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

Abstract

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.

High-Efficiency, Mass-Producible, and Colored Solar Photovoltaics Enabled by Self-Assembled Photonic Glass

“…Here, we propose using a self-assembled photonic structure for colorizing PVs, consisting of dielectric microspheres with short-range correlations on the scale of visible wavelengths. Such photonic pigments have already been found in some living organisms, producing noniridescent structural colors that are visually pleasing. , Inspired by nature, recently some researchers have artificially made similar nanostructures by self-assembled colloidal microspheres, named photonic glass. − Because of the isotropic structure and purely dielectric building blocks, easily tunable and angle-independent colors could be generated, with no fading and low parasitic absorption of light. , In this case, we presume that photonic glass is a highly promising technology for developing colored PVs, and it is fully verified in this study.…”

Structure-Tunable Construction of Colloidal Photonic Composites via Kinetically Controlled Supramolecular Crosslinking

“…A discretely circular ring pattern in the 2D FFT for the composite assembled at pH 3.9 suggests its isotropically short-range-ordered structure (Figure d) . In contrast, CPCs obtained at pH 6.6 and 8.2 have anisotropically long-range-ordered structures, as indicated by the sharp hexagonal peak patterns (Figure d) . Correspondingly, the calculated Ψ 6 was 0.300, 0.815, and 0.899 for the composites obtained with a pH of 3.9, 6.6, and 8.2, respectively.…”

“…When increasing pH in the range of 3.9–8.2, the composites exhibited a bright color (Figure c). A discretely circular ring pattern in the 2D FFT for the composite assembled at pH 3.9 suggests its isotropically short-range-ordered structure (Figure d) . In contrast, CPCs obtained at pH 6.6 and 8.2 have anisotropically long-range-ordered structures, as indicated by the sharp hexagonal peak patterns (Figure d) .…”

Inverse Opal Photonic Hydrogels for Blue‐Edge Slow Photon‐Enhanced Photodynamic Antibacterial Therapy

“…Moreover, the long‐range‐ordered structure can be further evidenced by the apparent hexagonal pattern in the 2D fast Fourier transform (2D FFT), as shown in the inset. [ 17 ] To study the microstructure of IOPGs after etching, wet IOPG 694 was freeze‐dried, and its cross section was observed. As shown in Figure 2e, the thickness of IOPG 694 was approximately ≈120 µm.…”