Electrochemical Characterization of Nanomaterials and Development of New Electrochemical Methods

Thesis (Ph.D.)--University of Washington, 2018This dissertation focuses on studying fundamental properties of nanomaterials with electrochemical methods and the development of new electrochemical methods to study single nanoparticles and vesicles. Chapter 1 introduces nanomaterials including nanoparticles and nanoparticle films and addresses the importance of single-nanoparticle study with electrochemical methods. This chapter also discusses the electrochemical methods that are employed in the following chapters. Chapter 2 discusses the electrochemical characterization of uniform ultrathin nanoparticle films that can be fabricated by layer-by-layer assembly with well-controlled film thickness and composition. The electrocatalytic activity towards oxygen reduction reaction of the film are studied with voltammetric techniques. Chapter 3 discusses the characterization of single Janus Au-SiO2 nanoparticle with single-nanoparticle collision method. The apparent electroactive area of single Janus nanoparticles can be obtained from the transient current signals from hydrazine oxidation and proton reduction. The study in chapter 4 represents the first evidence that transient bipolar electrochemistry can happen on small free moving metal nanoparticles. This innovative study utilizes the highly focusing power of a nanopore for the applied voltage so that the potential drop across a 40 nm particle is sufficient to couple two electrochemical reactions. The use of nanopore and resistive-pulse sensing may be extended to future nanoparticle studies in ultrafast electrochemistry, nanoparticle catalyst screening, and gas nucleation on nanoparticle. In chapter 5 we design a high throughput electrochemical analyzer for counting and sizing single vesicles and propose its potential in integration with ultramicroelectrodes to obtain more complicated information of singe vesicles