等离子体增强化学气相沉积技术制备锗反蛋白石三维光子晶体

采用溶剂蒸发对流自组装法将单分散二氧化硅(SiO2)微球组装形成三维有序胶体晶体模板,以锗烷(GeH4)为先驱体气用等离子增强化学气相沉积法在350℃填充高折射率材料锗.获得了锗反蛋白石光子晶体.通过扫描电镜、X射线衍射仪对锗反蛋白石的形貌、成分、结构进行了表征.结果表明:锗在SiO2微球空隙内填充均匀,得到的锗为多晶态.锗反蛋白石光子晶体为三维有序多孔结构.等离子体增强化学气相沉积的潜在优势在于可实现材料的低温填充,从而以高分子材料为模板进行复型,得到多种结构的三维光子晶体.     

Synthesis of (Pb,La)(Zr,Ti)O3 Inverse Opal Photonic Crystals

(Pb,La)(Zr,Ti)O₃ (PLZT) inverse opal photonic crystals were synthesized by a sol-gel process with synthetic opal templates of monodisperse submicrometer polystyrene spheres. This process involves infiltration of precursors into the interstices of the opal template, followed by hydrolytic condensation of the precursors and removal of the polystyrene opal combined with crystallization of PLZT perovskite by calcination at a final temperature of 750°C. By this method, PLZT inverse opal photonic crystals with a periodical structure of 280 nm center-to-center distance between the air spheres are prepared from opal templates of polystyrene microspheres with a mean diameter of 400 nm. The PLZT inverse opals reflect yellow-green light strongly.     

ZnS-opal与反opal结构ZnS光子晶体的组装

以单分散SiO2微球为基元,在75%～80%湿度、30～45 ℃恒温密闭烘箱中垂直快速组装opal模板;以Zn(NO3)2（0.035 mol/L）、TAA乙醇溶液（0.05 mol/L）为前体,通过溶剂热法充填形成ZnS-opal复合光子晶体;ZnS-opal复合光子晶体在2%～5%的HF溶液中浸泡4～5 h后卸载模板,制得反opal结构ZnS基光子晶体;采用XRD、SEM、ＵV-Vis测试手段对反opal结构ZnS基光子晶体形貌、物相和光学性能进行了表征。结果表明：溶剂热法多次充填可使ZnS纳米晶在模板密堆积形成的空隙中均匀成核;经过酸处理的ZnS-opal中SiO2微球溶解、坍塌,形成蜂窝状三维有序介孔和反opal结构ZnS基光子晶体;相同粒径SiO2微球组装的opal模板、ZnS-opal以及反opal结构ZnS光子晶体均表现出光子带隙特性,但反opal结构ZnS光子晶体带隙位置相比前两者发生了蓝移。     

Filling behavior of ZnO nanoparticles into opal template via electrophoretic deposition and the fabrication of inverse opal

Combining colloidal crystal template (artificial opal) and electrophoretic deposition (EPD) process, well-ordered ZnO inverse opal can be formed by finding the optimum driving potential of EPD. Through providing the various driving potentials from −25 V, −10 V, −5 V to −2.5 V, the different mechanism of electrophoretically depositing ZnO nanoparticles into the colloidal crystal template was determined by the SEM observation of the filled templates. Because the nano-channels of colloidal crystal template are the network type, the results of surface jam, incomplete filling and perfect filling are found under specific applied voltages. The high-quality ZnO inverse opal can be only fabricated under the perfect nano-channel-filling condition. The filling behavior can be monitored dynamically by tracing the current transients, and the optimum conditions for filling the interstitial spaces of templates constructed from colloidal particles with 180 nm and 300 nm diameter can be obtained by applying a voltage of −5 V and −15 V, respectively. After the complete filling of ZnO nanoparticles into the colloidal crystal template consisting of 300 nm colloids, high-quality ZnO photonic crystal possessing an absorptive peak at the wavelength of 560 nm can be fabricated by removing the template. It is expected that the EPD can find extensive applications for preparing photonic crystals of various oxides only if their nanoparticles are available.     

