Increased energy prices and the growing attention on global warming are motivating the creation of economically viable alternatives to fossil fuels. Nanotechnologies have been recognized as one effective approach to solve energy problems. Therefore, to promote the improvement of research and to foster professional collaboration among researchers in energy-related nanotechnologies, we organized a symposium on "Nanotechnology for a Sustainable Energy Economy" as a part of the 243rd American Chemical Society National Meeting, which took place March 25-29, 2012 in San Diego, California, USA. Forty-four contributors from 12 countries presented their research works from industrial, university, and national laboratories in nanotechnology areas related to energy and fuel technologies. This ACS Symposium Series book was developed from this symposium. This book presents a very useful and readable collection of reviews and research papers in nanotechnologies for energy conversion, storage, and utilization, offering new results which are sure to be of interest to researchers, students, and engineers in the field of nanotechnologies and energy. The book focuses on the following topics: Li batteries (Chapters 1-4), supercapacitors (Chapter 5), dye-sensitized solar cells (Chapter 6), photocatalysis (Chapters 7-9), fuel cells (Chapter 10), electrocatalysis (Chapter 11), and electron beam lithography (Chapter 12). All 12 chapters were recruited from oral presentations at the symposium.