Functionalized Nanocarbons for Artificial Photosynthesis: From Fullerene to SWCNT, Carbon Nanohorn, and Graphene

Abstract

This chapter describes the recent advances in photosensitized electron transfer processes on nanocarbon surfaces functionalized with electron-donating or electron-accepting molecules. As nanocarbons, well-characterized fullerenes, size (diameter)-sorted single-walled carbon nanotubes (SWCNTs), carbon nanohorns (CNHs), graphene, and graphene oxide are mainly employed. These nanocarbons act as excellent electron acceptors, when they are linked to the light-absorbing electron donors such as porphyrins or phthalocyanines. Employing diameter-sorted SWCNT makes it possible to reveal the relationship between nanotube size and electronic structure, which strongly affect the photoelectron transfer properties. In these studies, for the confirmation of electron transfer processes, time-resolved spectroscopic methods have been widely used. The kinetic data obtained in solution are found to be quite useful to understand the electron transfer mechanisms. Photovoltaic cells constructed by employing these photosensitizing electron transfer systems are indicative of their potential uses to construct artificial photosynthetic systems for the light-to-electricity and light-to-fuel productions.