Preparation and characterization of electrodeposited Ag-doped ZnO inverse opals with a smooth surface

Ag-doped ZnO inverse opal structures were prepared by electrochemical deposition using polystyrene colloidal crystal templates. The Ag-doped ZnO structures had granular morphology, but this morphology became smooth using a three-dimensional (3D) porous template in the same electrolyte. The Ag-doped ZnO structures were characterized using energy-dispersive X-ray spectroscopy, and the lattice parameter was found to increase compared with undoped ZnO as verified by X-ray diffraction. Strong reflection photonic stop bands centered at 495 and 681 nm were detected from inverse opals templated from microspheres having diameters of 285 and 370 nm. The filling ratio of Ag-doped ZnO inverse opals using the template was lower than that of the uniform film growth of undoped ZnO. Moreover, photochemical cell analysis revealed that doped ZnO inverse opals with n- and p-type conductivities were successfully formed using electrolytes with different silver ion concentrations.     

Electrochemical fabrication of neuron-type networks based on crystalline oligopyrene nanosheets

Electrochemical polymerization of pyrene in boron trifluoride diethyl etherate (BFEE) produced oligopyrenes (pyrene oligomers) with repeat unit numbers of 2-15. The oligoyrenes grown at the working electrode are nanosheets with high crystallinity. As an array of microelectrodes or a semiconductive silicon wafer patterned with microelectrodes were used as the working electrode, a dendritic network of cyrstalline oligopyrene nanosheets was fabricated. The initially grown nanosheets on the microelectrodes act as nodes and the network with interconnects of the nanosheets grow from the nodes. The number and structure of the inconnectects can be controlled by the structure of the patterned electrode, the concentration of the monomer, the value of applied potential and the charge density used for electrochemical deposition. This is the first example of fabrication neuron-type network based on conductive organic nanosheets.     

Template synthesis of structured titania using inverse opal gels

Inverse opal gels with varied content of acid groups were used as templates to synthesize structured crystalline titania materials. TiO₂ with opal, inverse opal, and gradient structure were obtained by altering composition of the gels and precursor concentration. The mechanism of the template synthesis by using opal gels was proposed.     

Fabrication of Barium Strontium Titanate Inverse Opals by the Sol–Gel Process

Barium strontium titanate (BST) inverse opal photonic crystals (PCs) were fabricated by a process of self-assembly of a polystyrene opal template in combination with infiltration of BST nanoparticles into the voids of a template. In this process, stable monodispersed BST nanoparticles were prepared by dispersing a BST gel into a mixed solvent of 2-methoxyethanol and acetylacetone. Scanning electron microscopy images show that the inverse opals possess a face-centered cubic lattice with a center-to-center distance of the air spheres of 270 nm. The X-ray diffraction result reveals that a ferroelectric perovskite phase was obtained. A photonic bandgap in the visible range is observed from reflection spectra analysis and compared with the theoretical results.     

Studies on late formation of 3D ordered macroporous materials through colloidal crystal templates

Three-dimensional ordered macroporous (3DOM) materials are anticipated to exhibit improved performance in lots of applications due to their special structure. This paper presents the formation mechanism of 3DOM structure during the removal process of templates, which has not been systematically studied yet. Using polymer colloidal crystal template, 3DOM metallic materials were prepared by electrochemical deposition and dissolution. The results indicate that windows in inverse opals are formed because of the associated breaking of thin wall materials. There seems to be a critical thickness for the same wall materials. The existence of windows improved the formation of 3DOM structures during the removal process of templates.     

Quasi-radial growth of metal tube on si nanowires template

It is reported in this article that Si nanowires can be employed as a positive template for the controllable electrochemical deposition of noble metal tube. The deposited tube exhibits good crystallinity. Scanning electron microscope and transmission electron microscope characterizations are conducted to reveal the growth process of metal tube, showing that the metal tube grows quasi-radially on the wall of Si nanowire. The quasi-radial growth of metal enables the fabrication of thickness-defined metal tube via changing deposition time. Inner-diameter-defined metal tube is achieved by choosing Si nanowires with desired diameter as a template. Metal tubes with inner diameters ranging from 1 μm to sub-50 nm are fabricated.     

