Resonance behavior of the sensitivity of acoustic-wave chemical gas sensors

The effect of the resonance enhancement of the sensitivity of acoustic-wave chemical sensors is the-oretically predicted and substantiated experimentally. This enhancement is due to the peculiarities of the excitation of standing waves in the multilayer structure of the sensors. The obtained results provide the basis for the purposeful regulation of sensor sensitivity by selecting their design parameters. The effect discovered also offers promise from the standpoint of methodology: at the resonance conditions, sound velocity in the adsorbent film can be measured to a high precision. These experiments provide information on the elastic, dielectric, viscous-flow, and other properties of film materials and on their phase composition.     

Surface interpenetrating networks of polyacrylamide in poly(ethylene terephthalate) as a means of surface modification

Surface interpenetrating network (IPN) polymers are emerging hybrid materials in which the surface of existing polymers can be modified to preserve their chemical structure and bulk properties. A detailed structural characterization of poly(ethylene terephthalate) (PET) thin films on nanoscopically flat silicon wafers has been carried out by Scanning Probe Microscopy (SPM) and X-ray photoelectron spectroscopy (XPS). Examination of the surface of spin-coated annealed PET film by the SPM in tapping mode revealed a two-phase structure. One phase appeared as a dense crystalline fraction of the polymer while the other was identified as amorphous. These findings were supported by Differential Scanning Calorimetry (DSC), which recognized the crystallinity of annealed PET film at 30%. Modification of the PET surface with interpenetrating polyacrylamide (PAM) increased the roughness of the surface with uniform properties. The depth profiling with XPS revealed that PAM interpenetration extended down to 7.2 nm, confirming a three-dimensional character of the polymer modification, with a relative mass concentration of PAM at about 30.7% in the IPN interface.     

有机二硫化物润滑添加剂抗磨极压性能的密度泛函理论研究

用量子化学的密度泛函理论计算了12种有机二硫化物和铁原子簇的分子轨道指数及其与铁原子簇的化学吸附作用能, 探讨了这种作用能与抗磨性能的关系; 运用轨道能量近似原则讨论了有机二硫化物与铁原子的作用方式; 以前线电子密度、超离域性指数和原子净电荷作为判据分析了12种有机二硫化物与铁原子间键合的强弱、反应性的大小等表征有机二硫化物与金属作用强弱的参数。结果表明: 有机二硫化物与铁接触时, 在较缓和条件下, SS键优先断裂与金属发生化学吸附形成配位键, 起到抗磨作用; 在高负荷下, 与金属发生常规条件下不能发生的化学反应, 即CS键断裂生成无机膜, 起到极压作用; 且随着碳链的增长, 有机二硫化物的抗磨性能愈来愈好, 但极压性能愈来愈差; 运用量子化学计算得到的预测结果与摩擦学试验结果具有良好的一致性, 可为同类极压添加剂化合物的分子设计提供较为可靠的参考依据和理论方法。     

金属有机化学气相沉积法制备ZnO和ZnO∶Ni薄膜及其特性分析

采用金属有机化学气相沉积法制备了ZnO和ZnO∶Ni薄膜,并对它们的结构、光学和电学特性进行了对比研究.通过扫描电子显微镜( SEM)和X射线衍射(XRD)对薄膜的表面形貌和晶体结构进行了分析,结果表明,Ni元素的掺杂虽然降低了薄膜的晶体质量,但并未改变ZnO的纤锌矿结构.通过紫外-可见分光光度计对薄膜的光学特性进行了...     

Hard amorphous (diamond-like) carbons

The hard forms of amorphous carbon and hydrogenated amorphous carbon, also known as diamond-like carbon, have recently aroused considerable interest as coating materials. This paper reviews their preparation, structure and properties. These carbons contain both sp² and sp³ sites. A chemical bonding model is developed which describes the arrangement of these sites and which accounts for many of the electronic and mechanical properties. The review covers the various deposition methods and the deposition mechanisms, the characterisation of amorphous carbons by techniques such as diffraction, electron energy loss, Raman, infra-red, nuclear magnetic resonance, and thermal stability, their electronic structure, optical properties and electronic spectra, and their mechanical properties such as elastic modulus, hardness, wear rate, friction and film adhesion. The dependence of electronic and mechanical properties on deposition methods and conditions is studied, to assess which methods are most valuable for applications.     

