Biomedical Engineering Reference
In-Depth Information
Figure 11. Curve of the differential capacitance
C
against potential
E vs.
SCE for
DOPC-coated mercury in aqueous 0.1 M KCl. The inset shows
C
vs.
E
curves for
bare (dashed line) and DOPC-coated (solid line) mercury in 0.1M solutions of
tetramethylammonium (TMA) chloride, KCl and LiCl.
44
At the far negative potentials at which lipid desorption is
complete, the lipid molecules remain in close proximity of the
mercury surface for hours in the form of positively charged micel-
lar aggregates, and spread back readily on the electrode surface
with a positive shift in potential.
44,45
This desorption/re-adsorption
process was imaged by using epi-fluorescence microscopy and
including a small amount of an amphiphilic fluorescent dye mole-
cule in the lipid monolayer.
46
On a Hg electrode, as distinct from a
Au electrode, fluorescence can be detected even if the fluorophore
is at a small distance from the electrode. In fact, the fluorescence
quenching efficiency, due to nonradiative energy transfer to the
electrode, is by two to three orders of magnitude lower on Hg than
on Au. Upon scanning the potential progressively in the negative
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