Antireflection coatings produced on silicate glass from silicon dioxide sols with addition of poly(propylene glycols) at gel annealing temperature of 200°C

Thin transparent nanoporous silicon dioxide films with low refractive index (1.26–1.30) were formed on a glass substrate by deposition of a formulation that is based on silicon dioxide sol with addition of poly(propylene glycols) at a low gel annealing temperature of 200°C. The maximum optical transmission of glass with these antireflection coatings is 97.5–98.7%.     

Deposition of antireflection coatings onto silicate glass from a silicon dioxide sol containing a nonionogenic surfactant and oligoester based on propylene oxide

Possibility of obtaining low-refractive-index antireflection coatings composed of mesoporous silicon dioxide by simultaneous introduction of two organic compounds, oligoester based on propylene oxide and a nonionogenic surfactant, into a silicon dioxide sol was studied.     

Deposition of thin antireflection coatings based on mesoporous silicon dioxide by the sol-gel method in the presence of carbochain polymers and statistical copolymers

Antireflection coatings with a low refractive index (1.25–1.34) were prepared from mesoporous silicon dioxide by using carbochain polymers and statistical copolymers, instead of ionogenic and noionogenic surfactants and amphiphilic block-copolymers in a sol-gel process. The optimal concentration of the organic additive in the sol, at which a transparent film with the maximum antireflection effect is formed in the sol-gel process followed by heating of a sample, was determined.     

Poly(propylene glycols) as effective additives to the sol-gel process in fabrication of antireflection coatings onto silica glass

Possibility of obtaining mesoporous silicon dioxide antireflection coatings with low refractive index (1.20–1.277) by using additions of poly(propylene glycols) with various molecular masses in a sol-gel process was examined. It was demonstrated that the optimal concentration of poly(propylene glycols) in the sol, at which a sol-gel process followed by heating of a sample yields a transparent film with a maximum light transmission of 98.3–99.0%, depends on the average molecular mass of the additive.     

Silicon Dioxide Sol as a Component of Urea-Formaldehyde Adhesive

The possibility of combining an inorganic polymer, silicon dioxide sol, with urea-formaldehyde resins, was studied with the aim to prepare a binding agent for producing nontoxic chip boards. The kinetic characteristics of formaldehyde binding with silicon dioxide during complex binder curing were determined.     

树脂交换法制备白炭黑溶胶

用白炭黑溶胶作造纸工业的添加剂,可以改进纸的滞留性和脱水性,将带有阴离子的白炭黑溶胶与一些阳离子聚合物一起使用,效果更佳。在造纸工业中添加的白炭黑溶胶粒径应在4～7nm,比表面为700～300m^2／g,稳定性好,传统方法制备的白炭黑溶胶难于达到此要求。本文对用树脂交换法制备白炭黑溶胶的条件、影响因素、最佳工艺进行了探讨。     

Seeding Molecular Rotators on a Passivated Silicon Surface

Thermally activated rotation of single molecules adsorbed on a silicon‐based surface between 77 and 150 K has been successfully achieved. This remarkable phenomenon relies on a nanoporous supramolecular network, which acts as a template to seed periodic molecule rotors on the surface. Thermal activation of rotation has been demonstrated by STM experiments and confirmed by theoretical calculations.     

Preparation of hemispherical hollow silica microcapsules with different affinity surface by using spherical vaterite calcium carbonate as template

We developed a method to prepare hemispherical hollow silica microcapsules (HHSM) with different affinity surfaces using spherical vaterite calcium carbonate (SVCC) as a template. The preparation process composed of the adhesion of calcium carbonate onto the surface of methyl methacrylate (MMA) droplets followed by suspension polymerization, the partial etching of calcium carbonate on the polymethyl methacrylate (PMMA) mother particle, the formation of silicon dioxide powder by sol–gel reaction and their deposition onto the etched flat surface of calcium carbonate, the surface modification of deposited silicon dioxide with silane coupling agent, the removal of the mother particle with acetone, the formation of silicon dioxide powder by sol–gel reaction and deposition onto the exposed hemispherical surface of calcium carbonate, and the surface modification of deposited silicon dioxide with silane coupling agent. The synthesized microcapsules had a complete hemispherical structure and both hydrophilic and hydrophobic surfaces. Copyright © 2007 John Wiley & Sons, Ltd.     

