介质阻挡放电等离子体法制备优异光催化合成过氧化氢性能的氮空穴掺杂石墨相氮化碳（英文）

过氧化氢(H_2O_2)是一种绿色氧化剂,广泛应用于纺织、印染、造纸和医药等行业.目前,工业上采用蒽醌法制备H_2O_2,它由于需要多步加氢和氧化处理,因此能耗非常大.研究发现,采用贵金属催化剂可以将氢气和氧气直接合成H2O2,但催化剂价格过高,且反应本身存在爆炸风险.近年来,半导体光催化合成H_2O_2受到广泛关注.研究发现,在水存在下,光电子可以将氧气还原得到H_2O_2.介质阻挡放电(DBD)等离子体广泛应用于材料合成、挥发性有机物处理、汽车尾气净化和材料表面处理等.石墨相氮化碳(g-C_3N_4)是新型非金属光催化剂,以其性质稳定、能带适中和制备方便等优点而广受青睐.然而g-C_3N_4的比表面积和电荷分离效率较低,大大限制了其应用.本文采用DBD等离子体法在氢气气氛下制备了N空穴掺杂的石墨相氮化碳,采用XRD,N_2吸附,UV-Vis,SEM,TEM,XPS,EIS,EPR,O_2-TPD及PL等方法对催化剂进行了表征,并考察了N空穴对催化剂结构性质、光学性质及光催化合成H_2O_2性能的影响.结果显示,当DBD等离子体处理时间小于30 min时,所制催化剂颗粒尺寸显著小于焙烧法得到的,因而其比表面积显著提高.N空穴的引入降低了催化剂的能带,提高了可见光区的吸收.此外,N空穴作为反应活性位,既能吸附反应物氧气分子,又能捕获光电子并促进光电子从催化剂向氧气分子转移,进而发生后续还原反应.等离子体处理30 min得到的催化剂光催化合成H_2O_2性能最佳,是纯g-C_3N_4的11倍.本文为g-C_3N_4基催化剂的制备提供了一个新方法.     

Transparent,Ultrahigh‐Gas‐Barrier Films with a Brick–Mortar–Sand Structure

Transparent and flexible gas‐barrier materials have shown broad applications in electronics, food, and pharmaceutical preservation. Herein, we report ultrahigh‐gas‐barrier films with a brick–mortar–sand structure fabricated by layer‐by‐layer (LBL) assembly of XAl‐layered double hydroxide (LDH, X=Mg, Ni, Zn, Co) nanoplatelets and polyacrylic acid (PAA) followed by CO₂ infilling, denoted as (XAl‐LDH/PAA)_n‐CO₂. The near‐perfectly parallel orientation of the LDH “brick” creates a long diffusion length to hinder the transmission of gas molecules in the PAA “mortar”. Most significantly, both the experimental studies and theoretical simulations reveal that the chemically adsorbed CO₂ acts like “sand” to fill the free volume at the organic–inorganic interface, which further depresses the diffusion of permeating gas. The strategy presented here provides a new insight into the perception of barrier mechanism, and the (XAl‐LDH/PAA)_n‐CO₂ film is among the best gas barrier films ever reported.     

Synthesis and optical and electrochemical properties of copolymers containing 9,9‐dihexylfluorene and 9‐dimethylaminopropylcarbazole chromophores

Soluble and well‐defined 9,9‐dihexylfluorene and 9‐dimethylaminopropylcarbazole based copolymers PFCN and 5PFCN have been prepared by Suzuki coupling polymerization. For comparison, alternate copolymer of 9,9‐dihexylfluorene and 9‐hexylcarbazole (PFC) was also prepared with the same method. Furthermore, alternate copolymer of 9,9‐dihexylfluorene and 9‐dimethylethylammoniumpropylcarbazole (PFCNE) was prepared from PFCN by the ethylation of its dimethylaminopropyl groups with bromoethane. These copolymers were soluble in organic solvents and showed high glass‐transition temperatures (75–160 °C). The optimized architecture of PFCN from a simulation was a spiral, which was different from the linear structure of poly(9,9‐dihexylfluorene) (PFO). Thermogravimetric analysis showed that the residual weights of 5PFCN, PFCN, PFC, and PFCNE at 800 °C were all greater then 50%, whereas PFO showed complete thermal decomposition. Both the absorption and photoluminescence emission peaks of these copolymers showed blueshifts after the introduction of the carbazole units because of reduced conjugation. Moreover, the introduction of 9‐hexylcarbazole and 9‐dimethylamionpropylcarbazole moieties into copolymers PFC and PFCN, respectively, effectively prevented the excimer formation of PFO. According to cyclic voltammetry results, PFCNE containing quaternary amino pendant groups exhibited the most stable reduction–oxidation cycles. The turn‐on electric fields of their electroluminescence devices decreased with increasing carbazole content because of the more balanced carrier injection. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3882–3895, 2006     

