Simple synthesis conditions of WO₃ hydrate nanorods by solvothermal process

Abstract

Tungsten oxide (WO 3 ) hydrate nanorods were synthesized by solvothermal process under different condition (170-210ºC, acetic acid (0-10 ml). The morphologies of synthesized WO 3 hydrate nanorods were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). As the result, we found the optimal synthesis condition of WO 3 hydrate nanorods. In this optimal condition, the treatment temperature was 190ºC with no acetic acid in the reactive solution. The length and diameter of observed nanorods were approximately 1-20 m and 50-1000 nm, respectively. The XRD analysis revealed that the crystal structure of WO 3 hydrate (WO 3 (H 2 O) 0.33 ) nanorods has orthorhombic phase (Fmm2) with high crystallinity.Key words: Tungsten oxide, solvothermal, oxide nanorod IntroductionNanostructured WO3 materials are one of candidate used as electronic paper, photocatalyst and ionic sensor device due to its electronic functionalities and electrochromic properties. Nanostructured WO3 materials have great advantage in carrier transport and ionic exchange, since they have larger surface area and large interface of surrounding materials comparing to thin film phase. For this reason, nanostructured WO3 materials are expected to achieve efficient photocatalyst property and electrochromic properties than that's of WO3 thin film. Nanostructured WO3 materials have been synthesized by many researchers in past decades. For example, onedimensional (nanorod, nanowire and needle) WO3 materials were synthesized on the various substrates by thermal chemical vapor deposition (CVD) [1][2][3][4], thermal deposition [5], and vapor-solid growth process [6]. Many of these experiments need expensive metal-organic gases, high vacuum facilities [7], complex process [8] and high temperature conditions (500-2500ºC). It is difficult to fabricate large quantities of nanostructured WO3 with low-cost production. Therefore, fabrication methods of nanostructured WO3 have been demanded to replace the methods as mentioned.Recently, Chongshen Guo et al. synthesized Csdope WO3 nanorods by solvothermal process utilizing WCl6 ethanol solution at low temperature [9]. This solvothermal method has great advantage for mass production with low-cost due to its low temperature simple process. However, this method enables to synthesize only Cs-dope WO3 not non-dope WO3. Csdope WO3 is not suitable for device application, since highly doped Cs ions in WO3 suppress the photocatalytic effect and EC reaction. For device application purpose, solvothermal synthesis of non-dope WO3 is crucial. In this study, we have developed novel synthesis route of non-dope WO3 nanorods without using acetic acid and