Preparation of large-scale and angle-independent structural colors by additive of black polypyrrole

Non-iridescent Structurally Colored Pigments Based on CB@SiO2@TiO2 Core-Bishell Nanospheres with Enhanced Color Stability and Excellent Photocatalytic Activity

In recent years, artificial amorphous photonic structure (APS) materials with high color saturation and angle independence have been competitively reported. However, there is a lack of research into their functionalization and application in practical environments. Here, with practical applications in mind, we prepared APS pigments based on CB@SiO2@TiO2 core-bishell nanospheres and demonstrated high color saturation, enhanced color stability, and excellent photocatalytic activity. SiO2 effectively protected the carbon black particles from ablation during the calcination process. Paints composed of ethanol, ethyl cellulose (EC), and pigments could be spray-coated on any substrate to prepare a structurally colored coating without limitation. The coatings show good mechanical stability and photothermal stability. The color of the structurally colored pigments can be easily changed by adjusting the sizes of the CB@SiO2@TiO2 nanospheres. The photocatalytic activity of the pigments on formaldehyde (HCHO) and methylene blue (MB) solution and reaction kinetics of their degradation were studied by experiment. The results showed that the photocatalytic activity of the pigments increased with the increase of the TiO2 loading, and the degradation rate of HCHO reached 96.7% for 3 h and that of MB reached 97.9% for 60 min when the TiO2 shell thickness was 40 nm. The structurally colored pigments based on CB@SiO2@TiO2 nanospheres effectively solve the environmental problems caused by the application of pigments and have a promising future in the fields of color decoration, display, and painting.

Printing a Wide Gamut of Saturated Structural Colors Using Binary Mixtures, With Applications in Anticounterfeiting

Use of colloidal suspensions to generate structural colors has the potential to reduce the use of toxic metals or organic pigments in inkjet printing, coatings, cosmetics, and other applications, and is a promising avenue to create large-scale nanostructures that produce long-lasting colors. However, expanded use of structural colors requires a reduction in coffee-ring effects during printing, which currently requires intricately patterned substrates or high particle concentrations, and diversification of colors to compete with conventional printing inks. Here, we treat substrate surfaces with cold plasma to facilitate spontaneous assembly of particles into colloidal nanostructures, reducing the need for highly concentrated particle suspensions. Moreover, by employing binary mixtures, we can tune the lightness of the hue produced or change the hue itself, allowing us to cover wider regions of color space. We demonstrate the use of this cold-plasma approach on a variety of substrates, favoring substrate diversity on which printing can be performed. This methodology enables creation of high-resolution, complex designs and opens a path for extending the limits of anticounterfeiting applications by using binary mixtures.

Angle-Independent Structurally Colored PS@TiO2 Film with Excellent Underwater Superoleophobicity in Harsh Environments

Chemical pigments are damaging to the environment; however, a nontoxic substance (including TiO₂ and SiO₂) often appears white because of the incoherent multiple scattering. The addition of small black substances can enhance the structural color of the amorphous system. Herein, colored amorphous photonic crystals (APCs) with angle-independence were fabricated by TiO₂-coated polystyrene core-shell nanoparticles (PS@TiO₂ NPs) via a healthy and time-saving sprayed method. Compared with generally used collide materials, such as PS and SiO₂ NPs with smooth surfaces, the rough TiO₂ NPs shell structure has significant advances for the underwater oil-repellent property. Thanks to the TiO₂ NPs adhered to PS spheres, the multiscale roughness was enhanced and the PS@TiO₂/CB film was endowed with excellent underwater superoleophobicity without other extremely hydrophilic chemical compositions. Furthermore, the waterborne polyurethane improves the robustness of the film. This film is free from the adhesion of oil in the water, which can be employed into diverse undersurface systems and may boost the promising applications of APCs.