A Theoretical Investigation of the Decomposition Reactions of Ethyl Formate in the S0 State

This study revisits the stability of the possible conformations and the decomposition reactions of ethyl formate in the S₀ state using the (U)MP2, MP4SDTQ, CCSD(T), and (U)B3LYP methods with various basis sets. The transition states of the decomposition channels to HCOOH + C₂H₄, CO + CH₃CH₂OH, CH₂O + CH₃CHO, HCOH + CH₃CHO, C₂H₆ + CO₂, and H₂ + CH₂CHOCHO are determined. The microcanonical rate constants derived from the RRKM theory are calculated for each of the decomposition reactions. The high‐pressure limit rate constants are calculated for the decomposition channels to HCOOH + C₂H₄, CO + CH₃CH₂OH, and CH₂O + CH₃CHO.     

Catalysis by Using TiO2 Nanoparticles and Nanotubes

TiO2 has attracted considerable attention due to its stability, non-toxicity, low cost, and great potential for use as a photocatalyst in environmental applications. Since strong metal-support interaction (SMSI) of titania-supported noble metals was first reported in 1978, titania supported catalyst has been intensively studied in heterogeneous catalysis. However, the effective catalytic activity was restricted due to the low surface area of TiO2. Recently, TiO2-based nanotubes were extensively investigated because of their potentials in many areas such as highly efficient photocatalysis and hydrogen sensor.In the present study, formation of titanium oxide (TiO2) nanotubes was carried out by hydrothermal method, with TiO2 nanoparticle-powders immersed in concentrated NaOH solution in an autoclave at 110 ℃. Preparation of nano-size Pt on TiO2-nanoparticles or TiO2-nanotubes was performed by photochemical deposition method with UV irradiation on an aqueous solution containing TiO2 and hexachloroplatinic acid or tetrachloroauric acid. The TEM micrographs show that TiO2-nanotubes exhibit ～300 nm in length with an inner diameter of ～ 6 nm and the wall thickness of ～ 2 nm, and homogeneous nanosize Pt particles (～ 2 nm) were well-dispersed on both nanoparticle- and nanotube- titania supports. It also shows the nanotube morphology was retained up2o n Pt-immobilization. Nitrogen adsorption isotherm at 77K resulted a high surface area (～ 200m/g) of TiO2-nanotubes, which is about 40 times greater than that of "mother" TiO2 nanoparticles (～5 m/g). All the spectroscopic results exhibited that the nanotube structure was not significantly affected by the immobilized Pt particles. Ti K-edge XANES spectra of TiO2 nanotube and Pt/TiO2-nanotube represent that most titanium are in a tetrahedral coordination with few retained in the octahedral structure.In the in-situ FT-IR experiments, an IR cell was evacuated to a pressure of 10-5 torr at room temperature as soon as the catalyst-pellet, Pt/TiO2 or Pt/TiO2-nanotube, was placed inside the cell.Then, 60 torr of hydrogen was introduced into the cell and subsequently the temperature was programmed to increase from room temperature to 300℃ at a constant heating rate of 5℃/min.For Pt/TiO2, an IR peak at 2083 em-1 started to appear at 200℃ with a maximum intensity at 250℃ and then decreasing as temperature increased. The 2083 em-1 IR peak corresponds to the linearly adsorption of CO on the well-dispersed Pt sites. Simultaneously, the IR bands of gaseous methane at 3016 em-1 started to appear at 225℃ and the peak intensity increased with temperature. The results reveal that Pt/TiO2 can adsorb gaseous CO2 and further catalyzes the reduction of CO2 by H2 through the intermediate CO, which further produces gaseous methane. While for the Pt/TiO2-nanotube catalyst, methane was produced at relatively low temperature, 100℃, and it catalyzed the direct conversion of CO2 to CH4. The absence of intermediate CO-adsorption signals durinng the temperature programmed process indicates that the prepared TiO2 nanotube-supported nanosize Pt possesses a potent capability for CO2 adsorption and highly catalytic activity in the hydrogenation of CO2, and was superior to the conventional Pt/TiO2 catalyst. The catalytic activity of Pt/TiO2-nanotube was indeed significantly enhanced by the high surface area of TiO2-nanotubes.Details will be discussed.     

