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Bio-Inspired Structural Colors based on Linear Ultra-High Molecular Weight Block Copolymers
摘要： Ultra-high molecular weight (UHMW) block copolymers (BCPs) are promising candidates for the fabrication of photonic materials. Here, we demonstrate the synthesis and self-assembly capability of well-defined amphiphilic UHMW BCPs with overall molar masses up to 4432 kg mol-1 obtained via living anionic polymerization. BCP micelles featuring hydrodynamic diameters in the range of the wavelength of the visible light to the near infrared region (300-1143 nm) are used for colloidal crystal formation. By varying the BCP composition brilliant structural colours can be observed. Microphase separation of the UHMW BCPs in the bulk state reveals uniform domains and showing blue to green structural color transitions. Finally, we provide examples of how BCP structural control can be used to generate reversibly switchable solvatochromatic optical sensors.
关键词： morphology,block copolymers,structural colors,self-assembly,anionic polymerization,micellar photonic crystals,photonic materials
更新于2025-09-23 15:23:52
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Narrow Linewidth and Temperature Insensitive Blue Phase Liquid Crystal Films
摘要： Blue phase liquid crystal ?lms are quite useful in re?ective displays, ?exible photonic devices, and optical sensors. However, the effects of refractive index properties of re?lled liquid crystals and environment temperature on re?ection properties of blue phase liquid crystal ?lms are far from fully exploration. Herein, we demonstrate blue phase liquid crystal ?lms re?lled with different nematic liquid crystals. The effects of birefringence and average refractive index of re?lled nematic liquid crystals on the re?ection properties such as re?ectance, central wavelength, and linewidth of photonic band have been studies. The temperature effect on re?ectance and central wavelength has been studied. A narrow linewidth (19.4 nm) and temperature insensitivity blue phase liquid crystal ?lm has been fabricated by re?lling liquid crystals of DYX8013 with small birefringence. The narrow linewidth and excellent temperature insensitivity properties of BPLC ?lm can be applied in color re?ective display and ?exible photonic devices.
关键词： Photonic materials,photonic crystals
更新于2025-09-23 15:21:21
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Designing photonic materials with complete band gaps by topology optimization
摘要： Photonic materials may exhibit the propagation of electromagnetic waves is totally prohibited. To achieve a complete photonic band gap (CPBG) for transverse magnetic (TM) and transverse electric (TE) modes, the bi-directional evolutionary structure optimization (BESO) method originated from structural design is extended for this purpose. The optimization problem is formulated with maximizing the minimum imaginary part of complex wave vectors for TM and TE modes. According to sensitivity analysis, the material distribution within the primitive unit cell of photonic materials is adjusted step by step so as to enlarge the minimum imaginary part of wave vectors. In doing so, the CPBG at the specific frequency is obtained at the desired frequency, and the optimized structures of photonic materials with novel topological patterns are achieved. Numerical examples demonstrate that the effectiveness of the proposed topology optimization method for opening the CPBGs at various specified frequencies, which is of significance in controlling the propagation of electromagnetic waves of any polarization.
关键词： Topology optimization,Complete band gap,Evanescent waves,Photonic materials
更新于2025-09-23 15:21:01
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Photonic materials for high-temperature applications: Synthesis and characterization by X-ray ptychographic tomography
摘要： Photonic materials for high-temperature applications need to withstand temperatures usually higher than 1000 ?C, whilst keeping their function. When exposed to high temperatures, such nanostructured materials are prone to detrimental morphological changes, however the structure evolution pathway of photonic materials and its correlation with the loss of material’s function is not yet fully understood. Here we use high-resolution ptychographic X-ray computed tomography (PXCT) and scanning electron microscopy (SEM) to investigate the structural changes in mullite inverse opal photonic crystals produced by a very-low-temperature (95 ?C) atomic layer deposition (ALD) super-cycle process. The 3D structural changes caused by the high-temperature exposure were quantified and associated with the distinct structural features of the ceramic photonic crystals. Other than observed in photonic crystals produced via powder colloidal suspensions or sol-gel infiltration, at high temperatures of 1400 ?C we detected a mass transport direction from the nano pores to the shells. We relate these different structure evolution pathways to the presence of hollow vertexes in our ALD-based inverse opal photonic crystals. Although the periodically ordered structure is distorted after sintering, the mullite inverse opal photonic crystal presents a photonic stopgap even after heat treatment at 1400 ?C for 100 h.
关键词： Ptychography X-ray computed tomography,High-temperature applications,3D image analysis,Photonic materials,Low-temperature atomic layer deposition
更新于2025-09-23 15:21:01
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Modular Nanocomposite Films with Tunable Physical Organization of Cellulose Nanocrystals for Photonic Encryption
摘要： Reported herein is the novel achievement of uniform and tunable interference colors of nanocomposite films containing organized cellulose nanocrystals (CNCs) from dynamic hydrogel precursors. Homogeneous and amendable interference colors with broad range are obtained either by stacking the nanocomposite films to adjust the amount of CNCs in the propagation pathway of light or by regulating the rotation angles between the individual films to alter the relative organization of CNCs within the system. Moreover, the precise and controllable patterned CNC composite films with multicolors in one film are facilely fabricated for the first time from the patterned hydrogel precursors. Based on this stacking/rotation-method, these patterned nanocomposite films with tunable interference colors can be further applied as fundamental elements for optical encryption by establishing a ternary-coded decimal system with encoded decimal numerals, paving the way for the development of photonic functional materials based on CNCs.
关键词： nanocomposites,interference colors,cellulose nanocrystals,photonic materials,encryption
更新于2025-09-23 15:19:57
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Dislocation density level induced divergence between stress-free afterglow and mechanoluminescence in SrAl2O4: Eu2+, Dy3+
摘要： In this paper, we report on a new photonic behavior based on a series of photoluminescence and mechanoluminescence experiments conducted on Strontium aluminate (SrAl2O4) (SAO) co-doped with lanthanide ions such as Eu2+ (europium ion) and Dy3+ (dysprosium ion) (SAOED). It was observed that the increase of the dislocation density in SAOED decreased its stress-free afterglow while increasing its mechanoluminescence (ML). The dissimilar behavior between these two properties is yet to be reported in literature. We observed that as the lattice strain increased, the light intensity change ratio (LICR) during an applied exogenous tensile force increased while the stress-free afterglow decreased. As the crystallite size decreased, the LICR increased while the stress-free afterglow decreased. All the aforementioned observations resulted in the introduction of a newly joint stress-free afterglow-ML mechanism where the interstitial vacancy in the SAO host lattice should be taken in consideration. Based on the trap-depth reduction model, we derived a LICR expression and predicted the current ML behavior as well for other photonic materials. The fundamental findings presented in this work will drastically change the paradigm of mechanoluminescent material design and pave the way for the full development of this technology.
关键词： Dislocation,Stress sensor,Mechanoluminescence,Photonic materials,Photoluminescence
更新于2025-09-10 09:29:36