Fluorescence Anisotropy and Crystal Structure of Individual Semiconductor Nanocrystals

Abstract

We investigate the polarization state of the fluorescence emission of individual CdSe/ZnS nanocrystals and try to establish a correlation with their crystallographic properties. The crystallinity and orientation of the particles are examined by transmission electron microscopy (TEM). These micrographs are compared with simulated TEM images. The polarization of the fluorescence light is investigated with a method in which the orientation of the transition dipole can be determined within seconds even though the fluorescence shows strong intensity fluctuations. The results show that even spherical particles emit elliptically polarized light, which can in principle be explained by a 2D transition dipole (“bright plane”). For a few particles, we could directly compare the polarization state with the crystallographic structure of the same nanocrystals. The findings reveal that a well-defined polarization state can even be observed for particles with stacking faults and polycrystalline nanocrystals.

Time resolved photoluminescence anisotropy of CdSe/ZnS nanoparticles in toluene at 300 K

“…Thus, if the observed nanocrystal photoluminescence (PL) is due to this transition, emission of an individual nanocrystal should be circularly (or, in case of deviation from perfect symmetry, elliptically) polarized. This was indeed recently observed in experiments with single nanocrystals [2][3][4][5]. Low-temperature (1.5-10 K) experiments with ensembles of CdSe nanocrystals [6] have also directly confirmed the circular polarization of the luminescence.…”

Onion-like (CdSe)ZnS/CdSe/ZnS quantum-dot-quantum-well heteronanocrystals for investigation of multi-color emission

“…Nanocrystals such as (CdSe)ZnS (core)shell quantum dots typically reveal almost spherical, slightly elongated shapes according to the high-resolution transmission electron microscopy (HRTEM) measurements [25]. In our theoretical formalism, for simplicity we consider a spherically symmetric heteronanocrystal structure to separate its wavefunctions into the radial and angular parts, as presented in Eq.…”

Quantum dots and ionic liquid-sensitized effect as an efficient and green catalyst for the sensitive determination of glucose

“…5c shows the typical TEM image of CdSe QDs. Photoluminescence quantum yields (QY) were estimated by comparison of the fluorescence intensity with standard dye solutions with the same optical density at the excitation wavelength and similar fluorescence wavelength [31].…”