Influence of Fe Ions on the Optical Properties of Fe–ZnO Inverse Opals

In this work we study the influence of Fe ions doping concentration on the optical properties of ZnO inverse opals. The ZnO inverse opals were obtained by impregnating the PMMA opal template with a zinc acetate solution. After the solidification of this solution in the void spaces of the synthetic PMMA and the thermal removal of the PMMA template, it remained a regular 3-D ordered porous ZnO solid which constitutes an inverse opal. The ZnO:Fe inverse opals were obtained following the same procedure but using zinc acetate and iron nitrate solutions instead. Scanning Electron Microscopy (SEM) images show the close-packed self-assembly of PMMA opals, the surface morphology of ZnO inverse opals formed by spherical void spaces of 295 nm diameter, and a discontinuous surface morphology of the ZnO:Fe inverse opals. The XRD diffractogram of ZnO inverse opals shows peaks characteristic of ZnO with wurtzite phase, and the micro-Raman spectrum shows phononic lines corresponding also to the same crystallographic structure. The energy band gap of ZnO and ZnO:Fe inverse opals were calculated from their absorption spectra giving the values of 3.2 and 2.4 eV, respectively.     

Photocontrolled Healable Structural Color Hydrogels

Structural color hydrogels with healable capability are of great significance in many fields, however the controllability of these materials still needs optimizing. Thus, this work presents a healable structural color hydrogel with photocontrolling properties. The component parts of the hydrogel are a graphene oxide (GO) integrated inverse opal hydrogel scaffold and a hydrogel filler with reversible phase transition. The inverse opal scaffold provides stable photonic crystal structure and the hydrogel filler is the foundation of healing. Taking advantage of the prominent photothermal conversion efficiency of GO, the healable structural color material is imparted with photocontrolled properties. It is found that the structural color hydrogel shaped in complex patterns can heal under near‐infrared (NIR) irradiation. These features indicate that the optical controllable healable structural color hydrogel can be employed in various applications, such as constructing complex objects, repairing tissues, and so on.     

Preparation of platinum inverse opals using self-assembled templates and their application in methanol oxidation

Synthetic opals were prepared on indium tin oxide (ITO) glass substrates from a highly monodisperse polystyrene dispersion. Platinum was then electrodeposited through the interstitial space of the opal matrix. The platinum inverse opal (Pt-IOp) was subsequently obtained by the removal of the polystyrene template, leaving a highly ordered three dimensional structure. Both the opal template and platinum (Pt) inverse opal were characterised by scanning electron microscopy, UV–visible spectroscopy and cyclic voltammetry. The results confirmed that the Pt inverse opal (Pt-IOp) has a microporous structure with high surface area and exhibits excellent electrochemical property. The electrocatalytic application of the resulting nanostructured Pt inverse opal electrodes for methanol oxidation was also investigated. The nanostructured Pt-IOp electrode showed a catalytic activity and highly stable electrocatalytic performance in methanol oxidation.     

反蛋白石结构光子晶体及其应用的研究

反蛋白石结构光子晶体因具有完全光子带隙、制备材料广泛、特殊的周期结构、大的比表面积和连通的孔洞结构,近年来在自发辐射的调制、提高光催化反应速率和染料敏化太阳能电池反应速率等领域成为研究热点之一,并且在光、电、催化、传感、显示、检测等领域有着巨大的应用价值。介绍了反蛋白石结构光子晶体的基本概念及制备方法,阐述了反蛋白石结构在材料自发辐射的调制、能量传递的调制、促进物理化学反应、外界环境响应材料等方面的作用及其应用。     

Optimizing sol-gel infiltration for the fabrication of high-quality titania inverse opal and its photocatalytic activity

This article reports an optimized sol-gel opal infiltration technique for the fabrication of high-quality titania inverse opal. Different from previous reports, the presently proposed method is facile, efficient and suitable for other inorganic oxide. We have compared two different infiltration strategies and their influences on the structure, photonic properties and photocatalytic activity. The obtained titania inverse opal displays excellent photonic properties with photonic band gap at 320 nm and better photocatalytic effect, which is attributed to its high-quality inverse opal nanostructure. Reproducibility tests prove that the photocatalytic activity of the resultant titania inverse opal remains intact even after five repeated photocatalytic reactions under the same procedure and experimental conditions.     