Structural investigation of high‐transmittance aluminum oxynitride films deposited by ion beam sputtering

Aluminum oxynitride films were deposited by ion beam sputtering technique at room temperature. The optical properties and morphologies of the aluminum oxynitride films were studied and reported previously. It was found that the optical properties are closely related to the O contents in the films. In this study, the structures of the films were investigated by X‐ray diffractometer and XPS. Three oxidation states of N_1s in oxynitride films, N⁺, N²⁺ and N³⁺, were clearly deduced from N_1s spectra in the amorphous films fabricated under various oxygen partial pressures (P_O2). To our knowledge, three oxidation states of N_1s have not been simultaneously observed and reported in the aluminum oxynitride films previously. Corresponding bonding variations in Al_2p and O_1s spectra indicated more oxygen in oxynitride in the film as P_O2 increases. Three aluminum oxynitride networks, AlO₂N, AlO_2.5N and AlO₃N were deduced. Optical properties of aluminum oxynitride films resemble those of AlN and Al₂O₃ films when P_O2 is low and high during the deposition. The refractive indices and extinction coefficients of the aluminum oxynitride films can be adjusted by using proper P_O2 during the film depositions. Copyright © 2010 John Wiley & Sons, Ltd.     

Flexible nanocrystalline‐titania/polyimide hybrids with high refractive index and excellent thermal dimensional stability

In this study, a novel synthetic route was developed to prepare polyimide–nanocrystalline–titania hybrid optical films with a relatively high titania content (up to 50 wt %) and thickness (20–30 μm) from soluble polyimides containing hydroxyl groups. Two series of newly soluble polyimides were synthesized from the hydroxy‐substituted diamines with various commercial tetracarboxylic dianhydrides. The hydroxyl groups on the backbone of the polyimides could provide the organic–inorganic bonding and resulted in homogeneous hybrid solutions by controlling the mole ratio of titanium butoxide/hydroxyl group. AFM, SEM, TEM, and XRD results indicated the formation of well‐dispersed nanocrystalline‐titania. The flexible hybrid films could be successfully obtained and revealed relatively good surface planarity, thermal dimensional stability, tunable refractive index, and high optical transparency. A three‐layer antireflection coating based on the hybrid films was prepared and showed a reflectance of less than 0.5% in the visible range indicated its potential optical applications. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1433–1440, 2010     

Surface‐initiated atom transfer radical polymerization from porous poly(tetrafluoroethylene) membranes using the C?F groups as initiators

This work reports the surface‐initiated atom transfer radical polymerization (ATRP) from hydrogen plasma‐treated porous poly(tetrafluoroethylene) (PTFE) membranes using the C? F groups as initiators. Hydrogen plasma treatment on PTFE membrane surfaces changes their chemical environment through defluorination and hydrogenation reactions. With the hydrogen plasma treatment, the C? F groups of the modified PTFE membrane surface become effective initiators of ATRP. Surface‐initiated ATRP of poly(ethylene glycol) methacrylate (PEGMA) is carried out to graft PPEGMA chains to PTFE membrane surfaces. The chain lengths of poly(PEGMA) (PPEGMA) grafted on PTFE surfaces increase with increasing the reaction time of ATRP. Furthermore, the chain ends of PPEGMA grown on PTFE membrane surfaces then serve as macroinitiators for the ATRP of N‐isopropylacrylamide (NIPAAm) to build up the PPEGMA‐b‐PNIPAAm block copolymer chains on the PTFE membrane surfaces. The chemical structures of the modified PTFE membranes are characterized using X‐ray photoelectron spectroscopy. The modification increases the surface hydrophilicity of the PTFE membranes with reductions in their water‐contact angles from 120° to 60°. The modified PTFE membranes also show temperature‐responsive properties and protein repulsion features owing to the presence of PNIPAAM and PPEGMA chains. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2076–2083, 2010     

Micro fabrication of microlens arrays by micro dispensing

In this study, master of the microlens arrays is fabricated using micro dispensing technology, and then electroforming technology is employed to replicate the Ni mold insert of the microlens arrays. Finally, micro hot embossing is performed to replicate the molded microlens arrays from the Ni mold insert. The resin material is used as the dispensing material, which is dropped on a glass substrate. The resin is exposed to a 380 W halogen light. It becomes convex under surface tension on the glass substrate. A master for the microlens arrays is then obtained. A 150‐nm‐thick copper layer is sputtered on the master as an electrically conducting layer. The electroforming method replicates the Ni mold insert from the master of the microlens arrays. Finally, micro hot embossing is adopted to replicate the molded microlens arrays. The micro hot embossing experiment employs optical films of polymethylmethacrylate (PMMA) and polycarbonate (PC). The processing parameters of micro hot embossing are processing temperature, embossing pressure, embossing time, and de‐molding temperature. Taguchi's method is applied to optimize the processing parameters of micro hot embossing for molded microlens arrays. An optical microscope and a surface profiler are utilized to measure the surface profile of the master, the Ni mold insert and the molded microlens arrays. AFM is employed to measure the surface roughness of the master, the Ni mold insert and the molded microlens arrays. The sag height and focal length are determined to elucidate the optical characteristics of the molded microlens arrays. Copyright © 2009 John & Sons, Ltd.     

