Hydrothermal synthesis and characterization of self-assembled h-WO3 nanowires/nanorods using EDTA salts

One-dimensional (1D) self-assembled single-crystalline hexagonal tungsten oxide (h-WO3) nanostructures were synthesized by a hydrothermal method at 180 °C using sodium tungstate, ethylenediaminetetraacetic (EDTA) salts of sodium or ammonium, and sodium sulfate. Controlled morphological modification of h-WO3 nanowire bundles was achieved and hierarchical urchin-like structures were produced by simply substituting the sodium ions with ammonium ions in the EDTA salt solution. Self-assembled h-WO3 nanowire bundles and nanorods that formed urchin-like structures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. 1D self-assembled h-WO3 nanowire bundles of ∼100 nm diameter and 1–2 μm length were comprised of several individual uniform nanowires of 4–6 nm diameter. These individual nanowires served as building blocks of the bundles. Raman, cyclic voltammetry (CV), and photoluminescence (PL) spectroscopy studies revealed their structure, electrochemical response, and luminescence properties. The synthesis of 1D self-assembled h-WO3 nanowire bundles and urchin-like structures was differentiated by means of Na+- and NH4+-based EDTA salt solutions.