Diffraction Color Research Articles

Fourier Surfaces Reaching Full-Color Diffraction Limits.

Optical Fourier surfaces (OFSs), characterized by sinusoidally profiled diffractive optical elements, can outperform traditional binary-type counterparts by minimizing optical noise through selectively driving diffraction at desired frequencies. While scanning probe lithography (SPL), gray-scale electron beam lithography (EBL), and holographic inscriptions are effective for fabricating OFSs, achieving full-color diffractions at fundamental efficiency limits is challenging. Here, an integrated manufacturing process is presented, validated theoretically and experimentally, for fully transparent OFSs reaching the fundamental limit of diffraction efficiency. Leveraging holographic inscriptions and soft nanoimprinting, this approach effectively addresses challenges in conventional OFS manufacturing, enabling scalable production of noise-free and maximally efficient OFSs with record-high throughput (1010-1012 µm2h-1), surpassing SPL and EBL by 1010 times. Toward this end, a wafer-scale OFSs array is demonstrated consisting of full-color diffractive gratings, color graphics, and microlenses by the one-step nanoimprinting, which is readily compatible with rapid prototyping of OFSs even on curved panels, demanding for transformative optical devices such as augmented and virtual reality displays.

Synthesis of furan-based intramolecular donor–acceptor type chiral–electroactive polymers having optical activity, laser diffraction, and structural color functions

ABSTRACT A series of intramolecular donor–acceptor type monomers was polymerized in cholesteric liquid crystal (Ch-LC) electrolyte solution as a chiral liquid crystal molecular template with helical structure. The polymers thus obtained showing fingerprint pattern with iridescence via imprinting of Ch-LC medium were characterized by infrared spectroscopy, cyclic voltammetry, ultraviolet–visible spectroscopy, circular dichroism, scanning electron microscopy, polarizing microscopy, and reflectance spectroscopy to evaluate optical characters and structural color. The polymer showed optically active–electrochromism. The intramolecular donor–accepter type polymer has intermolecular chiral aggregation in the manner of Ch-LC by molecular form imprinting.

Characterization of Khaya Senegalensis Gum: Effects of Drying Methods on the Physicochemical Properties

The study was aimed to assess the effect of drying methods on physicochemical properties of Khaya senegalensis gum. Gum exudates obtained from the bark of Khaya senegalensis plant was extracted and subjected to freeze drying and vacuum oven drying. Gel permeation chromatography, Elemental analysis, attenuated total reflectance Fourier transforms Infra red spectroscopy were used to characterize the gum. The effect of drying methods on the gum samples were assessed based on Differential scanning calorimetry, Scanning electron microscopy, Dynamic vapour sorption, particle size analysis via laser diffraction techniques, colour and density measurements. An average molecular weight of 60 KDa expressed as the Dextran equivalent and a polydispersity of 2.17 with a retention time of 18,485 min was recorded for the vacuum dried gum. The vacuum dried gum occurred as irregular discreet coarse particles, containing both amorphous and crystalline portions due to a glass transition of 65◦ and melting temperature of 182.35◦C. It also displayed excellent flow and compressibility properties whereas the freeze-dried gum appeared flaky, porous with large surface area. The mechanism of water sorption was found to be initial surface adsorption and subsequently bulk absorption for both freeze dried and vacuum dried gum samples. The coarseness, water sorption and retention ability of the vacuum dried gum provides a potential for its use as a disintegrant in solid dosage formulations whereas the freeze-dried gum will be suitable for use as a binding agent due to its smaller particle sizes that enhanced solubility. Furthermore, the presence of nitrogen in Khaya senegalensis gum structure explains its partial solubility and the azo aromatic group suggests biodegradability and candidature for drug delivery to the colon. Keywords: Khaya senegalensis Gum; Average Molecular Weight; Amorphous; Crystalline; Direct Compression Excipient; Disintegrant 2 Freeze and vacuum dried Khaya senegalensis gum characterization

