Electric field-induced self-assembly of multiferroic core-shell nanocrystals in anisotropic liquid crystal medium

Here, we present the observations on the morphological appearance of multiferroic core-shell CoFe2O4/ZnO nanocrystals (CFZNCs) dispersed into the nematic liquid crystal (NLC, 5CB) matrix. A concentration-dependent patterning of CFZNCs clusters has been found to nucleate during the Fréedericksz transition on the application of sufficient dc bias across the CFZNCs/5CB samples. Well-ordered two-dimensional patterns were seen for intermediate doping concentrations of CFZNCs (0.05 wt. % and 0.1 wt. %), whereas, intense aggregation was observed at higher concentration (0.2 wt. %). It has been found that the size of the planarly aligned patterned domains (PPDs) varied (from 25 to 6 μm) on increasing the dc bias across the CFZNCs/5CB composite during the Fréedericksz transitions. Interestingly, the chain-like clusters of CFZNCs appeared on the circumference of the PPDs embedded within the homeotropically aligned 5CB material. The formation of PPDs could be attributed to the LC-anisotropy-imparted ordering of CFZNCs in the vicinity of Fréedericksz transition. We hope that the present work will add to our understanding of LC-imparted self-assembly of NCs/QDs in an anisotropic medium like LCs for facilitating their applications in the fabrication of photonic devices.