Amorphous photonic structures with high reflective index based on incorporating Fe3O4@SiO2 core/shell colloidal nanoparticles into silica nanospheres

Abstract

Amorphous photonic structures (APSs) with non-iridescent, non-fading, vivid structural colors have attracted great attention in several fields. Tremendous efforts have been dedicated to developing the effective and low-cost approaches for APSs with full-color displays. Resulting from the isotropic photonic pseudogap, APSs have non-iridescent structural colors. We demonstrate that incorporating Fe3O4@SiO2 black nanoparticles into the interspace of the periodically arranged SiO2 white nanospheres can synthesize APSs with different colors. The addition of Fe3O4@SiO2 black nanoparticles can enhance the saturation of the non-iridescent structural colors of the APSs by reducing the incoherent scattering in the visible spectrum. In this case, different non-iridescent colors originate from the different diameters of the SiO2 white nanospheres, and we obtained red, orange, yellow, green, and purple APSs with high reflective index successfully. The APSs with different colors may have potential applications in coatings, cosmetics, textiles, and displays. Moreover, as we use Fe3O4@SiO2 as the additive, APSs can be recycled through its magnetic property.

Spray‐Dried Photonic Balls with a Disordered/Ordered Hybrid Structure for Shear‐Stress Indication

“…[14,25] The broadband absorption properties of the iron oxide building blocks further allow optimization of color perception. [19] Scheme 1. a) Schematic illustration of the disordered/ordered structure of the photonic balls, based on silica and iron oxide nanoparticle building blocks and obtained via forced assembly in a kinetically controlled regime via spray-drying. b) At the beginning of the spray-drying process, the nanoparticles are randomly distributed in the water droplet.…”

“…This ultimately yields a whitish appearance of the supraparticle powder. [11,14,15] By incorporating broadband or spectrally selective light absorbers in form of nanoparticles (e.g., melanin, [16] polydopamin, [15] carbon black, [17,18] iron oxide, [19,20] gold, [11,18] or silver [18] ) within the supraparticle, the incoherently scattered light is absorbed, so that the constructive interference from the ordered layers toward the surface create a more homogenous color impression. Various manufacturing processes are described in the literature for the creation of photonic balls, such as microfluidics, [15,21] electrospray-assisted fabrication, [22] or micropipette injection.…”

Bright, Angle-Independent, Solvent-Responsive, and Structurally Colored Coatings and Rewritable Photonic Paper Based on High-Refractive-Index Colloidal Quasi-Amorphous Arrays

“…Active research has been conducted on creating noniridescent structural colors by packing polystyrene (PS), poly­(methyl methacrylate) (PMMA), and silica (SiO 2 ) colloidal crystals into quasi-amorphous arrays (QAAs) through a variety of strategies, including spin coating, drop-casting, evaporation-induced self-assembly, sputter deposition, and spray coating. − However, these noniridescent structural colors usually appear white and have low color visibility due to incoherent multiple scattering. , One method for solving this problem is to enhance the color saturation by introducing some light absorbers such as carbon black, iron oxide black nanoparticles, polydopamine (PDA), and cuttlefish ink in colloidal assemblies to absorb incoherently scattered light. − Nevertheless, the added black substances are physically mixed with the colloidal particles and tend to easily reunite due to the high surface energy, resulting in local segregation and thus a significant decrease in brightness. Furthermore, once the structurally colored films get wet due to the infiltration of water, ethanol, oil, and other liquids into the voids of the assemblies, the structural colors will immediately weaken or even disappear owing to the significant reduction of the refractive index contrast between the colloidal particles and the surrounding media.…”

“…However, in their work, the Fe 3 O 4 @SiO 2 nanoparticles (only 150 nm) do not act as building blocks of the photonic structure but only as a black dopant to suppress the incoherent scattering of light. Direct fabrication of quasi-amorphous pigments with bright, angle-independent structural colors on a large scale using Fe 3 O 4 @SiO 2 as building blocks has not been reported . In this paper, the spraying process was adopted just because spray coating is a relatively facile approach for rapid patterning of noniridescent structural colors over a large area on both planar and curved surfaces.…”

“…Direct fabrication of quasi-amorphous pigments with bright, angleindependent structural colors on a large scale using Fe 3 O 4 @ SiO 2 as building blocks has not been reported. 39 In this paper, the spraying process was adopted just because spray coating is a relatively facile approach for rapid patterning of noniridescent structural colors over a large area on both planar and curved surfaces. Compared with the traditional self-assembly approach, spray coating is time-saving and cost-effective and more suitable for mass production.…”