The field-driven alignment of colloidal CdSe/CdS core/shell NRs was investigated by measuring their time-dependent optical response in the presence of alternating (AC) electric fields. Dodecane-based dispersions of CdSe/CdS NRs were loaded into 50 µm thick sample cells (Figure in Supporting Information) and exposed to uniform AC fields as depicted in Figure . In order to avoid accumulation of NRs at the electrodes, a sufficiently high AC frequency (2 kHz) was chosen, ensuring that the dynamic alignment of NRs occurs at a faster time scale compared to the cell transit time of any charged species. Concurrently, the time-dependent optical transmittance of the samples were monitored at 405 nm using a collimated light source and a photoreceiver (see Figure ). The CdSe/CdS NRs used in this study were synthesized following a procedure 33 described in literature, and the materials properties of samples were characterized using transmission electron microscopy (TEM), powder X-ray diffraction (XRD), and UV-vis spectroscopy (Figure ), in addition to optical anisotropy measurements detailed below.