Surface Modification of TiO2 Nanocrystals by WOx Coating or Wrapping: Solvothermal Synthesis and Enhanced Surface Chemistry

Year: 2015

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

Autors Affiliation: IMM CNR, Ist Microelettron & Microsistemi, I-73100 Lecce, Italy; IMDEA Energy Inst, Electrochem Proc Unit, Mostoles 28935, Spain; Univ Rey Juan Carlos, Ctr Apoyo Tecnol, NMR Unit, Mostoles 28933, Spain; Univ Brescia, Dept Informat Engn, SENSOR Lab, I-25133 Brescia, Italy; CNR, INO, I-25133 Brescia, Italy; Univ Barcelona, IREC, Catalonia Inst Energy Res, Barcelona 08930, Spain; ICMAB CSIC, Inst Ciencia Mat Barcelona, Bellaterra 08193, Spain; ICREA, Barcelona 08010, Cat, Spain; Univ Barcelona, Dept Elect, M2E IN2UB XaRMAE, E-08028 Barcelona, Spain; ICN2, Bellaterra 08193, Catalonia, Spain.

Abstract: TiO2 anatase nanocrystals were prepared by solvothermal processing of Ti chloroalkoxide in oleic acid, in the presence of W chloroalkoxide, with W/Ti nominal atomic concentration (R-w) ranging from 0.16 to 0.64. The as-prepared materials were heat-treated up to 500 degrees C for thermal stabilization and sensing device processing. For R0.16, the as-prepared materials were constituted by an anatase core surface-modified by WOx monolayers. This structure persisted up to 500 degrees C, without any WO3 phase segregation. For Rw up to R0.64, the anatase core was initially wrapped by an amorphous WOx gel. Upon heat treatment, the WOx phase underwent structural reorganization, remaining amorphous up to 400 degrees C and forming tiny WO3 nanocrystals dispersed into the TiO2 host after heating at 500 degrees C, when part of tungsten also migrated into the TiO2 structure, resulting in structural and electrical modification of the anatase host. The ethanol sensing properties of the various materials were tested and compared with pure TiO2 and WO3 analogously prepared. They showed that even the simple surface modification of the TiO2 host resulted in a 3 orders of magnitude response improvement with respect to pure TiO2.

Journal/Review: ACS APPLIED MATERIALS & INTERFACES

Volume: 7 (12)      Pages from: 6898  to: 6908

More Information: Authors acknowledge CSIC/CNR Project No. 2010IT0001 (SYNCAMON) and the SOLAR Project No. DM19447. We thank G. B. Pace for the help with the sample preparation, and N. Poll for the help with the sensing measurements. J.A. and A.Z. acknowledge ICN2 Severo Ochoa Excellence Grant.
KeyWords: TiO2; solvothermal synthesis; metal oxide nanocrystals; surface modification; gas sensors; nanocomposites
DOI: 10.1021/acsami.5b00632

Citations: 20
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