Subtractive Structural Modification of Morpho Butterfly Wings

Different from studies of butterfly wings through additive modification, this work for the first time studies the property change of butterfly wings through subtractive modification using oxygen plasma etching. The controlled modification of butterfly wings through such subtractive process results in gradual change of the optical properties, and helps the further understanding of structural optimization through natural evolution. The brilliant color of Morpho butterfly wings is originated from the hierarchical nanostructure on the wing scales. Such nanoarchitecture has attracted a lot of research effort, including the study of its optical properties, its potential use in sensing and infrared imaging, and also the use of such structure as template for the fabrication of high‐performance photocatalytic materials. The controlled subtractive processes provide a new path to modify such nanoarchitecture and its optical property. Distinct from previous studies on the optical property of the Morpho wing structure, this study provides additional experimental evidence for the origination of the optical property of the natural butterfly wing scales. The study also offers a facile approach to generate new 3D nanostructures using butterfly wings as the templates and may lead to simpler structure models for large‐scale man‐made structures than those offered by original butterfly wings.     

Optical properties of SiO2 and ZnO nanostructured replicas of butterfly wing scales

SiO₂ and ZnO inverse structure replicas have been synthesized using butterfly wings as templates. The laser diffraction performance of the SiO₂ inverse structure replica was investigated and it was found that the zero-order light spot split into a matrix pattern when the distance between the screen and the sample was increased. This unique diffraction phenomenon is closely related to the structure of the SiO₂ inverse structure replica. On the other hand, by analyzing the photoluminescence spectrum of the ZnO replica, optical anisotropy in the ultraviolet band was demonstrated for this material.      

Cardiomyocytes‐Actuated Morpho Butterfly Wings

Morpho butterflies are famous for their wings' brilliant structural colors arising from periodic nanostructures, which show great potential value for fundamental research and practical applications. Here, a novel cellular mechanical visualizable biosensor formed by assembling engineered cardiac tissues on the Morpho butterfly wings is presented. The assembled cardiomyocytes benefit from the periodic parallel nanoridges of the wings and can recover their autonomic beating ability with guided cellular orientation and good contraction performance. As the beating processes are accompanied by the cardiomyocytes' elongation and contraction, the elastic butterfly wing substrate undergoes the same cycle of deformations, which causes corresponding synchronous shifts in their structural colors and photonic bandgaps for self‐reporting of the cell mechanics. It is demonstrated that this self‐reporting performance can be further improved by adding oriented carbon nanotubes in the nanoridges of the wings for the culture. In addition, taking advantage of the similar size of the cardiomyocyte and a single Morpho wing scale, the investigation of single‐cell‐level mechanics can be realized by detecting the optical performance of a single scale. These remarkable properties make these butterfly wings ideal platforms for biomedical research.     

Photonic crystals with tunable optical stop band through monodispersed silica–polypyrrole core-shell spheres

We prepared monodispersed silica–polypyrrole core-shell spheres (SiO₂–Ppy) using adsorbed surfactant bilayers on silica as templates and demonstrated the construction of photonic crystal with tunable stop band from SiO₂–Ppy core-shell spheres. Since the photonic stop band is very dependent on the refractive index, it can be tuned by simply changing the refractive index of Ppy shell via changing doping level. In fact, the stop band was shifted about 15 nm when the photonic crystal was exposed to fuming sulfuric acid due to the change of the doping level of Ppy shell.     

Replication of butterfly wing in TiO2 with ordered mesopores assembled inside for light harvesting

The replication of butterfly wing in TiO2 with ordered mesopores assembled inside in situ was prepared by the method of ultrasonication and then calcination. The resultant replica presents high surface area, excellent light absorbance in visible range of 400-500 nm and a narrowest band-gap at 2.94 eV in comparison with TiO2 replica without ordered mesopores and commercial TiO2 powder, attributing to the combination of the functionality from the inorganic oxide and the fine hierarchical biological structures and well-distributed mesopores. The facile method is expected to be used for mass product of TiO2 replicas from butterfly wings for potential application in Dye-Sensitized Solar Cells.     

Crystallization and morphology of mordenite zeolite influenced by various parameters in organic-free synthesis

A series of mordenite zeolites with different morphologies were synthesized via a facile organic-free hydrothermal route, and characterized by X-ray diffraction, scanning electron microscopy, X-ray fluorescence spectrometer and N₂ adsorption-desorption techniques. Influences of synthetic parameters, including seed crystal, silicon precursor, SiO₂/Al₂O₃, Na₂O/SiO₂ and H₂O/SiO₂, on mordenite crystallization were investigated systematically. It was found that mordenite zeolites with various morphologies, such as fiber-like, rod-like, prism-like and needle-like ones could be synthesized in control. Especially, novel nano fiber-like MOR crystals with high c/b aspect ratio were prepared from low silica concentration system, which was manipulated by using small initial SiO₂/Al₂O₃ ratio, large H₂O/SiO₂ and silicon source with slow dissolution rate. Moreover, mordenite samples with various morphologies exhibited different mesopore property and thermal stability.     

