2 research outputs found
Evidence for the Ligand-Assisted Energy Transfer from Trapped Exciton to Dopant in Mn-Doped CdS/ZnS Semiconductor Nanocrystals
Trapping of charge carriers is the
major process competing with
radiative recombination or transfer of charge carriers important in
the application of semiconductor nanocrystals in photonics and photocatalysis.
In typical semiconductor quantum dots, trapping of charge carriers
usually leads to quenching of exciton luminescence. In this study,
we present evidence indicating that thiol ligands on the surface that
quench exciton luminescence can have an opposite effect on sensitized
dopant luminescence in doped semiconductor nanocrystals by facilitating
the recovery of the trapped exciton for sensitization. Despite the
increase in hole trapping by the added octanethiol to the surface
of Mn-doped CdS/ZnS nanocrystals, the sensitized Mn luminescence increased
by the added octanethiol and the enhancement became stronger with
increasing Mn doping concentration. While the role of octanethiol
as the hole trap and the enhancement of Mn luminescence may seem contradictory,
the thiol-induced enhancement of Mn luminescence is possible, since
thiols play dual role as the hole trap and as the facilitator of the
energy transfer from the trapped exciton to Mn, in contrast to the
pre-existing hole traps that inhibit the energy transfer
Photoinduced Separation of Strongly Interacting 2‑D Layered TiS<sub>2</sub> Nanodiscs in Solution
Colloidal 2-D layered transition
metal dichalcogenide (TMDC) nanodiscs synthesized with uniform diameter
and thickness can readily form the vertically stacked assemblies of
particles in solution due to strong interparticle cohesive energy.
The interparticle electronic coupling that modifies their optical
and electronic properties poses a significant challenge in exploring
their unique properties influenced by the anisotropic quantum confinement
in different directions taking advantage of the controlled diameter
and thickness. Here, we show that the assemblies of 2-D layered TiS<sub>2</sub> nanodiscs are efficiently separated into individual nanodiscs
via photoexcitation of the charge carriers by pulsed laser light,
enabling the characterization of the properties of noninteracting
TiS<sub>2</sub> nanodiscs. Photoinduced separation of the nanodiscs
is considered to occur via transient weakening of the interparticle
cohesive force by the dense photoexcited charge carriers, which facilitates
the solvation of each nanodisc by the solvent molecules