Purely Visible-Light-Induced Photochromism in Ag-TiO2 Nanoheterostructures
authors Tobaldi, DM; Gallo, MJH; Otero-Irurueta, G; Singh, MK; Pullar, RC; Seabra, MP; Labrincha, JA
nationality International
journal LANGMUIR
keywords ENHANCED PHOTOCATALYTIC ACTIVITY; SILVER NANOPARTICLES; NANO-TITANIA; MULTICOLOR PHOTOCHROMISM; OPTICAL-PROPERTIES; SENSING PROPERTIES; PLASMON RESONANCE; DOPED TIO2; FILMS; AG
abstract We report titania nanoheterostructures decorated with silver, exhibiting tuneable photochromic properties for the first time when stimulated only by visible white light (domestic indoor lamp), with no UV wavelengths. Photochromic materials show reversible color changes under light exposure. However, all inorganic photochromic nanoparticles (NPs) require UV light to operate. Conventionally, multicolor photochromism in Ag-TiO2 films involves a change in color to brownish-gray during UV-light irradiation (i.e., reduction of Ag+ to Ag-0) and a (re)bleaching (i.e., (re)oxidation of Ag-0 to colorless Ag+) upon visible-light exposure. In this work, on the contrary, we demonstrate visible-light-induced photochromism (ranging from yellow to violet) of 1-10 mol % Ag-modified titania NPs using both spectroscopic and colorimetric CIEL*a*b* analyses. This is not a bleaching of the UV-induced color but a change in color itself under exposure to visible light, and it is shown to be a completely different mechanism driven by the interfacial charge transfer of an electron from the valence band of TiO2 to that of the AgxO clusters that surround the titania to the usual UV-triggered photochromism reported in titania-based materials. The quantity of Ag or irradiation time dictated the magnitude and degree of tuneability of the color change, from pale yellow to dark blue, with a rapid change visible only after a few seconds, and the intensity and red shift of surface plasmon resonance induced under visible light also increased. This effect was reversible after annealing in the dark at 100 degrees C/15 min. Photocatalytic activity under visible light was also assessed against the abatement of nitrogen oxide pollutants, for interior use, therefore showing the coexistence of photochromism and photocatalysis both triggered by the same wavelength in the same material, making it a multifunctional material. Moreover, we also demonstrate and explain why X-ray photoelectron spectroscopy is an unreliable technique with such materials.
publisher AMER CHEMICAL SOC
issn 0743-7463
year published 2017
volume 33
issue 20
beginning page 4890
ending page 4902
digital object identifier (doi) 10.1021/acs.langmuir.6b04474
web of science category Chemistry, Multidisciplinary; Chemistry, Physical; Materials Science, Multidisciplinary
subject category Chemistry; Materials Science
unique article identifier WOS:000402497900002

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