Photoelectron Emission at Diamond-Liquid Interfaces

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

TECHNICAL SUMMARY Diamond has an unusual property known as negative electron affinity (NEA) that allows it to act as a solid-state source of electrons when illuminated with ultraviolet light. The combination of diamond's NEA with its outstanding chemical stability allows it to be used as a solid-state source of electrons operating under non-vacuum conditions, even able to directly inject electrons into liquids. The proposed research supported by the Solid State and Materials Chemistry Program, will investigate the factors controlling the efficiency of electron emission into liquids such as water and tetrahydrofuran. Research efforts will focus on understanding the materials factors that control the electron emission process and identifying conditions that will increase electron emission with a broader spectrum of excitation wavelengths and on enhancing the stability of NEA. Methods to be explored include doping with phosphorus or nitrogen, and manipulation of the electrochemical double-layer at the diamond-electrolyte interface. These measurements will provide fundamental new insights into factors that control the efficiency and stability of photoelectron emission under non-vacuum conditions. This research could enable new technological applications in several fields of science and technology such as improved field-emitter displays and enable new types of chemical transformations in liquids. The project will support training and mentoring of students, including undergraduates and high school students, and efforts to engage with state legislators and other decision-makers to inform about the societal impact of scientific research. NON-TECHNICAL SUMMARY The emission of electrons from solid materials underlies many existing technologies such as computer displays. Most materials require high temperature and high vacuum conditions in order to emit electrons and therefore cannot be used in water and other liquids. However, diamond, even when used as inexpensive thin films and/or commercial-grade diamond powder, has the unusual ability to emit electrons into liquids at room temperature when illuminated with ultraviolet light, although with relatively low efficiency. This project will explore several different approaches to improving the ability of diamond to emit electrons into liquids. If this work is successful it could lead to improved computer display technologies and to new, energy-efficienct ways to initiate important chemical reactions, including transformation of inexpensive starting materials into more useful products, such as liquid fuels. The project will support training and mentoring of students, including undergraduates and high school students, and efforts to engage with state legislators and other decision-makers to inform about the societal impact of scientific research.