Synthesis of a magneto-chromatic tunable Fe3O4-HPAM colloid

Colloids of soft magnetic (Fe3O4) submicrometer particles, formed by magnetic nanoparticle clusters, coated with a polyelectrolyte (hydrolyzed polyacrylamide; HPAM) were fabricated successfully in situ with a highly controllable chemical approach. The formation mechanism of submicron particles was analyzed under the amounts of HPAM, urea, citrate, and metallic precursors. This mechanism was followed by SEM. The results showed that the physicochemical properties of the HPAM favored physical interactions with the reactants, promoting the formation of dense-packed magnetic micrometer clusters in one-step synthesis. The results showed that the physicochemical properties of the HPAM favored physical interactions with the reactants, promoting the formation of dense-packed magnetic micrometer clusters in one-step synthesis. The different estimated radii of these particles in solution (hydrodynamic and gyration) and dried (internal radius) decrease when the HPAM amount increases. Moreover, the particles exhibited a superparamagnetic behavior with a magnetization of 48.2 emu/g, 50.3 emu/g, and 54.3 emu/g when the amounts were 0.5 g, 1 g, and 2g of HPAM, respectively. Consequently, the optical response of the colloids to the application of a rotating magnetic field (RMF) parallel to the horizontal plane where they were located exhibited a behavior similar to photonic structures since their reflection spectrum showed a periodic diffraction color that closely matches the frequency of the RMF.

Deterministic rendering of structural color induced by atypical nano-gratings in ultra-precision diamond cutting

Ultra-precision diamond cutting (UPC) has been recently proposed for fast generation of nano-gratings to render diffractive structural color on various metallic surfaces. However, the complex nanoscale generation mechanism and atypical grating topography provide the significant challenges for deterministic rendering of structural color with standard representations. In this paper, an innovative diffraction prediction model is firstly proposed to describe the diffractive spectrum of atypical gratings under the full considerations of cutting process parameters, double working facets, material optical properties and environmental conditions. The standard CIE 1931 chromaticity diagram for grating-induced structural color is released for color gamut determination and optimization, where the color gamut range is defined by a novel concept of average saturation. The experimental results demonstrate the deterministic generation of three groups of nano-gratings with desired 3D topography, of which the measured angle-dependent diffractive spectrum and rendering color attributes show good agreements with theoretical results. Moreover, the new topography-modulation based strategies for achieving maximal color gamut and manipulating the ternary color attributes are clarified. The outcome of this paper lays the scientific foundations for deterministic rendering and performance enhancement of structural color enabled by UPC processes.

Light diffraction by sarcomeres produces iridescence in transmission in the transparent ghost catfish.

Despite the elaborate varieties of iridescent colors in biological species, most of them are reflective. Here we show the rainbow-like structural colors found in the ghost catfish (Kryptopterus vitreolus), which exist only in transmission. The fish shows flickering iridescence throughout the transparent body. The iridescence originates from the collective diffraction of light after passing through the periodic band structures of the sarcomeres inside the tightly stacked myofibril sheets, and the muscle fibers thus work as transmission gratings. The length of the sarcomeres varies from ~1 μm from the body neutral plane near the skeleton to ~2 μm next to the skin, and the iridescence of a live fish mainly results from the longer sarcomeres. The length of the sarcomere changes by ~80 nm as it relaxes and contracts, and the fish shows a quickly blinking dynamic diffraction pattern as it swims. While similar diffraction colors are also observed in thin slices of muscles from non-transparent species such as the white crucian carps, a transparent skin is required indeed to have such iridescence in live species. The ghost catfish skin is of a plywood structure of collagen fibrils, which allows more than 90% of the incident light to pass directly into the muscles and the diffracted light to exit the body. Our findings could also potentially explain the iridescence in other transparent aquatic species, including the eel larvae (Leptocephalus) and the icefishes (Salangidae).

