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A Semiconducting Material Exhibiting Visible-Light Promoted Photochromism, Photoluminescent and Photocatalytic Activity

submitted on 27.12.2018 and posted on 28.12.2018 by David Maria Tobaldi, Luc Lajaunie, Miguel López‐Haro, Rute Ferreira, Matteo Leoni, Maria Paula Seabra, José Calvino, Luís Carlos, Joao Antonio Labrincha
Multifunctional materials working under solely visible-light are expected to play a significant role in photo-electronics, in particular photo-switches, photo-optical sensors, smart windows, displays, optical storage memories, and self-cleaning materials.
In this work, we have modified the surface of a versatile semiconductor material (TiO2) with a noble metal (copper), and simultaneously doped its lattice with a rare-earth element (neodymium). Exploiting the ability of a semiconductor to generate an exciton upon excitation, a multifunctional material working with visible-light and showing photochromic, photoluminescent and photocatalytic activity was engineered. Advanced transmission electron microscopy techniques – aberration-corrected imaging combined with image simulation, statistical analyses and electron energy-loss spectroscopy – were used to characterise thoroughly the structure and local chemical environment as a function of the Nd3+ content, as well as to link the variation of these aspects to the evolution of the physico-chemical properties. Combined X-ray, spectroscopic and microscopy technique results showed that Nd entered the TiO2 lattice in a substitutional fashion. When at 1 mol%, neodymium atoms were ultra-dispersed inside the TiO2 (anatase) structure. On the contrary, when the neodymium mol% was higher than 1 mol%, neodymium atoms mostly clustered at the surface of the grains, forming a dense network. Furthermore, the Cu-modified / Nd-doped TiO2 exhibited faster (two times), as well as a reversible photoswitching that was remarkably more stable compared to standard Cu-TiO2 photochromic material. The same material also displayed visible-light and solar-light induced photocatalytic activity in the gas-solid phase (degradation of benzene, one of the most hazardous pollutants found indoor) superior to unmodified titania (1.35 and nearly 3.00 times higher, with a LED visible- and solar-light lamps, respectively). It was demonstrated that the optimum amounts of copper and neodymium, for both photochromic and photocatalytic performances, were 1 mol%.



CICECO-Aveiro Institute of Materials

Fundação para a Ciência e Tecnologia

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MAT2017- 87579-R



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University of Aveiro



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Declaration of Conflict of Interest

No conflict of interest