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Photochromic materials whose color can reversibly change under visible light exposure are good candidates for many applications like photooptical sensors, smart inks and paints, displays or optical storage. Among these materials, inorganic Ag:TiO2 films have been proven to be stable over time and to exhibit multicolor photochromism leading to potential high-performance systems. However, their fabrication processes are often based on laboratory equipment not adapted to industrialization and usually involve thermal treatments not compatible with soft materials, which limit the application range. The present paper proposes an alternative way to produce photochromic Ag:TiO2 films compatible with industrialization and with soft substrates. An aqueous ink, made of a dispersion of TiO2 nanoparticles and silver ions, was formulated from a commercial TiO2 suspension and a silver salt by adding a thickener and a surfactant to satisfy inkjet process requirements. The inkjet printing process was optimized on polyethylene terephthalate substrates to form thin inorganic films after IR annealing. Such a process can be adapted to any kind of substrates, in particular flexible and non-heat-resistant substrates, and can be scaled at the industrial level. The photochromic behavior of the fabricated films was finally assessed successfully after an activation step. [ABSTRACT FROM AUTHOR]

Mesoporous TiO 2 films loaded with silver nanoparticles grown photocatalytically, which are initially brown, change their color under visible laser irradiations. In this article, we compare the multicolor photochromisms of amorphous and anatase phases of TiO 2. The mesoporous films are impregnated with silver salt and then exposed to a low-intensity UV laser light to grow silver nanoparticles. The Ag–TiO 2 films are then exposed to visible laser beams, and the influences of several exposure parameters on the photochromic behavior are examined. Most of the previous studies have reported a poor stability of the photoinduced colors under day light or even in the dark, and few of them demonstrated the ability to get various colors on the same sample. These inconveniences limit the application field of such materials. On the other hand, except in our previous studies, only crystalline TiO 2 is generally used, in its anatase or rutile phase. In this article we show that mesoporous films of amorphous and anatase phases of TiO 2 respond in an efficient manner to light excitation and that multiple colors can be obtained on both kinds of films. For the first time on such Ag–TiO 2 films we show that the various photoinduced colors are stable over considerable months. Visible intensity is shown to have a significant influence on the film behavior, which was not identified in previous studies. The laser-induced spectral changes are also shown to depend on the incident laser polarization. The photochromic behaviors are characterized in terms of color changes and spectral variations. The reproducibility of the photochromic process along reduction/oxidation cycles is demonstrated, and the stability of different laser-induced colors is reported on 6-month-old samples. [ABSTRACT FROM AUTHOR]

Mesoporous TiO 2 films loaded with silver nanoparticles grown photocatalytically, which are initially brown, change their color under visible laser irradiations. In this article, we compare the multicolor photochromisms of amorphous and anatase phases of TiO 2. The mesoporous films are impregnated with silver salt and then exposed to a low-intensity UV laser light to grow silver nanoparticles. The Ag–TiO 2 films are then exposed to visible laser beams, and the influences of several exposure parameters on the photochromic behavior are examined. Most of the previous studies have reported a poor stability of the photoinduced colors under day light or even in the dark, and few of them demonstrated the ability to get various colors on the same sample. These inconveniences limit the application field of such materials. On the other hand, except in our previous studies, only crystalline TiO 2 is generally used, in its anatase or rutile phase. In this article we show that mesoporous films of amorphous and anatase phases of TiO 2 respond in an efficient manner to light excitation and that multiple colors can be obtained on both kinds of films. For the first time on such Ag–TiO 2 films we show that the various photoinduced colors are stable over considerable months. Visible intensity is shown to have a significant influence on the film behavior, which was not identified in previous studies. The laser-induced spectral changes are also shown to depend on the incident laser polarization. The photochromic behaviors are characterized in terms of color changes and spectral variations. The reproducibility of the photochromic process along reduction/oxidation cycles is demonstrated, and the stability of different laser-induced colors is reported on 6-month-old samples. [ABSTRACT FROM AUTHOR]

Silver nanoparticles were created inside mesoporous titania thin films by different reduction processes. We investigated the influence of the reduction method on the colour and photochromism of these amorphous TiO2films. The results highlight brown films by optical reduction, gray films by thermal reduction, and red, purple or orange films by chemical reduction. The different size distributions and localizations of the nanoparticles, characterized by UV-visible spectroscopy and electron microscopy, give various photochromic behaviours when exposed to visible laser light. We especially report the bleaching of different film colours under laser exposure. [ABSTRACT FROM AUTHOR]

The photochromism of heterogeneous silver nanoparticles grown thermally in mesoporous TiO2 films is investigated under visible laser illuminations with different irradiances. At low irradiance, a selective oxidation occurs that changes the film color in accordance with the illuminant wavelength. At higher irradiance, the oxidation of large nanoparticles is going with the formation of many small nanoparticles in their vicinity, which gives the films an orangy color whatever the wavelength. This color fades after long exposure times at a laser line. The laser polarization has also an influence on the dichroism of the colored films. [ABSTRACT FROM AUTHOR]