QDs are fluorescent nanocrystals of semiconducting materials
(e.g., CdSe) whose electronic characteristics depend on
the size and shape of the individual crystals. QD particles with
smaller sizes have wider band gaps and thus need more energy
to excite and emit light with shorter wavelength. QDs
have broad absorption spectra but narrow and stable fluorescent
emission spectra. Thus QDs are especially suitable for
multiplex detection using one excitation light source. The
emission spectrum of QDs is w10e20 times brighter than an