Plasticizers' effect on pH indicator film based on starch and red grape skin extract for monitoring fish freshness

AbstractThis work aimed to develop a novel colorimetric indicator film from cassava starch, isomalt and glycerol with 20% wt.% of grape skin extract (GSE) by casting to be used as an indicator of fish freshness. The plasticizers were used in the concentration of 33% at five levels: 100/0, 70/30, 60/40, 50/50 and 0/100 (%w/w isomalt/glycerol). Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD) and RGB colour analysis showed the homogenous distribution of GSE in the starch matrix. The presence of GSE reduces the thermal stability, k1 value, solubility, swelling values and the %E and increases the tensile strength (TS), revealing its plasticizing potential action in the presence of isomalt. The influence of pH on the colours of the film containing GSE and its indicator activity were evaluated. The results showed that the film produced operates in a wide pH range, being an excellent candidate as an indicator for monitoring fish freshness.

Fungal Biodeterioration of a Historical Manuscript Dating Back to the 14th Century: An Insight into Various Fungal Strains and Their Enzymatic Activities.

This study aims to assess the deterioration aspects of a historical manuscript dating back to the 14th century that was deposited in the Library of the Arabic Language Academy, Cairo, Egypt. The study aims at the exploration of the role of various fungal strains that had colonized this deteriorated manuscript in its biodeterioration through their efficacy in the secretion of various hydrolytic enzymes. To evaluate the deterioration, various techniques, including visual inspection, attenuated total reflectance Fourier transform infrared (ATR-FTIR), scanning electron microscopy (SEM), X-Ray diffraction analysis (XRD), color change, and pH value, were utilized. The fungal strains linked to the historical document were isolated, identified, and evaluated for their deterioration activities. The findings demonstrate that the manuscript exhibits a variety of deterioration signs including color change, brittleness and weakness, erosion, and removal of the grain surface pattern in leather binding. According to the ATR-FTIR, the chemical composition of the historical paper and leather underwent some alterations. The historical paper has a lower level of cellulose crystallinity than the control sample. Penicillium chrysogenum (two isolates), P. citrinum (four isolates), Aspergillus ustus (three isolates), A. terreus (two isolates), A. chinensis (one isolate), Paecilomyces sp. (one isolate), and Induratia sp. (one isolate) were among the fourteen fungal strains identified as being associated with the historical manuscript. These fungal strains produced several hydrolytic enzymes with high activity, such as cellulase, amylase, gelatinase, and pectinase, which play a key role in biodegradation.

Designing 3D Polymeric Structures through Capillary Wetting on Colloidal Monolayer

AbstractColloidal lithography has provided a facile means to create regular micro‐ and nano‐patterns by employing colloidal crystals as masks. However, the patterns are usually restricted to 2D as most techniques do not exploit the spherical shape of colloidal masks. Here, 3D structures are designed by utilizing capillary wetting of liquified photoresists on colloidal monolayers of silica particles. The silica particles are anchored at planar air‐photoresist interfaces to have an equilibrium contact angle without interfacial deformation for thick polymer layers. By contrast, when the polymer layers are thin enough, they wet the colloidal monolayer by forming periodic wavy interfaces to provide a constant Laplace pressure. The photo‐crosslinking of the photoresist and subsequent removal of silica particles leave behind periodic nanostructures with 3D‐undulated surfaces. Importantly, the structure and waviness are further controllable by adjusting the polymer thickness relative to the particle radius. As the shape of the interface is determined by capillarity, the 3D structures are reproducible as long as the dimension is smaller than the capillary length. The use of photoresists enables the production of micropatterns of the periodic wavy structures by photolithography. As one of the potential applications, structurally‐colored patterns are demonstrated with enhanced plasmonic and diffraction colors.

Designing Multicolor Graphics of Plasmonic Metasurfaces through Gradual Protrusion of Particles at Free Interface