Two-dimensional infrared investigation of N-acetyl tryptophan methyl amide in solution

The linear infrared and two-dimensional infrared (2D IR) spectra in the amide-I region of N-acetyl tryptophan methyl amide (NATMA) in solvents of varying polarity are reported. The two amide-I transitions have been assigned unambiguously by using 13C isotopic substitution of the carbonyl group. The amide unit at the amino end shows a lower transition frequency in CH2Cl2 and methanol, while the acetyl end has a lower transition frequency in D2O. Multiple conformers exist in CH2Cl2 and methanol, but only one conformer is evident in D2O. The 2D IR cross peaks from the intermode coupling yield off-diagonal anharmonicities 2.5 +/- 0.5, 3.25 +/- 0.5, and 3.0 +/- 0.5 cm(-1) in CH2Cl2, methanol, and D2O, respectively, which by simple matrix diagonalization yield the coupling constants 8.0 +/- 0.5, 8.0 +/- 1.0, and 5.5 +/- 1.0 cm(-1). The major conformer in CH2Cl2 corresponds to a C7 structure, in agreement with that found in the gas phase [Dian, B. C.; Longarte, A.; Mercier, S.; Evans, D. A.; Wales, D. J.; Zwier, T. S. J. Chem. Phys. 2002, 117, 10688-10702] with intramolecular hydrogen bonding between the acetyl end C=O and the amino end N-H. The backbone dihedral angles (phi, psi) are determined to be in the ranges of (-55 +/- 5 degrees , 30 +/- 5 degrees ), (120 +/- 10 degrees , -20 +/- 10 degrees ), and (+/-160 +/- 10 degrees , +/-75 +/- 10 degrees ) in CH2Cl2, methanol, and D2O, respectively.     

The role of pyrrhotite (Fe7S8) and the sample texture in the hydrothermal transformation of pentlandite ((Fe,Ni)9S8) to violarite ((Ni,Fe)3S4)

The catalytic role of pyrrhotite (Fe₇S₈) in the reaction kinetics of the hydrothermal transformation of pentlandite ((Fe,Ni)₉S₈) to violarite ((FeNi₂S₄) was found to depend on the physical form of pyrrhotite. Pyrrhotite in fine scale intergrown with pentlandite boosts the reaction, whereas in a mechanical mixture of pyrrhotite and pentlandite, it plays the opposite role. This phenomenon was interpreted as result of dissolution of pyrrhotite under reaction conditions.     

Preparation and Characterization of Mixed‐Valent Nickel Oxide/Nickel Hexacyanoferrate Hybrid Films and Their Electrocatalytic Properties

Polynuclear mixed‐valent nickel oxide and nickel hexacyanoferrate hybrid film was prepared on glassy carbon electrode by multiple scan cyclic voltammetry. The film growth was monitored using electrochemical quartz crystal microbalance (EQCM). The cyclic voltammogram of the nickel hexacyanoferrate film is characterized by single redox couple whereas nickel oxide/nickel hexacyanoferrate hybrid film exhibits two redox couples. Cyclic voltammetric features suggest that the charge transfer process in both films resembles that of surface‐confined redox species. In stronger basic solution (pH ≥9), nickel hexacyanoferrate film was gradually converted into nickel oxide film during potentiodynamic cycling. The peak potential of nickel oxide redox couple moved into more negative side with increasing pH of contacting solution whereas the peak potential of nickel hexacyanoferrate redox couple remains the same. Electrocatalytic behavior of hybrid film coated electrodes toward ascorbic acid, hydrazine and hydroxylamine was investigated using cyclic voltammetry technique. Analytical application of nickel oxide/nickel hexacyanoferrate hybrid film electrode was tested in amperometry and flow injection analysis.     

Four New Lariciresinol‐Based Lignan Glycosides from the Roots of Rhus javanica var. roxburghiana

The four new lariciresinol‐based lignan glycosides, (?)‐lariciresinol 4′‐(6″‐O‐feruloyl‐β‐D ‐glucopyranoside) ( 1 ), (?)‐lariciresinol 4′‐(4″,6″‐di‐O‐feruloyl‐β‐D ‐glucopyranoside) ( 2 ), 5,5′‐dimethoxylariciresinol 4′‐(4″,6″‐di‐O‐feruloyl)‐β‐D ‐glucopyranoside) ( 3 ), and 4‐O‐[α‐(1,2‐dihydroxyethyl)syringyl]‐5,5′‐dimethoxylariciresinol 4′‐(4″,6″‐di‐O‐feruloyl‐β‐D ‐glucopyranoside) ( 4 ), together with two known ones, lariciresinol 4′‐β‐D ‐glucopyranoside) ( 5 ) and tortoside B ( 6 ), were isolated from the BuOH extract of Rhus javanica var. roxburghiana roots, and their structures were established by means of various spectroscopic techniques.