Inverse Face‐Centered Cubic Thin Film Photonic Crystals

Recent work on a technique for fabricating inverse fcc photonic crystals from a colloidal system of monodisperse microspheres and titania nanoparticles is described. The technique can be used to produce photonic crystals with other background materials that are available as nanoparticles. The Figure shows the Moiré pattern of a typical photonic crystal sample.     

Tunable photonic nanojet achieved using a core–shell microcylinder with nematic liquid crystal

A tunable photonic nanojet achieved using a core–shell microcylinder with nematic liquid crystal is reported. The core–shell microcylinder can be obtained by the infiltration of liquid crystal into the air core of a microcylinder. The refractive indices of the liquid crystals can be changed by rotating the directors of the liquid crystals. Therefore, we were able to control the flow direction of the photonic nanojet in two-dimensional core–shell microcylinder structures. Using high resolution finite-difference time-domain simulation, we demonstrate that the photonic nanojet can be continuously tuned in the core–shell microcylinder. The horizontal and vertical shifts of photonic nanojet depend strongly on the director of the liquid crystals. Such a mechanism of nanojet adjustment should open up a new application for using visible light to detect nanoparticles, optical gratings, and single molecules with subwavelength spatial resolution.     

Near-field photonic forces

A review of recent advancements in photonic forces is presented. We discuss in detail the interaction of light and sub-wavelength particles on a substrate illuminated by total internal reflection, and we study the optical forces experienced by the particles. The effects of plasmon-mode excitations on the resulting photonic forces on metallic particles are also addressed. Moreover, we explore the possibility of using the metallic tip of a classical apertureless microscope to create optical tweezers, and thus to achieve a selective manipulation of nanoparticles.     

LED-excited emission of opal loaded with silver nanoparticles

The emission spectra of opal photonic crystals loaded with silver nanoparticles have been measured under UV excitation. The spectra are found to markedly differ from the spectrum of plain (uninfiltrated) opal: silver nanoparticles give rise to an extra, long-wavelength emission band and change the shape of the spectrum. We have calculated the dispersion laws for the two lower photon branches and the corresponding dependences of the refractive index on frequency for the plain and silver-infiltrated photonic crystals.     

Embedment of ZnO nanoparticles in the natural photonic crystals within peacock feathers

Inspired by the embedment of emission species in synthetic photonic crystals to display novel optical properties, the natural photonic crystals within peacock feathers are chosen as the matrix to embed ZnO nanoparticles through an in situ approach. Peacock feathers function as the supporting substrate and provide reactive sites for the in situ synthesis of hexagonal ZnO nanoparticles. Herein, ZnO nanoparticles exhibit photoluminescence in the visible range and are supposed to be tailored by the peacock feather, having potential applications in optoelectronics and optical communications.     

Photoluminescence and energy transfer investigation from SiO2: Tb,Au inverse opals to rhodamine-B dyes

Energy transfer has attracted extensive attention due to its widespread applications in medical diagnostics, DNA analysis and lighting devices. There are few reports on the energy transfer from rare earth ions to dyes. In the present work, the SiO₂:Tb inverse opals with and without Au nanoparticles were prepared, and the organic rhodamine-B (RhB) dyes were filled into the voids of SiO₂:Tb inverse opals. Non-radiative and radiative energy transfer processes from the SiO₂:Tb inverse opals to the RhB were observed. The influence of Au nanoparticles and photonic band gap on the energy transfer from SiO₂:Tb inverse opals to the RhB was investigated. The Au nanoparticles enhanced energy transfer was observed due to the surface plasmon resonance effects of the Au nanoparticles. When the emission peaks from the SiO₂:Tb inverse opal is overlapped with the photonic band gap, the emission suppression of the SiO₂:Tb inverse opal as well the emission enhancement of the RhB dyes were obtained, which is attributed to improved energy transfer caused by the photonic band gap. The steady state rate equations were used to explain enhancement of energy transfer caused by the photonic band gap.     

