Spectroelectrochemical Evaluation of a ZnO Optically Transparent Electrode Prepared by the Spin‐spray Technique

We present a novel zinc oxide (ZnO) optically transparent electrode (OTE) prepared by the spin‐spray technique for spectroelectrochemistry. The spin‐spray technique can deposit ZnO film at a low cost, high rate deposition, and at a low temperature (<100 °C) in a single step. This new technique provides good optical transparency and electrical conductivity for ZnO. The electrochemical and spectroelectrochemical properties of the ZnO electrode were investigated for varying thicknesses of ZnO using methylene blue as a redox indicator. A ZnO OTE chip that includes three electrodes on a glass chip was developed for thin‐layer spectroelectrochemistry. Moreover, the ZnO films were successfully applied in an electrochemical‐localized surface plasmon resonance (LSPR) method for methylene blue detection by using them as a transparent conducting substrate for loading gold nanoparticles.     

Preparation and characterization of wet poly(vinyl chloride)-polypyrolle composite film

Wet poly(vinyl chloride) (wPVC) coated glassy carbon (GC) electrode was prepared by casting a DMF solution of poly(vinyl chloride) on glassy carbon and immersing it in methanol, and then in water. The wPVC coated GC (wPVC/GC) electrode showed electrochemical activity in aqueous solution; therefore, it was possible to obtain a wPVC/polypyrolle (PPy) composite by electropolymerization from aqueous solution of pyrolle (Py) into the wPVC matrix on the electrode. PPy segregated in wPVC matrix and the mechanical properties of PPy was improved by forming a composite without changing the electrochemical properties of PPy. The PPy/wPVC ratio can be controlled by controlling the concentration of PVC in DMF solution.     

Atmospheric-pressure Penning ionization mass spectrometry

A preliminary study on the atmospheric-pressure Penning ionization (APP(e)I) of gaseous organic compounds with Ar* has been made. The metastable argon atoms (Ar*: 11.55 eV for (3)P(2) and 11.72 eV for (3)P(0)) were generated by the negative-mode corona discharge of atmospheric-pressure argon gas. By applying a high positive voltage (+500 to +1000 V) to the stainless steel capillary for the sample introduction (0.1 mm i.d., 0.3 mm o.d.), strong ion signals could be obtained. The ions formed were sampled through an orifice into the vacuum and mass-analyzed by an orthogonal time-of-flight mass spectrometer. The major ions formed by APP(e)I are found to be molecular-related ions for alkanes, aromatics, and oxygen-containing compounds. Because only the molecules with ionization energies less than the internal energy of Ar* are ionized, the present method will be a selective and highly sensitive interface for gas chromatography/mass spectrometry.     

Observation of CO(2) in Fourier transform infrared spectral measurements of living Acholeplasma laidlawii cells

In monitoring the time course of conformational disorder by Fourier transform infrared spectroscopy for intact Acholeplasma laidlawii cells grown at 37 degrees C on binary fatty acid mixtures containing oleic acid and for cells grown on pure palmitic acid, an absorption band at 2343 cm(-1) was observed. The band intensity was found to increase with time. This band was not observed in the spectra for isolated membranes. It is suggested that the 2343 cm(-1) band is due to CO(2) dissolved in water, most likely produced at the final point of fermentation of amino acid by this microorganism.     

Determination of cell asymmetry in temperature-modulated DSC

The quality of measurement of heat capacity by differential scanning calorimetry (DSC) is based on the symmetry of the twin calorimeters. This symmetry is of particular importance for the temperature-modulated DSC (TMDSC) since positive and negative deviations from symmetry cannot be distinguished in the most popular analysis methods. Three different DSC instruments capable of modulation have been calibrated for asymmetry using standard non-modulated measurements and a simple method is described that avoids potentially large errors when using the reversing heat capacity as the measured quantity. It consists of overcompensating the temperature-dependent asymmetry by increasing the mass of the sample pan.On leave from Toray Industries, Inc., Otsu, Shiga 520, JapanOn leave from Toray Research Center, Inc., Otsu, Shiga 520, JapanThis work was supported by the Division of Materials Research, National Science Foundation, Polymers Program, Grant # DMR 90-00520 and the Division of Materials Sciences, Office of Basic Energy Sciences, U. S. Department of Energy at Oak Ridge National Laboratory, managed by Lockheed Martin Energy Research Corp. for the U. S. Department of Energy, under contract number DE-AC0S-96OR22464. Support for instrumentation came from TA Instruments, Inc. and Mettler-Toledo, Research support was also given by ICI Painls, and Toray Industries, Inc.     

