2 research outputs found
Norbornadiene End-Capping of Cross-Coupling Polymerizations: A Facile Route to Triblock Polymers
The potential use of conjugated polymers in device applications
is often limited by their less than optimal physicochemical properties.
This work describes an efficient protocol to end-cap conjugated polymers
synthesized via palladium-catalyzed cross-coupling polymerizations
with norbornene groups. Specifically, the hydroarylation of norbornadiene
is shown to be a high-yielding end-capping method. These strained
bicyclic alkenyl end groups can be transformed into macroinitiators
via ring-opening metathesis polymerization and can polymerize other
strained monomers, such as norbornene, yielding elastomeric triblock
copolymers
Determination of the Energy Band Gap Depending on the Oxidized Structures of Quantum Dots
Theoretical and experimental studies on the changes of
the optical
properties of CdSe/CdS/ZnS (core/double-shell) quantum dots (QDs)
during the oxidation process were first performed. An effective medium
approach using the modified Khon–Sham equation presents a new
method to predict the effects of the oxidation and to determine the
oxidized ratio of nanoscale materials by a quantitative comparison
with the experimental photoluminescence (PL) changes. As the oxidation
progressed from the CdSe/CdS/ZnS nanocrystal surface, the PL peak
shifted to longer wavelength and the quantum efficiency (QE) continuously
decreased. It was also found that such changes were accelerated when
the thickness of the outermost ZnS shell became thinner than a monolayer.
The radial wave functions showed that the electron carriers rapidly
extended into the shell region while the hole carriers spread very
little into the core region. This indicates that the electrons are
the key carriers to induce the changes in the energy band gap and
the QE