Biomedical Engineering Reference
In-Depth Information
Figure 6. Coulomb blockade and electronic state quantization in metal nanoparti-
cles. Differential pulse voltammetry on suspensions of DPV responses for hex-
anethiol-capped Au nanoparticles with core diameters of 1.6 and 1.1 nm (top and
bottom curve, respectively). The 1.6 nm diameter particles exhibit 15 equally
spaced Coulomb blockade peaks, each corresponding to the transfer of one addi-
tional electron per particle. The 1.1 nm diameter particles exhibit a gap and unequal
peak spacing due to additional contributions from the discretization of the electron-
ic spectrum. Reprinted with permission from Ref. 126, Copyright (2003) American
Chemical Society.
plex, molecular-like behavior upon further reduction of the nano-
particle dimensions. For a more extensive survey of metal nano-
particles electrochemistry and associated discreteness effects, we
refer the reader to the recent review by Murray.
125
Step-like voltammograms were also reported for experiments
in which two nanoelectrodes were immersed in a bulk solution
containing a 1:1 mixture of the reduced:oxidized forms of a ferro-
cene derivative.
127
This behavior was attributed to Coulomb block-
ade, supported by the observation that the double-layer capacitanc-
es of the nanoelectrodes, estimated to be <1 aF by virtue of their
small area, is consistent with the observed '
E
. This argument,
however, neglects the contribution to
C
tot
of the capacitance be-
tween the dot and its environment. While this is often a good ap-
Search WWH ::
Custom Search