title: Surface modification of TiO₂ nanocrystals by WO(x) coating or wrapping: solvothermal synthesis and enhanced surface chemistry.
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 °C for thermal stabilization and sensing device processing. For R(0.16), the as-prepared materials were constituted by an anatase core surface-modified by WO(x) monolayers. This structure persisted up to 500 °C, without any WO3 phase segregation. For R(w) up to R(0.64), the anatase core was initially wrapped by an amorphous WO(x) gel. Upon heat treatment, the WO(x) phase underwent structural reorganization, remaining amorphous up to 400 °C and forming tiny WO3 nanocrystals dispersed into the TiO2 host after heating at 500 °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.
authors.affiliation: †Istituto per la Microelettronica e i Microsistemi, IMM-CNR, Via Monteroni, 73100 Lecce, Italy.
authors.forename: Mauro
authors.initials: M
authors.lastname: Epifani
authors.affiliation: ‡Electrochemical Processes Unit, IMDEA Energy Institute, Avda. Ramón de la Sagra 3, 28935 Móstoles, Spain.
authors.forename: Raül
authors.initials: R
authors.lastname: Díaz
authors.affiliation: §NMR Unit,Centro de Apoyo Tecnológico, Universidad Rey Juan Carlos, c/Tulipán, s/n, 28933 Móstoles, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Force
authors.affiliation: ∥SENSOR Lab, Department of Information Engineering, Brescia University and CNR-INO, Via Valotti 9, 25133 Brescia, Italy.
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Comini
authors.affiliation: ⊥Catalonia Institute for Energy Research, IREC, Universitat de Barcelona, c/Jardins de les Dones de Negre 1, 08930 Sant Adria del Besos, Barcelona, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Manzanares
authors.affiliation: ⊥Catalonia Institute for Energy Research, IREC, Universitat de Barcelona, c/Jardins de les Dones de Negre 1, 08930 Sant Adria del Besos, Barcelona, Spain.
authors.forename: Teresa
authors.initials: T
authors.lastname: Andreu
authors.affiliation: #Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus de la UAB, 08193 Bellaterra, Spain.|⧫Institut Català de Nanociència i Nanotecnologia (ICN2), Campus UAB, 08193 Bellaterra, Catalonia, Spain.
authors.forename: Aziz
authors.initials: A
authors.lastname: Genç
authors.affiliation: #Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus de la UAB, 08193 Bellaterra, Spain.|⊗Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys 23, 08010 Barcelona, CAT Spain.|⧫Institut Català de Nanociència i Nanotecnologia (ICN2), Campus UAB, 08193 Bellaterra, Catalonia, Spain.
authors.forename: Jordi
authors.initials: J
authors.lastname: Arbiol
authors.affiliation: †Istituto per la Microelettronica e i Microsistemi, IMM-CNR, Via Monteroni, 73100 Lecce, Italy.
authors.forename: Pietro
authors.initials: P
authors.lastname: Siciliano
authors.affiliation: ∥SENSOR Lab, Department of Information Engineering, Brescia University and CNR-INO, Via Valotti 9, 25133 Brescia, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Faglia
authors.affiliation: ⊥Catalonia Institute for Energy Research, IREC, Universitat de Barcelona, c/Jardins de les Dones de Negre 1, 08930 Sant Adria del Besos, Barcelona, Spain.|○M2E-IN2UB-XaRMAE, Departament d'Electrònica, Universitat de Barcelona, c/Martí i Franquès 1, 08028 Barcelona, Spain.
authors.forename: Joan R
authors.initials: JR
authors.lastname: Morante
keywords: TiO2; gas sensors; metal oxide nanocrystals; nanocomposites; solvothermal synthesis; surface modification