Large ZnO Mesocrystals of Hexagonal Columnar Morphology Derived from Liquid Crystal Templates

Large ZnO mesocrystals of hexagonal columnar morphology have been successfully synthesized by using liquid crystals (LCs) of cetyltrimethylammonium bromide (CTAB, CH3(CH2)(15)N+ (CH3)(3)Br-) as templates. The LC-templated growth process is established by monitoring the crystal morphology, phase evolution at various temperature stages for both ZnO building blocks and CTAB templates, where there is a phase transition and interaction between the two involved. In contrast to the well-studied mesocrystals derived from solutions, we propose a new formation scheme for the large mesocrystals, on the basis of our experimental observations using X-ray diffraction phase analysis, Fourier transform infrared, scanning electron microscopy, and transmission electron microscopy conducted at various stages of mesocrystal growth. The resultant mesocrystals are characterized by a level of mesoporosity and internal surfaces, where there is a large population of oxygen vacancies, as confirmed by their photoluminescence behavior.