Solvothermal, Chloroalkoxide-based Synthesis of Monoclinic WO3 Quantum Dots and Gas-Sensing Enhancement by Surface Oxygen Vacancies

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• 作者：Mauro Epifani ; Elisabetta Comini ; Ra眉l D铆az ; Teresa Andreu ; Aziz Gen莽 ; Jordi Arbiol ; Pietro Siciliano ; Guido Faglia ; Joan R. Morante
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2014
• 出版时间：October 8, 2014
• 年：2014
• 卷：6
• 期：19
• 页码：16808-16816
• 全文大小：503K
• ISSN：1944-8252

文摘

We report for the first time the synthesis of monoclinic WO₃ quantum dots. A solvothermal processing at 250 掳C in oleic acid of W chloroalkoxide solutions was employed. It was shown that the bulk monoclinic crystallographic phase is the stable one even for the nanosized regime (mean size 4 nm). The nanocrystals were characterized by X-ray diffraction, High resolution transmission electron microscopy, X-ray photoelectron spectroscopy, UV鈥搗is, Fourier transform infrared and Raman spectroscopy. It was concluded that they were constituted by a core of monoclinic WO₃, surface covered by unstable W(V) species, slowly oxidized upon standing in room conditions. The WO₃ nanocrystals could be easily processed to prepare gas-sensing devices, without any phase transition up to at least 500 掳C. The devices displayed remarkable response to both oxidizing (nitrogen dioxide) and reducing (ethanol) gases in concentrations ranging from 1 to 5 ppm and from 100 to 500 ppm, at low operating temperatures of 100 and 200 掳C, respectively. The analysis of the electrical data showed that the nanocrystals were characterized by reduced surfaces, which enhanced both nitrogen dioxide adsorption and oxygen ionosorption, the latter resulting in enhanced ethanol decomposition kinetics.

Keywords:

tungsten trioxide; gas-sensing; solvothermal synthesis