Tunable Optical Anisotropy of Seeded CdSe/CdS Nanorods

We demonstrate structurally tunable optical anisotropy of seeded-growth CdSe/CdS dot-in-rod heterostructures using polarized excitation spectroscopy. The elongated anisotropic CdS shell confers optical anisotropy to the electronic transitions of the CdSe core. Although a rod-shaped shell geometry is a necessary precondition to observing polarized optical properties, the degree of linear polarization is not a strong function of aspect ratio. Rather, tuning the local anisotropy of the emissive core materials by changing the thickness of the anisotropic shell changes the degree of optical anisotropy more dramatically. As the diameter of the core material comprises a greater share (>90%) of the dot-in-rod diameter, the anisotropy of the CdSe core states doubles compared to those for which the core represents <50% of the heterostructure diameter.