High efficiency solution infiltration routes to thin films with photonic properties

A chemical bath deposition (CBD) method has been developed to prepare three-dimensionally-ordered macroporous films of CdS and TiO₂, using colloidal crystals as templates. A series of sequential, short infill/rinse/anneal steps are employed to effect complete infiltration of SiO₂ (opal) thin films with CdS or TiO₂. Removal of templates allows fabrication of macroporous inverse replica structures that exhibit periodic modulation of dielectric behaviour and have potential for use in photonic applications. A study of the photonic properties of films indicates that the multi-step CBD method is a useful approach for infiltration of opal interstices.     

Dual gratings interspersed on a single butterfly scale

Iridescent butterfly wing colours result from the interaction of light with sub-micrometre structures in the scales. Typically, one scale contains one such photonic structure that produces a single iridescent signal. Here, however, we show how the dorsal wings of male Lamprolenis nitida emit two independent signals from two separate photonic structures in the same scale. Multiple independent signals from separate photonic structures within the same sub-micrometre device are currently unknown in animals. However, they would serve to increase the complexity and specificity of the optical signature, enhancing the information conveyed. This could be important during intrasexual encounters, in which iridescent male wing colours are employed as threat displays. Blazed diffraction gratings, like those found in L. nitida, are asymmetric photonic structures and drive most of the incident light into one diffraction order. Similar gratings are used in spectrometers, limiting the spectral range over which the spectrometer functions. By incorporating two interchangeable gratings onto a single structure, as they are in L. nitida, the functional range of spectrometers could be extended.     

Formation of Si nanocrystals utilizing a Au nanoscale island etching mask

Si nanocrystals were formed by using a Au nanoscale island etching mask. A high-resolution transmission electron microscopy image showed that the Si nanocrystals were created on a SiO_x layer, and the luminescence peak related to Si nanocrystals was observed in the cathodoluminescence spectrum. Capacitance-voltage measurements demonstrate a metal-insulator-semiconductor behavior with a flatband voltage shift for the Al/SiO₂/nanocrystalline Si/SiO₂/p-Si structures, indicative of the existence of the Si nanocrystals embedded into the SiO_x layer. These results indicate that Si nanocrystals embedded into the SiO_x layer can be formed by using a Au island etching mask.     

Synthesis of magnetically separable Sn doped magnetite/silica core-shell structure and photocatalytic property

Sn doped Fe₃O₄/SiO₂ core-shell structures with the magnetic and photocatalytic properties have been successfully synthesized using Fe₃O₄ microspheres as the precursor. The morphology, phase and structure of the bifunctional products were investigated by X-ray powder diffraction, transmission electron microscopy, selected-area electron diffraction, high-resolution transmission electron microscopy, energy dispersive spectroscopy, and scanning electron microscopy. The effects of the amount and hydrolysis rate of tetraethyl orthosilicate on the preparation of the Fe₃O₄/SiO₂ core-shell structures were investigated. Low concentration and slow hydrolysis rate of tetraethyl orthosilicate were useful to obtain the uniform silica coated Fe₃O₄. The magnetic measurements indicated that the Sn doped Fe₃O₄/SiO₂ core-shell structures showed ferromagnetic property and the magnetic saturation value slightly decreased after coated the silica layer. The magnetic Sn doped Fe₃O₄/SiO₂ core-shell structures exhibited good photocatalytic activity in the degradation of methyl orange and could be separated by applying an appropriate magnetic field.     

Synthesis of Fe3O4/SiO2/Polypyrrole magnetic nanocomposite polymer powder: Investigation of structural properties and ability to purify of edible sea salts

In this study, Fe₃O₄/SiO₂/polypyrrole magnetic nanocomposite polymer powder was chemically synthesized. The structure of the prepared composite powders were studied using scanning electron microscopy, FTIR and XRD techniques. The results showed that the prepared composites have a nanometer structure. The FTIR results confirmed the electrostatic interactions between the composite components. XRD also showed the crystal structure of Fe₃O₄ and its composites. Optimal nanocomposite powder was used to purify the salt of Lake Urmia. Salt samples were treated with powder and the chemical properties of salt were investigated before and after treatment. Qualitative tests performed on salt included COD, BOD, organic compounds, heavy metals, nitrate and nitrite, and color characteristics. Finally, the efficiency of the nanoparticle powder in the lake salt treatment was calculated. The results showed that the composite powder reduced BOD and COD as well as the heavy metal salts of the lake. Also, the organic compounds in the salt decreased and the color factors such as the white index of the salt increased. Under optimal conditions, Fe₃O₄/SiO₂/PPy composite showed the best performance at 37 min of purification time. In general, Fe₃O₄/SiO₂/PPy composite can be easily used to purify sea salts and also reduce environmental pollutants.     

