Shape-controlled synthesis of titania with 4-pentyl-4-biphenylcarbonitrile as a structure aligning agent under the influence of magnetic field

Abstract

The synthesis of shape-controlled materials remains a big challenge today. The aim of this research is to explore the effects of magnetic field and line in the synthesis of shape-controlled titanium dioxide. 4-Pentyl-4-biphenylcarbonitrile (5CB), a liquid crystal, has been used as an alignment agent. In this research, the synthesis of shape-controlled titanium dioxide with liquid crystal as a structurealigning agent is demonstrated using sol-gel method under a magnetic field. The mixture of 4-pentyl-4-biphenylcarbonitrile (5CB), tetra-n-butyl orthotitanate (TBOT), 2-propanol and water underwent slow hydrolysis under magnetic field (up to 0.3 T). The obtained titanium dioxide samples were characterized by scanning electron microscopy (SEM), diffuse reflectance ultraviolet-visible (DR UV-Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy and photoluminescence spectroscopy. Interesting results were observed when an external magnetic field was applied in the hydrolysis of TBOT in the presence of 5CB liquid crystal. The titanium dioxide is ‘needle’ like in shape when the reaction mixture containing tetra-n-butyl orthotitanate (TBOT), 2-propanol and water was placed under external magnetic field. The titanium dioxide is spherical in shape when the reaction mixture was not under the influence of magnetic field. The DR UV-Vis spectra showed that the absorption peak of shape-controlled titanium dioxide synthesized under magnetic field decreased compared to the sample synthesized without magnetic field due to the chromophore-chromophore interaction. Furthermore, photoluminescence spectra showed a decreased in the intensity of shape-controlled titanium dioxide and an increased in the intensity of photoluminescence peak of liquid crystal, suggesting the occurrence of electron transfer from titanium dioxide to liquid crystal during ultraviolet irradiation. Based on these results, strong interaction has occurred between 5CB and titanium dioxide. This interaction was required to control the shape of titanium dioxide with liquid crystal under magnetic field during the hydrolysis process. Based on this synthetic approach, this research has generated new perspectives for the application of magnetic field in shape-controlled synthesis of titanium dioxide with liquid crystal as a structure-aligning agent.