Catalyst-free growth and luminescence response of single-crystalline ZnO nanorods

The production mechanism of single crystalline ZnO nanoscale rods, either in array or block form has been reported alongwith their optical emission characteristics. The elongated vertical nanorods have been characterized by a preferred growth direction along (002) crystallographic plane which becomes prominent with the growth duration. The single-crystalline nature of the nanorods is evident from the electron diffraction studies. Apart from the vertical nanorods, random nanorods and hexagonal shaped nano-blocks have also been found upon changing the pH of the growth solution. With a reference to the relevant growth mechanism of the nanostructures, the optical emission due to band edge and various native defects have been identified via normalized Gaussian fitting incorporated onto the photoluminescence spectra. In contrast to the blocks of nanodisks and random nanorods, the band edge emission (~388 nm) has been found to be significantly enahnced over defect mediated emissions in the vertical nanorods. Owing to long range ordering and enhanced periodicity, single crystalline ZnO would find better scope as compared to conventional polycrystalline systems.