Active site structure of NO decomposition on perovskite(-like) oxides: An investigation from experiment and density functional theory

Active site structure for NO decomposition carried out on perovskite-like oxides were discussed based on the N-2 yield measured from LaSrNi1-x,AlxO4 with different B-site cations and from La2-ySryCuO4 with different crystal phases. Results show that the active site contains two oxygen vacancies, two transition metals, and one lattice-oxygen, with the oxygen vacancy locating on the apex of MO6 octahedron, and the lattice oxygen locating between the two transition metals (i.e., M-O-M plane). Density functional theory (DFT) analysis to the structure shows that this new active site is the most active structure for NO adsorbing, and hence, for NO decomposition. The similar trend of the relative energies that are required for the formation of oxygen vacancies with f form (calculated from DFT), the amount of oxygen vacancies, and the activities (N-2 yield) certifies this result further.

Fabrication and characterization of DNA/QPVP-Os redox-active multilayer film

Calf thymus DNA was immobilized on functionalized glassy carbon, gold and quartz substrates, respectively, by the layer-by-layer (LBL) assembly method with a polycation QPVP-Os, a quaternized poly(4-vinylpyridine) partially complexed with osmium bis(2,2'-bipyridine) as counterions. UV-visible absorption and surface plasmon resonance spectroscopy (SPR) showed that the resulting film was uniform with the average thickness 3.4 nm for one bilayer. Cyclic voltammetry (CV) showed that the total surface coverage of the polycations increases as each QPVP-Os/DNA bilayer added to the electrode surface, but the surface formal potential of Os-centered redox reaction shifts negatively, which is mainly attributed to the intercalation of redox-active complex to DNA chain. The electron transfer kinetics of electroactive QPVP-Os in the multilayer film was investigated by electrochemical impedance experiment for the first time. The permeability of Fe(CN)(6)(3-) in the solution into the multilayer film depends on the number of bilayers in the film. It is worth noting that when the multilayer film is up to 4 bilayers, the CV curves of the multilayer films display the typical characteristic of a microelectrode array.

Copolymers derived from bismaleimide oligomer with active solvent

An oligomer from 4, 4'-bis(maleimido)diphenyl methane and methylenedianiline were dissolved in active solvent N,N-dimethyl acrylamide in a solid content up to 50-70%; the solution was poured in a sheet-shaped module and irradiated b y Co-60 with the dose from 20 to 350 kGy at room temperature. The polymerized sheet was postcured at 180degreesC to obtain a transparent red-orange sheet with tensile strength above 100 MPa. The glass transition temperature before and after postcuring was around 100degreesC and 150-180degreesC, respectively. Styrene was used along with DMAA to decrease the water absorption for the copolymers.

Amplified spontaneous emission and gain from optically pumped films of dye-doped polymers

The amplified spontaneous emission and gain characteristics of various fluorescent dyes, 2-(1,1-dimethylethyl)-6(2-(2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H-benzo[ij] quinolizin-9-1)ethenyl)-4H-pyran-4-ylidene) propanedinitrile (DCJTB) and 4-dicyanomethylene-2-methyl-6-(p-dimethyl-aminostyryl)-4H-pyran (DCM), doped in polystyrene (PS) matrices were studied and compared. It was found that DCJTB has a larger net gain, 40.72 cm(-1), a lower loss, 2.49 cm(-1), and a lower threshold, 0.16 (mJ/pulse)/cm(2), than DCM, which has a net gain of 11.95 cm(-1), a loss of 9.25 cm(-1), and a threshold of 4(mJ/pulse)/cm(2). The improvement of performance in DCJTB PS films is attributed to the larger free volume of DCJTB caused by the introduction of steric spacer groups into the DCJTB molecule.

Direct electrochemistry and bioelectrocatalysis of horseradish peroxidase immobilized on active carbon

For the first time horseradish peroxidase (HRP) immobilized on the surface of active carbon powder modified at the surface of a glassy carbon electrode has been shown to undergo a direct quasi-reversible electrochemical reaction. Its formal potential, E-o/, is -0.363 V in phosphate buffer solution (pH 6.8) at a scan rate of 100 mV/s and is almost independent of the scan rate in the range of 50-700 mV/s. The dependence of E-o/ on the pH of the buffer solution indicated that the conversion of HRP-Fe(III)/HRP-Fe(II) is a one-electron-transfer reaction process coupled with one-proton-transfer. The experimental results also demonstrated that the immobilized HRP retained its bioelectrocatalytic activity to the reduction of H2O2. Furthermore, the HRP adsorbed oil the surface of the active carbon powder can be stored at 4 degreesC for several months without any loss of the enzyme activity. The method presented for immobilizing HRP can be easily extended to immobilize and obtain the direct electrochemistry of other enzymes.

Direct electrochemical reaction of horseradish peroxidase immobilized on the surface of active carbon powders

It is reported for the first time that horseradish peroxidase (HRP) immobilized on the active carbon can undergo a direct quasi-reversible electrochemical reaction. In addition, the immobilized HRP showed the stable bioelectrocatalytic activity for the reduction of H2O2.

