In the last 30 days

• Open/close Hydrodynamic Instabilities Driven by Acid-base Neutralization Reaction in Immiscible System

  Ahmed Asad et al 2010 Chin. J. Chem. Phys. 23 513 Tag this article

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  The hydrodynamic instabilities driven by an acid-base neutralization reaction, in contact along a plane interface, placed in a Hele-Shaw cell under the gravitational field are reported. The system consists of the heavier aqueous tetramethyle-ammonium hydroxide below the lighter layer of organic phase with propionic acid as reacting specie. The effect of chemical composition on hydrodynamic instabilities during interfacial mass transfer accompanied by a neutralization reaction is investigated. Depending on the initial concentration of the reacting species, Marangoni convection in the form of roll cells or trains of waves is observed. Mach-Zehnder interferometer is used to measure the change in base concentration at the time of instability formation. The results show that the instabilities resulted from the convection flow are more efficient to the mechanism of mass transfer and can drastically alter pattern formation in the system.

• Open/close Synthesis of Various Metal/TiO₂ Core/shell Nanorod Arrays

  Wei Zhu et al 2011 Chin. J. Chem. Phys. 24 91 Tag this article

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  We present a general approach to fabricate metal/TiO ₂ core/shell nanorod structures by two-step electrodeposition. Firstly, TiO ₂ nanotubes with uniform wall thickness are prepared in anodic aluminum oxide (AAO) membranes by electrodeposition. The wall thickness of the nanotubes could be easily controlled by modulating the deposition time, and their outer diameter and length are only limited by the channel diameter and the thickness of the AAO membranes, respectively. The nanotubes' tops prepared by this method are open, while the bottoms are connected directly with the Au film at the back of the AAO membranes. Secondly, Pd, Cu, and Fe elements are filled into the TiO ₂ nanotubes to form core/shell structures. The core/shell nanorods prepared by this two-step process are high density and free-standing, and their length is dependent on the deposition time.

• Open/close Preparation and Characterization of Electrodeposited-Annealed CuInSe₂ Thin Films for Solar Cells

  Zhong-wei Zhang et al 2011 Chin. J. Chem. Phys. 24 225 Tag this article

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  CuInSe ₂ (CIS) films with good crystalline quality were synthesized by electrodeposition followed by annealing in Se vapor at 530 °C. The morphology, composition, crystal structure, optical and electrical properties of the CIS films were investigated by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, Raman spectroscopy, UV-VIS-NIR spectroscopy, and admittance spectroscopy. The results revealed that the annealed CIS films had chalcopyrite structure and consisted of relatively large grains in the range of 500–1000 nm and single grain of films extend usually through the whole film thickness. The band gap of CIS films was 0.98 eV and carrier concentration was in the order of 10 ¹⁶ cm ⁻³ after etching the Cu-Se compounds on the film surface. Solar cells with the structure of AZO/i-ZnO/CdS/CIS/Mo/glass were fabricated. Current density vs. voltage test under standard reported condition showed the solar cells with an area of 0.2 cm ² had a conversion efficiency of 0.96%. The underlying physics was also discussed.

• Open/close Nearly Free Electron State in Graphane Nanoribbon Superlattice

  Qiao-hong Liu et al 2011 Chin. J. Chem. Phys. 24 22 Tag this article

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  Nearly free electron (NFE) state has been widely studied in low dimensional systems. Based on first-principles calculations, we identify two types of NFE states in graphane nanoribbon superlattice, similar to those of graphene nanoribbons and boron nitride nanoribbons. Effect of electron doping on the NFE states in graphane nanoribbon superlattice has been studied, and it is possible to open a vacuum transport channel via electron doping.

• Open/close Analysis of the LIF Spectroscopy of Nickel Hydride in 19000–21400 cm⁻¹

  Jing-ru Guo et al 2008 Chin. J. Chem. Phys. 21 308 Tag this article

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  The laser-induced fluorescence (LIF) excitation spectrum of NiH was recorded in the spectral region from 15000 cm ⁻¹ to 21400 cm ⁻¹, with the NiH molecules produced by the reaction of sputtered nickel atoms with methanol under supersonic jet conditions. The 19000–21400 cm ⁻¹ portion of the spectrum of NiH is reported for the first time. Twenty-four bands were observed and classified into seven electronic transitions. Every band was rotationally analyzed. Higher vibrational levels of many excited states, A, B, D, E, F, and G, were observed and the complete set of spectroscopic parameters, vibrational frequency, unharmonic constant, rotational constant, and equilibrium length of these states were obtained. Some bands were reassigned.

• Open/close A Surface Femtosecond Two-Photon Photoemission Spectrometer for Excited Electron Dynamics and Time-Dependent Photochemical Kinetics

  Ze-feng Ren et al 2010 Chin. J. Chem. Phys. 23 255 Tag this article

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  A surface femtosecond two-photon photoemission (2PPE) spectrometer devoted to the study of ultrafast excited electron dynamics and photochemical kinetics on metal and metal oxide surfaces has been constructed. Low energy photoelectrons are measured using a hemispherical electron energy analyzer with an imaging detector that allows us to detect the energy and the angular distributions of the photoelectrons simultaneously. A Mach–Zehnder interferometer was built for the time-resolved 2PPE (TR-2PPE) measurement to study ultrafast surface excited electron dynamics, which was demonstrated on the Cu(111) surface. A scheme for measuring time-dependent 2PPE (TD-2PPE) spectra has also been developed for studies of surface photochemistry. This technique has been applied to a preliminary study on the photochemical kinetics on ethanol/TiO ₂(110). We have also shown that the ultrafast dynamics of photoinduced surface excited resonances can be investigated in a reliable way by combining the TR-2PPE and TD-2PPE techniques.