AbstractMetal nanostructures show plasmonic colors in the absence of pigments, which are promising for various optical applications. Colloidal lithography is one of the cost‐effective methods for a wide‐area production of plasmonic metasurfaces. However, it remains an important challenge to regioselectively control plasmonic property in a facile and reliable manner. Here, a novel strategy is reported to produce multicolor plasmonic graphics using the gradual protrusion of colloids at a water‐resin interface. Particles anchored at free interfaces slowly migrate toward the equilibrium position. Therefore, the degree of protrusion into the opposite phase is determined by the duration of aging. With this phenomenon, dimple arrays with controlled depths is produced by capturing the particles at the water‐resin interface through photopolymerization and removing the particles. Directional deposition of aluminum on the dimple arrays renders plasmonically colored surfaces, where the resonant wavelengths, or colors, vary with dimple depth. As the resin is regioselectively photocurable by ultraviolet irradiation through photomasks, plasmonic graphics can be produced. In addition, multi‐steps of regioselective photocuring with controlled durations of incubation produce multicolor graphics. The graphics show consistent plasmonic colors for specular reflection while displaying iridescent diffraction colors from hexagonal arrays of dimples for off‐specular conditions, enhancing the visibility of graphics.

Formulation and Evaluation of Biscuits from Functional Flour Mixture to enhance of antioxidants reflecting on nutrition in Patients

AbstractPatients are at risk of malnutrition as a result of their, disease and the treatment. Support and intervention Nutrition is important for those patients. The aim of this study was to formulate and evaluate types of biscuits formed from mixture of oat flour, wheat germ, flaxseed, pomegranate peel and wheat flour with different percentages for supporting nutrition for patients. Methods: by using :oat flour, wheat germ, flaxseed, pomegranate peel and wheat flour and their blends for production of biscuits from functional flour blend suitable for nutritional support for patients. Biscuit made of 100% wheat flour was prepared for control sample. For all chemical composition, starch gelatinization, diffraction scanning colorimetry (DSC), colour attributes and sensory properties of biscuits were studied. Oat flour was added to wheat flour at 10, 20, 30, 40 and 50% level. Results: Farinograph parameters showed that water absorption was increased as the percentage of oat flour increased in wheat flour. Diffraction Scanning Colorimetry and Visco-amylograph parameters were significantly affected. Results also showed that Hunter colour parameters (L*, a* & b*) of biscuits were darker as mixing level of oat flour increased, but sample which contained oat flour, wheat germ, flaxseed and Pomegranate peel had an excellent nutritional values and (good) acceptable characters that made it to be suitable for patients for support their nutritional defects due to the treatments( chemo & radiotherapy) with difficulty in having their nutritional requirements. It could be concluded that: oat flour + wheat germ+ flaxseed + Pomegranate peel could be used with wheat flour to formulate biscuit characterized with its good sensorial properties, higher nutritive value, in addition to their positive effect on the rheological characteristics.

High-harmonic diffractive lens color compensation.

Large diameter, high-harmonic diffractive lenses could find applications in future space telescopes. Residual chromatic aberrations from these lenses can cause significant blurring. Solutions to reduce chromatic dispersion and other aberrations to diffraction-limited performance are discussed. A design example based on a 240-mm-diameter, 1-m focal length multi-order diffractive engineered lens operating over the astronomical R-Band (589-727 nm) is presented. The design example uses a relay subsystem with four times smaller diameter than the primary. This color corrector includes both refractive and diffractive optical elements and reduces the longitudinal chromatic aberrations by more than a factor of 30 compared to the primary lens alone, while maintaining the effective focal length and numerical aperture of the system.

Computing the Bidirectional Scattering of a Microstructure Using Scalar Diffraction Theory and Path Tracing

AbstractMost models for bidirectional surface scattering by arbitrary explicitly defined microgeometry are either based on geometric optics and include multiple scattering but no diffraction effects or based on wave optics and include diffraction but no multiple scattering effects. The few exceptions to this tendency are based on rigorous solution of Maxwell's equations and are computationally intractable for surface microgeometries that are tens or hundreds of microns wide. We set up a measurement equation for combining results from single scattering scalar diffraction theory with multiple scattering geometric optics using Monte Carlo integration. Since we consider an arbitrary surface microgeometry, our method enables us to compute expected bidirectional scattering of the metasurfaces with increasingly smaller details seen more and more often in production. In addition, we can take a measured microstructure as input and, for example, compute the difference in bidirectional scattering between a desired surface and a produced surface. In effect, our model can account for both diffraction colors due to wavelength‐sized features in the microgeometry and brightening due to multiple scattering. We include scalar diffraction for refraction, and we verify that our model is reasonable by comparing with the rigorous solution for a microsurface with half ellipsoids.