Biomimetic fabrication of α-Fe2O3 with hierarchical structures as H2S Sensor

A facile sol–gel method is developed for the fabrication of α-Fe₂O₃ with quasi-honeycomb like structures inherited from Papilio paris butterfly wings. The exquisite hierarchical architecture is faithfully maintained in α-Fe₂O₃ from the skeleton of butterfly wings at the levels from macro to nano-scales. When used as a chemical sensor, the obtained α-Fe₂O₃ replica (P-α-Fe₂O₃) showed a much higher performance than that of the compared α-Fe₂O₃ nanoparticles synthesized under the same condition without biotemplate (S-α-Fe₂O₃). The P-α-Fe₂O₃-based sensor has a sensitivity of 19.2–50 ppm H₂S, which is four times more than that of S-α-Fe₂O₃, accompanied by a rapid response/recovery time within 1/10 s even at a relatively low working temperature of 180 °C. Compare to the S-α-Fe₂O₃, surface area of which cannot be detectable, the high sensing feature of P-α-Fe₂O₃ would be attributed to the relatively high-specific surface area 24.12 m²/g thus fabricated together with the unique 3D-network structures, which provide channel for the diffusion of H₂S. This strategy is expected to be used in fabrication of other kinds of metal oxide with unique structures for the potential application in gas sensor.     

Optimization of crystal growth of hierarchical porosity ZSM-5 zeolite based on coal fly ash “waste utilization”

In this study, ZSM-5 zeolite with hierarchical porosity structure was synthesized by hydrothermal method using Al(OH)₃, SiO₂ extracted from coal fly ash as aluminum source and silicon source. The optimal synthesis parameters of ZSM-5 zeolite were determined via an orthogonal analysis table. The optimum synthesis conditions were: SiO₂/Al₂O₃/Na₂O/hexadecyltrimethylammonium bromide/tetrapropyl ammonium bromide/H₂O = 1/0.08/0.25/0.05/0.17/50, and the optimum crystallization temperature and crystallization time were 160 °C and 48 h, respectively. Scanning electron microscopy showed that the synthesized ZSM-5 zeolite exhibited a spherical shape. Nitrogen adsorption-desorption and Brunauer-Emmett-Teller measurement analysis displayed that the best sample ZSM-5 molecular sieve showed a typical type IV isotherm, and the micropores and mesopores coexisted in the sample, indicating the successful preparation of ZSM-5 zeolite with hierarchical porosity structure. The crystal growth of ZSM-5 under different hydrothermal conditions follows the “S” adjustment.     

Comprehensive analysis of retroreflection in Papilio crino Fabricius, 1792 wings

Multilayer thin‐film structures in the wings of a butterfly; Papilio crino produce a colourful iridescence from reflected light. In this investigation, scanning electron microscope images show both the concave cover scales and pigmented air‐chamber ground scales. The microstructures with the concavities retroreflect incident light, thus causing the double reflection. This gives rise to both the colour mixing and polarisation conversion clearly depicted in the optical images. The result of the numerical and theoretical analysis via the CIELAB, and optical reflection and transmission of light through the multilayer stacks with the use of transfer method show that the emerging colouration on the Papilio crino is structural and is due to the combination of colours caused by multiple bounces within the concavities. The butterfly wing structure can be used as the template for designing the photonic device.Inspec keywords: bio‐optics, scanning electron microscopy, photodiodes, optical sensors, optical images, light reflection, reflectivity, colour, optical links, multilayers, optical multilayers, light polarisationOther keywords: pigmented air‐chamber ground scales, concavities, incident light, double reflection, colour mixing, polarisation conversion, optical images, numerical analysis, theoretical analysis, optical reflection, multilayer stacks, emerging colouration, butterfly wing structure, papilio crino fabricius, thin‐film structures, colourful iridescence, reflected light, electron microscope images, concave cover scales     

Hopping conduction on PPy/SiO2 nanocomposites obtained via in situ emulsion polymerization

This work describes the preparation and electrical characterization of conducting polypyrrole (PPy) and silica nanocomposites. Four samples were investigated: (i) pure PPy, (ii) PPy-covered SiO₂ spherical nanoparticles, (iii) PPy-covered SiO₂ spherical nanoparticles modified with 3-aminopropyltriethoxysilane (APS), and (iv) PPy-covered SiO₂ fibers. Structural characterization was made by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrical conductivity was measured from 80 K to 300 K and three-dimensional variable range hopping conduction was observed. From the hopping parameter the mean hopping distance was obtained as well as the density of active center and the energy associated with it.     

