Engineering the Light‐Transport Mean Free Path in Silica Photonic Glasses

Espinha, André; Ibisate, Marta; Blanco, Alberto; López, Cefe

doi:10.1002/ppsc.201500202

Cited by 7 publications

(6 citation statements)

References 24 publications

(26 reference statements)

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“…In 2007, García et al. developed a simple drop-cast method to produce polystyrene (PS)-based structures. , The same method was used by Espinha et al to produce PS-based photonic glasses. However, their method involves use of calcium chloride salt to cause flocculation of the colloidal suspensions (Figure a).…”

Section: Introductionmentioning

confidence: 99%

Tailoring Disorder and Quality of Photonic Glass Templates for Structural Coloration by Particle Charge Interactions

Häntsch

Shang

Lei

et al. 2021

ACS Appl. Mater. Interfaces

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To obtain high-quality homogeneous photonic glass-based structural color films over large areas, it is essential to precisely control the degree of disorder of the spherical particles used and reduce the crack density within the films as much as possible. To tailor the disorder and quality of photonic glasses, a heteroaggregation-based process was developed by employing two oppositely charged equal-sized polystyrene (PS) particle types. The influence of the particle size ratio on the extent of heteroaggregation in the suspension mixes is investigated and correlated with both the morphology and the resultant optical properties of the films. The results show that the oppositely charged particle size ratio within the mix greatly influences the assembled structure in the films, affecting their roughness, crack density, and the coffee-ring formation. To better differentiate the morphology of the films, scanning electron microscopy images of the microstructures were classified by a supervised training of a deep convolutional neural network model to find distinctions that are inaccessible by conventional image analysis methods. Selected compositions were then infiltrated with TiO2 via atomic layer deposition, and after removal of the PS spheres, surface-templated inverse photonic glasses were obtained. Different color impressions and optical properties were obtained depending on the heteroaggregation level and thus the quality of the resultant films. The best results regarding the stability of the films and suppression of coffee-ring formation are obtained with a 35 wt % positively charged over negatively charged particle mix, which yielded enhanced structural coloration associated with improved film quality, tailored by the heteroaggregation fabrication process.

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Section: Introductionmentioning

confidence: 99%

Tailoring Disorder and Quality of Photonic Glass Templates for Structural Coloration by Particle Charge Interactions

Häntsch

Shang

Lei

et al. 2021

ACS Appl. Mater. Interfaces

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“…PGs macroscopic in size have been rarely reported so far. Only lower index materials such as polystyrene (PS) [7,[11][12][13][14], poly(methyl methacrylate) (PMMA) [7,12], or silica (SiO 2 ) [15][16][17] were studied. Attempts with higher refractive index materials were done with not perfectly monodisperse zinc sulfide spheres (ZnS, n ZnS = 2.4) dispersed in deionized water or isopropanol [18], or with irregularly shaped TiO 2 particles [19].…”

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confidence: 99%

Tunable high-index photonic glasses

Schertel

Wimmer

Besirske

et al. 2019

Phys. Rev. Materials

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Materials with extreme photonic properties such as maximum diffuse reflectance, high albedo, or tunable band gaps are essential in many current and future photonic devices and coatings. While photonic crystals, periodic anisotropic structures, are well established, their disordered counterparts, photonic glasses (PGs), are less understood despite their most interesting isotropic photonic properties. Here, we introduce a controlled high index model PG system. It is made of monodisperse spherical TiO2 colloids to exploit strongly resonant Mie scattering for optimal turbidity. We report spectrally resolved combined measurements of turbidity and light energy velocity from large monolithic crack-free samples. This material class reveals pronounced resonances enabled by the possibility to tune both the refractive index of the extremely low polydisperse constituents and their radius. All our results are rationalized by a model based on the energy coherent potential approximation, which is free of any fitting parameter. Surprisingly good quantitative agreement is found even at high index and elevated packing fraction. This class of PGs may be the key to optimized tunable photonic materials and also central to understand fundamental questions such as isotropic structural colors, random lasing or strong light localization in 3D.

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“…To demonstrate that the color from the Mie resonances can be combined with structural color arising from short‐ranged correlations, we prepare amorphous, glassy packings of the particles by evaporating the ethanol at 80 °C. We pack the powders between two glass slides and manually apply enough pressure to make a packed glassy film.…”

mentioning

confidence: 99%

Solution‐Processable Photonic Inks of Mie‐Resonant Hollow Carbon–Silica Nanospheres

Kim

Hwang

Lee

et al. 2019

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Whereas ordinary color comes from selective absorption by pigments or dyes, [1,2] structural color comes from coherent scattering from nanostructures. [3,4] However, ordered nanostructures lead to structural color that depends strongly on the viewing angle, which limits its practical applications. By contrast, materials with short-range order, such as colloidal glasses [5][6][7][8] or blue bird feathers, [9][10][11][12][13] show structural color that is independent of angle. While these materials could in principle be used in applications that require structural color that is indistinguishable from pigment, they also tend to diffuse or multiply scatter light, leading to colors that are not saturated. The multiple scattering can be suppressed by dyes such as carbon black.An alternative approach is to rely on the wavelengthdependent scattering of the particles themselves. Cho et al. [14] Hollow carbon-silica nanospheres that exhibit angle-independent structural color with high saturation and minimal absorption are made. Through scattering calculations, it is shown that the structural color arises from Mie resonances that are tuned precisely by varying the thickness of the shells. Since the color does not depend on the spatial arrangement of the particles, the coloration is angle independent and vibrant in powders and liquid suspensions. These properties make hollow carbon-silica nanospheres ideal for applications, and their potential in making flexible, angle-independent films and 3D printed films is explored. Photonic Inks

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Engineering the Light‐Transport Mean Free Path in Silica Photonic Glasses

Cited by 7 publications

References 24 publications

Tailoring Disorder and Quality of Photonic Glass Templates for Structural Coloration by Particle Charge Interactions

Tailoring Disorder and Quality of Photonic Glass Templates for Structural Coloration by Particle Charge Interactions

Tunable high-index photonic glasses

Solution‐Processable Photonic Inks of Mie‐Resonant Hollow Carbon–Silica Nanospheres

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