Electrochemical Characterization of Nanomaterials and Development of New Electrochemical Methods

Abstract

This 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.