Direct Route to Tungsten Oxide Nanorod Bundles: Microstructures and Electro-Optical Properties

Abstract

In the present research, tungsten oxide nanorod bundles were synthesized by a unique plasma arc gas condensation method that was both noncatalytic and template-free. W 18 O 49 nanorod bundles were prepared by directly evaporating tungsten bulk in an oxygen-deficient environment. The as-prepared tungsten oxide nanorod bundles were characterized by FESEM, HRTEM, XRD, UV−visible spectroscopy, and PL measurements. The field-emission property was also evaluated. FESEM images showed bundlelike morphology; XRD and HRTEM results confirmed that the nanorod bundles were in a single-crystalline monoclinic W 18 O 49 phase, with the growth direction along [010]. Also, oxygen deficiencies within the nanostructures induced the red-shift phenomenon and blue emission observed in the UV−visible and photoluminescence spectra. The field-emission measurement showed that the tungsten oxide nanorod bundles exhibited low turn-on and threshold voltages, which were about 3.5 and 4.6 V/μm, respectively. These results indicate that the tungsten oxide nanorod bundles are a promising candidate for field-emitter applications.