Converting solar energy into electricity is a reasonable way to ameliorate the current untenable energy situation. One way to harness solar energy is to mimic the mechanisms already present in natural photosynthesis. A key component of many artificial photosynthetic systems is the linker connecting the dye to an electrode. Studying the associated electron transport process is important for improving linker efficiency. Similarly it is important to be able to control the electron transfer to the dye from a water oxidation catalyst, and to be able to improve the lifetime of the charge separated state. Natural photosynthesis provides a blueprint for this in the tyrosine-histidine pair in photosystem II. In this work, research on these topics is described.

Titanium dioxide (TiO2) is widely used for photocatalysis and solar cell applications, and the electronic structure of bulk TiO2 is well understood. However, the surface structure of nanoparticulate TiO2, which has a key role in properties such as solubility and catalytic activity, still remains controversial. Detailed understanding of surface defect structures may help explain reactivity and overall materials performance in a wide range of applications. In this work we address the solubility problem and surface defects control on TiO2 nanoparticles. We report the synthesis and characterization of ∼4 nm TiO2 anatase spherical nanoparticles that are soluble and stable in a wide range of organic solvents and water. By controlling the temperature during the synthesis, we are able to tailor the density of defect states on the surface of the TiO2 nanoparticles without affecting parameters such as size, shape, core crystallinity, and solubility. The morphology of both kinds of nanoparticles was determined by TEM. EPR experiments were used to characterize the surface defects, and transient absorption measurements demonstrate the influence of the TiO2 defect states on photoinduced electron transfer dynamics.