Hydrothermally Produced Cobalt Oxide Nanostructures at Different Temperatures and Effect on Phase Transition Temperature and Threshold Voltage of Nematic Liquid Crystal Host

Abstract

In this study, cobalt oxide Co3O4 nanostructured material is synthesized by hydrother- mal method by using different concentration of cobalt acetate salt at unique hydrother- mal reaction time for five different hydrothermal reaction temperatures 105, 120, 140, 160, and 180?C. The obtained nanoparticles are annealed at 300?C for 5 h. Co3O4 nanostructures are determined by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV-vis spectroscopy. The hydrothermally produced samples were reannealed at 550?C, and morphological and structural properties were investi- gated deeply again. The effect of annealing temperature on morphologies and crystal- line structure of cobalt oxide nanoparticle (NP) was also investigated. Nanopyramids and nanorods are two main morphologically obtained structures from the hydrothermal experiment. Nematic liquid crystal mixture E7 is doped with Co3O4 nanorod. Phase transition and threshold voltage of pure and Co3O4 NP-doped E7 LC are examined successfully. It reveals that for Co3O4 NP-doped E7 phase transition temperature and threshold voltage increased very slightly. Keywords: