Cu-TiO2 Hybrid Nanoparticles Exhibiting Tunable Photochromic Behavior


Pure and copper-modified photocatalytic TiO2 nanopowders were prepared via a green sol gel route and heated to 450 degrees C. Copper does not enter the TiO2 lattice but forms as smaller similar to 2 nm Cu-based nanocrystals, decorating the surface of similar to 10 nm TiO2 nanoparticles. The surface of the larger TiO2 nanopartides (NPs) is partially covered by much smaller Cu NPs, attached to the surface of the larger NPs but not completely covering them due to the small quantity present (1-10 mol % Cu). This retards the anatase-to-rutile phase transition and titania domain growth through a grain-boundary pinning mechanism. These hybrid nanopartides show tunable photochromic behavior under both UVA and visible light. Under LTVA, Cu2+ nanopartides reduce to Cu+, and then to Cu-0. Under visible-light, Cu2+ reduces to Cu, although to a lesser extent. The induced photochromism can be tuned by varying the light source or exposure time. One mol % Cu causes a reduction of Cu2+, and lowers the d-d absorption band, to 50% after only 12 s, and 95% after 10 min, under UVA-light, and has a reduction of 25% in 1 min, 50% in 4 min, and 80% in 1 h under visible-light. This is the first report of inorganic compounds, in this case Cu-TiO2 hybrid nanopartides, to exhibit tunable photochromism under both UVA and visible-light exposure. This rapid and sensitive effect can potentially be used to modify, tune, or monitor the progress of photoactivated behavior in a new generation of smart/active multifunctional materials and photoactive devices or sensors.



subject category

Chemistry; Science & Technology - Other Topics; Materials Science


Tobaldi, DM; Rozman, N; Leoni, M; Seabra, MP; Skapin, AS; Pullar, RC; Labrincha, JA

our authors


D.M.T. is grateful to the ECO-SEE project (funding from the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement no 609234). Professors L. D. Carlos and R. A. S. Ferreira (Physics Department and CICECO-Aveiro Institute of Materials, University of Aveiro) are kindly acknowledged for the constructive and fruitful discussions. R.C.P. acknowledges the support of FCT Grant SFRH/BPD/97115/2013. This work was developed in the scope of the project CICECO-Aveiro Institute of Materials (ref. FCT UID/CTM/50011/2013), financed by national funds through the FCT/MEC and when applicable cofinanced by FEDER under the PT2020 Partnership Agreement. M. Ferro and RNME - University of Aveiro, FCT Project REDE/1509/RME/2005-are also acknowledged for HR-TEM analysis. M.L. wants to acknowledge the support of the Italian government with the Futuro in Ricerca project RBFR10CWDA.

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