Dresden 2011 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 48: Nanoparticles and Composite Materials II

CPP 48.5: Vortrag

Freitag, 18. März 2011, 11:30–11:45, ZEU 114

Blinking and spectral diffusion of single CdSe/ZnS colloidal nanoparticles — •Daniel Braam, Matthias Offer, Günther Prinz, Martin Geller, and Axel Lorke — Fakultät für Physik und CeNIDE, Universität Duisburg-Essen, 47048 Duisburg

Even though nanoparticles have been a main interest in research for decades, their luminecent behaviour still holds many secrets to disclose. The power-law of on- and off-times of random emission intermittency as well as several shifts in the emission wavelength still lack of a unified theory [1]. We investigated the excitonic structure of CdSe/ZnS core/shell nanoparticles using a micro-photoluminescence (µ-PL) setup with a 405 nm cw-laser. To ensure single-particle-PL we dispersed the nanoparticles in toluene with 1% PMMA and deposited these dilute solution through spin-coating on different substrates. We observed substrate-dependent emission intermittency up to nearly blinking-free emission, which we can attribute to a single CdSe nanoparticle. Spectral jumps of 25 meV in the emission can be assigned to excitonic transitions altered by a charged nanoparticle or an outer charged electronic trap state [2]. Furthermore, we observed a phonon replica of 25 meV and smaller (<10 meV) energetic shifts of the emission lines which are likely due to random charge variation in the surrounding of the nanoparticle.

[1] P. Frantsuzov et al., Nature 4, 519 (2008).

[2] A. Efros, Nature Mat. 7, 612 (2008).