Photonic Crystal Hydrogel Enhanced Plasmonic Staining for Multiplexed Protein Analysis

Plasmonic nanoparticles are commonly used as optical transducers in sensing applications. The optical signals resulting from the interaction of analytes and plamsonic nanoparticles are influenced by surrounding physical structures where the nanoparticles are located. This paper proposes inverse opal photonic crystal hydrogel as 3D structure to improve Raman signals from plasmonic staining. By hybridization of the plasmonic nanoparticles and photonic crystal, surface‐enhanced Raman spectroscopy (SERS) analysis of multiplexed protein is realized. It benefits the Raman analysis by providing high‐density “hot spots” in 3D and extra enhancement of local electromagnetic field at the band edge of PhC with periodic refractive index distribution. The strong interaction of light and the hybrid 3D nanostructure offers new insights into plasmonic nanoparticle applications and biosensor design.     

Synthesis and characterizations of three-dimensional ordered gold- nanoparticle-doped titanium dioxide photonic crystals

We developed a simple method to prepare gold-nanoparticle-doped titanium dioxide (GTD) sol-gel solution. The optimized GTD sol-gel solutions were a mixture of TEA, titanium (IV) butoxide, HAuCl₄, and deionized water in 0.3:1:0.5:3 volume ratios at room temperature. Using this sol-gel solution, we fabricated the GTD photonic crystal structure by infiltrating this solution by dip-coating into a polystyrene (PS) template. It was found that high quality of thin films was obtained by infiltrating twice the PS templates with the synthesized GTD sol-gel solutions. Energy dispersive X-ray spectroscopy and X-ray photoelectron spectra revealed the doping of TiO₂ and Au in the GTD photonic crystals. X-ray diffraction showed that TiO₂ and Au existed as anatase phase and metallic Au phase, respectively, in the GTD photonic crystals. The results indicated that the gold nanoparticles were doped into the framework of the photonic crystals.     

Borosilicate nanoparticles prepared by exothermic phase separation

Nanoparticles play an important role in chemical and biological sciences due to their ability to bind and concentrate many molecules on their surface. Polymers and silica are widely used to make nanoparticles, but efforts to make nanoparticles from borosilicate glass--which exhibits high tolerance to chemicals and solvents, combined with excellent mechanical and thermal stability--have proved unsuccessful. Here we show that borosilicate nanoparticles (100-500 nm in size) can be synthesized by simply mixing a silicon-boron binary oxide solution, prepared using non-aqueous organic solvents, with water. This induces a vigorous exothermic phase separation in which borosilicate nanoparticles burst out of a silica phase. In addition to potential applications in the life sciences, monodisperse borosilicate particles could also have applications in the production of photonic bandgap devices with high optical contrast, contrast agents for ultrasonic microscopy or chemical filtration membranes.     

Emission spectra of silver-infiltrated opal photonic crystals under excitation through optical fibers

The emission spectra of opal photonic crystals loaded with silver nanoparticles have been measured in a 180° geometry under UV and visible excitation. The spectra of silver-infiltrated opal under excitation through optical fibers are found to differ from the spectra of plain (uninfiltrated) opal: the infiltrated silver shifts the emission maximum to longer wavelengths and changes the shape of the spectrum. We have calculated the dispersion laws for two photonic bands and the corresponding frequency dependences of the refractive index for the photonic crystals studied.     

Nanoparticle-assisted high photoconductive gain in composites of polymer and fullerene

Polymer-inorganic nanocrystal composites offer an attractive means to combine the merits of organic and inorganic materials into novel electronic and photonic systems. However, many applications of these composites are limited by the solubility and distribution of the nanocrystals in the polymer matrices. Here we show that blending CdTe nanoparticles into a polymer-fullerene matrix followed by solvent annealing can achieve high photoconductive gain under low applied voltages. The surface capping ligand renders the nanoparticles highly soluble in the polymer blend, thereby enabling high CdTe loadings. An external quantum efficiency as high as approximately 8,000% at 350 nm was achieved at -4.5 V. Hole-dominant devices coupled with atomic force microscopy images show a higher concentration of nanoparticles near the cathode-polymer interface. The nanoparticles and trapped electrons assist hole injection into the polymer under reverse bias, contributing to efficiency values in excess of 100%.     

