196 9 Optical Properties
Applications that are most interesting from scientific and economic viewpoints
are found in biotechnology and medical diagnostics. To attach the particles exactly
at the targets, it is necessary to attach antibodies, peptides or proteins at the surface
of the particles. These compounds are selected to attach exactly at the intended
receptor. A typical example is displayed in Figure 9.17 [8]. In this figure zincsulfide-coated cadmium selenide particles, (CdSe)(ZnS) were functionalized for
two different targets, one to attach at the surface (Figure 9.17a) and the other one
localizes in the cell nucleus. (Figure 9.17b).
Figure 9.16 Emission spectrum of CdSe with particle sizes around 2 nm. As the structure of
these small particles is no longer stable, they fluctuate. Therefore, the emission spectrum is
very broad [9].
300
400
500
600
700
800
wavelength [nm]
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
luminescence
intensity
[a.u.]
Figure 9.17 Cadmium selenide, CdSe
particles coated with zinc sulfide, ZnS
functionalized to stain different parts of
living cancer cells according to Smith et al.
[8]. For such an application, the surface is
functionalized with antibodies, peptides or
proteins to attach exactly at the intended cell
receptor. (a) The nanoparticles are
functionalized to attach at the cell surface.
(b) Due to different functionalization, the
quantum dots are localized in the cell
nucleus. (Reproduced with
permission of John Wiley & Sons.)
(a)
(b)