DOI: 10.25549/usctheses-c127-666431
title: One-dimensional nanostructures for novel biosensor and transparent electronics applications

description: This dissertation presents one-dimensional nanostructures for novel biosensors and transparent electronics applications. In chapter 1, background information regarding nanomaterials studied in this dissertation is described. ❧ In chapter 2, I describe the first application of antibody mimic proteins (AMPs) in the field of nanobiosensors. In2O3 nanowire based biosensors have been configured with an AMP (Fibronectin, Fn) to detect nucleocapsid (N) protein, a biomarker for severe acute respiratory syndrome (SARS). Using these devices, N protein was detected at sub-nanomolar concentration in the presence of 44 µM bovine serum albumin as a background. Furthermore, the binding constant of the AMP to Fn was determined from the concentration dependence of the response of our biosensors. ❧ In chapter 3, I demonstrate an In2O3 nanowire-based biosensing system that is capable of performing rapid, label-free, electrical detection of cancer biomarkers directly from human whole blood collected by a finger prick. Detection of multiple cancer biomarkers with high reliability at clinically meaningful concentrations from whole blood collected by a finger prick using this sensing system is demonstrated. ❧ In chapter 4, I introduce a top-down nanobiosensor based on polysilicon nanoribbon with enhanced yield and device uniformity. The polysilicon nanoribbon devices can be fabricated by conventional photolithography with only easily available materials and equipments required, thus results in great time and cost efficiency as well as scalability. The devices show great response to pH changes with a wide dynamic range and high sensitivity. Biomarker detection is also demonstrated with clinically relevant sensitivity. Such results suggest that polysilicon nanoribbon devices exhibit great potential toward a highly efficient, reliable and sensitive biosensing platform. ❧ In chapter 5, I demonstrate the first printed nanobiosensor application based on separated semiconducting single-walled carbon nanotubes. The printed nanosensors exhibit reliable sensing to pH variation. We have successfully achieved the detection of Estradial, a commonly used hormone biomarker, as a proof of concept for using printed nanobiosensors on disease diagnosis. ❧ High-performance fully transparent thin-film transistors (TTFTs) on both rigid and flexible substrates with transfer printed aligned nanotubes as the active channel and indium-tin oxide as the source, drain and gate electrodes is reported in chapter 6. Such transistors are fabricated through low temperature processing, which allows device fabrication even on flexible substrates. Transparent transistors with high effective mobilities (~1,300 cm2V-1s-1) were first demonstrated on glass substrates via engineering of the source and drain contacts, and high on/off ratio (3 × 104) was achieved using electrical breakdown. In addition, flexible TTFTs with good transparency were also fabricated and successfully operated under bending up to 120˚. All of the devices showed good transparency (~80% on average). The transparent transistors were further utilized to construct a fully transparent and flexible logic inverter on a plastic substrate, and also used to control commercial GaN light–emitting diodes (LEDs) with light intensity modulation of 103. Our results suggest that aligned nanotubes have great potential to work as building blocks for future transparent electronics. ❧ In chapter 7, a summary of all topics in this dissertation is described. Future work regarding the nanobiosensor project is also proposed.