Stimulus-responsive nonclose-packed photonic crystals: fabrications and applications

Abstract

Stimulus-responsive photonic crystals (PCs) possessing unconventional non-closely packed structures have received growing attention due to their unique capability of mimicking the active structural colors of natural organisms (for example, chameleons’...

Mechanochromic and Solvomechanochromic Fluorescent Photonic Crystals for Dual-Mode Modulating Fluorescence and Multilevel Anticounterfeiting

“…The high reflectance can be attributed to both highly ordered structures and the large refractive index contrast − (Δ n = 0.060) between particles ( n = 1.460) and PEGPEA ( n = 1.520). Generally, the band gap broadens and reflectance improves when Δ n increases, ,,− thereby enhancing the stability of silica particles in acrylates and thus facilitating the ordered packing. The ETPTA-based FPC (Figure S6) exhibits high reflectance but no mechanochromic and solvatochormic properties due to the high self-cross-linking degree of ETPTA.…”

A bio-inspired colorimetric sensor based on ethylene glycol – non-close-packed photonic crystals for visual monitoring of ammonia

“…Colorimetric sensors based on photonic crystals (PCs) have gained interest in the visual sensing of physical, 17–22 chemical 23–25 and biological stimuli. 26–28 Photonic crystals are periodic dielectric materials, 29,30 and their photonic band gap (PBG) satisfies Bragg's diffraction law: n eff 2 = n A 2 f A + n B 2 (1 − f A )where m is the diffraction order, λ is the photonic band gap, d is the lattice distance, θ is the angle of incidence, n eff is the effective refractive index, n A and n B are the refractive index of medium A and B, respectively, and f A is the total volume percentage of medium A.…”

“…The structural colour can be tuned when changing the parameters in Bragg's diffraction law; therefore, the PCs are combined with hydrogels to obtain hydrogel-based photonic crystal sensors. 21,31–33 The visual sensing of volatile organic compounds (VOCs) and gaseous molecules is achieved with the changing of the effective refraction or lattice distance of the PCs; 34–38 however, the practical application of the traditional hydrogel-based photonic crystal sensors is limited due to various factors, e.g. environmental stability and limited deviation of the reflective peak, which is not conducive to the visual sensing in the entire colour range.…”

Lattice Transformation-Induced Retroreflective Structural Colors

“…The unique compositions, nonclosely packed structures, and good stretchability are the keys to these characteristics. Although mechanochromic PCs (MPCs) − based on nonclose-packing structures , have been widely investigated, however, most of them show negligible retroreflective colors. Both retroreflective and reflective structural colors have been used for visually sensing the strain of kinesio tapes and for anticounterfeiting (Figure b).…”