Solvothermal, Chloroalkoxide-based synthesis of monoclinic WO<inf>3</inf> quantum dots and gas-sensing enhancement by surface oxygen vacancies

Mauro Epifani, Elisabetta Comini, Raül Díaz, Teresa Andreu, Aziz Genc, Jordi Arbiol, Pietro Siciliano, Guido Faglia, Joan R. Morante

    Research output: Contribution to journalArticleResearchpeer-review

    59 Citations (Scopus)

    Abstract

    © 2014 American Chemical Society. We report for the first time the synthesis of monoclinic WO3 quantum dots. A solvothermal processing at 250 °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-vis, 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 °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 °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.
    Original languageEnglish
    Pages (from-to)16808-16816
    JournalACS Applied Materials and Interfaces
    Volume6
    Issue number19
    DOIs
    Publication statusPublished - 8 Oct 2014

    Keywords

    • gas-sensing
    • solvothermal synthesis
    • tungsten trioxide

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