Shane Ardo - US grants

Professor Shane Ardo of the University of California-Irvine is supported by the Chemical Catalysis program in the Division of Chemistry to investigate dye-sensitized solar cells (DSSCs). DSSCs are an inexpensive alternative to commercial solar cells but have exhibited low solar-energy-conversion efficiencies that hamper their commercialization. This project is investigating an alternative reaction to dramatically increase the efficiency of iodide-containing DSSCs, from their current world-record efficiency of ~12% to over 20%. The project promotes the progress of science and facilitates environmental stewardship. Outreach workshops accompany this research program with the aim of increasing the participation and interest of female middle-school students in research related to solar energy conversion.

The research is motivated by a new mechanism of operation for DSSCs and dye-sensitized functional assemblies for solar fuels where multiple-electron-transfer redox-shuttle chemistry is driven at molecular electrocatalysts co-anchored to dye-sensitized nanocrystalline TiO2. Fundamental studies include (i) surface-confined electrocatalysis of multiple-electron-transfer redox-shuttle oxidation, (ii) self-exchange electron transfer between molecules anchored to the TiO2 surface, and (iii) (slow) recombination of electrons in TiO2 with oxidized surface-anchored molecules. Several series of polymeric materials and Pt and Pd organometallic coordination compounds are synthesized and investigated for their ability to facilitate inner-sphere iodide oxidation electrocatalysis. The molecular structure of dyes is varied to identify those with the most rapid self-exchange electron transfer and slowest recombination. TiO2-bound electrocatalysts and dyes are studied simultaneously in order to interrogate the effects of several interacting functions and with the aim of realizing efficient light-driven iodide electrocatalysis. The electrocatalysis work is performed using a rotating ring-disk electrode setup and/or cyclic voltammetry to assess the catalytic competency of the molecules. Dye phenomena are interrogated using spectroelectrochemistry and nanosecond pump-probe transient-absorption and time-resolved photoluminescence (polarization) spectroscopies. In addition to spectrally modeling transient spectra and polarization kinetics, numerical models and Monte Carlo simulations helps clarify what controls the rate of (desired) self-exchange electron transfer and (undesired) recombination.

Equal access to scientific inquiry and STEM careers is an important goal for the National Science Foundation and for the nation as a whole. However, minority students are not participating in the scientific enterprise in proportion to their representation within the general population. One barrier is the lack of connections between scientists at minority-serving institutions (MSIs) and at primarily white institutions (PWIs). This disconnect leads to a self-perpetuating cycle of primarily PWI graduates entering the highest ranks of academia and industry, relying on networks of trust that favor elite institutions in areas such as research collaborations. One possible solution is to build new faculty-based networks that thrive on mutual trust and exchange between MSIs and PWIs. This workshop will convene a group of faculty from MSIs and PWIs to begin a conversation about how to develop such a network.

The two-day workshop, to be held June 25-26, 2018 at the University of California, Irvine, will engage approximately 40 faculty members (20 from MSIs and 20 from PWIs) in a series of exercises to facilitate the development of partnerships across institutional types, and to begin the planning stages for writing proposals to support the partnerships. Faculty will meet each other, engage in discussion about model partnerships, and formulate ideas that could be used for grant proposals to be submitted to private foundations and national funding agencies. Workshop assessment will be conducted using surveys to measure how social networks have changed because of the meeting, and to follow up with partnerships established at the meeting to determine if they led to the submission or awarding of grants. Workshop discussions will be aggregated to develop a policy paper on best practices in developing MSI-PWI networks, which will be circulated publicly via posting on the University of California, Irvine website for the Division of Teaching and Learning, and by public presentation at relevant conferences and regional meetings.

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.

In this project, funded by the Chemical Structure, Dynamics & Mechanism B Program of the Chemistry Division, Professor Shane Ardo of the Department of Chemistry at the University of California-Irvine is developing a series of photo-acid and photo-base molecules with specifically designed proton donor and proton acceptor groups. The goal of this research is to use these molecules to evaluate the driving-force dependence for rate constants associated with excited-state proton transfer, which is important for solar energy utilization. The project lies at the interface of organic and photophysical 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 with middle school students that promote interest in STEM (science, technology, engineering and mathematics) and foster trust in scientists and science will also be part of the funded project.

Photo-acids and photo-bases are molecules whose acidity changes reversibly upon absorption of light. This can result in excited-state proton transfer, with energetics described using the well-known Förster cycle analysis. Recently, Professor Shane Ardo and his group showed that many photo-acids and photo-bases that do not undergo excited state proton transfer due to kinetic limitations can be re-engineered to overcome this barrier through the introduction of proton acceptor and/or proton donor buffer species. This allowed the research team to accurately predict excited state acidity, and thus standard state driving force, for proton transfer. In this project, they aim to validate their new method and then use it to quantify the relationship between standard-state driving force and activation free energy for proton-transfer reactions, including in the Marcus inverted region. They also aim to leverage this fundamental understanding to design and demonstrate photochemical protonic energy conversion systems that use light to modulate the protonation state of two buffer species. They attempt to answer the following critical questions: 1) Are driving-force-dependent theories for the kinetics of electron transfer and proton transfer, e.g. Rehm–Weller, Marcus–Cohen, Agmon–Levine, suitable to describe excited-state proton transfer reactions? 2) Can the ground-state acidity/basicity of photo-acids/photo-bases be tuned so that buffers and/or protic solvents serve as proton donors/acceptors for regeneration of the ground-state conjugate base/acid of photo-acids/photo-bases?

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.