Synthesis of Acrylamide Molecularly Imprinted Polymers Immobilized on Graphite Oxide through Surface-Initiated Atom Transfer Radical Polymerization

A novel acrylamide (AA) molecularly imprinted polymer was synthesized by atom transfer radical polymerization (ATRP) on graphite oxide (GO) particles. Propionamide (PAM) was used as a dummy template molecule, hydroxy ethyl acrylate (HEA) as a functional monomer, ethylene glycol dimethacrylate (EDMA) as a crosslinking agent, and acetonitrile as both solvent and dispersion medium. Scanning electron microscopy (SEM) images and infrared spectroscopy (IR) confirmed that the molecularly imprinted polymers (MIP) were successfully grafted onto the surface of the GO particles. The corresponding adsorption kinetic curves and adsorption isotherms showed that the AA adsorption reached equilibrium after 5 h, with large amounts of AA being adsorped in the first 100 min. The maximum AA adsorption capacity was 123.48 µmol g^?1 according to Scatchard analysis, which indicated that the MIP possesses good AA adsorption capacity. This MIP-GO material was used to selectively determine AA in fried food samples.     

用XRD和TPR技术考察制备方法和灼烧温度对钙钛矿型结构形成以及性质的影响

本文用柠檬酸络合物分解法、碳酸盐共沉淀分解法、硝酸盐直接分解法和陶瓷法合成了轻、重稀土钙钛矿型氧化物LnMnO_3(Ln=Sm.Er).用X-射线衍射(XRD)和程序升温还原(TPR)技术考察了制备方法和灼烧温度对钙钛矿型结构形成的影响.实验结果表明,用柠檬酸络合物分解法可以在较低的温度下得到单一相的钙钛矿氧化物,而陶瓷法的灼烧温度比其他方法所需的温度要高得多。不同方法得到的产物SmMmO_3对CO氧化反应的活性为:柠檬酸法～碳酸盐法～硝酸盐法>陶瓷法。实验表明,TPR技术在某些体系中可作为灵敏的物相分析辅助手段,它可在制备或反应过程中原位观察体系结构的变化,实验中观察到,稀土氧化物能促进某些过渡金属氧化物在稀土氧化物表面分散,能阻止它们形成晶态.本文还讨论了钙钛矿型氧化物的形成机理,提出了过渡金属氧化物的扩散是形成钙钛矿结构反应速率的决定步骤观点。     

Excimer laser processing of ZnO thin films prepared by the sol-gel process

ZnO thin films were prepared on soda-lime glass from a single spin-coating deposition of a sol-gel prepared with anhydrous zinc acetate [Zn(C₂H₃O₂)₂], monoethanolamine [H₂NC₂H₄OH] and isopropanol. The deposited films were dried at 50 and 300 °C. X-ray analysis showed that the films were amorphous. Laser annealing was performed using an excimer laser. The laser pulse repetition rate was 25 Hz with a pulse energy of 5.9 mJ, giving a fluence of 225 mJ cm⁻² on the ZnO film. Typically, five laser pulses per unit area of the film were used. After laser processing, the hexagonal wurtzite phase of zinc oxide was observed from X-ray diffraction pattern analysis. The thin films had a transparency of greater than 70% in the visible region. The optical band-gap energy was 3.454 eV. Scanning electron microscopy and profilometry analysis highlighted the change in morphology that occurred as a result of laser processing. This comparative study shows that our sol-gel processing route differs significantly from ZnO sol-gel films prepared by conventional furnace annealing which requires temperatures above 450 °C for the formation of crystalline ZnO.     

Microporated PEG Spheres for Fluorescent Analyte Detection

Poly(ethylene glycol) (PEG) hydrogels have been used to encapsulate fluorescently labeled molecules in order to detect a variety of analytes. The hydrogels are designed with a mesh size that will retain the sensing elements while allowing for efficient diffusion of small analytes. Some sensing assays, however, require a conformational change or binding of large macromolecules, which may be sterically prohibited in a dense polymer matrix. A process of hydrogel microporation has been developed to create cavities within PEG microspheres to contain the assay components in solution. This arrangement provides improved motility for large sensing elements, while limiting leaching and increasing sensor lifetime. Three hydrogel compositions, 100% PEG, 50% PEG, and microporated 100% PEG, were used to create pH-sensitive microspheres that were tested for response time and stability. In order to assess motility, a second, more complex sensor, namely a FITC-dextran/TRITC-Con A glucose-specific assay was encapsulated within the microspheres.     

