ABSTRACT
The current intense interest in the use of semiconductor nanocrystals or quantum dots as fluorophores
in biological imaging and related applications can be traced to the 1998 publications by Bruchez et al. [1]
and Chan and Nie [2] that demonstrated the possibility of using water-dispersible semiconductor
nanoparticles as fluorescent probes in bioimaging. The advantages of such quantum dots over conven-
tional organic fluorophores include high brightness, stability against photobleaching, narrow and
symmetric emission spectra, and broad absorption spectra. Over the past half-dozen years, there has
been tremendous progress in the application of these quantum dots in biology and medicine, as detailed
elsewhere in this book. Several recent reviews of this rapidly advancing field are also available [3-6].
Biophotonic applications of semiconductor nanocrystals have focused overwhelmingly on the use of
CdSe-ZnSe core-shell quantum dots. These dots provide high quantum yield (up to 80%) with emission
that is tunable through the green and red portion of the visible spectrum by varying the CdSe core size.
More importantly, there are well-established and reproducible experimental methods for producing
high-quality CdSe-ZnSe core-shell quantum dots with narrow size distribution and correspondingly
narrow PL emission spectra. These are now available commercially from companies like Quantum Dot
Corporation (www.qdots.com) and Evident Technologies (www.evidenttech.com) as aqueous disper-
sions of quantum dots with surfaces modified for different applications in bioimaging and biophotonics.
