A simple method for growing high quantity tungsten-oxide nanoribbons under moist conditions

Abstract

Tungsten oxide is one of the most important transition metal oxide materials, which possesses some unique properties such as electrochromic, optochromic, and gaschromic properties. In this paper, we report a simple method for synthesizing high quantity tungsten oxide nanoribbons by oxidizing a tungsten plate under moist conditions. Using potassium iodide as the catalyst, tungsten oxide nanoribbons with a thickness of 40-100 nm, width up to 1 µm and length up to hundreds of micrometres are obtained on a large scale. The morphology, composition and crystal structure of the nanoribbons are characterized by various methods, such as scanning electron microscopy, transmission electron microscopy and x-ray diffraction. The nanoribbons comprise mainly monoclinic tungsten trioxide (WO 3 ) growing along the [001] direction and the orthorhombic WO 3 (H 2 O) 0.33 . The measured lattice parameters are β = 89.93 • , a = 0.7274 nm, b = 0.7501 nm, c = 0.3824 nm for WO 3 and a = 0.7359 nm, b = 1.251 nm, c = 0.7704 nm for WO 3 (H 2 O) 0.33 , respectively.

Growth and characterization of sodium–tungsten oxide nanobelts with U-shape cross section

“…Therefore, diffusion of sodium from soda-lime substrate toward the surface of the film and so its presence on the surface plays a key role for growth of the nanobelts. This can be similar to the role of potassium in formation of Q1D nanostructure of tungsten oxide, as reported recently [5][6][7]. As we know, melting point of pure WO 3 is 1473 1C, thus for growth of Q1D nanostructure of WO 3 by VS method, a high temperature (T41000 1C) is needed.…”

“…However, using a proper catalyst caused that tungsten oxide nanobelts or nanowires grow at a lower temperature. It has been recently shown that potassium and its salts have a good catalytic property for this purpose [5][6][7].…”

Long K‐Doped Titania and Titanate Nanowires on Ti Foil and FTO/Quartz Substrates for Solar‐Cell Applications

“…This indicates that the likely growth mechanism involves growth of K-doped titania nanowires from K-Ti-O alloy droplets, similar to the formation of tungsten oxide nanoribbons from a K-W-O alloy. [23] It should also be noted that changes in the surface morphology of the Ti foil after KF, K 2 CO 3 , or KOH droplets had dried on it (at room temperature) can be observed. In case of K 2 CO 3 , the main change is the appearance of potassium containing crystallites (as determined by energy-dispersive X-ray (EDX) analysis) on the Ti foil surface, while in the case of KF and KOH there is also an obvious change in the surface morphology in addition to the appearance of crystallites.…”

“…Potassium iodide has been previously used as a catalyst for the growth of tungsten oxide nanoribbons. [23] It has been proposed that the tungsten oxide nanoribbons grow by a vapor-liquidsolid (VLS) mechanism from a liquid K-W-O alloy. [23] To further clarify the role of KF in nanowire growth, 1 % solutions of K 2 CO 3 , KOH, and NH 4 F have been used instead of KF.…”

“…[22] We have fabricated titania and titanate nanowires by moisture-assisted direct oxidation of titanium in the presence of KF. It has been previously shown that the presence of water vapor during oxidation is necessary to produce a high yield of nanostructures by thermal oxidation in the case of tungsten oxide, [23] Potassium-doped titania and titanate nanowires are fabricated by moisture-assisted direct oxidation of titanium. The influence of the fabrication conditions on nanowire structure and morphology is investigated.…”