21Synthesis and Characterization of Quantum Dots
structure can stabilize and maximize the uorescence of core QDs [68–71]. A robust,
larger-bandgap inorganic shell (in the type-I structure) not only passivates surface atoms
but also buries the core semiconductor in a potential energy well, thus concentrating the
charge carriers in the NC core and keeping them away from their surrounding environ-
ment [69–71]. As a result, surface defect states, trap sites, and environmental factors will
have diminished impact on the optical property of QDs [69–74].
The core-shell QDs have most commonly been achieved in a two-step procedure [45]:
initial synthesis of core NCs, followed by a purication step, and subsequent shell growth.
Via this approach, ma