Electrospun camphorsulfonic acid doped poly(o-toluidine)–polystyrene composite fibers: Chemical vapor sensing

The electrospinning technique was utilized to produce camphorsulfonic acid (HCSA) doped poly(o-toluidine) (POT)–polystyrene (PS) composite fibers in the non-woven mat form. HCSA doped POT–PS composite fibers were fabricated on an interdigited gold (Au) substrate for use as a chemical vapor sensor. The composite fiber sensor responded to volatile chemicals in different ways, depending on the polarity of sensing chemicals. The surface morphology of the non-woven composite fiber mat after chemical vapor sensing was unchanged. This study highlights that composite fibers comprised of polyaniline derivative and a spinnable polymer do have potential for use as chemical sensors due to their good solubility in common solvents and detectable electrical changes at low fiber contents.     

PAN/PANI/rGO/Au复合纤维的制备及其催化、原位SERS监测性能研究

负载型贵金属纳米催化剂是提高贵金属催化剂利用率,降低经济成本的一种有效途径,也是一种新型的有潜力的表面增强拉曼光谱(SERS)的基底材料。本文首先利用静电纺丝技术构建了还原的氧化石墨烯(rGO)增强的聚丙烯腈/聚苯胺复合纤维(PAN/PANI/rGO),然后采用原位还原的方法在其表面生长金纳米颗粒得到了PAN/PANI/rGO/Au复合纤维,通过SEM, FTIR, XRD, XPS, Raman和UV-Vis光谱等手段对复合纤维进行了结构和形貌表征,最后以NaBH₄还原四硝基苯酚(4-NP)为模型,研究了复合纤维的催化性能和原位SERS检测该催化还原反应的过程,并将其与同种方法制备的PAN/PANI/GO/Au和PAN/PANI/Au复合纤维进行比较。结果表明,rGO增强的PAN/PANI/rGO/Au复合纤维具有优于PAN/PANI/GO/Au和PAN/PANI/Au复合纤维的催化活性、原位增强拉曼检测的能力和循环性能。     

Preparation of novel core-shell nanoparticles by electrochemical synthesis

Nanostructural gold/polyaniline core/shell composite particles on conducting electrode ITO were successfully prepared via electrochemical polymerization of aniline based on 4-aminothiophenol （4-ATP） capped Au nanoparticles. The new approach to the fabrication included three steps： preparation of gold nanoparticles as core by pulse electrodeposition; formation of ATP monolayer on the gold particle surface, which served as a binder and an initiator; polymerization of aniline monomer initiated by ATP molecules under controlled voltage lower than the voltammetric threshold of aniline polymerization, which assured the formation of polyaniline shell film occurred on gold particles selectively Topographic images were also studied by AFM, which indicated the diameter of gold nanoparticles were around 250 run. Coulometry characterization confirmed the shell thickness of polyaniline film was about 30 nm A possible formation mechanism of the Au/polyaniline core-shell nanocomposites was also proposed. The novel as-prepared core-shell nanoparticles have potential application in constructing biosensor when bioactive enzymes are absorbed or embedded in polyaniline shell film.     

In-situ chemical synthesis route for a fiber shaped gold-polyaniline nanocomposite

A facile synthesis route is described for the preparation of a gold-polyaniline nanocomposite material by polymerization of aniline hydrochloride using HAuCl4 as the oxidant. It was found that the oxidative polymerization of aniline hydrochloride leads to the formation of polyaniline with a fiber-like morphology, while the concomitant reduction of HAuCl₄ results in the formation of gold nanoparticles of diameter 2–7 nm. The gold nanoparticles were highly dispersed and stabilized throughout the polyaniline fibers while being in intimate contact with the polymer. The combination formed a uniform metal-polymer composite material.     

