Biomedical Engineering Reference
In-Depth Information
Figure 1.23
Interactions and transitions in the chiral molecule-QD system.
The solid vertical arrows represent light-induced transitions, and the hori-
zontal blue arrows depict the orbital and Coulomb couplings. The dotted
verticalarrowsshowrelaxationprocesses.Reprintedwithpermissionfrom
Ref. [33]. Copyright c
2011, Royal Society of Chemistry.
absorption cross-section of QD, it is expected that the CD signal will
haveapeakintheexcitonbandofQD.Inthemolecularband,theCD
is given as:
Im
P
·
μ
12
·
m
12
.
ω
∼
CD
mol
(
)
(1.49)
The QD, on the contrary, will modify the CD signal in the molecular
band through its high refractive index effect on
P
. Figure 1.23
illustrates both mechanisms of interaction mentioned above.
1.7.2
Experiments with Chiral Quantum Dots
Chirality can be induced on excitons in semiconductor QDs
using bio-conjugation with chiral ligands. Figure 1.24 shows the
absorption spectra of such QDs involving enantiomers (
D
-Pen and
L
-
Pen).Methods ofpreparation ofsuchchiral conjugatescanbefound
in Refs. [29] and [50]. CD studies of the particles gave particularly
striking results [50].
D
-and
L
-penicillamine stabilized particles
produced corresponding mirror image CD scans (Fig. 1.25), while
the particles prepared with a racemic mixture showed only a weak
