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Tuning Optical Activity of IV–VI Colloidal Quantum Dots in the Short-Wave Infrared (SWIR) Spectral Regime
The
achievement of tunable optical properties across a wide spectral
range, along with an efficient surface passivation of lead chalcogenide
(PbSe) colloidal quantum dots (CQDs), has significant importance for
scientific research and for technological applications. This paper
describes two comprehensive pathways to tune optical activities of
PbSe CQDs in the near-infrared (NIR, 0.75–1.4 μm) and
the short-wave infrared (SWIR, 1.4–3 μm) ranges. A one-pot
procedure enabled the growth of relatively large PbSe CQDs (with average
sizes up to 14 nm) exploiting programmable temperature control during
the growth process. These CQDs showed optical activity up to 3.2 μm.
In addition, PbSe/PbS core/shell CQDs prepared by an orderly injection
rate led to an energy red-shift of the absorption edge with the increase
of the shell thickness, whereas a postannealing treatment further
extended the band-edge energy toward the SWIR regime. A better chemical
stability of the CQDs with respect to that of PbSe core CQDs was attained
by shelling of PbSe by epitaxial layers of PbS, but limited to a short
duration (<1 day). However, air stability of the relatively large
PbSe as well as the PbSe/PbS CQDs over a prolonged period of time
(weeks) was achieved after a postsynthesis chlorination treatment