Fluorescence anisotropy measurements. The ensemble fluorescence anisotropy of colloidal CdSe/CdS NRs was measured using a home-built L-format optical setup (see Figure in Supporting Information) equipped with a 405 nm laser (RGBLase FBB-405-200-FS-C-1-0). The excitation beam was attenuated using a variable neutral density filter (NDC-25C-2) and polarized through a hand-mounted Glan-Taylor polarizer (Thorlabs GT15-A). The PL emission from the sample was collected at 90° relative to the excitation beam using coaligned irises (Thorlabs ID25) and polarized using a second Glan-Taylor polarizer (Thorlabs GT15-A) before being directed to a free-space biased Si Photodetector (Thorlabs DET100A2).