Superhydrophobicity from composite nano/microstructures: Carbon fabrics coated with silica nanoparticles

This study demonstrates the hydrophobic coating of silica nanoparticles onto microscaled carbon fabrics (CFs) and investigates the superhydrophobic behavior of composite nano/microstructures. The two-tier composite surfaces are based on regularly ordered carbon fibers (8-10 µm in diameter) that are coated with SiO₂ nanoparticles with an average size of 300-500 nm. The microscale fiber is used here as the primary surface roughness, while the silica nanoparticles serve as the secondary roughness, mimicking the lotus leaf in nature. Increasing the density of silica on CFs showed significant effects on the enhancement of static contact angle, decrease of contact angle hysteresis, and superhydrophobic stability. The results can be attributed to the fact that the higher density of silica coating results in more tortuous three-phase contact line, thus facilitating the self-cleaning effect.     

金核/铂壳纳米粒子的光化学合成及电催化活性

在含不同摩尔比的Au(Ⅲ)和Pt(Ⅳ)离子的PEG(聚乙二醇)-丙酮溶液中,采用光化学共还原法合成了一组Au@Pt复合纳米粒子,并以炭黑分别对其负载制成Au@Pt/C催化剂。借助于UV-Vis、TEM和HR-TEM的表征,证实复合纳米粒子为球形的核/壳结构;分别以XPS、EDS和电化学方法分析了复合粒子的化学状态、结构特点和Au@Pt/C催化剂的催化性质。结果表明,不同Au:Pt摩尔比的Au@Pt/C催化剂对甲醇氧化反应具有良好的催化活性和稳定性,其中Au:Pt=1:1时形成的Au@Pt/C催化剂电催化活性最高,约为商品Pt/C催化剂的4倍。简要讨论了核/壳结构产生高催化活性的主要原因。     

Conductive fibers from enzymatically synthesized polyaniline

Conducting polyaniline (PANI) fibers have been spun from a water-soluble form of PANI which was enzymatically synthesized. The enzyme, horseradish peroxidase (HRP) was used to polymerize aniline in the presence of sulfonated polystyrene (SPS) to directly form a water-soluble, conducting, PANI/SPS complex which combines moderate electrical conductivity with appreciable processability. The PANI/SPS complex was spun into fibers from aqueous solution using a dry-spinning technique. Thermal studies which included thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and DMA show that the complex has very good thermal stability and a T_g at 150°C. Mechanical properties of the fibers show a tenacity of 0.34 cN/dtex for the as-spun fibers with an increase to 0.56 cN/dtex after thermal stretch alignment. Wide angle X-Ray diffraction shows the presence of two weak peaks at d values of 4.16 Å and 2.95 Å for the drawn fibers, while no crystalline reflections were observed for cast films. The drawn fibers also show an order of magnitude improvement in conductivity. These results show that some degree of fiber orientation and crystallinity may be induced during processing.     

Preparation and tribological studies of nanocomposite films fabricated using spin-assisted layer-by-layer assembly

Uniform and smooth composite multilayer films composed of gold nanoparticles and polyelectrolytes ([Au/(PAH-PSS)_nPAH]_m) multilayers were fabricated on a silicon substrate using a time-and cost-efficient spin-assisted layer-by-layer (SA-LbL) self-assembly technique. The microstructure and morphology of the multilayer films were characterized by means of transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The tribological behavior of the composite multilayer films was evaluated using a ball-on-plate tribometer. It was found that the density of the monolayer of gold nanoparticles on the silicon substrate was dependent on the deposition time, but the coverage of the Si substrate by the gold nanoparticle kept almost unchanged at a deposition duration above 30 min. The antiwear life and load-carrying capacity of the [Au/(PAH-PSS)_nPAH]_m composite film substantially increased with increasing number of the polymer bilayers and gold nanoparticles monolayer, which could be attributed to the robust organic-inorganic nanocomposite structure and PAH and PSS fragments transferred onto the counterpart surface.     