Flow mechanisms in dense silica-metal oxide-water suspensions

The rheological properties of dense silica in water suspensions (approx. 50% solids by volume) containing additions of metal oxides were examined. Metal oxides used were ferric, zinc and stannic. To prevent settling, testing was performed in a rheometer which was modified to provide for continual stirring of the materials. Relatively small oxide additions had the effect of thickening the mixtures and making them non-Newtonian. Different rate-limiting steps for flow were identified depending on the particular mixture, testing temperature and shear strain rate. Flow could be described using empirical equations which are identical to those often used to describe plastic flow in solid crystalline materials.     

有ITO透明导电膜的平面分层介质系统的电磁波性能理论研究

理论研究了有ITO(indium tin oxide)透明导电膜的多层平面分层介质系统的电磁性能，给出的理论曲线和实测曲线符合很好.多层平面分层介质系统的电磁性能与ITO膜(方块电阻为8Ω)所在界面位置和平面分层介质系统层数及各层厚度等有关.优化设计了一种含有ITO透明导电膜的厚度仅7.35mm的四层平面分层介质系统，其在8—18GHz频段内电磁波反射性能很好.作为多层平面分层系统中的ITO导电膜，其方块电阻应低于30Ω，并且越小，其反射性能越好. 关键词： 多层平面介质系统 电磁性能 ITO透明导电膜     

恒流应力下E2PROM隧道氧化层的退化特性研究

在电容测量的基础上研究了薄隧道氧化层在恒定Fowler-Nordheim(F-N)隧穿电流下的退化情况. 这种退化是恒流应力和时间的函数，对恒流应力大小的依赖性更加强烈，隧道氧化层在F-N电流下的退化是注入电荷密度(Q_inj)的函数. 在较低Q_inj下氧化层中发生正电荷俘获，在较高Q_inj下发生负电荷俘获，导致栅压变化的反复. 关键词： 2PROM')" href="#">E²PROM 隧道氧化层 退化 恒流应力     

Unusual Behavior of Nanocrystalline Strontium Oxide Toward Hydrogen Sulfide

The thermodynamically favored reaction of solid strontium oxide with gaseous hydrogen sulfide is kinetically enhanced to a large degree by the use of higher surface area nanocrystalline SrO in the form of brush-like collections of metal oxide fibers. An unusual feature is that the reaction SrO + H₂S SrS + H₂O proceeds stoichiometrically at room temperature, but at higher temperatures the reaction efficiency goes down, apparently due to rapid temperature induced crystal growth of the nanocrystalline SrO. The samples studied vary in crystallite size from 20 to 27nm, while average particle size (nanocrystal aggregates) varies in the following order; aerogel prepared SrO (100nm) 相似文献   

Ultrasound-assisted facile one-pot synthesis of ternary MWCNT/MnO2/rGO nanocomposite for high performance supercapacitors with commercial-level mass loadings

Commercial application of supercapacitors (SCs) requires high mass loading electrodes simultaneously with high energy density and long cycle life. Herein, we have reported a ternary multi-walled carbon nanotube (MWCNT)/MnO₂/reduced graphene oxide (rGO) nanocomposite for SCs with commercial-level mass loadings. The ternary nanocomposite was synthesized using a facile ultrasound-assisted one-pot method. The symmetric SC fabricated with ternary MWCNT/MnO₂/rGO nanocomposite demonstrated marked enhancement in capacitive performance as compared to those with binary nanocomposites (MnO₂/rGO and MnO₂/MWCNT). The synergistic effect from simultaneous growth of MnO₂ on the graphene and MWCNTs under ultrasonic irradiation resulted in the formation of a porous ternary structure with efficient ion diffusion channels and high electrochemically active surface area. The symmetric SC with commercial-level mass loading electrodes (∼12 mg cm⁻²) offered a high specific capacitance (314.6 F g⁻¹) and energy density (21.1 W h kg⁻¹ at 150 W kg⁻¹) at a wide operating voltage of 1.5 V. Moreover, the SC exhibits no loss of capacitance after 5000 charge−discharge cycles showcasing excellent cycle life.