Surface modification, heterojunctions, and other structures: composing metal oxide nanocrystals for chemical sensors

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

doi:10.1117/12.2078017

13 March 2015 Surface modification, heterojunctions, and other structures: composing metal oxide nanocrystals for chemical sensors

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

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Proceedings Volume 9364, Oxide-based Materials and Devices VI; 936415 (2015) https://doi.org/10.1117/12.2078017
Event: SPIE OPTO, 2015, San Francisco, California, United States

Abstract

The modification of the surface reception properties of nanocrystalline structures is of great interest in environmental, catalysis and energy related applications. For instance, an oxide surface covered with a layer of another oxide opens the possibility of creating the nanosized counterparts of bulk catalytic systems. A relevant example is the TiO₂-WO₃, which is an active catalysts in a broad range of reactions. The chemical synthesis of the colloidal, nanocrystalline version of such system will first be exposed, by coupling suitable sol-gel chemistry with solvothermal processing. Then, the range of obtained structures will be discussed, ranging from WO_x-surface modified TiO₂ to TiO₂-WO₃ heterojunctions. The complex structural evolution of the materials will be discussed, depending on the W concentration. A summary of the acetone sensing properties of these systems will be shown. In particular, the surface activation of the otherwise almost inactive pure TiO₂ by surface deposition of WO₃-like layers will be highlighted. Addition of the smallest W concentration boosted the sensor response to values comparable to those of pure WO₃, ranging over 2-3 orders of magnitude of conductance variation in presence of ethanol or acetone gases. Simple analysis of the sensing data will evidence that the combination of such nanocrystalline oxides results in catalytic activation effects, with exactly opposite trend, with respect to pure TiO₂, of the activation energies and best responses.

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Mauro Epifani, Elisabetta Comini, Raül Díaz, Aziz Genç, Jordi Arbiol, Teresa Andreu, Pietro Siciliano, Guido Faglia, and Joan R. Morante "Surface modification, heterojunctions, and other structures: composing metal oxide nanocrystals for chemical sensors", Proc. SPIE 9364, Oxide-based Materials and Devices VI, 936415 (13 March 2015); https://doi.org/10.1117/12.2078017

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KEYWORDS

Oxides

Sensors

Titanium dioxide

Nanocrystals

Metals

Catalysis

Heterojunctions

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