Electro-oxidation of hydrazine on electrodes modified with vitamin B12

In this paper we report a kinetic study of the electro-oxidation of hydrazine catalyzed by vitamin B₁₂ pre-adsorbed on an ordinary pyrolytic graphite electrode. Kinetic parameters were determined by linear sweep voltammetry and rotating-disk electrode polarization curves. The order of the reaction is 1 in OH⁻ ions and Tafel plots give slopes of 80 mV/decade. A possible redox-catalysis mechanistic scheme is proposed.     

Fe73.5Cu1Nb3Si13.5B9非晶粉/硅橡胶压磁复合材料的制备与性能研究

采用机械共混法制备Fe73.5Cu1Nb3Si13.5B9非晶粉/硅橡胶压磁复合材料,并对其压磁性能进行研究,结果表明.Fe73.5Cu1Nb3Si13.5B9非晶粉/硅橡胶复合材料具有良好的压磁性能.且压磁性能稳定性和阻抗蠕变性能优异,可用于新型压力传感器用力敏元件.     

Synthesis and characterization of B13C2 boron carbide ceramic by pulsed electric current sintering

Approximately 400 nm grain sized boron-carbon ceramic was synthesized by the pulsed electric current sintering (PECS) method using boron and carbon powders. Relative density of up to 95% was achieved at sintering temperature of 1900 °C. This ceramic was composed with B₁₃C₂ as major phase and few B₄C and C, which were characterized by X-ray diffraction (XRD) and Rietveld refinement quantitative analysis and chemical analysis (CA) and electron probe microanalysis (EPMA). The microstructure was also observed via transmission electron microscope (TEM).     

Electrochemical reduction of 2,4-dinitrophenol on nanocomposite electrodes modified with mesoporous silica and poly(vitamin B1) films

Electrochemical reduction of 2,4-dinitrophenol was investigated on a glassy carbon electrode modified with a nanocomposite Santa Barbara Amorphous silica (SBA-15) film and poly(vitamin B₁) film. For sensitive and selective detections, vanadium pentoxide and cerium oxide nanoparticles were incorporated into the matrix of SBA-15. 2,4-Dinitrophenol was reduced on the modified electrode at −0.39 and −0.25 V, corresponding to the reduction of 4-dinitrophenol and 2-dinitrophenol, respectively. Both cathodic peak currents were controlled by the diffusion of 2,4-dinitrophenol. The amplitude of the peak currents was proportional to the 2,4-dinitrophenol concentration in the range of 3.0–30 μM. The modified electrode demonstrated a long lifetime for the detection of 2,4-dinitrophenol. The detection limit of 2,4-dinitrophenol was 0.5 μM. Moreover, the modified electrode was used successfully to detect 2,4-dinitrophenol in lake water.     

TiO2 photocatalyst loaded on hydrophobic Si3N4 support for efficient degradation of organics diluted in water

TiO₂ photocatalyst loaded on Si₃N₄ (TiO₂/Si₃N₄) was prepared by a conventional impregnation method and its photocatalytic performance for the degradation of organics (2-propanol) diluted in water was compared with that of TiO₂ photocatalysts (TiO₂/SiO₂, TiO₂/Al₂O₃, and TiO₂/SiC) loaded on various types of supports (SiO₂, Al₂O₃, and SiC). The formation of the well-crystallized anatase phase of TiO₂ was observed on the calcined TiO₂/Si₃N₄ photocatalyst, while a small anatase phase of TiO₂ was observed on the TiO₂/SiC photocatalyst and amorphous TiO₂ species was the main component on the TiO₂/SiO₂ and TiO₂/Al₂O₃ photocatalysts. The measurements of the water adsorption ability of photocatalysts indicated that the TiO₂/Si₃N₄ photocatalyst exhibited more hydrophobic surface properties in comparison to other support photocatalysts. Under UV-light irradiation, the TiO₂/Si₃N₄ photocatalyst decomposed 2-propanol diluted in water into acetone, CO₂, and H₂O, and finally, acetone was also decomposed into CO₂ and H₂O. The TiO₂/Si₃N₄ photocatalyst showed higher photocatalytic activity than TiO₂ photocatalyst loaded on other supports. The well-crystallized TiO₂ phase deposited on Si₃N₄ and the hydrophobic surface of Si₃N₄ support are important factors for the enhancement of photocatalytic activity for the degradation of organic compounds in liquid-phase reactions.     