Color tunability of upconversion emission in YBO3: Yb, Er inverse opal

Upconversion (C) light-emitting photonic band gap materials (YBO₃: Yb, Er) with inverse opal structure were prepared by a self-assembly technique in combination with a sol-gel method. The effect of the photonic stop-band on the upconversion luminescence of Er³⁺ ions has been investigated in the YBO₃: Yb, Er inverse opals. Significant suppression of the green or red UC emission was detected if the photonic band-gap overlaps with the Er³⁺ ions emission band. We successfully achieved the color tuning of the UC optical properties of the inverse opal by controlling the structure of the photonic crystal.     

Mesoporous inverse opal TiO2 film as light scattering layer for dye-sensitized solar cell

The light harvesting efficiency of dye-sensitized solar cells was enhanced by using a scattering layer. Such as sphere type TiO2, inverse photonic crystal TiO2, hollow spherical TiO2. Among these materials, the TiO2 with inverse photonic crystal (IPC) structure, synthesized by self-assembly using spherical templates, has attracted much attention due to their photonic crystal characteristics and light scattering effects. However, when applied in the DSSCs, the surface area of IPC is very low that caused insufficient adsorption amount of dye molecules. In the present work, a scattering layer with mesoporous inverse photonic crystal (MIPC) TiO2 film was fabricated by the sol-gel reactions with surfactant-assisted sol-gel method using poly(methyl methacrylate) as the template and titanium (IV) isopropoxide as the TiO2 precursor. After removing the PMMA and surfactant, a highly ordered macroporous structure with mesopores were successfully obtained. The surface area and total pore volume of the MIPC were 82 m2/g and 0.31 cm3/g, respectively, which is much larger than those of the IPC. The DSSCs with the scattering layer of MIPC film exhibited 18 and 10% higher photo-conversion efficiency than those of cells only with a nano-crystalline TiO2 film and with scattering layer of IPC film. From UV-visible spectra of dye solutions, the MIPC film showed a higher amount of absorbed dye molecules than those of the reference and IPC films. Accordingly, an increase in the photo-current density through abundant adsorption of the dye, coupled with inherent light scattering ability can improve overall photo-conversion efficiency.     

Influence of preparation methods on the properties of self-assembled films of octadecylphosphonate on Nitinol: XPS and EIS studies

The NiTi alloy (Nitinol), with its favorable micro-structured properties and self-passivity (resembling that of pure Ti) is used as an implant material for arterial stents and orthodontic wires. During the long term contact of the alloy with aggressive environment of human body, corrosion by releasing Ni^2 + ions can occur. Thus, the usefulness of such material can be dramatically enhanced if its interface structure and surface chemistry are controlled. The octadecylphosphonate interface (ODP) synthesis, which involves a self-assembled covalently (monodentate type) bonded film of octadecylphosphonic acid (ODPA) on the oxide covered NiTi surface, produces stable and corrosion resistant interfaces. This paper introduces integrated approach to the characterization of the NiTi/ODP interfacial architecture as well as the structure of the electrified ODP/solution interface using high-resolution XPS and in situ EIS measurements. The main focus of this work was to determine the influence of the ODPA deposition method (spray and immersion) on the depth-dependent structural characteristics and orientation of ODPA molecules in the surface film by means of angle resolved XPS. Mechanically strong and chemically stable NiTi/phosphonate interfaces have the potential for their successful implementation in stent technologies.     

Mesoporous silica obtained by polycondensation of octahydridooctasilsesquioxane

Mesoporous silica, due to its porosity and morphological features, have been considered a fascinating material for many technological applications. In this report, we describe the preparation of a structurally stable mesoporous silica material using octahydridooctasilsesquioxane (T₈ ^H). The structure and properties of final samples were determined by XRD, FT-IR, and TEM methods. Structural analysis has shown that the siliceous material is amorphous but mesoporous. BET surface area, pore volumes, and pore size distribution were measured using nitrogen sorption methods—data were collected from the adsorption branch using BJH method for mesopores and t-plot method for micropores. It was found that the cage-type structure of T₈ ^H molecules and the process conditions determine the specific morphology of the cross-linked products. Completely inorganic, mesoporous silica of a narrow pore distribution was obtained. It was found that the materials have large surface area and pores in the meso range (2–5 nm). The amount of mesopores and the characteristic surface area of the prepared samples strongly depended on the reaction conditions.     

