technique for future studies of radionuclides in high temperature melts.

<p>In this dissertation several metalloproteins, both metal transport proteins and the classic metalloprotein hemoglobin, are investigated using a variety of biophysical and electrochemical techniques. In each case, thermodynamic measurements provide insight into the role and mode of action of the metalloprotein under investigation. In Chapters 2 and 3, we focus on the thermodynamic properties of the metal while bound by the protein. In Chapter 4, we focus on the thermodynamic properties of the protein with and without the metal. In Chapter 5, we utilize both the metal and the protein as our probe.</p> <p>In Chapter 2, we probe the thermodynamic properties of the heme-bound iron to elucidate the structure-function relationships underlying two important physiological responses of hemoglobin (Hb): the Root Effect of hemoglobin from certain fish and the different nitrite reactivities of hemoglobins from clams. Hemoglobins of some fish exhibit significantly lowered oxygen affinity at low pH, allowing for proton-mediated release of O₂. This phenomenon, known as the Root Effect, serves as a proton-driven pump delivering O₂ to the swim bladders and eyes of the fish. The clam, ,<italic>L. pectinata</italic>, expresses functionally distinct Hb I that transports H₂S and Hb II that transports O₂. These two hemoglobins differ widely in their reactivity with nitrite, a reactant of great importance to the study of vasodilation in humans. The structural basis of the extreme pH-sensitivity of the Root Effect Hbs and the extreme reactivities of the <italic>Lucina Hbs</italic> with nitrite are debated. Focusing on the metal as the probe, we investigate the reduction potentials of these Hbs using spectroelectrochemistry and compare our findings with oxygen binding studies performed by our collaborators. In both cases, our data strongly suggest that steric hindrance is the determining factor governing the respective physiological response of each hemoglobin. </p> <p>In Chapter 3, we again use the metal as the probe to determine the reduction potential of titanium bound by transferrin (Tf). Tf is the human iron transport protein that can also bind titanium. To address the possible mechanisms of titanium transport through the hypothesized redox-mediated Fe₂-Tf transport pathway, a modified spectroelectrochemistry (SEC) method was developed to measure the electrochemical properties of metalloproteins with very negative potentials. However, the reduction potential of Ti₂-Tf is far too negative to access with our system. As an alternative approach, the redox properties of several model titanium and iron compounds were characterized in order to develop a linear free energy relationship (LFER) allowing us to estimate the reduction potential of Ti₂-Tf to be ca. -900 mV vs. NHE. Our results indicate that the reduction potential of Ti₂-Tf is too low to be reduced by biological reducing agents and suggest that transferrin-mediated titanium transport follows a different mechanism than iron transport.</p> <p>In Chapter 4, our focus shifts to the thermodynamic properties of the protein. Some pathogenic Gram-negative bacteria such as <italic>N. gonorrhoeae</italic> steal iron from their human host by expressing a receptor (TbpA/TbpB), which binds the human iron transport protein transferrin (Tf). Once iron crosses the outer membrane, ferric binding protein (FbpA) transports it across the periplasm to the cytosol. Focusing on the protein, we investigated the protein-protein interactions involved in this transport process and the roles that TbpA and TbpB play with the use of an H/D exchange and mass spectrometry based method termed SUPREX. We report herein the first direct measurement of periplasmic FbpA binding to the outer membrane protein TbpA and we demonstrate that both TbpA and TbpB individually can deferrate Tf without energy supplied from TonB, resulting in sequestration by apo-FbpA.</p> <p>In Chapter 5, we extend our investigation of the <italic>N. gonorrhoeae</italic> iron uptake system by using the metal as the probe in one case and the protein as the probe in another case. TbpA, the &#946;-barrel receptor protein that is required for utilization of Fe₂-Tf as an iron source, has a plug domain which we hypothesize binds iron and interacts with FbpA on the periplasmic side of the outer membrane. Utilizing SUPREX to monitor the thermodynamic properties of protein folding, we investigate 1) the possible interactions between the TbpA-plug and FbpA and 2) the ability of the TbpA-plug to bind iron. </p> <p>Focusing on the metal as the probe, we designed an experimental apparatus to investigate the possible thermodynamic effects of the TbpA/TbpB receptor on the release of iron from Tf. We report the use of a competitive iron chelator and equilibrium dialysis allows for the spectroscopic monitoring of iron release from Tf in the absence of FbpA, but in the presence of opaque bacterial membrane preparations containing the receptor.</p> / Dissertation

