Ordered Porous Gold Electrodes to Enhance the Sensitivity of Enzyme-Based Glucose Sensors

Glucose sensors are essential tools for diabetes patients to use in monitoring their blood glucose levels. However, to be able to detect glucose in non-invasively collected physiological fluids, such as tears and urine, the sensitivity of these glucose sensors must be significantly higher than sensors that are currently used to detect glucose concentrations in blood. Increasing the specific surface area of enzyme-based glucose sensors through the use of ordered porous gold electrodes has been shown to enhance the sensitivity of these sensors. The enzyme-based ordered porous gold glucose sensor was demonstrated to be suitable in detecting glucose concentrations ranges that are similar to those occurring in tears. Although sensitivity of the glucose sensor is enhanced, the saturation threshold of the sensor is lowered. Further optimizations of the porous gold electrodes are required to eliminate signal saturation of these improved sensors

Optically Active Nanoparticle Coated Polystyrene Spheres

Nanoparticles (NPs) with either plasmonic or upconverting properties have been selectively coated onto the surfaces of polystyrene (PS) spheres, imparting their optical properties to the PS colloids. These NP coated PS spheres have many potential applications, such as in medicine as drug-delivery systems or diagnostic tools. To prepare the NP coated PS spheres, gold or core-shell NaYF4Tm0.5Yb30/NaYF4 NPs were synthesized and separately combined with amino-functionalized PS spheres. The mechanism by which the NPs adhered to the PS spheres is attributed to interactions of the NP and a polyvinylpyrrolidone additive with the surfaces of the PS spheres. Two-photon fluorescence microscopy and SERS analysis demonstrate the potential applications of these NP coated PS spheres

Platinum Ordered Porous Electrodes: Developing a Platform for Fundamental Electrochemical Characterization

High surface area platinum electrodes with an ordered porous structure (Pt-OP electrodes) have been prepared and characterized by electrochemical methods. This study builds a foundation upon which we can seek an in-depth understanding of the limitations and design considerations to make efficient and stable Pt-OP electrodes for use in electrochemical applications. A set of Pt-OP electrodes were prepared by controlled electrodeposition of Pt through a self-assembled array of spherical particles and subsequent removal of the spherical templates by solvent extraction. The preparation method was shown to be reproducible and the resulting electrodes were found to have clean Pt surfaces and a large electrochemical surface area (A ecsa) resulting from both the porous structure, as well as the nano- and micro-scale surface roughness. Additionally, the Pt-OP electrodes exhibit a surface area enhancement comparable to commercially available electrocatalysts. In summary, the Pt-OP electrodes prepared herein show properties of interest for both gaining fundamental insights into electrocatalytic processes and for use in applications that would benefit from enhanced electrochemical response

Alternative Platinum Electrocatalyst Designs for Improved Platinum Utilization

Platinum electrocatalysts are important for a number of low and zero-emission energy technologies, including low temperature fuel cells. For reactions such as oxygen reduction at a fuel cell cathode, poor kinetics and harsh operating conditions (which lead to catalyst degradation) dictate the use of large volumes of Pt for efficient electrocatalysis. This need for a large quantity of Pt increases the cost of the fuel cell and makes the technology too expensive to compete with petroleum based energy alternatives typically used in automotive applications. Improving the effective utilization of Pt enables the same performance to be achieved with a smaller mass of Pt. A more effective use of Pt can be achieved through the use of alternative catalyst layer designs. The work presented in this thesis demonstrates three novel Pt catalyst layer designs with the aim of improving the effective utilization of Pt for electrocatalysis. These designs include pure Pt ordered porous electrodes (Pt-OP electrodes), supported Pt nanoparticle ordered porous electrodes (support@PtNP-OP electrodes) and nanobowl supported Pt NPs (support@PtNP nanobowls). These designs aim to enhance Pt utilization by improving: i) mass transport through the use of an open porous design; ii) Pt electrochemical stability via the use of stable materials throughout the electrocatalyst design and/or through support interactions; and iii) Pt catalytic activity via favorable interactions with support materials. The preparation of these new Pt electrocatalyst designs is presented through the use of sacrificial templates. The new materials were extensively characterized by electron microscopy, X-ray spectroscopy, and electrochemical methods. The alternative electrocatalyst designs demonstrated here provide new routes towards enhancing the utilization of Pt for electrocatalytic applications

Comprehensive Structural, Surface-Chemical and Electrochemical Characterization of Nickel-Based Metallic Foams

Nickel-based metallic foams are commonly used in electrochemical energy storage devices (rechargeable batteries) as both current collectors and active mass support. These materials attract attention as tunable electrode materials because they are available in a range of chemical compositions, pore structures, pore sizes, and densities. This contribution presents structural, chemical, and electrochemical characterization of Ni-based metallic foams. Several materials and surface science techniques (transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), focused ion beam (FIB), and X-ray photoelectron spectroscopy (XPS)) and electrochemical methods (cyclic voltammetry (CV)) are used to examine the micro-, meso-, and nanoscopic structural characteristics, surface morphology, and surface-chemical composition of these materials. XPS combined with Ar-ion etching is employed to analyze the surface and near-surface chemical composition of the foams. The specific and electrochemically active surface areas (As, Aecsa) are determined using CV. Though the foams exhibit structural robustness typical of bulk materials, they have large As, in the range of 200–600 cm2 g–1. In addition, they are dual-porosity materials and possess both macro- and mesopores

Comprehensive Structural, Surface-Chemical and Electrochemical Characterization of Nickel-Based Metallic Foams

Nickel-based metallic foams are commonly used in electrochemical energy storage devices (rechargeable batteries) as both current collectors and active mass support. These materials attract attention as tunable electrode materials because they are available in a range of chemical compositions, pore structures, pore sizes, and densities. This contribution presents structural, chemical, and electrochemical characterization of Ni-based metallic foams. Several materials and surface science techniques (transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), focused ion beam (FIB), and X-ray photoelectron spectroscopy (XPS)) and electrochemical methods (cyclic voltammetry (CV)) are used to examine the micro-, meso-, and nanoscopic structural characteristics, surface morphology, and surface-chemical composition of these materials. XPS combined with Ar-ion etching is employed to analyze the surface and near-surface chemical composition of the foams. The specific and electrochemically active surface areas (<i>A</i>_s, <i>A</i>_ecsa) are determined using CV. Though the foams exhibit structural robustness typical of bulk materials, they have large <i>A</i>_s, in the range of 200–600 cm² g^–1. In addition, they are dual-porosity materials and possess both macro- and mesopores