三甲基氯硅烷对纳米多孔二氧化硅薄膜的修饰

以正硅酸乙酯为先驱体,采用溶胶-凝胶法,结合旋转涂胶、超临界干燥工艺在硅片上制备了纳米多孔SiO2薄膜.用三甲基氯硅烷(TMCS)对该SiO2薄膜进行了表面修饰,采用FTIR、TG-DTA、AFM和椭偏仪等方法研究了TMCS修饰前后薄膜的结构、形貌、厚度与介电常数等性能.超临界干燥后的SiO2薄膜含有Si－O－Si与Si－OR结构,呈疏水性.在空气中250 ℃以上热处理后SiO2薄膜因含有Si－OH而呈吸水性. TMCS修饰后的SiO2薄膜在温度不高于450 ℃时可保持其疏水性和多孔结构. SiO2薄膜经TMCS修饰后基本粒子和孔隙尺寸增大,孔隙率提高,介电常数可降低至2.5以下.     

Preparation and characterization of nanoporous polyimide membrane by the template method as low‐k dielectric material

In order to decrease the resistance–capacitance delay and signal crosstalk in ultra large‐scale integrated circuits (ULSIC), dielectric materials with ultra low dielectric constants are developed to be the replacement of silicon dioxide. Introduction of air on the matrix material is an important method to reduce the dielectric constant, and polyimide (PI) is the most promising polymer to prepare porous matrix material for its distinct advantages. PI membrane with nanopores was prepared by the method of template method (i.e. thermolysis of polystyrene nanospheres in the matrix) following the synthesis of template. The nanoporous membrane was characterized by Fourier transformer infrared, scanning electron microscopy, thermogravimetric analysis, and the dielectric constant of which was measured. Results showed that uniform nanopores about 100–200 nm were formed in the PI membrane, and dielectric constant of which was decreased to 2.08 from 3.34. The nanoporous membrane can be applied as potential low‐k dielectric material in ULSIC. Copyright © 2015 John Wiley & Sons, Ltd.     

Photocatalytic formulations for protein fibers: experimental analysis of the effect of preparation on compatibility and photocatalytic activities

In this article, we report an optimization study of a photocatalytic self-cleaning sol–gel formulation. In particular we studied the effect of formulation preparation time on the formation of anatase titanium dioxide sol and its compatibility to protein keratin-type wool fibers. The sols were formed by a low temperature sol–gel process. The nucleated anatase was characterized by UV–vis transmission, particle size distribution, X-ray diffraction, and transmission electron microscopy. The compatibility between the formulations and wool fibers is evaluated by field-emission scanning electron microscopy, UV transmission, and mechanical properties. The photocatalytic self-cleaning activity of coated fibers and its reproducibility are also discussed.     

Photoelectrochemical oxidation behavior of organic substances on TiO2 thin-film electrodes

The photoelectrocatalytic oxidation characteristics of salicylic acid, formic acid and methanol on anodized nanoporous titanium dioxide (TiO₂) thin-films were investigated by using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. From dark to ultraviolet illumination, the open circuit potential (OCP) and film resistance of TiO₂ films decreased markedly. A general equivalent circuit model was proposed for the photoelectrochemical system anodic TiO₂ thin-film electrode/test solution. The photoelectrochemical oxidation process of the organic compounds showed similar impedance features at OCP and was controlled by the charge transfer step. According to the polarization curves of the base solution and organic solutions, the kinetic rate curves for the photoelectrocatalytic oxidation of pure organic species were obtained as a function of the potential bias. One photooxidation peak was first observed at a bias potential of ca. 0.26 V for these species with low concentrations.     

Engineering the Distribution of Carbon in Silicon Oxide Nanospheres at the Atomic Level for Highly Stable Anodes

The application of high‐performance silicon‐based anodes, which are among the most prominent anode materials, is hampered by their poor conductivity and large volume expansion. Coupling of silicon‐based anodes with carbonaceous materials is a promising approach to address these issues. However, the distribution of carbon in reported hybrids is normally inhomogeneous and above the nanoscale, which leads to decay of coulombic efficiency during deep galvanostatic cycling. Herein, we report a porous silicon‐based nanocomposite anode derived from phenylene‐bridged mesoporous organosilicas (PBMOs) through a facile sol–gel method and subsequent pyrolysis. PBMOs show molecularly organic–inorganic hybrid character, and the resulting hybrid anode can inherit this unique structure, with carbon distributed homogeneously in the Si‐O‐Si framework at the atomic scale. This uniformly dispersed carbon network divides the silicon oxide matrix into numerous sub‐nanodomains with outstanding structural integrity and cycling stability.     