Free energy profiles for penetration of methane and water molecules into spherical sodium dodecyl sulfate micelles obtained using the thermodynamic integration method combined with molecular dynamics calculations

The free energy profiles, ΔG(r), for penetration of methane and water molecules into sodium dodecyl sulfate (SDS) micelles have been calculated as a function of distance r from the SDS micelle to the methane and water molecules, using the thermodynamic integration method combined with molecular dynamics calculations. The calculations showed that methane is about 6-12 kJ mol(-1) more stable in the SDS micelle than in the water phase, and no ΔG(r) barrier is observed in the vicinity of the sulfate ions of the SDS micelle, implying that methane is easily drawn into the SDS micelle. Based on analysis of the contributions from hydrophobic groups, sulfate ions, sodium ions, and solvent water to ΔG(r), it is clear that methane in the SDS micelle is about 25 kJ mol(-1) more stable than it is in the water phase because of the contribution from the solvent water itself. This can be understood by the hydrophobic effect. In contrast, methane is destabilized by 5-15 kJ mol(-1) by the contribution from the hydrophobic groups of the SDS micelle because of the repulsive interactions between the methane and the crowded hydrophobic groups of the SDS. The large stabilizing effect of the solvent water is higher than the repulsion by the hydrophobic groups, driving methane to become solubilized into the SDS micelle. A good correlation was found between the distribution of cavities and the distribution of methane molecules in the micelle. The methane may move about in the SDS micelle by diffusing between cavities. In contrast, with respect to the water, ΔG(r) has a large positive value of 24-35 kJ mol(-1), so water is not stabilized in the micelle. Analysis showed that the contributions change in complex ways as a function of r and cancel each other out. Reference calculations of the mean forces on a penetrating water molecule into a dodecane droplet clearly showed the same free energy behavior. The common feature is that water is less stable in the hydrophobic core than in the water phase because of the energetic disadvantage of breaking hydrogen bonds formed in the water phase. The difference between the behaviors of the SDS micelles and the dodecane droplets is found just at the interface; this is caused by the strong surface dipole moment formed by sulfate ions and sodium ions in the SDS micelles.     

The class number one problem for some non-abelian normal CM-fields

Let be a non-abelian normal CM-field of degree any odd prime. Note that the Galois group of is either the dicyclic group of order or the dihedral group of order We prove that the (relative) class number of a dicyclic CM-field of degree is always greater then one. Then, we determine all the dihedral CM-fields of degree with class number one: there are exactly nine such CM-fields.

     

Photoemission study of electronic structure evolution across the metal-insulator transition of heavily B-doped diamond

We studied the electronic structure evolution of heavily B-doped diamond films across the metal-insulator transition (MIT) using ultraviolet photoemission spectroscopy (UPS). From high-temperature UPS, through which electronic states near the Fermi level (E_F) up to ∼5k_BT can be observed (k_B is the Boltzmann constant and T the temperature), we observed the carrier concentration dependence of spectral shapes near E_F. Using another carrier concentration dependent UPS, we found that the change in energy position of sp-band of the diamond valence band, which corresponds to the shift of E_F, can be explained by the degenerate semiconductor model, indicating that the diamond valence band is responsible for the metallic states for samples with concentrations above MIT. We discuss a possible electronic structure evolution across MIT.     

Radical pair dynamics observed with pulse-mode product-yield-detected ESR

Three pulse sequences have been employed for laser and microwave-pulse irradiation in the pulse mode product-yield-detected ESR technique to detect the dynamical feature of transient radical pair. In this method, the decrease in spin adduct yield as functions of delay times for irradiation/termination of the microwave pulse after the laser pulse are simulated with the Runge-Kutta method for a detailed reaction model to obtain the rate constants of cage product formation, escape of the radical pair, as well as the hydrogen abstraction reaction. As the representative reaction systems, photoreduction of anthraquinone, anthraquinone-2-sulfonate, and benzophenone in SDS micellar solution were employed. Effects of cyclohexene, added as a hydrogen donor, NaCl and Ethanol, added to change the microviscosity of micelle, on these reaction rate constants have been tested.     

Thermal Stability of Oxidized Single‐Walled Carbon Nanotubes: Competitive Elimination and Decomposition Reaction Depending on the Degree of Functionalization

The thermal stability of oxidized single‐walled carbon nanotubes (SWNTs) with various degrees of oxidation was investigated. The oxidized SWNTs exhibited lower absorption and radial breathing mode (RBM) peaks and a higher intensity ratio of the D band to the G band (D/G) in their absorption and Raman spectra than those of the pristine SWNTs. After the thermal treatment, the D/G ratio of the oxidized SWNTs almost recovered its original intensity, regardless of the degree of oxidation. The absorption, photoluminescence (PL), and RBM peaks could not recover their original intensities when the oxidation degree was high. The results indicate that the elimination and decomposition reactions proceeded competitively depending on the degree of oxidation. In addition, a new PL peak was observed in the near‐infrared region, and the PL peak intensity increased with the subsequent thermal treatment. The theoretical calculations provided an insight into the possible pathways for the decomposition of oxidized SWNTs, showing that the O₂ elimination and CO/CO₂ evolution proceed competitively during thermal treatment.