Imidazolium-based Ionic liquids on Morphology and Optical Properties of ZnO Nanostructures

ZnO nanostructures have been synthesized by a simple reflux method, using different ionic liquids, such as 1-benzyl-3-methylimidazolium bromide ([BzMIM][Br]), 1,1'-(1,4 phenylenebis (methylene)) bis (3-methyl-1H-imidazol-3-ium) bromide ([MM-1,4-DBzIM2][Br]2) and 1-phenacyl-3-methylimidazolium bromide ([PMIM][Br]), with different amount of sodium hydroxide in water. Also the effect of reaction time on morphology of ZnO nanostructure using 1-octhyl-3-methylimidazolium bromide, [OMIM][Br] is reported. The structure, morphology and optical properties of samples were characterized by means of XRD, SEM and UV-visible absorption. The results show that benzoyl group at position-1 of imidazole ring causes nanosheet ZnO morphology. The time dependent experiments displayed that ZnO nanoparticle arrays and nanosheet ZnO were created. The width and diameter of the resulting ZnO nanosheets can be readily controlled. A possible formation mechanism based on evidence has been discussed. The band gaps are estimated to be 2.57-2.89 eV according to the results of the optical measurements of the ZnO nanostructures. This study shows that ionic liquid may be effect on band gap energy.