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2019
Journal Article
Titel
Fluorescence Quantum Yield and Single-Particle Emission of CdSe Dot/CdS Rod Nanocrystals
Abstract
The fluorescence quantum yield (QY) of CdSe dot/CdS rod (DR) nanoparticle ensembles is dependent on the shell growth and excitation wavelength. We analyze the origin of this dependency by comparing the optical properties of DR ensembles to the results obtained in single-particle experiments. On the ensemble level, we find that the QY of DRs with shell lengths shorter than 40 nm exhibits no dependence on the excitation wavelength, whereas for DRs with shell lengths longer than 50 nm, the QY significantly decreases for excitation above the CdS band gap. Upon excitation in the CdSe core, the ensemble QY, the fluorescence wavelength, and the fluorescence blinking behavior of individual particles are only dependent on the radial CdS shell thickness and not on the CdS shell length. If the photogenerated excitons can reach the CdSe core region, the fluorescence properties will be dependent only on the surface passivation in close vicinity to the CdSe core. The change in QY upon excitation above the band gap of CdS for longer DRs cannot be explained by nonradiative particles because the ratio of emitting DRs is found to be independent of the DR length. We propose a model after which the decrease in QY for longer CdS shells is due to an increasing fraction of nonradiative exciton recombination within the elongated shell. This is supported by an effective-mass-approximation-based calculation, which suggests an optimum length of DRs of about 40 nm, to combine the benefit of high CdS absorption cross section with a high fluorescence QY.
Author(s)
Hinsch, Alexandra
Institute of Physical Chemistry, University of Hamburg, Grindelallee 117, D-20146 Hamburg, Germany
Lohmann, Sven-Hendrik
Institute of Physical Chemistry, University of Hamburg, Grindelallee 117, D-20146 Hamburg, Germany
Strelow, Christian
Institute of Physical Chemistry, University of Hamburg, Grindelallee 117, D-20146 Hamburg, Germany
Kipp, Tobias
Institute of Physical Chemistry, University of Hamburg, Grindelallee 117, D-20146 Hamburg, Germany
Würth, Christian
Division Biophotonics, Federal Institute for Materials Research and Testing (BAM), Richard-Willstätter-Str. 11, D-12489 Berlin, Germany
Geißler, Daniel
Division Biophotonics, Federal Institute for Materials Research and Testing (BAM), Richard-Willstätter-Str. 11, D-12489 Berlin, Germany
Kornowski, Andreas
Institute of Physical Chemistry, University of Hamburg, Grindelallee 117, D-20146 Hamburg, Germany
Wolter, Christopher
Institute of Physical Chemistry, University of Hamburg, Grindelallee 117, D-20146 Hamburg, Germany
Weller, Horst
Institute of Physical Chemistry, University of Hamburg, Grindelallee 117, D-20146 Hamburg, Germany
Resch-Genger, Ute
Division Biophotonics, Federal Institute for Materials Research and Testing (BAM), Richard-Willstätter-Str. 11, D-12489 Berlin, Germany
Project(s)
Hamburger Zentrum für ultraschnelle Beobachtung (CUI): Struktur, Dynamik und Kontrolle von Materie auf atomarer Skala