Fabrication of Nickel Nanostructure Arrays Via a Modified Nanosphere Lithography

In this paper, we present a modified nanosphere lithographic scheme that is based on the self-assembly and electroforming techniques. The scheme was demonstrated to fabricate a nickel template of ordered nanobowl arrays together with a nickel nanostructure array-patterned glass substrate. The hemispherical nanobowls exhibit uniform sizes and smooth interior surfaces, and the shallow nanobowls with a flat bottom on the glass substrate are interconnected as a net structure with uniform thickness. A multiphysics model based on the level set method (LSM) was built up to understand this fabricating process by tracking the interface between the growing nickel and the electrolyte. The fabricated nickel nanobowl template can be used as a mold of long lifetime in soft lithography due to the high strength of nickel. The nanostructure–patterned glass substrate can be used in optical and magnetic devices due to their shape effects. This fabrication scheme can also be extended to a wide range of metals and alloys.     

Influence of pores arrangement on stability of photonic structures during sintering

Discrete Element Method (DEM) has been used for numerical investigation of sintering-induced structural deformations occurring in inverse opal photonic structures. The influence of the initial arrangement of template particles on the stability of highly porous inverse opal α-Al₂O₃ structures has been analyzed. The material transport, densification, as well as formation of defects and cracks have been compared for various case studies. Three different stages of defects formation have been distinguished starting with local defects ending with intrapore cracks. The results show that the packing of the template particles defined during the template self-assembly process play a crucial role in the later structural deformation upon thermal exposure. The simulation results are in very good agreement with experimental data obtained from SEM images and previous studies by ptychographic X-ray tomography.     

Effect of the combination of inverse opal photon superficial areaic crystal and heterojunction on active free radicals and its effect on the mechanism of photocatalytic removal of organic pollutants

For the inverse opal photocatalyst, hydraulic pressure and other problems caused by the ordered structure of the inverse opal photocatalyst make it difficult for the pollutants to enter the structure quickly and effectively, so the effective control of its structure has become an urgent problem to be solved. Here, multi-heterojunction inverse opal structure catalyst with multi-level branched pore structure is prepared by the sol-gel method. The special three-dimensional dendritic porous structure solves the problem that a pollutant solution is difficult to effectively enter a skeleton with the traditional ordered inverse opal photocatalyst. This structure can also lead to the nanocrystallization of TZS powders, thus promoting the formation of the intermediate product ZrTiO₄ and optimizing the heterogeneous interface in the TiO₂–ZrO₂ heterojunction, thereby successfully constructing the multi-heterostructure and effectively improving the redox ability. Furthermore, by adjusting the loading amount of TZS, the matching of the heterojunction and the inverse opal structure can be effectively controlled, the matching of the photonic band gap and the forbidden bandwidth can be effectively adjusted, and the degradation efficiency is greatly improved. This study provides a new idea for effective collaboration between multi-heterogeneous interfaces and 3D branch fractal structures.     

Inverse Opal Structure of Nitrogen-Doped Titanium Oxide with Enhanced Visible-Light Photocatalytic Activity

Nitrogen-doped titanium oxide inverse opal structure was synthesized to combine both chemical and physical modifications on n -TiO₂ by the polystyrene sphere self-assembly followed by a sol–gel process. Enhanced visible-light absorption and subsequently enhanced photodegradation efficiency were observed in this unique structure, which can be attributed to both nitrogen-doping effect and inverse opal structure effect. Our work suggests that the coupling of photonic band gap structure with photocatalytic materials is a promising approach to achieve maximum enhancement for various photocatalytic materials, especially for environmental applications and solar cell devices.     

Patterned Si thin film electrodes for enhancing structural stability

A patterned film (electrode) with lozenge-shaped Si tiles could be successfully fabricated by masking with an expanded metal foil during film deposition. Its electrochemical properties and structural stability during the charge-discharge process were examined and compared with those of a continuous (conventional) film electrode. The patterned electrode exhibited a remarkably improved cycleability (75% capacity retention after 120 cycles) and an enhanced structural stability compared to the continuous electrode. The good electrochemical performance of the patterned electrode was attributed to the space between Si tiles that acted as a buffer against the volume change of the Si electrode.     