Fluorinated phenylated polyphenylenes with nanoporous structures and ultralow dielectric constants formed in supercritical carbon dioxide

New fluorinated bis(tetraarylcyclopentadienones) are synthesized, and their compositions and structures are investigated by elemental analysis and IR, Raman, ¹H, ¹³C, and ¹⁹F NMR spectroscopy. The fluorinated bis(tetraarylcyclopentadienones) are used to prepare a number of new fluorinated phenylated polyphenylenes that combine high thermal and mechanical characteristics and low dielectric constants (2.54?C2.74) with solubility in organic solvents. With the use of supercritical carbon dioxide, thermally stable nanoporous materials with ultralow dielectric constants (1.58?C1.97) are designed on the basis of phenylated polyphenylenes. For phenylated polyphenylenes, the described approach to the synthesis of nanoporous structures with the use of supercritical carbon dioxide is developed for the first time. This approach provides the basis for creation of new breakout technologies in the field of microelectronics.     

Determination of glycine,alanine, and leucine at different solution ph with the aid of donnan potential sensors based on hybrid membranes

The cross sensitive sensors whose analytical signal is the Donnan potential (PD-sensors) were developed for the determination of the amino acids glycine, alanine, and leucine in acidic and alkaline solutions. Hybrid materials based on perfluorinated sulfo cation-exchange membranes Nafion and MF-4SC with incorporated zirconium dioxide and silicon dioxide nanoparticles, including those with modified surfaces containing proton-acceptor groups, were used in the PD-sensors. The sensitivity of the PD-sensors to hydronium ions, which interfere with the determination of amino acids at pH < 7, was considerably decreased due to the use of the membranes obtained by an in situ method that contained silicon dioxide nanoparticles with amine-containing groups. The greatest sensitivity of the PD-sensors to the anions of amino acids at pH > 7 and the smallest sensitivity to the cations K⁺ were observed in hybrid membranes, which combined an increased rate of anion transfer and a low moisture capacity. The use of the PD-sensors based on hybrid membranes makes it possible to determine the cations, anions, and zwitterions of amino acids over a wide range of pH with a sufficiently high accuracy.     

Polyurea based aerogel for a high performance thermal insulation material

Less fragile lightweight nanostructured polyurea based organic aerogels were prepared via a simple sol–gel processing and supercritical drying method. The uniform polyurea wet gels were first prepared at room temperature and atmospheric pressure by reacting different isocyanates with polyamines using a tertiary amine (triethylamine) catalyst. Gelation kinetics, uniformity of wet gel, and properties of aerogel products were significantly affected by both target density (i.e., solid content) and equivalent weight (EW) ratio of the isocyanate resin and polyamine hardener. A supercritical carbon dioxide (CO₂) drying method was used to extract solvent from wet polyurea gels to afford nanoporous aerogels. The thermal conductivity values of polyurea based aerogel were measured at pressures from ambient to 0.075 torr and at temperatures from room temperature to −120 °C under a pressure of 8 torr. The polyurea based aerogel samples demonstrated high porosities, low thermal conductivity values, hydrophobicity properties, relatively high thermal decomposition temperature (~270 °C) and low degassing property and were less dusty than silica aerogels. We found that the low thermal conductivities of polyurea based aerogels were associated with their small pore sizes. These polyurea based aerogels are very promising candidates for cryogenic insulation applications and as a thermal insulation component of spacesuits.     

