(418o) Continuous Synthesis of Freestanding ZnO Nanorods In a Flame Reactor

ZnO is an II-VI semiconductor material with a large band gap (3.37 eV), which can be excited by UV radiation and hence can be used in making optoelectronic devices. ZnO belongs to the non-centrosymmetric point group 6mm. This property inherently present in ZnO can be exploited for its use in piezoelectric applications and pyroelectric applications. ZnO exhibits a wide variety of growth morphologies such as nanoparticles, nanorods, nanobelts, nanocages etc., Literature shows that these wide variety of morphologies of ZnO can be synthesized by using different liquid phase and gas phase routes. The current work discusses the synthesis of ZnO nanorods by using a Counterflow Diffusion Flame (CDF) Reactor.

Unlike other conventional methods used for production of ZnO nanorods, we propose a technique that can be used to synthesize ZnO nanorods in the absence of a substrate. The substrate free growth process makes the process continuous and hence can be used for large-scale production of ZnO nanorods. We show that ZnO nanorods of various aspect ratios can be synthesized using our process by just varying process parameters like gas flow rate and precursor flow rate. The effect of adding dopants like SnO2 and Al2O3 on the growth of ZnO nanorods is also being studied. Synthesized ZnO nanorods have been characterized by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), and Selected Area Electron Diffraction (SAED). The surface growth direction and normal growth directions of the ZnO nanorods have been determined by using the SAED patterns. Also, a probable growth mechanism for the synthesized ZnO nanorods is proposed in the current work. The orientation and the homogeneity of the ZnO nanorods is an important factor for its use in optoelectronic devices.