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2003
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In the Laboratory
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Characterizing the Behavior and Properties of an Excited Electronic State: Electron-Transfer Mediated Quenching of Fluorescence
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Lars Poulsen, Arantza Zabala Ruiz, Steen Uttrup Pedersen, and Peter R. Ogilby
Department of Chemistry, Aarhus University, DK-8000 Aarhus C, Denmark
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July 2003
Vol. 80 No. 7
p. 819
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| Abstract |
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We have designed a series of laboratory exercises to illustrate a range of key concepts traditionally encountered in a general course on physical chemistry. In these exercises, optical spectroscopic measurements, electrochemical measurements, kinetic measurements, and computer modeling are used to characterize the properties and behavior of an electronic excited state. Specifically, students are asked to use these tools to answer a question posed at the outset: "Upon interaction with a series of molecules, Q, are the fluorescent states of 9-cyano- and 9,10-dicyanoanthracene quenched via an electron transfer process?" In the laboratory, students experimentally quantify rate constants, kq (exp), for cyanoanthracene excited state removal by the molecules Q in a Stern–Volmer study of fluorescence quenching. In other experiments, students collect information that allows them to independently calculate the rate constants, kq (calc), for these same molecules Q that would be expected if quenching proceeds via an electron transfer process. Upon comparison of these respective kq values in a Rehm–Weller plot of both kq (exp) and kq (calc) against the Gibbs energy of electron transfer, the students ascertain that the quenching reaction studied indeed proceeds via electron transfer.
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| Supplement |
A detailed description of these experiments, including background materials, appendices, and recommended further reading, along with instructor notes, are available.
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 Contents |
JCE2003p0819W.doc (Microsoft Word)
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| More Information |
Citation |
Poulsen, Lars; Ruiz, Arantza Zabala; Pedersen, Steen Uttrup; Ogilby, Peter R. J. Chem. Educ. 2003 80 819.
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Keywords |
Diffusion; Electrochemistry; Excited States / Energy Transfer; Fluorescence Spectrometry; Kinetics; UV-Vis Spectroscopy
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History |
Created:
Last Updated: |
June 4, 2003
February 28, 2005
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| Home > JCE Print > Journal of Chemical Education > Issues >
2003
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July
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819
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