Abstract:
In this work, we have synthesized water-soluble L-cysteine-capped alloyed CdSeTe
core QDs and investigated the structural and optical properties of deposition of each
of CdS, CdS/ZnSe and CdS/ZnSe/ZnS shell layers. Photophysical results showed
that the overcoating of a CdS shell around the alloyed CdSeTe core (QY = 8.4%)
resulted in an effective confinement of the radiative exciton with an improved QY
value of 93.5%. Subsequent deposition of a ZnSe shell around the CdSeTe/CdS
surface decreased the QY to 24.7% but an increase in the QY value of up to 49.5%
was observed when a ZnS shell was overcoated around the CdSeTe/CdS/ZnSe
surface. QDs with shell layers showed improved stability relative to the core. Data
obtained from time-resolved fluorescence measurements provided useful insight
into the variations in the photophysical properties of the QDs upon the formation of
each shell layer. Our study suggests that the formation of the CdSeTe/CdS
core/shell QDs meets the requirements of quality QDs in terms of high PL QY and
stability, hence further deposition of additional shells are not necessary in improving
the optical properties of the core/shell QDs.