Polymer‐Based Photonic Crystals

In this report, we highlight the development of polymers as 1D photonic crystals and subsequently place special emphasis on the activities in self‐assembled block copolymers as a promising platform material for new photonic crystals. We review recent progress, including the use of plasticizer and homopolymer blends of diblock copolymers to increase periodicity and the role of self‐assembly in producing 2D and 3D photonic crystals. The employment of inorganic nanoparticles to increase the dielectric contrast and the application of a biasing field during self‐assembly to control the long‐range domain order and orientation are examined, as well as in‐situ tunable materials via a mechanochromic materials system. Finally, the inherent optical anisotropy of extruded polymer films and side‐chain liquid‐crystalline polymers is shown to provide greater degrees of freedom for further novel optical designs.     

Metallosupramolecular Photonic Elastomers with Self‐Healing Capability and Angle‐Independent Color

Photonic elastomers that can change colors like a chameleon have shown great promise in various applications. However, it still remains a challenge to produce artificial photonic elastomers with desired optical and mechanical properties. Here, the generation of metallosupramolecular polymer‐based photonic elastomers with tunable mechanical strength, angle‐independent structural color, and self‐healing capability is reported. The photonic elastomers are prepared by incorporating isotropically arranged monodispersed SiO₂ nanoparticles within a supramolecular elastomeric matrix based on metal coordination interaction between amino‐terminated poly(dimethylsiloxane) and cerium trichloride. The photonic elastomers exhibit angle‐independent structural colors, while Young's modulus and elongation at break of the as‐formed photonic elastomers reach 0.24 MPa and 150%, respectively. The superior elasticity of photonic elastomers enables their chameleon‐skin‐like mechanochromic capability. Moreover, the photonic elastomers are capable of healing scratches or cuts to ensure sustainable optical and mechanical properties, which is crucial to their applications in wearable devices, optical coating, and visualized force sensing.     

Optical properties of a carbon-zirconia quantum-dot photonic crystal

We report the optical properties of a new type of photonic crystal: a transparent fused silica matrix containing quantum dots—nanoparticles of another material. In this study, nanoparticles consist of graphite zones several nanometers in size, stabilized by zirconia. The photonic crystal is prepared by high-temperature annealing (1200°C) of synthetic opal infiltrated with zirconia and a small amount of carbon. We demonstrate selective reflection of visible light from the surface of the quantum-dot crystal under broadband illumination. Such crystals are potentially attractive as narrow-band selective filters that would reflect the exciting light in Raman measurements and might be used to convert short-wavelength broadband radiation to quasi-monochromatic light in the visible range.     

Mechanically Milled Irregular Zinc Nanoparticles for Printable Bioresorbable Electronics

Bioresorbable electronics is predominantly realized by complex and time‐consuming anhydrous fabrication processes. New technology explores printable methods using inks containing micro‐ or nano‐bioresorbable particles (e.g., Zn and Mg). However, these particles have seldom been obtained in the context of bioresorbable electronics using cheap, reliable, and effective approaches with limited study on properties essential to printable electronics. Here, irregular nanocrystalline Zn with controllable sizes and optimized electrical performance is obtained through ball milling approach using polyvinylpyrrolidone (PVP) as a process control agent to stabilize Zn particles and prevent cold welding. Time and PVP dependence of the ball milled particles are studied with systematic characterizations of morphology and composition of the nanoparticles. The results reveal crystallized Zn nanoparticles with a size of ≈34.834 ± 1.76 nm and low surface oxidation. The resulting Zn nanoparticles can be readily printed onto bioresorbable substrates and sintered at room temperature using a photonic sintering approach, leading to a high conductivity of 44 643 S m^?1 for printable zinc nanoparticles. The techniques to obtain Zn nanoparticles through ball milling and processing them through photonic sintering may potentially lead to a mass fabrication method for bioresorbable electronics and promote its applications in healthcare, environmental protection, and consumer electronics.     

Supramolecular Photonic Hydrogel for High-Sensitivity Alkaline Phosphatase Detection via Synergistic Driving Force

