Increasing the optical response of TiO2 and extending it into the visible region through surface activation with highly stable Cu5 clusters

María Pilar de Lara-Castells; Andreas W. Hauser; José M. Ramallo-López; David Buceta; Lisandro J. Giovanetti; M. Arturo López-Quintela; Félix G. Requejo

doi:10.1039/C9TA00994A

Increasing the optical response of TiO₂ and extending it into the visible region through surface activation with highly stable Cu₅ clusters†

María Pilar de Lara-Castells,

*^a Andreas W. Hauser,

*^b José M. Ramallo-López,

^c David Buceta,

*^d Lisandro J. Giovanetti,

^c M. Arturo López-Quintela

^d and Félix G. Requejo

Author affiliations

* Corresponding authors

^a Instituto de Física Fundamental (C.S.I.C.), Serrano 123, Madrid, Spain
E-mail: Pilar.deLara.Castells@csic.es

^b Graz University of Technology, Institute of Experimental Physics, Petersgasse 16, 8010 Graz, Austria
E-mail: andreas.w.hauser@gmail.com

^c Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), CONICET, Dto. de Química, Fac. de Ciencias Exactas, UNLP, Argentina

^d Lab. Nanomag, Instituto de Investigaciones Tecnológicas, Universidad de Santiago de Compostela, E-15782 Santiago de Compostela, Spain
E-mail: david.buceta@gmail.com

Abstract

The decoration of semiconductors with subnanometer-sized clusters of metal atoms can have a strong impact on the optical properties of the support. The changes induced differ greatly from effects known for their well-studied, metallic counterparts in the nanometer range. In this work, we study the deposition of Cu₅ clusters on a TiO₂ surface and investigate their influence on the photon-absorption properties of TiO₂ nanoparticles via the computational modeling of a decorated rutile TiO₂ (110) surface. Our findings are further supported by selected experiments using diffuse reflectance and X-ray absorption spectroscopy. The Cu₅ cluster donates an electron to TiO₂, leading to the formation of a small polaron Ti³⁺ 3d¹ state and depopulation of Cu(3d) orbitals, successfully explaining the absorption spectroscopy measurements at the K-edge of copper. A monolayer of highly stable and well fixated Cu₅ clusters is formed, which not only enhances the overall absorption, but also extends the absorption profile into the visible region of the solar spectrum via direct photo-induced electron transfer and formation of a charge-separated state.

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Article information

DOI: https://doi.org/10.1039/C9TA00994A
Article type: Paper
Submitted: 25 Jan 2019
Accepted: 15 Feb 2019
First published: 16 Feb 2019
This article is Open Access

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J. Mater. Chem. A, 2019,7, 7489-7500

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Increasing the optical response of TiO₂ and extending it into the visible region through surface activation with highly stable Cu₅ clusters

M. Pilar de Lara-Castells, A. W. Hauser, J. M. Ramallo-López, D. Buceta, L. J. Giovanetti, M. A. López-Quintela and F. G. Requejo, J. Mater. Chem. A, 2019, 7, 7489 DOI: 10.1039/C9TA00994A

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Journal of Materials Chemistry A