3D Mesoporous Graphene: CVD Self‐Assembly on Porous Oxide Templates and Applications in High‐Stable Li‐S Batteries

A nanostructured carbon with high specific surface area (SSA), tunable pore structure, superior electrical conductivity, mechanically robust framework, and high chemical stability is an important requirement for electrochemical energy storage. Porous graphene fabricated by chemical activation and liquid etching has a high surface area but very limited volume of electrochemically accessible mesopores. Herein, an effective strategy of in situ formation of hierarchically mesoporous oxide templates with small pores induced by Kirkendall diffusion and large pores attributed to evaporation of deliberately introduced volatile metal is proposed for chemical vapor deposition assembly of porous graphene frameworks (PGFs). The PGFs inherit the hierarchical mesoporous structure of the templates. A high SSA of 1448 m² g⁻¹, 91.6% of which is contributed by mesopores, and a mesopore volume of 2.40 cm³ g⁻¹ are attained for PGFs serving as reservoirs of ions or active materials in electrochemical energy storage applications. When the PGFs are applied in lithium‐sulfur batteries, a very high sulfur utilization of 71% and a very low fading rate of ≈0.04% per cycle after the second cycle are achieved at a current rate of 1.0 C. This work provides a general strategy for the rational construction of mesoporous structures induced by a volatile metal, with a view toward the design of hierarchical nanomaterials for advanced energy storage.     

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.     

Sputtering fabrication of large scale ZnO nanobowl arrays using colloidal crystal templates

Ordered ZnO nanobowl arrays over cm2 areas were prepared by magnetron sputtering using the self-assembled polystyrene spheres arrays as templates. The process started with self-assembled sedimentation of there-dimensional (3D) hexagonal polystyrene sphere arrays. By depositing ZnO within the interstitials of 3D polystyrene colloidal crystal templates using magnetron sputtering, large-area ordered ZnO nanobowl sheets were prepared after removing the spheres by annealing. The whole nanobowl sheet could be lifted off, leaving accidentally observed inverse opal structures. The sizes of the nanobowls could be controlled by the size of the polystyrene spheres, the height of nanobowl sheets could be altered by changing sputtering parameters.     

Internal structure visualization and lithographic use of periodic toroidal holes in liquid crystals

The formation of a large-area ordered structure by organic molecular soft building blocks is one of the most exciting interdisciplinary research areas in current materials science and nanotechnology. So far, several distinct organic building blocks--including colloids, block copolymers and surfactants--have been examined as potential materials for the creation of lithographic templates. Here, we report that perfect ordered arrays of toric focal conic domains (TFCDs) covering large areas can be formed by semi-fluorinated smectic liquid crystals. Combined with controlled geometry, that is, a microchannel, our smectic liquid-crystal system exhibits a high density of TFCDs that are arranged with remarkably high regularity. Direct visualization of the internal structure of the TFCDs clearly verified that the smectic layers were aligned normal to the side walls and parallel to the top surface, and merge with the circular profile on the bottom wall surface. Moreover, we demonstrate a new concept: smectic liquid-crystal lithography. Grown in microchannels from a mixture of liquid-crystal molecules and fluorescent particles, TFCDs of the smectic liquid crystals acted as a template, trapping particles in an ordered array. Our findings pose new theoretical challenges and potentially enable lithographic applications based on smectic liquid-crystalline materials.     

Hierarchically Molecular Imprinted Porous Particles for Biomimetic Kidney Cleaning

Blood purification by adsorption of excessive biomolecules is vital for maintaining human health. Here, inspired by kidney self-purification, which removes a number of biomolecules with different sizes simultaneously, hierarchical molecular-imprinted inverse opal particles integrated with a herringbone microfluidic chip for efficient biomolecules cleaning are presented. The particle possesses combinative porous structure with both surface and interior imprints for the specific recognition of small molecules and biomacromolecules. Additionally, the presence of the herringbone mixer largely improve the adsorption efficiency due to enhanced mixing. Moreover, the inverse opal framework of the particles give rise to optical sensing ability for self-reporting of the adsorption states. These features, together with its reusability, biosafety, and biocompatibility, make the platform highly promising for clinical blood purification and artificial kidney construction.     

