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

Year: 2014

Authors: Epifani M., Comini E., Diaz R., Andreu T., Genz A., Arbiol J., Siciliano P., Faglia G., Morante JR.

Autors Affiliation: CNR, IMM, I-73100 Lecce, Italy; Univ Brescia, Dept Informat Engn, SENSOR Lab, I-25133 Brescia, Italy; CNR, INO, I-25133 Brescia, Italy; IMDEA Energy Inst, Electrochem Proc Unit, Mostoles 28935, Spain; Catalonia Inst Energy Res, IREC, Barcelona 08930, Spain; CSIC, ICMAB, Inst Ciencia Mat Barcelona, Bellaterra 08193, Spain; Passeig Lluis Co, ICREA, Barcelona 08010, Spain; Univ Barcelona, Dept Elect, M2E, IN2UB,XaRMAE, E-08028 Barcelona, Spain.

Abstract: We report for the first time the synthesis of monoclinic WO3 quantum dots. A solvothermal processing at 250 degrees 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 degrees 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 degrees 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.

Journal/Review: ACS APPLIED MATERIALS & INTERFACES

Volume: 6 (19)      Pages from: 16808  to: 16816

More Information: Authors acknowledge CSIC/CNR project 2010IT0001 (SYNCAMON) and the SOLAR project DM19447. We thank Giovanni Battista Pace for the help with the sample preparation, and Nicola Poll for the help with the sensing measurements.
KeyWords: tungsten trioxide; gas-sensing; solvothermal synthesis
DOI: 10.1021/am504158r

Citations: 70
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