Biomedical Engineering Reference
In-Depth Information
Fig. 5.1
DPV of two
different batches of CdTe
NPs at a 0.06-cm
2
Pt
working electrode with scan
toward positive or negative
potentials.
a
9.6
μ
M CdTe
NPs in 5:1 (v/v) benzene/
acetonitrile containing 0.1 M
TBAP.
b
32
μ
M CdTe NPs
in CH
2
Cl
2
containing 0.1 M
TBAPF6. Reproduced with
permission from Ref. [
2
].
Copyright 2004, American
Chemical Society
One large anodic peak at 0.7 V was proposed as a multielectron reaction, and the
other anodic peak appeared because of oxidation of reduced species. Gao et al. [
3
]
and Greene et al. [
4
] reported the voltammetric current peaks of QDs in aqueous
solution and concluded that the electrochemical bandgap was located at potentials
inside the valence-band edge, which was explained by hole injection into the sur-
face traps of the particles.
To deeply understand the QDs electrochemical property, a full investigation
into the effects of different parameters on the QDs electrochemical response was
needed, which included the QDs size, the capping stabilizer, the value of pH, and
the coexisted chemicals. Given the fact that the cyclic voltammetry (CV) is very
sensitive to the nanocrystalline surface state and could provide complimentary
information for a better understanding of the special size-dependent properties of
semiconductor QDs, the size effect on the reduction and oxidation potentials was
studied via CV in an aqueous buffer solution with the thiol-capped CdTe QDs as
the object [
5
]. CV studies of CdTe in aqueous solution demonstrated that the size
effect on the reduction and oxidation potentials could be attributed to the energetic
band positions, owing to the quantum size effect. In contrast to a prediction based
on the quantum size effect, the oxidation peak moves to more negative potential as
the nanocrystalline size decreases.