All-solid-supercapacitor based on polyaniline and sulfonated polymers

All-solid-supercapacitor based on chemically synthesized polyaniline (PANI) and sulfonated polymers have been reported. Poly vinyl sulfonic acid (PVSA) is used as a proton conducting solid electrolyte. Fluorinated ethylene propylene copolymer grafted with acrylic acid and sulfonated (FEP-g-AA-SO₃H) membrane was used as the separator. Composite electrodes were prepared from PANI, PVSA, electronically conducing carbon and poly tetra fluroethylene (PTFE) powder. Electrochemical studies of the supercapacitor were carried out in a unit cell. The unit cell consisted of three layers structure: composite electrode//FEP-g-AA-SO₃H//composite electrode. This symmetric configuration of supercapacitor represents type1 (p-p) class, since both the electrodes were made from p-dopable PANI based composite electrodes. Optimization of solid electrolyte in the composite electrode was carried out. Supercapacitor was characterized by cyclic voltammetry and charge–discharge cycles. Capacitance of 98 F/g of PANI was obtained. The reduction in the capacitance after 1500 cycles was found to less than 20%. The non-ideal behavior of the supercapacitor was analyzed by impedance analysis.     

Preparation,FTIR spectroscopic characterization and isothermal stability of differently doped conductive fibers based on polyaniline and polyacrylonitrile

Conductive fibers based on polyaniline (PANI) and polyacrylonitrile (PAN) were obtained by stirring with magnetic bar. This research was conducted to investigate conducting fibers of polyaniline:polyacrylonitrile (PANI:PAN) composite with different weight ratios of aniline in PAN matrix. The fibers were prepared by stirring process. The best conductivity behavior of the fibers was obtained with 5 mL of aniline. The fibers obtained were characterized using Fourier-transform infrared spectra (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The variation of electrical conductivity with different type doping agents (HCl, H₂SO₄ and HClO₄) and the stability in terms of DC electrical conductivity retention was studied in an oxidative environment by isothermal characteristics.     

A novel formation process of polyaniline micro-/nanofiber network on solid substrates

By a chemical oxidative polymerization of aniline on solid substrates treated with Au nanoparticles (Au-NPs) deposition and 4-aminothiophenol (ATP) modification, polyaniline (PANI) fibers were obtained in micro-/nanosize with two-dimensional network structures. The observation by laser scanning microscopy (LSM) indicated that the formation of PANI fibrous network occurred during the drying process rather than the polymerization. It was suggested the ATP modification on Au-NPs deposited substrate resulted in an inhomogeneous grafting of solution-formed PANI on the solid substrates, which self-aggregated to the fibrous network structure with the evaporation of water due to interchain interactions. The influence of polymerization conditions on the formation of fibrous network and the conducting property of the prepared film were discussed. Results from the gas sensing of the as-prepared PANI sensor upon exposure to NH₃ confirmed that the sensitivity and responding rapidity was improved greatly by the PANI 2D fibrous network structure. Especially, a rapid response in resistance change on NH₃ with low concentration indicated that the developed method in this work can be used to fabricate highly sensitive PANI gas sensors.     

Preparation of Au/ polypyrrole composite nanoparticles and study of their electrocatalytical reduction to oxygen with (without) lacasse

The colloids of Au/polypyrrole (AuPPy) composite nanoparticles were prepared by oxidizing pyrrole monomer with HAuCl₄ in a cetyltrimethylammonium bromide (CTAB) solution. Scanning electron microscopy (SEM) suggests the AuPPy nanoparticles in the form of regular spheres, approximately 200 nm in diameter. The resulting colloid of AuPPy composite nanoparticles strongly adheres to the surface of Au electrodes and exhibits better electrocatalytical reduction of oxygen than bare Au electrodes. It means that the complex procedures of centrifuge and wash are avoided. Also, no linker molecules are needed and the immobilization of nanoparticles is achieved easily in a single-step procedure. The experimental parameters were optimized with regard to the concentration of pyrrole and HAuCl₄. The direct electron transfer of laccase is observed after it is immobilized on AuPPy modified electrodes by glutaraldehyde. With the help of mediator 2,2′-azino-bis-(3-ethylbenzothiazoline-sulfonic acid) (ABTS), laccase electrode gives an electrocatalytical reduction wave of oxygen at least at 0.8 V. This material is an excellent choice for the design of metal nanoparticle modified electrodes or biosensors     