Potential modulated attenuated total reflectance (PM-ATR) spectroscopy is a novel technique that makes it possible to sensitively monitor spectroscopic changes in an adsorbed molecular film as a function of applied potential. Here, PM-ATR was used to study charge transfer processes in Prussian blue (PB) and cytochrome c (cyt c) films deposited on indium tin oxide (ITO) electrodes.The electron transfer rate of PB films determined by PM-ATR was found to be in good agreement with the rate determined by conventional cyclic voltammetry, which validates the optical technique.The relationship between molecular orientation and electron transfer in adsorbed cyt c monolayers was investigated using PM-ATR. The electron transfer rate measured using TM polarized light was four-fold greater than that measured using TE polarized light. These data are the first to correlate a distribution of molecular orientations with a distribution of electron transfer rates in a redox-active molecular film.

Graphene research is nowadays one of the worldwide most prominent fields of interest in material science due to many extraordinary properties of graphene and related materials. However, the different techniques of synthesis and subsequent handling and/or treatment have a substantial impact on the properties of the graphene and thus a lot of efforts have been focused on developing of the advanced methods for graphene preparation and characterization. Graphene can be easily produced by oxidation and consequent exfoliation of the bulk graphite; however, resulting graphene oxide needs to be reduced back to graphene-like structure due to partial restoration of sp2 network. Herein, a detailed study of the structural evolution of the graphene oxide during electrochemical treatment has been performed using X-ray photoelectron, Raman and infrared spectroscopies and the results were compared with non-oxidized graphene nano-platelets. Additionally, graphene oxide in composite with LiFePO4 olivine material, which is electrochemically almost inactive in a freshly made state, has been tested by repeated electrochemical cycling. Using various electrochemical methods, the progressive electrochemical activity enhancement has been observed and spontaneous graphene reduction was identified as responsible for this...

The biodiesel industry produces millions of kilograms of low-value glycerol, which must be either stored or disposed of, creating environmental concerns. Even though glycerol is utilized as a raw material within various industries its supply is still superior to the demand. Upgrading this biodiesel by-product into value-added products using electrochemical technologies is a promising approach and will make biodiesel production more environmentally friendly with added financial benefits. Precious metals are the state-of-the-art electro-catalysts for the oxidation of organic compounds, and so are a logical choice for the electro-oxidation of glycerol. Two factors that hinder their use in this regard for commercial applications include their cost and susceptibility to poisoning by the carbonyl (CO) species formed during the electro-oxidation process. The use of inexpensive transition metals as the principal metals in a catalyst composite is thus appealing, leading to the selection of nickel (Ni). Furthermore, its high activity, anti-poison ability and long-term stability in alkaline solutions make it an attractive candidate for glycerol electrooxidation reaction (GEOR). The main thrust of this work is to develop a deeper understanding of the factors involved in controlling the selectivity of the product reaction without 3 carbon cleavage on non-precious metal surfaces. To overcome a trial-and-error approach, we took advantage of modern synthesis and characterization techniques for metal alloy nanoparticles and advances in rapid identifications and quantifications of products based on infrared spectroscopy. These tools were expected to provide the foundation for the detailed understanding of GEOR mechanism hence would pave the way for the rational design of catalysts to produce specific high value-added chemicals. We cared out extensive research to determine the effect of size, morphology, shape, support, experimental conditions and catalyst preparation methods on the catalytic performance of Ni. The thesis aims to demonstrate how the selectivity of unsupported Ni nanoparticles for GEOR can be improved via interaction of Ni with low noble and transition metals content. Enhanced selectivity towards C3 and C2 products such as glycerate, lactate, oxalate and tartronate, was achieved by simply adding less than 20 atomic percent of any of bismuth (Bi), Pd or Au onto Ni nanoparticles. Furthermore, the composition effect of carbon supported NiₓM₁₋ₓ (M = Bi, Pd and Au) nanomaterials were combined with Pt/C and commercial silver nanoparticles for cathodic hydrogen production and CO₂ electro-reduction, respectively. These rich-phase of Ni(OH)₂ catalysts were highly active and selective towards C-C bond breaking products leading to 100% selectivity of formate after 1 hr electrolysis and 100% conversion of glycerol after 24 hr at +1.55 V. Lastly, the first principles calculations based on the density functional theory (DFT) insights provided an explanation to understand the electronic structure, magnetism and reactivity of our catalysts. Core@shell (Mm@Nin) nanoparticles of 13-, 54- and 55-atoms with different elements concentrations matched the experimental results and assisted us with a better understanding of some of the microscopic phenomena involved with the reactivity of bimetallic nanoparticles.

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