The preparation of TiO2/SiO2 composite hollow spheres with hydrophobic inner surface and their application in controlled release

The TiO₂/SiO₂ composite hollow spheres (CHSs) with hydrophobic inner surface have been successfully synthesized by using carboxyl-functionalized polystyrene spheres as templates. The inner titania shell was selectively modified with stearic acid (SA). The morphologies, structures, drug loading amounts and release rates were characterized and investigated by SEM, TEM, XRD, N₂ adsorption-desorption isotherms, FT-IR, TG and HPLC analysis. Due to the hydrophobic interaction, the modified inner surface slowdown the release of the hydrophobic drug into the aqueous environment. The SA modified CHSs displayed higher drug loading amounts as well as lower release rates than that of unmodified spheres. The studies demonstrate that composite hollow spheres are promising for the multifunctional controlled release.     

蝶翅构型TiO2/等离子体纳米金复合体系全光谱二氧化碳光还原特性研究

以红珠灰蝶为生物模板,使用原子层沉积法构筑三维构型TiO_2光催化材料以增强其光捕获能力;使用种子生长法制备具有宽幅可见光波段吸收能力的等离子体共振金纳米棱结构,并将其负载于蝶翅构型TiO_2上以得到全光谱响应的复合光催化体系;采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、紫外-可见分光光度计、X射线衍射仪(XRD)等表征了所制备的样品;对样品进行了二氧化碳还原性能测试,结果表明在全光谱照射下,负载有金纳米棱的蝶翅构型TiO_2的二氧化碳光还原性能比无结构的提升了54%。     

Formation of silica nanotubes with spring-like pore channels in the walls

A chiral low-molecular-weight amphiphile, l-16Val6PyBr, was synthesized from l-valine, which can cause physical gels in water, benzene and nitrobenzene. Silica nanotubes with spring-like pore channels in the walls were prepared using the self-assemblies of it as templates via a single-templating approach. The morphologies and pore architectures of the silica nanotubes were studied using transmission electron microscopy (TEM), field-emission scanning electron microscopy, powder X-ray diffraction and N₂ sorptions. The TEM images taken after different reaction times indicated a cooperation mechanism. Moreover, nanoworms with concentric circular pore channels and nanoflakes with vertical pore channels were prepared by changing the concentration of the catalyst.     

Three-dimensional (3D) sea-urchin-like hierarchical TiO2 microspheres: growth mechanism and highly enhanced photocatalytic activity

Three-dimensional (3D) sea-urchin-like hierarchical TiO₂ microspheres were synthesized by a template-free hydrothermal method. The effects of preparation parameters on the microstructure of 3D sea-urchin-like hierarchical TiO₂ were investigated using scanning electron microscopy (SEM), transmission electron microscopy, X-ray diffractometer, energy-dispersive X-ray spectrometer and Brunauer–Emmett–Teller technologies. The growth mechanism and photocatalytic activity of 3D sea-urchin-like TiO₂ microspheres were discussed. The results of electron microscopy characterizations SEM showed that the microspheres were consisted of numerous one-dimensional (1D) nanorods. A three-step growth model: oxygenated to be 1D nanorods, self-assembly and protonation, was proposed to illustrate the growth mechanism of sea-urchin-like structures. The synthesized 3D sea-urchin-like hierarchical TiO₂ microspheres exhibited a better photocatalytic activity for photodegradation of rhodamine B under sunlight irradiation compared to that of P25, which was attributed to the special 3D hierarchical nanostructure, the increased number of surface active sites and anatase crystal structure.     

Synthesis of the uniform hollow spherical Sr2SiO4:Eu2+ phosphors via an h-BN protective method

The uniform hollow spherical Sr₂SiO₄:Eu²⁺ green emitting phosphors have been successfully synthesized using hollow silica spheres as templates by an h-BN protective method. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results directly confirmed the existence of the hollow spherical structure with a narrow size distribution and a shell thickness of 15–25 nm. The h-BN protective film, observed by high resolution TEM, plays an important role in the formation of the hollow spherical morphology and the improvement of photoluminescence properties. Comparing with the Sr₂SiO₄:Eu²⁺ micron-phosphor prepared by the traditional solid state reaction method, the hollow spherical phosphor with nano-sized grains exhibits stronger green emission under ultraviolet–blue light excitation. This could be attributed to the elimination of surface defects by the h-BN coating. This research gives an economic and convenient way to synthesize uniform spherical phosphors with high quantum efficiency.