BTA@SPANI-POSS环氧涂层的制备及防腐性能

为提高环氧涂层在腐蚀环境下的防腐性和持久性,合成一种负载有缓蚀剂苯并三唑(BTA)的苯并三唑@磺化聚苯胺功能化倍半硅氧烷(BTA@SPANI-POSS),随后将 BTA@SPANI-POSS 与环氧树脂共混得到 BTA@SPANI-POSS 环氧涂料, 最后在 Q235 碳钢上制备数种复合环氧涂层。通过红外光谱、紫外可见光谱、扫描电子显微镜对 BTA@SPANI-POSS 的结构、 缓蚀性能、表面形貌进行表征,利用接触角测量仪、电化学工作站研究所制备涂层的疏水性能和防腐性能。研究表明,随着 SPANI-POSS 的添加,涂层沾湿性能降低。电化学阻抗谱(EIS)和塔菲尔极化曲线测试结果表明,与 SPANI-POSS 环氧涂层相比,负载有 BTA 的 BTA@SPANI-POSS 环氧涂层对金属基底具有更高和更持久的保护能力,其中试样 EB_1.5%的腐蚀电流密度 i_corr为 16.67 ? A·cm^?2 ,其极化电阻 R_p为 2.467 M?·cm² ,具有较低的腐蚀动态速率。在 3.5 wt.% NaCl 溶液中浸泡 15 d 后环氧涂层仍具有良好的防腐蚀效果,其阻抗值 Z_0.01Hz 仍保留有第 1 d 时的 26.89%,表现出优异的长期稳定性和防腐性能。归因于 SPANI-POSS 与 BTA 之间的协同作用,所制备的 BTA@SPANI-POSS 环氧涂层在浸泡过程中与碳钢基底发生络合反应,从而起到长时间的保护作用。     

Structural Evolution of Silicon Oxynitride Fiber Reinforced Boron Nitride Matrix Composite at High Temperatures

The structural evolution of a silicon oxynitride fiber reinforced boron nitride matrix (Si-N-O_f/BN) wave-transparent composite at high temperatures was investigated. When heat treated at 1600 °C, the composite retained a favorable bending strength of 55.3 MPa while partially crystallizing to Si₂N₂O and h-BN from the as-received amorphous structure. The Si-N-O fibers still performed as effective reinforcements despite the presence of small pores due to fiber decomposition. Upon heat treatment at 1800 °C, the Si-N-O fibers already lost their reinforcing function and rough hollow microstructure formed within the fibers because of the accelerated decomposition. Further heating to 2000 °C led to the complete decomposition of the reinforcing fibers and only h-BN particles survived. The crystallization and decomposition behaviors of the composite at high temperatures are discussed.     

A sonochemical method for the synthesis of polyaniline and Au–polyaniline composites using H2O2 for enhancing rate and yield

We report on a simple and novel sonochemical method for the preparation of polyaniline (PANI), as well as its composite, with Au nanoparticles. This technique utilizes ultrasound radiation as an energy source to facilitate the reaction by reducing the reaction time, as well as significantly increasing the yield. The tremendous increase in the reaction rates is explained on the basis of the intensive bubble collapse conditions, which rapidly generate the oxidative radicals necessary for polymerization.     

Tensile behavior of hybrid tungsten composites with zirconium carbide nanoparticles and tungsten fibers

Hybrid tungsten composites reinforced with zirconium carbide (ZrC) nanoparticles and tungsten fibers were developed by the conventional powder metallurgy process (ball-mill mixing of powders and fibers followed by spark plasma sintering). The synergistic and mutual influences of the fibers and nanoparticles on tungsten were investigated in tensile behavior and fracture-energy tests. Aided by the ZrC nanoparticles, up to 30% of the fibers could be embedded in the tungsten matrix. The fracture energy was maximized by co-introducing 0.2 wt% ZrC particles with 20 wt% short tungsten fibers. The fracture-energy enhancement of the short fibers is contributed by pseudo-toughness from the fiber–matrix interface, inherent toughness from the fibers themselves, and grain refinement (by 50%) of the tungsten matrix. The fracture energy of the composite is very sensitive to the ZrC content, because the two-way action of ZrC weakens the pseudo-toughness of the interface energy.     