Efficient blue‐green‐emitting poly[(5‐diphenylamino‐1,3‐phenylenevinylene)‐alt‐(2,5‐dihexyloxy‐1,4‐phenylenevinylene)] derivatives: Synthesis and optical properties

New poly(phenylene vinylene) derivatives with a 5‐diphenylamino‐1,3‐phenylene linkage (including polymers 2 , 3 , and 5 ) have been synthesized to improve the charge‐injection properties. These polymers are highly photoluminescent with fluorescent quantum yields as high as 76% in tetrahydrofuran solutions. With effective π‐conjugation interruption at adjacent m‐phenylene units, chromophores of different conjugation lengths can be incorporated into the polymer chain in a controllable manner. In polymer 2 , the structural regularity leads to an isolated, well‐defined emitting chromophore. Isomeric polymer 3 of a random chain sequence, however, allows the effective emitting chromophores to be joined in sequence by sharing a common m‐phenylene linkage (as shown in a molecular fragment). Double‐layer light‐emitting‐diode devices using 2 , 3 , and 5 as emitting layers have turn‐on voltages of about 3.5 V and produce blue‐green emissions with peaks at 493, 492, and 482 nm and external quantum efficiencies up to 1.42, 0.98, and 1.53%, respectively. In comparison with a light‐emitting diode using 2 , a device using 3 shows improved charge injection and displays increased brightness by a factor of ～3 to 1400 cd/m² at an 8‐V bias. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2307–2315, 2006     

Coumarin‐containing poly(fluorenediylvinylene)s: Synthesis,photophysics, and electroluminescence

Two new poly(fluorenediylvinylene)s (CV and CF) with coumarin side chains were synthesized via Heck coupling. The coumarin segments were attached to the C‐9 of fluorene through alkyl spacers. The polymers were soluble in common organic solvents such as tetrahydrofuran (THF), chloroform, dichloromethane, and toluene. The photoluminescence (PL), electroluminescence (EL), and electrochemical behavior of these polymers were studied. CV and CF thin films exhibited broad‐band, bluish‐green and orange PL emissions, with maxima at 475 and 585 nm, respectively. These PL maxima were redshifted in comparison with those measured in THF solutions. Aggregate formation played an important role in the solid state. The aggregation was more pronounced in CF thin films than CV thin films. Both polymers oxidized and reduced irreversibly. Light‐emitting devices (LEDs) with indium tin oxide hole‐injecting and aluminum electron‐injecting electrodes were prepared and studied. The LEDs made of CV emitted green light, and the LEDs made of CF exhibited an orange EL emissions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5750–5762, 2006     

Atmospheric DBD plasma Deposition of ECO‐Friedly Release Liners for Pressure Sensitive Adhesive Tapes

The presented paper reports on the development of eco‐friendly non‐silicone containing release liners on plastic foils for pressure sensitive adhesive tapes. A solvent free process based on aerosol assisted dielectric barrier discharge (DBD) plasma deposition was used to obtain nano‐sized coatings. Various precursors have been investigated ranging from hydrocarbons and fluorinated hydrocarbons to (meth)acrylates and fluorinated (meth)acrylates. Best results were obtained using 2‐ethylhexyl acrylate. To improved the stability of release properties upon ageing, addition of photo initiators and acrylic cross‐linkers have been evaluated. Tape adhesion tests showed stable release values below 25 cN/20 mm for 2‐ethylhexyl acrylate plasma coatings with acrylic cross‐linkers. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Characterisation of light emitting diodes (LEDs) for application in digital holographic microscopy for inspection of micro and nanostructured surfaces