稳定的ZrO2基SOFC中CeO2夹层的制备方法和作用机制

Sm、Gd和Y掺杂的CeO₂夹层是解决固体氧化物燃料电池的电极和电解质间物理化学性质不相容问题的最佳材料，已经展示出广泛的应用前景。本文介绍了CeO₂粉体的各种合成方法以及对粉体性能的影响。综述了制备CeO₂夹层薄膜的各种方法，其中包括直流反应磁控溅射（Reactively direct current magnetron sputtering）物理方法；火焰辅助气相沉积（Flame assisted vapor deposition，FAVD）和溶胶凝胶法（Sol-gel）等化学方法；电泳沉积法（Electrophoretic deposition, EPD）、丝网印刷法（Screen printing）和浸渍涂布法（dipping deposition）等陶瓷成型方法，评述了这些方法的优缺点，详细介绍了近年来采用上述方法制备的CeO₂夹层薄膜的性能以及对电池性能的改进，论述了CeO₂夹层提高电池性能的作用机制。综合分析了这些制备方法的异同和特点，指明了该领域的发展前景。阐述了开展CeO₂夹层研究对我国SOFC发展的重大意义。     

Ordered polymeric microhole array made by selective wetting and applications for electrochemical microelectrode array

In this paper, we report the microelectrode array fabrication using selective wetting/dewetting of polymers on a chemical pattern which is a simple and convenient method capable of creating negative polymeric replicas using polyethylene glycol (PEG) as a clean and nontoxic sacrificial layer. The fabricated hole-patterned polypropylene film on gold demonstrated enhanced electrochemical properties. The chemical pattern is fabricated by microcontact printing using octadecanethiol (ODT) as an ink on gold substrate. When PEG is spin-cast on the chemical pattern, PEG solution selectively dewets the ODT patterned areas and wets the remaining bare gold areas, leading to the formation of arrayed PEG dots. A negative replicas of the PEG dot array is obtained by spin-coating of polypropylene (PP) solution in hexane which preferentially interacts with the hydrophobic ODT region on the patterned gold surface. The arrayed PEG dots are not affected the during PP spin-coating step because of their intrinsic immiscibility. Consequently, the hole-patterned PP film is obtained after PEG removal. The electrochemical signal of the PP film demonstrates the negligible leakage current by high dielectric and self-healing of defects on the chemical pattern by the polymer. This method is applicable to fabrication of microelectrode arrays and possibly can be employed to fabricate a variety of functional polymeric structures, such as photomasks, arrays of biomolecules, cell arrays, and arrays of nanomaterials.     

Covalently networked monolayer-protected nanoparticle films

Covalently networked films of nanoparticles can be assembled on various substrates from functionalized monolayer-protected clusters (MPCs) via ester coupling reactions. Exposure of a specifically modified substrate to alternating solutions of 11-mercaptoundecanoic acid exchanged and 11-mercaptoundecanol exchanged MPCs, in the presence of ester coupling reagents, 1,3-dicyclohexylcarbodiimide and 4-(dimethylamino)pyridine, results in the formation of a multilayer film with ester bridges between individual nanoparticles. These films can be grown in a controlled manner to various thicknesses and exhibit certain properties that are consistent with films having other types of interparticle connectivity, including chemical vapor response behavior and quantized double layer charging. Ester coupling of MPCs into assembled films is a straightforward and highly versatile approach that results in robust films that can endure harsher chemical environments than other types of films. The stability of these covalent films is assessed and compared to other more traditional MPC film assemblies.     

Multifunctional chemical vapor sensors of aligned carbon nanotube and polymer composites

Partially coating perpendicularly aligned carbon nanotube arrays with an appropriate polymer thin film along their tube length provides a novel concept for developing new sensors of high sensitivity, good selectivity, and excellent environmental stability for the detection of a broad class of chemical vapors with low power consumption. The absorption and desorption of chemical vapors by the polymer matrix cause changes in the inter-tube distance and, hence, the surface resistance across the nanotube film. Simple measurements of the resistance change, therefore, constitute the nanotube-polymer chemical vapor sensors. These rationally designed, aligned carbon nanotube-polymer composite films are flexible and can be effectively integrated into many systems for a wide range of potential applications, including their use as multifunctional sensors for sensing chemical vapors, mechanical deformations, thermal and optical exposures.     

