Molecular Photonic Materials

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In this project, funded by the Chemical Structure, Dynamic & Mechanism B Program of the Chemistry Division, Professor Gerald Meyer of the Department of Chemistry at the University of North Carolina at Chapel Hill is characterizing intermolecular electron transfer reactions for molecules anchored to metal oxide surfaces. The goal of this research is to exploit self-exchange reactions as a means to transport charge across oxide surfaces for applications in optoelectronic devices, namely for the conversion of solar energy into stored chemical energy or electricity (e.g. dye-sensitized solar cells). The project lies at the interface of physical organic, inorganic, and materials chemistry, and is therefore well suited to the education of scientists at all levels. This group is also well-positioned to provide the highest level of education and training for students underrepresented in science. Outreach activities to grade school students in local and rural North Carolina are also part of the funded project. Research has shown that photo-oxidized dye molecules anchored to the sensitized mesoporous nanocrystalline (anatase) TiO2 thin films commonly used for dye-sensitized solar cells undergo self-exchange intermolecular electron transfer reactions (termed hole-hopping) with dynamics and efficiencies that can be tuned at the molecular level. These findings provide an opportunity to transport charges to desired locations without a loss in Gibbs free energy. Particular focus wiis being given to address the following fundamental questions: How can molecular structure be tuned to control intermolecular electron transfer? Is there a correlation between self-exchange reactions in fluid solution and those on oxide surfaces? Does self-exchange electron transfer between dyes influenced unwanted recombination reactions? Can self-exchange with molecules that contain two (or more) redox active groups be controlled by the bridge that links them? A kinetic approach that enables redox equilibria at the adiabatic/non-adiabatic border to be quantified for the first time is being utilized. The desired electron transfer chemistry is being initiated by pulsed light excitation or with an applied potential and quantified by in situ spectro-electrochemistry, absorption anisotropy, chronoabsorptometry, and transient absorption spectroscopy.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.