Partial coherent light sources open up prospects for phase noise reduction in digital holographically reconstructed phase distributions by suppressing multiple reflections in the experimental setup. Thus, light emitting diodes (LEDs) are investigated for application in digital holographic microscopy. First, the spectral properties and the resulting coherence length of an LED are characterised. In addition, an analysis of dispersion effects and their influence on the hologram formation is carried out. The coherence length of LEDs in the range of a few micrometers restricts the maximum interference fringe number in off-axis holography for spatial phase shifting. Thus, the application of temporal phase-shifting-based digital holographic reconstruction techniques is compared to spatial phase-shifting-based methods. It is demonstrated that LEDs are applicable for digital holographic microscopy in connection with both spatial and temporal phase-shifting-based techniques for reduction of noise in comparison to a laser-light-based experimental setup.     

Full wave analysis of non-radiative dielectric waveguide modulator for the determination of electrical equivalent circuit

This paper reports the determination of electrical equivalent circuit of ON/OFF modulator in non-radiative dielectric (NRD) guide configurations at Ka-band. Schottky barrier mixer diode is used to realize this modulator and its characteristics are determined experimentally using vector network analyzer. Full wave FEM simulator HFSS is used to determine an equivalent circuit for the mounted diode and modulator in ON and OFF states. This equivalent circuit is used to qualitatively explain the experimental characteristics of modulator.      

Enhanced efficiency of polyfluorene derivatives: Organic–inorganic hybrid polymer light‐emitting diodes

Two novel organic–inorganic hybrid polyfluorene derivatives, poly{(9,9′‐dioctyl‐2,7‐fluorene)‐co‐(9,9′‐di‐POSS‐2,7‐fluorene)‐co‐[2,5‐bis(octyloxy)‐1,4‐phenylene]} (PFDOPPOSS) and poly{(9,9′‐dioctyl‐2,7‐fluorene)‐co‐(9,9′‐di‐POSS‐2,7‐fluorene)‐co‐bithiophene} (PFT2POSS), were synthesized by the Pd‐catalyzed Suzuki reaction of polyhedral oligomeric silsesquioxane (POSS) appended fluorene, dioctyl phenylene, and bithiophene moieties. The synthesized polymers were characterized with ¹H NMR spectroscopy and elemental analysis. Photoluminescence (PL) studies showed that the incorporation of the POSS pendant into the polyfluorene derivatives significantly enhanced the fluorescence quantum yields of the polymer films, likely via a reduction in the degree of interchain interaction as well as keto formation. Additionally, the blue‐light‐emitting polyfluorene derivative PFDOPPOSS showed high thermal color stability in PL. Moreover, single‐layer light‐emitting diode devices of an indium tin oxide/poly(3,4‐ethylene dioxythiophene):poly(styrene sulfonate)/polymer/Ca/Al configuration fabricated with PFDOPPOSS and PFT2POSS showed much improved brightness, maximum luminescence intensity, and quantum efficiency in comparison with devices fabricated with the corresponding pristine polymers PFDOP and PFT2. In particular, the maximum external quantum efficiency of PFT2POSS was 0.13%, which was twice that of PFT2 (0.06%), and the maximum current efficiency of PFT2POSS was 0.38 cd/A, which again was twice that of PFT2 (0.19 cd/A). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2943–2954, 2006     

Ni/4H-SiC 肖特基势垒磁场下输运性质的分析

采用高真空电子束蒸发的方法将镍 (Ni)淀积在 4H SiC(0 0 0 1)面上 ,制备出良好的Ni/4H SiC肖特基接触 .研究了Ni/4H SiC肖特基势垒在强磁场和低温下的I -V特性 ,并以热电子发射理论为基础 ,结合弛豫近似玻尔兹曼方程对Ni/4H SiC肖特基势垒在磁场下的输运性质进行了分析和计算 ,发现电流的变化与磁场的平方和电压成线性关系 ,和温度成反比关系 ,与实验结果基本符合