Fast Interfacial Electron Transfer: Evidence for Inverted Region Kinetic Behavior
Abstract
Interfacial electron transfer (ET) in a prototypical semiconductor- liquid junction system (aq. Fe(CN)64-/3- with TiO2) can be initiated by directly pumping a molecule to surface charge transfer transition (max = 430nm). The return electron transfer(ET) kinetics, which can be monitored by visible-region transient-absorbance spectroscopy, reveal a well-defined fast component (r = 270ns) and a less well defined slow component (us -> ms). Detailed studies in the shorter time regime show that: (1) the interfacial ET rate is independent of laser pump power and, therefore, truly first order, (2) the kinetics are activationless, and (3) the kinetics are inverted, i.e. the ET rate decreases when the free energy driving force is increased by increasing the formal potential of the iron(III)-based electron acceptor. The results are broadly consistent with the predictions of contemporary, multimode quantum rate theories; they are also consistent with the findings of a prior study (by time- dependent scattering) of the Franck-Condon effects accompanying the reaction.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 19, 1993
- Accession Number
- ADA262434
Entities
People
- Hong Lu
- Janice N. Preiskorn
- Joseph T. Hupp
Organizations
- Northwestern University