Assembly of Nanometer-Sized Hollow Sphere Colloidal Crystals for Applications as Tunable Photonic Materials

Abstract

Electrically responsive photonic crystals, capable of transforming crystal structures and changing intrinsic structural colors in response to external electrical energies, can serve as optically active components for promising technological applications. Unfortunately, the deformation of inverse opal photonic crystals generally weakens the structural stability and leads to poor color tuning repeatability, while most color-tunable colloidal photonic crystals suffer from low color saturation as a result of small refractive index difference between the colloids and matrices. Inspired by cephalopod skins, nanometer-sized hollow silica sphere/poly­(3,4-ethylenedioxythiophene)–polystyrene sulfonate photonic crystals are self-assembled using a scalable coating technique. The as-engineered photonic crystals exhibit a conspicuous structural color that is tunable on demand by applying varied voltages. Importantly, their appearance and expanded crystalline lattice can be maintained without any electric field under ambient conditions and simultaneously recovered by applying an oxidation potential. The reversibility and the dependence of hollow sphere size and thickness on electrochromic behaviors are also investigated in this study.

Cephalopods as a Natural Sensor-Display Feedback System Inspiring Adaptive Technologies

“…3c). 56,57 Finally, color in a material can be manipulated through adaptive structural coloration ( Fig. 3d).…”

“…In this method, the material is infused with crystalline substances that possess reflective properties. [56][57][58] By adjusting the spacing between crystals and crystalline layers, it becomes possible to modify the wavelength of incident light and generate different colors reminiscent of adaptive iridophores.…”

“…The resultant photonic crystal could be activated by controlling the applied voltage, causing structural colors to change between green, yellow, orange, and red at 0, −0.3, −0.7, and −1.0 V, respectively, over 100 reversible cycles. 56 Inspired by cephalopod dual function of simultaneous pressure detection and visualization, Guo et al have fabricated a hybrid device that responds to pressure changes and generates a capacitance signal from a real-time visual color change. 70 The device is created using magnetron-sputtered tungsten oxide (WO 3 ) on 3-D printed structures layered on an ionic gel (polyvinyl alcohol/H 3 PO 4 ), which is sandwiched between two indium tin oxide (ITO) electrodes.…”

Bio‐inspired photonic crystals: Tailoring the dielectric building blocks to control the light propagation

“…Since the electrostatic interactions are quite common among the charged colloidal nanoparticles and other building blocks for a photonic structure, thereby it is convenient and flexible to control the periodicity of such photonic structures with the help of an external electric field. Two strategies have been developed to achieve the color manipulation under an applied electric field, either by changing the lattice of the photonic structures via expansion/contraction of the dielectrics filling in the void of the colloidal nanoparticles or by electric field induced compression/relaxation of the building blocks [186–188] . To achieve this objective, tremendous effects have been devoted to the electrically tunable photonic materials during the past decades.…”

Photonic Crystal Films Based on Polymer Particles with a Core/Shell Structure Responding to Ethanol

“…Photonic crystals (PCs) are a class of materials that are promising both for studying new fundamental phenomena in quantum and nonlinear optics and for creating hierarchical materials with new physical, physicochemical, or biological properties. − The fundamental property of PCs is a spatially periodic change of its permittivity with a period comparable to the light wavelength. − Since the reflection wavelength of a polymer film based on PCs can be easily varied by changing the diameter of monodisperse polymer particles, − it is possible to create optical sensor materials based on polymeric PCs. Also, the reflection wavelength of the PC-based film can be modulated by changing the lattice spacing due to external influences, such as temperature, pressure, and the presence of volatile organic compounds. − PCs with tunable optical properties have great potential for a wide range of applications such as strain sensors or smart labels. − …”