Optimizing the Processability of Selenium Nanowires and Their Chemical Transformation into Polymer Coated Semiconductor Materials

摘要

This thesis seeks out to optimize the sonochemically-induced synthesis and the ease of handling high-aspect-ratio selenium nanowires. Understanding the selenium nanowire’s surface chemistry is crucial to controlling their dimensions during growth and to facilitate the manipulation of these materials. The surface chemistry of the nanowires was analyzed with a variety of surface sensitive techniques and electron microscopy. This knowledge of the surface chemistry of selenium nanowires was utilized to increase their colloidal stability. A stable dispersion of selenium nanowires improves the ease of handling and processing these materials for subsequent assembly or use in templated reactions. For example, surfactant stabilized nanowires enhanced their colloidal stability in media that are otherwise poor at stabilizing the nanowires and improved the uniformity of products from templated reactions on the nanowire surfaces. We also discovered that dispersions of selenium nanowires in a low dielectric constant solution could be organized by electrokinetic techniques into fibers that oriented along the electric field. We developed a general method for the assembly of the selenium nanowires into either macroscopic fibers or an array of fibers of various lengths over large areas. Isolated fibers of selenium nanowires could reversibly bend in response to electrostatic charges. These flexible selenium fibers also exhibited a photoconductive response when illuminated with white light. These properties of selenium nanowires can degrade over time as these nanowires are susceptible to oxidative damage, but we were able to demonstrate the first passivation of selenium nanowires with a thin layer of polystyrene. The thin layer of polystyrene was grafted onto the selenium surfaces by a surface-initiated atom transfer radical polymerization reaction. These encapsulated nanostructures demonstrate an enhanced resistance towards oxidative damage, such as corrosion. We were also able to synthesize polystyrene encapsulated copper selenide nanowires by a similar route in a template-engaged reaction in conjunction with a surface-initiated atom transfer radical polymerization reaction.