Stretchable Biaxial and Shear Strain Sensors Using Diffractive Structural Colors

Structural colors that can be changed dynamically, using either plasmonic nanostructures or photonic crystals, are rapidly emerging research areas for stretchable sensors. Despite the wide applications of various techniques to achieve strain-responsive structural colors, important factors in the feasibility of strain sensors-such as their sensing mechanism, stability, and reproducibility-have not yet been explored. Here, we introduce a stretchable, diffractive, color-based wireless strain sensor that can measure strain using the entire visible spectrum, based on an array of cone-shaped nanostructures on the surface of an elastomeric substrate. By stretching or compressing the substrate, the diffractive color can be tuned according to the changing grating pitch. Using the proposed method, we designed three types of strain-sensing modes: large-deformation (maximum 100%) tensile strain, biaxial 2D strain, and shear strain (maximum 78%). The strain sensors were fabricated, and applicability to strain-sensing was evaluated.

Highly sensitive α-amanitin sensor based on molecularly imprinted photonic crystals

α-amanitin is the most toxic amanita in mushrooms with lethal dose to humans around 0.1 mg. Kg−1. Hence, early identification of the poison would improve survival rates and prevent lethal poisoning cases. In this study, molecularly imprinted photonic crystal (MIPC) sensor was prepared by combining molecular imprinting with photonic crystal templates and tested towards the detection of α-amanitin. In this process, synthesized moiety of α–amanitin was utilized as template, dispersed SiO2 colloidal photonic crystal as carrier, methacrylic acid (MAA) as functional monomer, and ethylene glycol dimethacrylate (EDGMA) as crosslinker. The adsorption behavior of MIPC towards α-amanitin in ethanol solution showed shifts in diffraction peaks of MIPC upon binding with α-amanitin molecules. The reflection peak wavelength varied linearly with α-amanitin concentration according to the correlation formula: λ = 15.417c+489.17 (R2 = 0.9985). The recognition process was accompanied by gradual color change in MIPC film. The prepared MIPC sensor possessed wide linear range (10−9–10−3 mg L−1), change in visual color, low detection limit (10−10 mg L−1), short response time (2 min), and good reusability. The MIPC film was then tested towards the detection of α-amanitin in real biological samples (mushroom, urine, and serum) and showed reasonable shift in diffraction peaks and color change upon soaking in solutions spiked with α-amanitin at 10−6 mg L−1 and 10−3 mg L−1, suggesting the suitability of the film for the rapid identification of α-amanitin in complex sample matrices. Overall, the proposed sensor looks promising for the rapid identification of α-amanitin in clinical analysis and food poisoning.

Recovery Behavior of Microstructured Thiol-Ene Shape-Memory Film

In this work, surface microstructurization was coupled with shape-memory polymer to generate reversibly tunable surface properties. A photopolymerizable thiol-ene composition comprising a mixture of pentaerythritol tetrakis(3-mercaptopropionate) (PETMP), 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TTT) and 2,2-dimethoxy-2-phenylacetophenone (DMPA) was used to prepare microstructured thiol-ene shape-memory film via casting and UV polymerization on the electron beam lithography fabricated arrays of 1 µm and 2 µm square pits. The mechanical deformation via compression and recovery of the surface microstructure were investigated. Results show that, after heat treatment of the deformed thiol-ene film, the recovery yields for microstructures were not worse than 90% ± 2% and 93% ± 2% for structures imprinted with 1 µm and 2 µm square pit micro imprint stamps. Additionally, heat treatment of deformed thiol-ene film resulted in the recovery of intense diffraction colors and laser diffraction patterns. This study opens up an avenue of incorporating microstructured shape-memory films for new products, e.g., optical security devices, superhydrophobic coatings, medical diagnostics and biosensors.

2D Au Nanosphere Arrays/PVA-PBA-Modified-Hydrogel Composite Film for Glucose Detection with Strong Diffraction Intensity and Linear Response.

