Filtern
Erscheinungsjahr
- 2008 (2) (entfernen)
Dokumenttyp
Sprache
- Englisch (2)
Referierte Publikation
- ja (2)
Schlagworte
- Fluorescence (2)
- Acoustic levitation (1)
- CdSe (1)
- CdSe-ZnS (1)
- Dyes (1)
- Energy transfer (1)
- Nanocrystal (1)
- Nanocrystals (1)
- Quantum dot (1)
- Quantum dots (1)
- Quantum yield (1)
- Semiconductor (1)
- Shell (1)
- Stability (1)
- Stability test (1)
- Ultrasonic trap (1)
- ZnS shell (1)
We investigated the correlation between the thickness of the ZnS shell of CdSeZnS quantum dots (QDs), the stability of the particles, and the fluorescence quantum yield. As a measure for stability, a new shell quality test was developed. This test is based on the reaction of the QDs with photochemically formed thiophenol radicals and communicates an imperfect ZnS shell by a rapid and complete loss of fluorescence. The quantum yield increases from less than 5% for unshelled CdSe up to 50%, with an increase in ZnS shell thickness up to 0.60.8 nm. At the same time, the particles become significantly more stable, as revealed by the shell test.
Acoustic levitation is used as a newtool to study concentration-dependent processes influorescence
spectroscopy. With this technique, small amounts of liquid and solid samples can be measured
without the need for sample supports or containers, which often limits signal acquisition and
can even alter sample properties due to interactions with the support material. We demonstrate
that, because of the small sample volume, fluorescence measurements at high concentrations
of an organic dye are possible without the limitation of inner-filter effects, which hamper such
experiments in conventional, cuvette-based measurements. Furthermore, we show that acoustic
levitation of liquid samples provides an experimentally simple way to study distance-dependent
fluorescence modulations in semiconductor nanocrystals. The evaporation of the solvent during
levitation leads to a continuous increase of solute concentration and can easily be monitored by
laser-induced fluorescence.