Plasmon-Enhanced Surface-State
Emission of CdSe Quantum
Dots and Its Application to Microscale Luminescence Patterns
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Abstract
In this paper, we report distinct enhancement of surface-state
emissions (SSEs) of colloidal CdSe quantum dots (QDs) via coupling
to localized plasmons (LPs) in Ag nanostructures. The roles of oleic
acid (OA) ligand on QDs in the formation of Ag nanostructures and
in the intense enhancement of SSEs of CdSe QDs are explored. We find
that OA ligand on CdSe QDs plays a critical role in modifying the
morphology of the contacted Ag, which consequently impacts the coupling
of QD emitters with LPs in Ag. A systematic study of size effect of
QDs on coupling of SSEs with LPs shows that as-deposited small Ag
particles favorably enhance the SSEs of small-size CdSe QDs. The OA
ligand on QDs yields better Ag crystallinity and clear corners during
the annealing process; therefore, it promotes reshaping of small Ag
particles into larger ones, favorable to enhance the SSEs of large-size
CdSe QDs. The annealed QDs/Ag hybrid structures are more stable than
the unannealed ones due to the loss of the OA ligand in the heating
process. The selective coupling of QD emitters with LPs in Ag nanostructures
allows feasible realization of microscale fluorescent color patterns.
The approach of OA-assisted modification of plasmonic properties of
Ag nanostructures provides a new route to synthesizing bright luminescence
materials and devices that use colloidal QDs