Structurally-colored photonic hydrogels which are fabricated by introducing hydrogels into thin films or photonic crystal structures are promising candidates for biosensing. Generally, the design of photonic hydrogel biosensors is based on the sensor-analyte interactions induced charge variation within the hydrogel matrix, or chemically grafting binding sites onto the polymer chains, to achieve significant volume change and color variation of the photonic hydrogel. However, relatively low anti-interference capability or complicated synthesis hinder the facile and low-cost fabrication of high-performance photonic hydrogel biosensors. Here, a facilely prepared supramolecular photonic hydrogel biosensor is developed for high-sensitivity detection of alkaline phosphatase (ALP), which is an extensively considered clinical biomarker for a variety of diseases. Responding to ALP results in the broken supramolecular crosslinking and thus increased lattice distancing of the photonic hydrogel driven by synergistic repulsive force between nanoparticles embedded in photonic crystal structure and osmotic swelling pressure. The biosensor shows sensitivity of 7.3 nm spectral shift per mU mL⁻¹ ALP, with detection limit of 0.52 mU mL⁻¹. High-accuracy colorimetric detection can be realized via a smartphone, promoting point-of-care sensing and timely diagnosis of related pathological conditions.     

Hierarchical nanoparticle bragg mirrors: tandem and gradient architectures

To manipulate electrons in semiconductor electronic and optical devices, the usual approach is through materials composition, electronic bandgap, doping, and interface engineering. More advanced strategies for handling electrons in semiconductor devices include composition-controlled heterostructures and gradient structures. By analogy to the manipulation of electrons in semiconductor crystals by electronic bandgaps, photons in photonic crystals can be managed using photonic bandgaps. In this context, the simplest photonic crystal is the Bragg mirror, a periodic dielectric construct whose photonic bandgap is engineered through variations of the optical thickness of its constituent layers. Traditionally the materials comprising these periodic dielectric layers are nonporous, and they have mainly been used in the field of optical and photonic devices. More recently these Bragg mirrors have been made porous by building the layers from nanoparticles with functionality and utility that exploit their internal voids. These structures are emerging in the area of photonic color-coded chemical sensing and controlled chemical release. Herein, a strategy for enhancing the functionality and potential utility of nanoparticle Bragg mirrors by making the constituent dielectric layers aperiodic and porous is described. It is exemplified by prototypical tandem and gradient structures that are fully characterized with regards to their structure, porosity, and optical and photonic properties.     

Multifunctional Photonic Nanomaterials for Diagnostic,Therapeutic, and Theranostic Applications

The last decade has seen dramatic progress in the principle, design, and fabrication of photonic nanomaterials with various optical properties and functionalities. Light‐emitting and light‐responsive nanomaterials, such as semiconductor quantum dots, plasmonic metal nanoparticles, organic carbon, and polymeric nanomaterials, offer promising approaches to low‐cost and effective diagnostic, therapeutic, and theranostic applications. Reasonable endeavors have begun to translate some of the promising photonic nanomaterials to the clinic. Here, current research on the state‐of‐the‐art and emerging photonic nanomaterials for diverse biomedical applications is reviewed, and the remaining challenges and future perspectives are discussed.     

Mechanochromic Photonic Gels

Polymer gels are remarkable materials with physical structures that can adapt significantly and quite rapidly with changes in the local environment, such as temperature, light intensity, electrochemistry, and mechanical force. An interesting phenomenon observed in certain polymer gel systems is mechanochromism – a change in color due to a mechanical deformation. Mechanochromic photonic gels are periodically structured gels engineered with a photonic stopband that can be tuned by mechanical forces to reflect specific colors. These materials have potential as mechanochromic sensors because both the mechanical and optical properties are highly tailorable via incorporation of diluents, solvents, nanoparticles, or polymers, or the application of stimuli such as temperature, pH, or electric or strain fields. Recent advances in photonic gels that display strain‐dependent optical properties are discussed. In particular, this discussion focuses primarily on polymer‐based photonic gels that are directly or indirectly fabricated via self‐assembly, as these materials are promising soft material platforms for scalable mechanochromic sensors.     

Se-SiO2三维光子晶体的制备

报道了一种新的调节二氧化硅光子晶体带隙的方法;通过化学镀向SiO2胶体晶体中填充半导体材料Se,获得了Se-SiO2两种介质复合的三维光子晶体;采用扫描电子显微镜(SEM)、X射线衍射和紫外-可见光谱仪(UV-VIS)等对Se-SiO2三维光子晶体的形貌、结构和光学性能进行了观察测试.研究结果表明,Se以纳米晶粒的形式均匀地包覆在SiO2微球表面,形成了Se壳层,与相同晶格周期的SiO2光子晶体相比,Se-SiO2光子晶体的带隙发生了明显的红移.