2D nanoparticle arrays by partial dissolution of ordered pore films

A low cost and simple route was presented to fabricate large-scale ordered nanoparticle arrays by partial dissolution of ordered pore films (or monolayer inverse opal) in a solution. By this method, we have fabricated Fe₂O₃ and In₂O₃ hexagonal close-packed nanoparticle arrays. This method is also applicable for synthesis of other material nanoparticle arrays. The particle size in the arrays can be controlled by the dissolution time, which is, additionally, beneficial to study size dependent optical, magnetic, electrochemical, thermodynamic, catalytic properties of nanoparticls.     

TiO2 inverse opal based CdS/CdSe quantum dot co-sensitized solar cells

CdS and CdSe quantum dots were introduced as co-sensitizers into TiO₂ inverse opal quantum dot sensitized solar cells. Herein, the three-dimensionally ordered porous TiO₂ inverse opal film leads to a better infiltration of both sensitizers and hole transporting material, and the smaller surface area of TiO₂ inverse opal film is effectively offset by the incorporating of co-sensitization. It was found that the presence of CdS/CdSe co-sensitizers provides enhanced light absorption, and leads to a lower recombination rate of the electrons due to the stepwise structure of band edge in TiO₂/CdS/CdSe, which resulted in the observed enhanced photocurrent and energy conversion efficiency of the solar cells. A cell efficiency of 1.01 % has been attained.     

Mix and Match: Organic and Inorganic Ions in the Perovskite Lattice

Materials science evolves to a state where the composition and structure of a crystal can be controlled almost at will. Given that a composition meets basic requirements of stoichiometry, steric demands, and charge neutrality, researchers are now able to investigate a wide range of compounds theoretically and, under various experimental conditions, select the constituting fragments of a crystal. One intriguing playground for such materials design is the perovskite structure. While a game of mixing and matching ions has been played successfully for about 150 years within the limits of inorganic compounds, the recent advances in organic–inorganic hybrid perovskite photovoltaics have triggered the inclusion of organic ions. Organic ions can be incorporated on all sites of the perovskite structure, leading to hybrid (double, triple, etc.) perovskites and inverse (hybrid) perovskites. Examples for each of these cases are known, even with all three sites occupied by organic molecules. While this change from monatomic ions to molecular species is accompanied with increased complexity, it shows that concepts from traditional inorganic perovskites are transferable to the novel hybrid materials. The increased compositional space holds promising new possibilities and applications for the universe of perovskite materials.     

Hierarchical wood cellulose fiber/epoxy biocomposites – Materials design of fiber porosity and nanostructure

Delignified chemical wood pulp fibers can be designed to have a controlled structure of cellulose fibril aggregates to serve as porous templates in biocomposites with unique properties. The potential of these fibers as reinforcement for an epoxy matrix (EP) was investigated in this work. Networks of porous wood fibers were impregnated with monomeric epoxy and cured. Microscopy images from ultramicrotomed cross sections and tensile fractured surfaces were used to study the distribution of matrix inside and around the fibers – at two different length scales. Mechanical characterization at different relative humidity showed much improved mechanical properties of biocomposites based on epoxy-impregnated fibers and they were rather insensitive to surrounding humidity. Furthermore, the mechanical properties of cellulose-fiber biocomposites were compared with those of cellulose-nanofibril (CNF) composites; strong similarities were found between the two materials. The reasons for this, some limitations and the role of specific surface area of the fiber are discussed.     

纳米PbS/SiO2气凝胶介孔组装体的制备及光学特性

对用自行研制的ＳＣＤ－Ｉ型高压釜制备的ＳiO2气凝胶与用胶体化学方法制备的ＰbS纳米粒子的组装体系的光学性能进行了研究,用透射电镜观察了其形貌,用光吸收谱仪及荧光光谱仪测定其光吸收谱及荧光谱。发现样品的光吸收边随温火温度升高由可见逐渐移到红外波段,样品的光致发光强度随退火温度上升先增强直至５７３Ｋ,而后随退火温度上升而减弱,我们认为光吸这红移是由量子限域效应引起的,而荧光强度变化与ＰbS表面缺陷及激光子的复合几率变化有关。