Synthesis and properties of thermoplastic polyimides with ether and ketone moieties

A series of polyimides containing ether and ketone moieties were synthesized from 1,3‐bis(4‐fluorobenzoyl) benzene and several commercially available dianhydrides via a conventional two‐step polymerization. The inherent viscosities of Polyamide acids ranged from 0.46 to 0.73 dL/g. Thermal properties, mechanical properties, and thermalplasticity of the obtained polimide films were investigated by focusing on the chemical structures of their repeat units. These films were amorphous, flexible, and transparent. All films displayed low T_gs (184–225 °C) but also excellent thermal stability, the 5% weight loss temperature was up to 542 °C under nitrogen. The films showed outstanding mechanical properties with the modulus up to 3.0 GPa and the elongation at break in the range of 8–160%. The uniaxial stretching of PI‐a at high temperature was studied owing to its excellent flexibility. The PI‐a had an elongation at break up to 1600% at 245 °C and the uniaxially stretched film exhibited a much higher modulus (3.9 GPa) and strength (240 MPa) than undrawn film. The results indicated that PI‐a can potentially be used to prepare materials such as fiber, ultra‐thin film or ultra‐high modulus film. All the obtained films also demonstrated excellent thermoplasticity (drop of E′ at T_g > 10³) which made the polyimides more suitable for melt processing. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2878–2884, 2010     

Placement and characterization of pairs of luminescent molecules in spatially separated regions of nanostructured thin films

Methods of making mesostructured sol-gel silicate thin films containing two different molecules deliberately placed in two different spatially separated regions in a one-step, one-pot preparation are developed and demonstrated. When the structure-directing agent is the surfactant cetyltrimethylammonium bromide, the structure is 2-D hexagonal with lattice spacings between 31.6 and 42.1 angstroms depending on the dopant molecules and their concentrations. The three general strategies that are used to place the molecules are philicity (like dissolves like), bonding, and bifunctionality. These strategies take advantage of the different chemical and physical properties of the regions of the films. These regions are the inorganic silicate framework, the hydrophobic organic interior of the micelles, and the ionic interface between them. Luminescent molecules that possess the physical and chemical properties appropriate for the desired strategies are chosen. Lanthanide and ruthenium complexes with condensable trialkoxysilane groups are incorporated into the silicate framework. 1,4-Naphthoquinone, pyrene, rhodamine 6G and coumarin 540A, and lanthanides with no condensable trialkoxysilanes occupy the hydrophobic core of micelles by virtue of their hydrophobicity. The locations of the molecules are determined by luminescence spectroscopy and by luminescence lifetime measurements. In all cases, the long-range order templated into the thin film is verified by X-ray diffraction. The simultaneous placement of two molecules in the structured film and the maintenance of long-range order require a delicate balance among film preparation methodology, design of the molecules to be incorporated in specific regions, and concentrations of all of the species.     

Targeting of an appropriate amylose type starch for specific product applications

Some varieties of maize are known to produce starches with different chemical and physical properties. These characteristics have been recognized over the years to provide different functional properties. Amylose, in particular, has been used to provide unique functionality in numerous applications where gel strength and rigidity, as well as film forming capability, have been desired qualities. In recent years, researchers have begun to recognize that amylose is not a single chemical substance, but rather a diverse group of glucans differing in molecular size, and branching characteristics. The main shared attribute of all “amylose” polymers is their common ability to bind iodine. This binding ability is still the basis for most routine amylose determination assays. We have shown that there are uniquely different amylose polymers, and our laboratory has reported on some of the differences in physical properties. This paper reports how these unique physical properties can be applied effectively to practical applications.     

硫化物纳米级粒子化膜的形成与气相性质的影响

采用偏振光反光度、紫外及可见光谱、电子显微镜形貌观察、粒子大小测定及电子衍射等方法加以系统研究硫化锌纳米级粒子化膜的制备与气相性质的影响．     

硫化物纳米级粒子化膜的形成与气相性质的影响

采有偏振光反光度，紫外及可见光谱，电子显微镜形貌观察，粒子大小测定及电子衍射等方法以加系统研究硫化锌钠米级粒子化膜的制备与气相性质的影响。     

Influence of Precursor Chemistry on the Formation of MTiO3 (M = Ba,Sr) Ceramic Thin Films

Thin films of BaTiO3 and SrTiO3 were prepared by a chemical solution deposition method. The impact of the precursor on the processing, on the microstructure, and on the dielectric properties has been studied by systematically varying the alkyl chain length of the used Ba- and Sr-carboxylates. In addition, the effect of stabilizing the Ti-alkoxide precursor by acetylacetone has been investigated. The decomposition process, the crystallization behavior, and the film morphology were analyzed by glancing incidence XRD, reflectance FT-IR and field emission SEM. Distinct precursor effects on the thin film morphology and properties were revealed. Part of this influence can be attributed to an intermediate complex carbonate phase which forms for selected carboxylates with short alkyl chains. The high transformation temperature of this intermediate phase to the perovskite obviously has a marked influence on the crystallization and densification process of the alkaline earth titanate thin films. We correlate the morphological differences of the films to their dielectric properties.     

