Unraveling the interfacial electron transfer dynamics of electroactive microbial biofilms using surface-enhanced Raman spectroscopy.
The electron transfer (ET) processes of electroactive microbial biofilms have been investigated by combining electrochemistry and time-resolved surface-enhanced resonance Raman (TR-SERR) spectroscopy. This experimental approach provides selective information on the ET process across the biofilm-electrode interface by monitoring the redox-state changes of heme cofactors in outer membrane cytochromes (OMCs) that are in close vicinity (i.e., within 7 nm) to the Ag working electrode. The rate constant for heterogeneous ET of the surface-confined OMCs (sc-OMCs) of a mixed culture derived electroactive microbial biofilm has been determined to be 0.03 s(-1) . In contrast, according to kinetic simulations the ET between sc-OMCs and their redox partners, embedded within the biofilm, is a much faster process with an estimated rate constant greater than 1.2 s(-1) . The slow rate of heterogeneous ET and the lack of high-spin species in the SERR spectra rule out the direct attachment of the sc-OMCs to the electrode surface.
Institut für Chemie, Sekr. PC14, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin, Germany.
Hoang K
HK
Ly
Falk
F
Harnisch
Siang-Fu
SF
Hong
Uwe
U
Schröder
Peter
P
Hildebrandt
Diego
D
Millo
D001419:Bacteria / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development*; D019149:Bioreactors / Q000382:microbiology*; D003580:Cytochromes / Q000378:metabolism; D004566:Electrodes; D004579:Electron Transport; D012834:Silver / Q000737:chemistry; D013059:Spectrum Analysis, Raman; D013499:Surface Properties
D003580:Cytochromes; D012834:Silver