Fluorescence anisotropy and crystal structure of individual semiconductor nanocrystals

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.