• Open/close Growth of High Magnetic α-Fe₂O₃ and Fe₃O₄ Nanowires via an Oxide Assisted Vapor-Solid Process

  Ming Chang and Nai-feng Hsu 2011 Chin. J. Chem. Phys. 24 109 Tag this article

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  We describes a controllable synthesis procedure for growing α-Fe ₂O ₃ and Fe ₃O ₄ nanowires. High magnetic hematite α-Fe ₂O ₃ nanowires are successfully grown on Fe _0.5Ni _0.5 alloy substrates via an oxide assisted vapor-solid process. Experimental results also indicate that previous immersion of the substrates in a solution of oxalic acid causes the grown nanowires to convert gradually into magnetite (Fe ₃O ₄) nanowires. Additionally, the saturated state of Fe ₃O ₄ nanowires is achieved as the oxalic acid concentration reaches 0.75 mol/L. The average diameter and length of nanowires expands with an increasing operation temperature and the growth density of nanowires accumulates with an increasing gas flux in the vapor-solid process. The growth mechanism of α-Fe ₂O ₃ and Fe ₃O ₄ nanowires is also discussed. The results demonstrate that the entire synthesis of nanowires can be completed within 2 h.

• Open/close Synthesis of Multishell Carbon Nanotube Composites via Template Method

  Wen-bo Li et al 2011 Chin. J. Chem. Phys. 24 206 Tag this article

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  Multishell nanotubes of polyaniline and carbon were synthesized via a template approach. A thin layer of MnO ₂ coated on carbon nanotubes acts as a reactive template for the consequent formation of the polyaniline coating. The polyaniline-carbon nanotubes show enhanced dispersibility in water and can be possibly used as a functional material of electrochemical capacitors with improved performance. The general method operates by coating carbon nanotubes on functional materials such as poly (3,4-ethylenedioxythiophene), polypyrrole, silica, and carbon.

• Open/close Synthesis and Characterization of Supported CuInSe₂ Nanorod Arrays on Rigid Substrates

  Zhong-wei Zhang et al 2011 Chin. J. Chem. Phys. 24 115 Tag this article

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  Copper indium diselenide nanorod arrays were electrodeposited on tungsten/silicon rigid substrates using porous anodic alumina as growth template. The porous anodic alumina templates were prepared by anodizing aluminum films which were sputtered onto the tungsten/silicon substrates. A selective chemical etching was used to penetrate the barrier layer at the bottom of the alumina channels before electrodeposition, which enables direct electrical and chemical contact with the underside substrate electrode. The as-deposited samples were annealed at 450 °C in vacuum. Scanning electron microscopy revealed that the nanorods were dense and compact with diameter of about 100 nm, length of approximate 1 μm, and the aspect ratio of 10. X-ray diffraction, micro-Raman spectroscopy, and high resolution transmission electron microscopy showed that chalcopyrite polycrystalline structure and high purity CuInSe ₂ nanorods were obtained. The grain size was large in the rod axial direction. Energy-dispersive X-ray spectroscopy showed the composition was nearly stoichiometric. The energy band gap of this nanorod arrays was analyzed by fundamental absorption spectrum and was evaluated to be 0.96 eV.

• Open/close Hydrogen Production by Low-temperature Steam Reforming of Bio-oil over Ni/HZSM-5 Catalyst

  Song-bai Qiu et al 2011 Chin. J. Chem. Phys. 24 211 Tag this article

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  We investigated high catalytic activity of Ni/HZSM-5 catalysts synthesized by the impregnation method, which was successfully applied for low-temperature steam reforming of bio-oil. The influences of the catalyst composition, reforming temperature and the molar ratio of steam to carbon fed on the stream reforming process of bio-oil over the Ni/HZSM-5 catalysts were investigated in the reforming reactor. The promoting effects of current passing through the catalyst on the bio-oil reforming were also studied using the electrochemical catalytic reforming approach. By comparing Ni/HZSM-5 with commonly used Ni/Al ₂O ₃ catalysts, the Ni ₂₀/ZSM catalyst with Ni-loading content of about 20% on the HZSM-5 support showed the highest catalytic activity. Even at 450 °C, the hydrogen yield of about 90% with a near complete conversion of bio-oil was obtained using the Ni ₂₀/ZSM catalyst. It was found that the performance of the bio-oil reforming was remarkably enhanced by the HZSM-5 supporter and the current through the catalyst. The features of the Ni/HZSM-5 catalysts were also investigated via X-ray diffraction, inductively coupled plasma and atomic emission spectroscopy, hydrogen temperature-programmed reduction, and Brunauer-Emmett-Teller methods.