Passivation of CdSe Quantum Dots by Graphene and MoS<sub>2</sub> Monolayer Encapsulation
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Abstract
The encapsulation of a monolayer
of CdSe quantum dots (QDs) by
one-to-three layer graphene and MoS<sub>2</sub> sheets protects the
QDs from oxidation. Photoluminescence (PL) from the QD cores shows
a much slower decrease in core diameter over time due to slower oxidation
in regions where the QDs are covered by van der Waals (vdW) layers
than in those where they are not, for chips stored both in the dark
and in the presence of light. PL mapping shows that the CdSe QDs under
the central part of the vdW sheet age slower than those near its edges,
because oxidation of the covered QDs is limited by transport of oxygen
from the edges of the vdW sheets and not transport across the vdW
layers. The transport of oxygen to the covered QDs is analyzed by
coupling the PL results and a model of QD core oxidation