基于羧酸银的光敏热成像技术进展

最近10年,光敏热显影成像材料在技术上取得了重要进展,特别是以羧酸银作为银源的这类材料.这些进展集中体现在1995年为满足商品需要而研制成功的世界上第一个具有高分辨力、可作诊断使用的医用X射线胶片的Kodak DryView激光成像片上.此后,采用同样技术的一类特殊片种,即高反差的印刷胶片也随之问世.这些产品的实践应用都相当成功,已被多家公司所采用.这些新产品得益于三个方面的技术进展:改进成像层的照相性质、高影像质量和低成本的激光成像硬件,这也是此研究工作的焦点.在这类材料上所取得的重要成就反映在它们的高分辨力、高最大密度、低最小密度以及整张胶片性质的均一性上.所有这些优点,再加上超过100年的影像稳定性,使原来“老”的光敏热显影技术发生了一次脱胎换骨的变化,成为了当今最新的一种硬拷贝成像介质.     

GeS2 and GeSe2 PECVD from GeCl4 and Various Chalcogenide Precursors

The plasma enhanced chemical vapor depositions of germanium chalcogenide thin films from germanium tetrachloride, hydrogen sulfide and alkyl chalcogenides were studied to determine the viability of these reagents for thin film deposition. Hydrogen sulfide is a commonly used reagent for this technique and was used to determine optimal reaction conditions for thin film deposition. Germanium tetrachloride, alkylsulfides and alkylselenides were also employed because of their lower potential toxicities and higher availabilities compared to their more typical congeners: germane, hydrogen sulfide and hydrogen selenide in the formation of germanium chalcogenides. Alkylsulfides were found to be unsuitable for the deposition of germanium sulfides, however alkylselenide precursors were used successfully for the deposition of germanium selenides. The relative mass flow rates, reactor pressure, substrate temperature and plasma power density were studied for their effects on germanium chalcogenide deposition. These parameters affected the composition, deposition rate, film quality, and spectroscopic properties of the deposited films.     

Synthesis and Color-tunable Fluorescence Properties of Schiff Base Zinc （II） Complexes Used as Electroluminescent Materials

Four kinds of bis(N-alkylsalicylaldiminato) zinc(ll) complexes were synthesized, and their molecular structures were determined by FT-IR and elemental analysis. Their photoluminescence properties were determined, which indicated that they could emit strong fluorescence varying from blue to yellow to reddish orange depending on their different molecular structures. They had good thermostability, solubility and film forming capability, and can be used as organic electroluminescent materials. These new complexes may afford the feasibility to realize full-color display with materials based on similar molecular structures.     

Introduction of O-butyrylchitosan with a photosensitive hetero-bifunctional crosslinking reagent to silicone rubber film by radiation grafting and its blood compatibility

Based on an in vitro test for an improvement of the blood compatibility of silicone rubber (SR) films by grafting O-butyrylchitosan (OBCS), OBCS was covalently immobilized onto SR film surface using the photosensitive hetero-bifunctional crosslinking reagent, 4-azidobenzoic acid, which was previously bonded to OBCS by reaction between an acid group of the crosslinking reagent and a free amino group of OBCS. Surface properties of SR film were investigated by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), electron spectroscopy for chemical analysis (ESCA) and the water contact angle measurements. The blood compatibility of SR film was evaluated by platelet rich plasma (PRP) contacting experiments and the results were observed by scanning electron microscopy (SEM). The state of platelet adhesion was described. The suitable modifications could be carried out to tailor SR films biomaterial to meet the specific needs of different biomedical applications. These results suggest that the blood compatible of SR films/OBCS films show their suitability as potential biomaterials.     

Deformation controlled assembly of binary microgel thin films

We describe the assembly of two-component, hydrogel microparticle (microgel) monolayer films onto solid substrates via passive Coulombic adsorption from solution. By using two different microgel types with nearly identical sizes but different degrees of softness, the influence of particle deformation on film composition was determined. Determination of the microgel properties using a variety of light scattering techniques allowed for predictions of the film composition as a function of solution composition using a random sequential adsorption (RSA) model. The films were then studied via atomic force microscopy (AFM), and surface coverage and population statistics were determined from the images and compared to the model predictions. Deviations from the predicted particle adsorption behavior can be directly traced to differences in particle softness, deformation, and particle footprint following adsorption, which biases the particle coverage to the more rigid (smaller footprint) particles. Furthermore, by using a mixture of degradable and nondegradable core/shell particles, the identity of the particles can be unambiguously determined by measuring AFM height changes following erosion of the core from the microgels. These results show that, regardless of the solution diffusion properties of soft particles, their competition for surface adsorption from a binary mixture is largely dictated by their interactions with the surface and their deformation at the surface.