Fabrication of patterned nanostructures with various metal species on Si wafer surfaces by maskless and electroless process

Maskless and electroless fabrication was demonstrated to form patterned nanostructures of various metal species, based upon the process previously developed by the authors. In this process, the metallic nanostructures were formed on the surface of clean, hydrogen terminated p-(1 0 0) Si wafer with pre-patterned nanoscopic defects, which were confirmed to possess higher activity for the reductive deposition reaction of the metal ion species. The deposition was achieved spontaneously and selectively at the defect sites on the wafer surface by immersing into dilute aqueous fluoride solution containing trace amount of metal ion species. By optimizing the formation condition of the patterned defects and composition of the solution, fabrication of patterned nanostructures of various metallic species such as Au, Ag, and Co, was achieved. Formation of the patterned nanostructures to 10 μm² in extent, as well as control of the feature size of the deposits by adjusting the formation condition of the patterned defects were also attempted.     

Investigation of controllable self-organized honeycomb micro-structure

Patterned micro- and nanostructure are of great significance in industrial applications such as electronics, optics and sensors. Microporous honeycomb film of polyhpenylene oxide (PPO) was fabricated as the template via evaporation of solution in carbon bisulfide under humid ambience. The effect of fabrication conditions on patterned microstructure was investigated by self-organization experiments to build quantitative relationship between ambient conditions such as humidity, concentration and honeycomb microstructure (diameter and height), through which the honeycomb film formation can be controlled to self-organize desirable PPO patterned microstructure. Especially, the height of honeycomb was derived from the diameter of honeycomb, and its validity was clarified by morphological comparison between PPO template and PDMS molded structure. Moreover, soft mold experiments were conducted to demonstrate its high efficiency and excellence as an alternative to construct regular micro-pattern.     

One-step fabrication of N-doped TiO2 inverse opal films with visible light photocatalytic activity

N-doped TiO₂ inverse opal films were fabricated by a novel method through one-step coassembly of polymer colloidal spheres and titania precursor. This coassembly approach removed the need of preassembled colloidal crystal for precursor solution infiltration and respective chemicals for titania formation and nitrogen doping. Less crack films with well ordered inverse opal structure could be produced by adding appropriate amount of TiBALDH (titanium(IV)-bis-lactato-bis-ammonium dihydroxide) into the precursor solution. The films prepared at the optimized condition showed enhanced visible light photocatalytic activity, which could be attributed to both the N doping effect and their unique inverse opal structure.     

Flame-synthesis of carbon nanotubes on silicon substrates and their field emission properties

We reported the flame-synthesis of patterned multiwalled carbon nanotubes (CNTs) on silicon substrate by a shadow mask and their field emission properties. It was found that CNTs with tangled and curved morphology were preferentially grown around the cracked edges of Ni dot pattern. A crack-induced catalyst-activation growth mechanism was proposed. The patterned CNTs fabricated by such a simple flame-synthesis method exhibited good field emission characteristics with uniform emission patterns and reproducible and stable emission behaviors, although the CNTs possessed many defective graphite layers and showed relatively higher turn-on and threshold field than other reported CNTs grown by chemical vapor deposition. Our results demonstrated that such a low-cost and scaleable CNT pattern fabrication process can be expected to have favorable applications in field emission devices.     

Synthesis of hierarchically nanoporous silica films for controlled drug loading and release

Films with well-controlled porous structures provide many exciting application opportunities in chemistry and biology. Here we report the synthesis of a highly uniform, hierarchically nanoporous silica film structure, and its application in drug loading and release for antibacterial surface coating. Templated by both sub-micron poly-styrene (PS) particles and a triblock copolymer (F127), this hierarchically nanoporous film has two distinct pore sizes of 200 nm and 7 nm. The 7-nm mesopores provide high surface area and thus high adsorption capacity for drug molecules, and the 200-nm macropores facilitate the adsorption rate of drug molecules, especially for molecules with comparable sizes to mesopores. Fluorescence measurement of rhodamine release demonstrates that this hierarchically porous film has a higher adsorption capacity, efficiency and much longer molecule releasing time window than both the inverse opal film and the mesoporous film. When loaded with Ampicillin, this hierarchically porous film shows over 8 times longer of inhibition of E. coli growth than both the inverse opal film and the mesoporous film. This simple and versatile process allows for fabrication of a variety of surface-coated, hierarchically nanoporous films with different chemical compositions and applications.