Synthesis, characterization and flame retardant of UV-curable hybrid coatings containing SiO2–P2O5–B2O3 via sol–gel method

A ternary sol containing silicon, phosphorus and boron modified by ??-methacryloxypropyltrimethoxysilane was synthesized by sol?Cgel method. The ternary sol was incorporated into the organic matrix and UV-curable organic/inorganic hybrid coating materials were obtained. Hardness, transmittance, haze, cross-cut adhesion and abrasion resistance results showed that the mechanical properties of the hybrid coatings improved effectively with no comprising on optical properties by increasing sol content. Scanning electron microscopy and Energy Dispersive X-ray spectrometer studies indicated that inorganic particles were homogenously dispersed in the organic matrix. The flame retardancy of the UV-curable coatings was investigated by thermogravimetric analysis and microscale combustion calorimeter. The results showed that the incorporation of sol into the organic network led to an improvement in the thermal stability and flame retardancy of the hybrid coating materials. It is a desirable achievement to improve simultaneously both flame retardancy and mechanical properties of the coatings.     

A resistive-type humidity sensor using composite films prepared from poly(2-acrylamido-2-methylpropane sulfonate) and dispersed organic silicon sol

A composite material of dispersed organic silicon sol and poly(2-acrylamido-2-methylpropane sulfonate) (poly-AMPS) was used to make humidity sensor without protective film or complicated chemical procedures. The organic silicon sol was dispersed well in the poly-AMPS without using dispersion agent. Parameters that may affect the water-resistive but humidity-sensitive characteristic of composite material, the adding amount of organic silicon sol solution and the film of thermal treatment time, were investigated. The microstructure of the material was analyzed, and the humidity sensing and electrical properties of the sensor were measured. The sensor well responded to humidity with a relatively good linearity, though it depended on the applied frequency. The temperature influence between 15 and 35 °C was within −0.17 % relative humidity (RH)/°C in the range of 30–90% RH. The activation energy was maximum around 40% RH. The sensor showed the hysteresis within 5.9%, fast response time, long-term stability (75 days at least) and satisfactory resistance to high humidity atmosphere (97% RH) and chemical environment (20% C₂H₅OH vapor). Analyzing the structure and complex impedance plots of organic silicon sol/poly-AMPS was used to explain improvement in humidity sensing properties in comparison with nano-sized SiO₂ powder/poly-AMPS films.     

A structure-permeability relationship of ultrathin nanoporous silicon membrane: a comparison with the nuclear envelope

We report on a simple, quantitative relationship between structure and permeability of a novel ultrathin nanoporous membrane based on nanocrystalline silicon. Large permeability of the free-standing nanomembrane to Ru(NH3)63+, O2, or 1,1'-ferrocenedimethanol, which was able to be measured for the first time by employing scanning electrochemical microscopy, is proportional to the density (67 mum-2) and average radius (5.6 nm) of nanopores. As solution electrolyte concentration decreases down to 0.01 M, the nanopores are selectively "closed" against Fe(CN)64- because of electrostatic repulsion against negative charges at the pore wall. Permeability of the silicon nanomembrane was compared to permeability of the nuclear envelope to find that the channel diameter of the nuclear pore complex that perforates the nuclear envelope is much larger than the average diameter of the silicon nanopores and concomitantly a hypothetical diameter of 10 nm.     

Novel fabrication process using nanoporous anodic aluminum oxidation and MEMS technologies for gas detection

A class of nanoporous TiO₂ gas sensors processed by novel anodic aluminum oxidation (AAO) of Al thin films and microelectromechnical systems (MEMS) techniques are presented. To enhance the sensitivity and reduce the sensing dimensions of a gas sensor, a nanoporous surface of the gas-sensitive material on the sensor is required. These sensors can be implemented on silicon or silicon dioxide substrate featuring a thin membrane of micro-hotplate structure featuring micro-heaters, thermometers and electrodes, and thus operate as chemoresistive devices. Combining the AAO method with dry-etch process, a homogeneous and nanoporous SiO₂ surface of the sensor can be effectively configured by modulating various hole diameters and depth, hence replacing conventional photolithography and electrochemical etch. The process integration including AAO, reactive ion etch (RIE) and microfabrication is mainly developed and a feasibility study of PVD TiO₂ thin film deposition upon the porous device is also provided. TiO₂ thin films deposited on the nanoporous surface are investigated and compared with non-porous TiO₂ films. It is encouraging that our fabrication process is able to provide relatively high surface area to enhance sensitivity of the sensor without additional doping steps. Our promising experimental results have revealed these miniature and cost-effective devices are not only compatible, but applicable to smart bio-chemical sensors of next generation.