Redox electrocatalysis of floating nanoparticles: determining electrocatalytic properties without the influence of solid supports

peer-reviewedRedox electrocatalysis (catalysis of electron transfer reactions by floating conductive particles) is discussed from the point-of-view of Fermi level equilibration, and an overall theoretical framework is given. Examples of redox electrocatalysis in solution, in bipolar configuration and at liquid-liquid interfaces are provided, highlighting that bipolar and liquid-liquid interfacial systems allow the study of the electrocatalytic properties of particles without effects from the support, but only liquid-liquid interfaces allow measurement of the electrocatalytic current directly. Additionally, photo-induced redox electrocatalysis will be of interest, for example to achieve water splittin

Electrochemical investigation of electron-transfer cascades for the development of solar energy conversion based on artificial photosynthesis

Natural Photosynthesis process is the source of life; it converts the sunlight into chemical energy. This process takes place in the chloroplast of the green plants in a sophisticated and complex pathway. It involves electron transfer cascades from the photoexcited reaction centre to sustainable energy storage. As a route to develop new chemical systems for artificial photosynthesis in an efficient and fast electron transfer cascade, it is essential to propose three-dimensional molecular ensembles of both electrochemically and photochemically active systems.This thesis studies the behaviour of using L-cysteine and potassium iodide as electroactive species in a reduction reaction of chlorpromazine hydrochloride on glassy carbon electrodes and rotating glassy carbon disk electrodes with the aid of cyclic voltammetry and linear sweep voltammetry.The electrochemical characteristics of chlorpromazine hydrochloride (CPZ.HCl) in various concentrations, which induce catalytic oxidation reactions of different concentrations of the electroactive materials, are investigated. The experimental results show that the increase in oxidation peaks current of chlorpromazine hydrochloride depends on the concentrations of L-cysteine and potassium iodide. The current response was enhanced through fast transport via a rotating glassy carbon disk electrode. The peak potentials of chlorpromazine hydrochloride in the solution containing L-cysteine shift to more negative values for all concentrations and speeds; similarly for potassium iodide. The electrochemical reaction of chlorpromazine hydrochloride with the electroactive materials determined EC’ reactions. The diffusion coefficient for chlorpromazine hydrochloride was found to be 1.28×10-6 m2 s-1. This thesis studies the adsorption and electrochemical investigation of one of the derivatives of chlorophyll – chlorophyllin, at gold and glassy carbon electrodes. Parameters such as the adsorption time, the electrolyte nature and concentration and chlorophyllin concentration were investigated. The use of chlorophyllin as a redox mediator was examined, with a gold electrode being employed. The importance of gold electrode surface preparation in determining the mechanism of redox was described, and the environment of adsorption process of the different concentrations of chlorophyllin on the surface of the gold electrode had been elucidated in this study. The electrochemical method shows that the cyclic voltammetry responses of studied adsorption chlorophyllin pigment on the gold electrode were more efficient than glassy carbon electrode, with processes being more favourable in aqueous solution.Third, the oxidation reaction of various concentrations of chlorophyllin is investigated in the bulk solution in the presence of Triton X 100 and potassium iodide. The extraction and identification of chlorophyll in fresh spinach were examined by using thin layer chromatography and UV-visible spectrophotometry techniques. The cyclic voltammetry for this pigment was elucidated in the presence of Triton X 100 and vitamin K1 at the gold electrode, the mechanism of this reaction was suggested to be EC’.Lastly, this study has emphasised chlorophyll a and Total chlorophyll (Tchl), based on the effect of electrode materials and diameter, pH, solvent and electrolyte. The inducing of electron transfer of Tchl pigment was examined in presence and absence of vitamin K1 through light and dark atmosphere. The system of chlorpromazine-lyotropic liquid crystal (CPZ-LLC) was highlighted in this thesis. The effect of parameters such as electrode materials, electrode diameters and CPZ.HCl concentrations in this system have been documented. The self-assembled phase was recorded using polarising optical microscopy and X-ray scattering. The CPZ-LLC system was fabrication into photogalvanic cells. The power conversion efficiency (PCE) of this cell is (0.58%), which is useful and novel

Nanoscale Electrodes for Bionanosensing

Cancer is globally the second most common cause of death. Cancer burden rises to about 10 million deaths and more than 18 million new cases in 2018. Cancers are often diagnosed at a later stage preventing curative treatment. This underscores the need for an early stage diagnosis of cancer. Consequently, screening methods that can test patients’ samples taken by less invasive methods capable of early stage diagnosis are highly sought for. Based on this motivation, here we developed lab-on-a-chip diagnostic systems that can be used for early detection of cancer. Three different types of nanoscale electrodes were fabricated: (i) nanogap electrodes (ii) nano interdigitated electrodes and (iii) nanodisc electrodes and the possibility of using them for sensing and signal transduction were investigated. Chapter 2 describes the fabrication of nanogap device using conventional optical lithography and DNA detection across it using the electrical method. Chapter 3 details the fabrication of nano interdigitated electrodes (nIDEs) and their electrochemical validation. Chapter 4 describes the biosensing application of nIDEs using nanoparticle sandwich assay for the detection of DNA molecules. Chapter 5 describes the capturing of tdEVs on nIDEs, and its quantification using a sandwich immunosorbent assay on nIDEs. Chapter 6 proposes a new type of nanoscale electrodes which are termed as nanodisc electrodes. Chapter 7 explores the possibility of developing the nanodisc technology to a business idea. In short, the whole thesis tries to explore the different possibilities in developing a sensor that can be useful for cancer diagnosis

Unconventional Electrochemistry in Micro-/Nanofluidic Systems

Electrochemistry is ideally suited to serve as a detection mechanism in miniaturized analysis systems. A significant hurdle can, however, be the implementation of reliable micrometer-scale reference electrodes. In this tutorial review, we introduce the principal challenges and discuss the approaches that have been employed to build suitable references. We then discuss several alternative strategies aimed at eliminating the reference electrode altogether, in particular two-electrode electrochemical cells, bipolar electrodes and chronopotentiometry