Flame Aerosol Synthesis of Freestanding ZnO Nanorods

Abstract

ZnO can be made into many nanostructures that have unique properties for advanced applications, such as pie-zoelectric and pyroelectric materials. ZnOnanorod is one of the nanostructures that possess advanced properties. This paper reports a gas phase flame process to continuously synthesize aerosols of ZnOnanorods in large quantities. Unlike previous work, our process shows that pure ZnOnanorods can be made in a freestanding form rather than growing on a substrate surface. It was found that the ZnOnanorods preferentially grow in the ther-modynamically stable direction [001] in the gas phase with different aspect ratios, depending on flame process conditions. The ZnOnanorod aerosols are highly crystalline and have a hexagonal geometry. Raman and photo-luminescence spectroscopic studies showed that there are no structural defects in the nanorods, which have energy band gap of 3.27 eV in the near UV region. It was demonstrated that the gas phase flame reactor can provide a convenient means for continuous production of highly pure aerosols of ZnOnanorods.