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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 TiO2 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.

A new route for Fe 3 O 4 @MIL-100(Fe) core-shells is proposed via in situ one-step hydrothermal strategy, in which Fe 3 O 4 microspheres not only serve as magnetic cores but also provide Fe(III) for MIL-100(Fe) synthesis. The MIL-100(Fe) is uniformly grown as a shell on the surface of Fe 3 O 4 , and the shell thickness can be fine-tuned from 73.5 to 148 nm by simply controlling the reaction time. Compared with Fe 3 O 4 , the surface area and pore volume of the Fe 3 O 4 @MIL-100(Fe) are significantly increased while the magnetism is barely affected. The application of Fe 3 O 4 @MIL-100(Fe) in adsorption was tested using several dyes as model analytes, and showed high adsorption capacity (221 mg g −1 ) towards methylene blue (MB), which is based on electrostatic interactions and size filter effect. The MB adsorption isotherm follows Langmuir model and pseudo second-order kinetic model. Intra-particle diffusion model reveals that both film and pore diffusions are involved in the rate limiting steps. The adsorption is controlled by enthalpy change rather than entropy effect. ΔH, ΔS and ΔG values indicated that the adsorption process was spontaneous and exothermic. Simple synthesis procedure, immense magnetism, high adsorption capacity and excellent reusability of Fe 3 O 4 @MIL-100(Fe) make it an attractive candidate for application of MB removal from polluted environmental samples. [ABSTRACT FROM AUTHOR]

A new route for Fe 3 O 4 @MIL-100(Fe) core-shells is proposed via in situ one-step hydrothermal strategy, in which Fe 3 O 4 microspheres not only serve as magnetic cores but also provide Fe(III) for MIL-100(Fe) synthesis. The MIL-100(Fe) is uniformly grown as a shell on the surface of Fe 3 O 4 , and the shell thickness can be fine-tuned from 73.5 to 148nm by simply controlling the reaction time. Compared with Fe 3 O 4 , the surface area and pore volume of the Fe 3 O 4 @MIL-100(Fe) are significantly increased while the magnetism is barely affected. The application of Fe 3 O 4 @MIL-100(Fe) in adsorption was tested using several dyes as model analytes, and showed high adsorption capacity (221mgg -1 ) towards methylene blue (MB), which is based on electrostatic interactions and size filter effect. The MB adsorption isotherm follows Langmuir model and pseudo second-order kinetic model. Intra-particle diffusion model reveals that both film and pore diffusions are involved in the rate limiting steps. The adsorption is controlled by enthalpy change rather than entropy effect. ΔH, ΔS and ΔG values indicated that the adsorption process was spontaneous and exothermic. Simple synthesis procedure, immense magnetism, high adsorption capacity and excellent reusability of Fe 3 O 4 @MIL-100(Fe) make it an attractive candidate for application of MB removal from polluted environmental samples., (Copyright © 2017 Elsevier Inc. All rights reserved.)