Studies on the rectifying effect of the heterojunction between porous silicon and water-soluble copolymer of polyaniline

Rectifying diodes of the heterojunction between porous silicon (PS) and water-soluble copolymer of polyaniline (PAOABSA) with the rectifying ratio of 5.0 × 10⁴ at ±3 V bias were fabricated and the rectifying characteristics of the heterojunction diode, Al/PS-PAOABSA/Au cell, were measured as a function of the sulfonated degree and thickness of the PAOABSA copolymer films, as well as the oxidation of silicon exposed to air. It was found that decreasing the sulfonated degree and thickness of the PAOABSA copolymer films is favorable for enhancement of rectifying characteristics of the heterojunction diodes. Moreover, it was noted that the oxidation of silicon exposed to air is harmful for the rectifying effect of the heterojunction diodes.     

Spectral and adsorption characteristics of Au(III) and Au(0) composite materials

The adsorption of HAuCl₄ chloroauric acid on silica modified with γ-aminopropyltriethoxysilane (aminosilica) and on aluminum oxide is studied. Diffuse-scattering spectra of these Au(III) composite materials and their reduced Au(0) composites are recorded in the visible and infrared spectral ranges. Au(III) composites are selective with respect to the adsorption of phenylacetylene (PA) from octane due to the formation of π-complexes with Au(III). Au(III)-aluminum oxide composite material has a much larger capacity for PA adsorption than does aminosilica composite with the same gold content. The formation of coordination bonds between free aminopropyl groups of the silica carrier and gold atoms prevents PA adsorption. The formation of such bonds is manifested in a shift in λ_max of the spectral line from 408 to 522 and 546 nm with a decrease in [Au(III)] concentration from 400 to 120 and 60 μmol/g. The decrease in the intensity and the red shift of the absorption bands of NH₂ stretching vibrations in the infrared spectra of the specimen upon modification also confirms the supposition. There are absorption bands of free hydroxyl radicals, but no band of bound radicals in the infrared spectra of Au(0) composites. The electronic spectra (λ_max = 511, 504, and 512 nm) are close for all three specimens that differ in gold content, which means that the sizes of immobilized Au(0) nanoparticles are similar. Upon the sorption of HAuCl₄ on a Au(III)-aluminum oxide specimen, the absorption band of surface OH groups disappears, however, in Au(0) composite, it appears again near 3105 cm^?1.     

Effect of adding Pd nanoparticles to dimercaptan-polyaniline cathodes for lithium polymer battery

The electrochemical properties of 2,5-dimercapto-1,3,4-thiadiazole (DMcT)—polyaniline (PAn) composite films containing Pd nanoparticles (average diameter: 28 nm) were investigated. Compared to DMcT–PAn composite film, the DMcT–PAn composite film containing Pd nanoparticles showed enhanced redox current and discharge capacity. The enhanced activity is attributed to the nanosize dispersion of the Pd catalyst particles within the DMcT–PAn matrix. UV-Vis spectroscopy and X-ray photoelectron spectroscopy (XPS) results confirmed the interactions between DMcT and Pd nanoparticles. We have obtained the positive effect of Pd nanoparticles addition on the redox activity of the DMcT–PAn composite.     

NO2 gas sensing based on ordered ultrathin films of conducting polymer and its nanocomposite

The metal oxides films are widely used for CO, aromatic hydrocarbon and NO₂, gas-sensing applications, but such sensors mostly lack selectivity and operate at high temperatures (300–500 °C). We focused on the use of organized ultrathin films of conducting polymers and their nanocomposites, which recognize selectively the NO₂ gases with a very high sensitivity (≤ppb). Polyhexylthiophene (PHTh), poly(ethylene dioxythiophene) (PEDT), PHTh–PEDT copolymer, sulfonated polyaniline, polyaniline (PANI)–SnO₂, polypyrrole (PPy)–SnO₂, PEDT-SnO₂, PHTh–SnO₂ and copolymer (HTh-EDT)–SnO₂ conducting polymer and nanocomposite thin films were fabricated and used for gas sensing applications. The physical properties (UV and FTIR) such films were investigated before and after the NO₂ gas treatment. Regioregular PHTh, its copolymer P(HTh-PEDT), and their metal oxide nanocomposites films detected NO₂ gas with a high sensitivity.