Assembling quantum dots (QDs) into nanoscale configurations over macroscopic dimensions is an important goal to realizing their electro-optical potential. In this Rapid Communication, we present a detailed study of a pentylcyanobiphenyl liquid crystal (LC) and a CdS QD colloidal dispersion by probing the dielectric property $\overline{\epsilon }$ and relaxation as a function of an applied ac electric field $E_{\text{ac}}$. In principle, dispersing QDs in a nematic LC medium can direct the dots to align in nearly one-dimensional chainlike structures along the nematic director and these assemblies of QDs can be directed by external electric fields. In a uniform planar aligned cell, the Fréedericksz switching of the $\text{LC}+\text{QDs}$ appears as a two-step process with the same initial switching field as the bulk but with the final $\overline{\epsilon }$ value larger than that for an aligned bulk LC. The relaxation of $\overline{\epsilon }$ immediately following the removal of $E_{\text{ac}}$ follows a single-exponential decay to its original value that is slower than the bulk but becomes progressively faster with increasing $E_{\text{ac}}$, eventually saturating. These results suggest that the arrangement of the QDs is mediated by the LC.

• Received 27 January 2009

DOI:https://doi.org/10.1103/PhysRevE.80.010701