Photocatalytic Color Switching of Transition Metal Hexacyanometalate Nanoparticles for High-Performance Light-Printable Rewritable Paper

Abstract

Developing efficient photoreversible color switching systems for constructing rewritable paper is of significant practical interest owing to the potential environmental benefits including forest conservation, pollution reduction, and resource sustainability. Here we report that the color change associated with the redox chemistry of nanoparticles of Prussian blue and its analogues could be integrated with the photocatalytic activity of TiO nanoparticles to construct a class of new photoreversible color switching systems, which can be conveniently utilized for fabricating ink-free, light printable rewritable paper with various working colors. The current system also addresses the phase separation issue of the previous organic dye-based color switching system so that it can be conveniently applied to the surface of conventional paper to produce an ink-free light printable rewritable paper that has the same feel and appearance as the conventional paper. With its additional advantages such as excellent scalability and outstanding rewriting performance (reversibility >80 times, legible time >5 days, and resolution >5 μm), this novel system can serve as an eco-friendly alternative to regular paper in meeting the increasing global needs for environment protection and resource sustainability.

Photocatalytic Self‐Doped SnO2−x Nanocrystals Drive Visible‐Light‐Responsive Color Switching

“…HEC was used to help maintain stable images/ patterns under ambient lighting by stabilizing the dye molecules through hydrogen bonding. [14] Theregions exposed to the laser beam turned colorless rapidly due to photoreduction of MB to LMB,while the unexposed area retained the original blue color of MB,p roducing ap attern with sufficient contrast to be observed with the naked eye.T he rewritable media showed good stability under office light condition for 2h( Figure 5c)and remained legible even after 4h( Figure S12), making the system suitable for applications that require temporary recording,s uch as writing boards in ac onference room. Thew riting can be erased completely in air by heating at 90 8 8Cf or about 15 min ( Figure S13).…”

“…Considering the dependence of the photoreductivity of SnO 2Àx NCs with redox potential of redox dyes,a nd wavelength-dependent color switching,various colored PCSS with wavelength-selective color switching may be achieved by using the mixture of dyes.F or example,amixture of SnO 2Àx / NR/MB/H 2 Ocould switch from blue-purple (with absorption peaks at 520 nm for NR and and 664 nm for MB) to red upon illumination with blue light (450 nm) since only MB can be photoreduced (Figure S10 a), while illumination with blue light of 420 nm could switch the system from purple to colorless directly (Figure S10 b), clearly demonstrating the possibility of wavelength-selective photoreversible color switching of mixed redox dyes. [14] Theregions exposed to the laser beam turned colorless rapidly due to photoreduction of MB to LMB,while the unexposed area retained the original blue color of MB,p roducing ap attern with sufficient contrast to be observed with the naked eye.T he rewritable media showed good stability under office light condition for 2h( Figure 5c)and remained legible even after 4h( Figure S12), making the system suitable for applications that require temporary recording,s uch as writing boards in ac onference room. HEC was used to help maintain stable images/ patterns under ambient lighting by stabilizing the dye molecules through hydrogen bonding.…”

Bistable and Reconfigurable Photonic Crystals—Electroactive Shape Memory Polymer Nanocomposite for Ink‐Free Rewritable Paper

“…Recent attempts to create and popularize rewritable paper can greatly lessen the heavy environmental burden brought about by traditional pulp and paper industry . Currently, paper‐replacement effort is developing around several distinct technologies: electrophoretic inks, electrowetting inks, cholesteric liquid crystals, reprintable coatings on paper, and responsive photonic crystals . Microencapsulated electrophoretic display was first introduced by an MIT group in 1998, which quickly enabled the commercially successful, monochromic e‐readers popular for their low power consumption due to its bistability and paper‐like legibility under illumination.…”

A Multiaddressable Dyad with Switchable Cyan/Magenta/Yellow Colors for Full‐Color Rewritable Paper

“…For these reasons, rewritable ink and rewritable paper, which can allow a single piece of paper to be reused multiple times, are now attracting much attention from the perspective of sustainable development. To date, numerous examples have been reported in this field that make use of both organic and inorganic materials . Among these works, interconversion between colorless and one or two different colors on a sheet of paper have been demonstrated by employing various external stimuli, such as electricity, heat, light, water, and metal ions .…”

“…To date, numerouse xamples have been reported in this field that make use of both organic and inorganic materials. Among these works, interconversion between colorless and one or two different colors on as heet of paper have been demonstratedb ye mploying various externals timuli, such as electricity, [2] heat, [3,4] light, [6][7][8][9][10][11][12] water, [16][17][18] and metal ions. [22] Nevertheless,i nm anyc ases, the communication of complex messages and images needs to be presented in full color to satisfy the demandso ft he readers.…”