Multilayer Track Etched Porous Templates for Unconventional Functional Nanostructure Manufacturing and Applications

Exploration of nanostructure arrays have led to the discovery of unique physiochemical properties that allow for novel applications of nanostructure arrays in fields such as field emission, chemical bio-sensing, energy harvesting, energy storage, and nanomedicine. These nanostructure arrays, composed of an arrangement of uniform nanostructures interconnected by a supporting substrate, have been explored in countless arrangements of nanostructure geometries, orientation, and composition as a means of developing a tuned nanostructure array for a desired application. A main issue that prohibits the disbursement of nanostructure arrays into practical applications is the high cost, low yield, and low degree of reproducibility associated with most nanostructure array fabrication methods. Additionally, many of these methods are limited to a constraint of the nanostructure array’s geometry, orientation, or composition, thus causing the fabrication method only to be practical for a specific nanoarrays. Among various nanofabrication methods, template assisted syntheses has been found to be able to produce functional nanomaterials with high aspect ratio and composition modulation, overcoming limitations of conventional top-down or bottom-up approaches. This template assisted method is fully scalable, and allows for a wide range of material compositions, with limitations of geometry corresponding to the limits of the template fabrication. Currently available nanoporous templates are single layer films containing uniform pore dimensions, which constrain the geometry and subsequent functionalization of nanostructures that can be produced. A key focus of this dissertation is on the development and characterization of a nanoporous template composed of multiple layers with distinct physiochemical properties, allowing precise control of pore sizes in individual layers, and selective dissolution of the constituent template materials, leading to efficient and reproducible fabrication of unique nanostructures to deliver functionalities that are un-obtainable in nanoparticles or nanowires/nanotubes. As a demonstration, partially exposed and fully exposed two-segment nanostructures were fabricated as a means to determine the capability of the multiple layer track etched template as a platform for nanofabrication/nanomanufacturing of nanostructure arrays. This dissertation continues and explores the unique partially exposed nanostructure array for its use as a sensor. Such a nanostructured sensor has shown greatly improved sensitivity when compared to thin film sensors, with the unique capability that these segmented nanostructure arrays can be mass produced when the fabrication process is integrated with roll-to-roll production. As a demonstration, a partially exposed two-segment nickel nanowire array was fabricated and tested for the non-enzymatic sensing of glucose, which demonstrated an increased sensitivity and unique electrochemical response when compared to normalized results from planar film sensor samples. To characterize the potential enhancement mechanism of the nanostructured arrays, the kinematics of the non-enzymatic detection were determined showing the nanostructured arrays had a clearly larger catalytic reaction rate, while diffusion coefficients remained constant between the nanostructured array and the planar film, indicating an enhancement from the nanostructuring of the Ni surface.