A novel glucose sensor was reported that consisted of two-dimensional (2D) Au nanosphere arrays and glucose-responsive hydrogel film. This sensor exhibited an intense diffraction signal and an obvious diffraction color on a quartz slide due to the strong diffraction intensity of the Au nanosphere arrays. Thus, glucose was detected via the variation of diffraction wavelength and diffraction color, without a high reflective mirror. In addition, by introducing poly(vinyl alcohol) (PVA) to crosslink the phenylboronic acid (PBA)-modified hydrogel film, the diffraction wavelength of the 2D Au nanosphere arrays/hydrogel composite film shifted in the same direction in high ionic strength condition. In particular, it showed a nearly linear red-shift when the glucose concentration increased from 0 mM to 20 mM. Moreover, this glucose sensor displayed good reproducibility. The nearly linear response and good reproducibility were highly helpful for improving practical application of this glucose sensor.

Instantaneous Magnetically Assembled and Hydrophilic Photonic Crystals with Controlled Diffraction Colors

The time-consuming assembling process of the traditional photonic crystals (PCs) and non-water-dispersibility of the reported magnetic responsive PCs (MRPCs) have greatly limited the application especially in the biotechnological fields. Herein, the hydrophilic and size-controllable Fe3O4@poly(4-styrenesulfonic acid-co-maleic acid) (PSSMA)@SiO2 MRPCs were fabricated by orderly assembling of the core–shell colloidal nanocrystal clusters via a two-step facile synthesis approach. Due to the rich carboxyl and hydroxyl groups of PSSMA, the obtained MRPCs have excellent properties of hydrophilicity, high surface charge which presented magnetically tunable photonic structural colors, and rapid reflection signal in aqueous solution under external magnetic field within 1 s. The diffraction color of the MRPCs in the entire visible range could be tuned by adjusting the magnetic strength or the nanoparticle size, which bring a clear change of the structure color from brilliant red to modena by the naked eye. Thus, th...

Microwave-assisted processing of cobalt aluminate blue nano-ceramic pigment using sol–gel method

In the present research, CoAl2O4 nano-pigment powder was synthesized by a combination of citrate–gel processing and microwave-assisted heating route. Blue CoAl2O4 ceramic nano-pigment was rapidly obtained after calcination in microwave oven. Thermal decomposition behavior of the as-synthesized precursor was monitored by DTA/TGA (differential thermal analysis/thermo-gravimetric analysis). The effects of various microwave exposure times (8–15 min) on the phase composition and difference in color were evaluated through X-ray diffraction (XRD) and CIE Lab color space system, respectively. The mean crystallite size of blue nano-pigment powders was determined by the X-ray line broadening technique. The optimum time of pigment processing by utilizing microwave oven was obtained at 15 min to get a sufficiently intense blue color. Scanning electron microscopy (SEM) and field emission SEM (FE-SEM) characterizations were employed to observe the size and morphology of optimum powder particles. Particles size analysis by SEM indicated that the majority of quasi-spherical particles have a small size in the range of nano which was in agreement with XRD results, while FE-SEM studies confirmed flower-like morphology of as-prepared powder.

First observation of 5DJ (J=1, 2, 3) emission transitions in Eu3+-activated rare-earth antimony garnet R3Sb5O12 (R=Y, Gd, La)

R2.9Eu0.1Sb5O12 (R=Y, Gd, La) polycrystalline powders were prepared by solid-state reaction and characterized by X-ray powder diffraction (XRD), photoluminescence, decay lifetimes, and CIE color coordinates. The phosphors can be efficiently excited by UV-light and presents the emission covering the entire visible spectrum. Except for the commonly reported 5D0–7F0,1,2,3,4 transitions of Eu3+ ions in R2.9Eu0.1Sb5O12 (R=Y, La), higher 5D1,2,3 states present stronger emission lines. This produces white emission in the single-phased phosphor, whereas R2.9Eu0.1Sb5O12 (R=Gd) shows orange emission due to the absence of 5D3,2 transitions. The emission mechanism from the high-energy levels of 5D1,2,3 Eu3+ ion in R2.9Eu0.1Sb5O12 (R=Y, Gd, La) phosphors is also discussed.