UC Berkeley

Some might view the "nano revolution" as one of the most important developments of our time, as nanomaterials have been and continue to be a seemingly endless source of new and exciting physics and have found application in almost every imaginable aspect of our lives. Carbon allotropes such as graphene, which is a single atomic layer of carbon atoms in a hexagonal lattice, carbon nanotubes (CNTs), which can be thought of as graphene sheets rolled up into cylinders, and graphene nanoribbons (GNRs) have garnered massive attention in recent years due to their remarkable properties and many potential uses. This work investigates the fundamental properties and applications of certain nanomaterials such as carbon allotropes, semiconducting metal oxide (SMO) nanoparticles, and others in the exciting fields of gas sensing, nanoelectromechanical oscillation, and optical near field enhancement. It also introduces a novel GNR synthesis technique.

Chapter 1 of this work is a brief introduction to the nanomaterials that will be investigated here. Chapter 2 presents experimental investigations into the interaction between gases and certain nanomaterials, including SMO nanoparticles, gold nanowires and thin films, CNTs, bare graphene, and graphene functionalized by a novel electrodeposition technique. New findings on the sensing mechanism of tungsten oxide nanoparticles for hydrogen sulfide gas are discussed. These findings suggest that previous models were incorrect or incomplete. Chapter 3 discusses sustained self-oscillations of a singly-clamped CNT under constant bias, a phenomenon which obviates the need for large external sources to drive nanomechanical oscillations. A model of the phenomenon is presented and used to guide scalable, top-down fabrication of self-oscillators. In chapter 4, a novel, clean technique for synthesizing GNRs with desired dimensions is demonstrated. It is shown that this method allows for transmission electron microscopy and electronic characterization of the GNRs during and after synthesis. A model of the underlying physical mechanism is proposed. In chapter 5, optical field enhancement near nanostructures, which has applications in optical antennae, photovoltaics, and near field optical microscopy, is modeled.