Immobilization and direct electrochemistry of copper-containing enzymes on active carbon

Two typical and important copper-containing enzymes, laccase (Lac) and tyrosinase (Tyr), have been immobilized on the surface of active carbon with simple adsorption method. The cyclic voltammetric results indicated that the active carbon could promote the direct electron transfer of both Lac and Tyr and a pair of well-defined and nearly symmetric redox peaks appeared on the cyclic voltammograms of Lac or Tyr with the formal potential, E-0', independent on the scan rate. The further experimental results showed that the immobilized copper-containing oxidase displayed an excellent electrocatalytic activity to the electrochemical reduction of O-2. The immobilization method presented here has several advantages, such as simplicity, easy to operation and keeping good activity of enzyme etc., and could be further used to study the direct electrochemistry of other redox proteins and enzymes and fabricate the catalysts for biofuel cell.

The use of CE-electrochemiluminescence with ionic liquid for the determination of bioactive constituents in Chinese traditional medicine

CE/tris(2,2-bipyridyl) ruthenium(ll) (Ru(bpy)(3)(2+)) electrochemiluminescence (ECL), CEECL, with an ionic liquid (IL) detection system was established for the determination of bioactive constituents in Chinese traditional medicine opium poppy which contain large amounts of coexistent substances. A minimal sample pretreatment which involves a one-step extraction approach avoids both sample loss and environmental pollution. As the nearby hydroxyl groups in some alkaloid such as morphine may react with borate to form complexes and IL, as a high-conductivity additive in running buffer, could cause an enhanced field-amplified effect of electrokinetic injection. Running buffer containing 25 mM borax-8 mM 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF(4)) IL (pH 9.18) was used which resulted in significant changes in separation selectivity and obvious enhancement in ECL intensities for those alkaloids with similar structures. Sensitive detection could be achieved when the distance between the Pt working electrode and the outlet of separation capillary was set at 150 mu m and the stainless steel cannula was fixed approximately 1 cm away from the outlet of the capillary. Quantitative analysis of four alkaloids was achieved at a detection voltage of 1.2 V and a separation voltage of 15 kV in less than 7 min.

Novel highly active binuclear neutral nickel and palladium complexes as precatalysts for norbornene polymerization

A series of binuclear neutral nickel and palladium complexes [(XC6H2CH=NC6H3-iPr(2))MRL](2) 4b-f (X=NO2, M=Ni, R=Ph, L=PPh3, 4b; X=H, M=Pd, R=Me, L=PPh3,4c; X=H,M=Pd, R=Me, L=Py, 4d; X=NO2,M=Pd, R=Me, L=PPh3, 4e; X=NO2, M=Pd, R=Me, L=Py, 4f) and [(C10H7CH=NC6H3-iPr(2))MRL](2) 8a-c (M=Ni, R=Ph, L=PPh3, 8a; M=Pd, R=Me, L=PPh3, 8b; M=Pd, R=Me, L=Py, 8c) have been synthesized and characterized. The structures of complexes 4e and 8b have also been confirmed by X-ray crystallographic analysis. With modified methylalummoxane (MMAO) as cocatalysts, these complexes and complex [(C6H3CH=NC6H3-iPr(2))NiPh(PPh3)](2) 4a are capable of catalyzing the addition polymerization of norbomene (NBE) with the high activity up to 2.3 x 10(8) g PNBE/(mol(M) h). The structure of complexes affects considerably catalytic activity towards norbomene polymerization. The polymers obtained with nickel complexes are soluble, while those obtained with palladium complexes are insoluble. Palladium complexes 4c, 4e and 8b bearing PPh3 ligands exhibit much higher activities than the corresponding complexes 4d, M and 8c bearing pyridine ligands under the same conditions.

Highly active, hexabutylguanidinium salt/zinc bromide binary catalyst for the coupling reaction of carbon dioxide and epoxides

An experimentally simple and inexpensive catalyst system based on hexabutylguanidinium/ZnBr, has been developed for the coupling of carbon dioxide and epoxides to form cyclic carbonates with significant catalytic activity under mild reaction conditions without using additional organic solvents (e.g. the turnover frequencies (TOF, h(-1)) values as high as 6.6 x 10(3) h(-1) for styrene oxide and 1.01 x 10(4) h(-1) for epichlorohydrin). This catalyst system also offers the advantages of recyclability and reusability. Therefore, it is a very effective, environmentally benign, and simple catalytic process. The special steric and electrophilic characteristics of hexabutylguanidinium bromide ionic liquid result in the prominent performance of this novel catalyst system.

An approach for fabricating self-assembled monolayer of Ag nanoparticles on gold as the SERS-active substrate

In this paper, an approach for fabricating an active surface-enhanced Raman scattering (SERS) substrate is adopted. This approach is based on the assembling of silver nanoparticles film on gold substrate. Rhodamine 6G (R6G) and p-aminothiophenol (P-ATP) were used as probe molecules for SERS experiments, showing that this new active substrate has sensitivity to SERS response. Tapping-mode atomic force microscopy (AFM) was also used to investigate the surface morphology following the fabricating process of the active SERS substrate, which showed that large quantities of silver nanoparticles were uniformly coated on the substrate.

Novel, highly active binuclear 2,5-disubstituted Amino-p-benzoquinone-nickel(II) ethylene polymerization catalysts

Reaction of salts of the 2,5-disubstituted amino-p-benzoquinone bridging ligand (la-e) with trans-bis(triphenylphosphane)phenylnickel(II) chloride results in the binuclear complexes 2a-e, which show high activities for ethylene polymerization without any cocatalysts. High-molecular-weight, moderately branched polyethylene of broad molecular-weight distribution was obtained.