Randall Goldsmith
From New Jersey, Undergrad at Cornell University
Nano 2022, 1-4420
r-goldsmith@northwestern.edu
When I'm not in the lab, I'm helping to maintain the Northwestern University Department of Chemistry Intramural Ultimate Frisbee Team as the Force of Nature that it has become.
Electron transfer (ET) is a critical process in nano-scale electronic and photonic devices including solar cells. Like many natural phenomena, electron transfer is a complex function of many system-specific variables. Our approach entails the synthesis of organic molecules with specific electron donors and acceptors fixed at a well defined distance about an intervening molecule that covalently bridges the donor and acceptor. Using the versatility of organic chemistry to design molecular structures and the probing power of ultrafast transient absorption and nanosecond transient electron spin resonance spectroscopy, we study ET rates as a function of molecular structure, while keeping as many system variables as possible constant and changing only the variable of interest. This procedure allows a logical and methodical approach to studying ET.
For example, previous attempts at examining the length dependence of ET have been complicated by bridges with oxidation potentials that shift as a function of length. Oligofluorenes (figure 1) have the novel property of possessing a relatively length independent oxidation potential. Consequently, for the first time we can deconvolute the length dependence of electron transfer from other bridge effects. The interesting turn over in ET rate as a function of distance (figure 2), previously attributed to the changing bridge oxidation potential, is seen to be something more fundamental to ET. A collaboration with Mark Ratner’s group is underway. Another ongoing project entails an investigation of the role of charge carrier coherence in multiple pathway ET.
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