Electrochemical activity, stability and degradation characteristics of IrO2-based electrodes in aqueous solutions containing C1 compounds

In this paper, we investigate the electrocatalytic behavior and degradation characteristics of IrO₂-based electrodes in Na₂SO₄ solutions containing C₁ compounds (CH₃OH, HCHO and HCOOH). Decreases are generally observed in the electrochemically active area, electrochemical stability and durability of the electrodes in aqueous solutions in the presence of these organic substrates. The following sequence holds for the influence of C₁ compounds on the electrode properties (i.e. activity and stability): CH₃OH > HCHO > HCOOH. The corrosion characteristics of electrode are studied by X-ray diffraction measurements. For the first time, the decomposition and dissolution of active oxide layers are quantitatively characterized from the decreases in cell volume of rutile-structured IrO₂ crystallite and from the increases in texture coefficient of (0 0 2) planes, respectively, as a result of the accelerated lifetime tests.     

Photo-electrochemical properties of amorphous WO3 supported on TiO2 hybrid catalysts

In this work, we have carried out ivestigations on photo-electrochemical energy conversion and storage on WO₃/TiO₂ hybrid materials. The band gap excitation of the hybrid WO₃/TiO₂ having an amorphous WO₃ phase led to an effective photo-charging to form a tungsten bronze structure by the intercalation of protons while a reversible discharging through de-intercalation could also be observed.     

Hematological Parameters and the State of Liver Cells of Rats After Oral Administration of Aflatoxin B1 Alone and Together with Nanodiamonds

Hematological parameters and the state of liver cells of rats were examined in vivo after the animals received aflatoxin B₁ (AfB₁) alone and together with modified nanodiamonds (MND) synthesized by detonation. The rats that had received the MND hydrosol had elevated leukocyte levels, mainly due to higher granulocyte counts and somewhat increased monocyte counts compared to control rats. Hematological parameters of the rats that had received AfB₁ alone differed from those of the control rats in another way: total white blood cell counts were significantly lower due to the decreased lymphocyte counts. In rats that had consumed AfB₁ with the MND hydrosol, changes in hematological parameters were less pronounced than in rats that had consumed either AfB₁ or MND. Electron microscopy showed that hepatocytes of the rats that had received the MND hydrosol or AfB₁ with the MND hydrosol contained elevated levels of lipid inclusions and lysosomes. Hyperplasia of the smooth endoplasmic reticulum (EPR) was revealed in liver specimens of the rats that had received AfB₁. Results of the study suggest the conclusion about mutual mitigation of the effects of nanoparticles and the mycotoxin on rats blood and liver cells after AfB₁ has adsorbed on MND.     

Effect of Zr-ion substitution in CeO2 on H2O2-assisted degradation of orange G

A series of Pd ion-substituted CeO₂–ZrO₂ solid solutions were synthesized using the solution combustion technique. H₂O₂-assisted degradation of orange G was carried out in the presence of the catalysts. The activity of the catalysts was found to increase with the introduction of the second component in the solid solution, as signified by an increase in the rate constants and lowering of activation energy. The study showed the involvement of lattice oxygen and the importance of reducibility of the compound for the reaction.     

CaO–ZrO2 Solid Solution: A Highly Stable Catalyst for the Synthesis of Dimethyl Carbonate from Propylene Carbonate and Methanol

CaO–ZrO₂ prepared by co-precipitation showed to be a well-performed catalyst for the transesterification of propylene carbonate (PC) and methanol. The characterization by X-ray powered diffraction (XRD) and Raman spectroscopy indicated that CaO was doped into the lattice of ZrO₂ to form CaO–ZrO₂ solid solution. Such a solid solution was a strong solid base, which was proved by CO₂ temperature program desorption (CO₂-TPD). As a result, the catalyst showed high stability towards the transesterification of propylene carbonate and methanol into dimethyl carbonate with high PC conversion, especially being subjected to the continuous production of dimethyl carbonate at reactive distillation reactor for 250 h without any obvious loss of activity at the PC conversion of 95%.     

Solid-phase photocatalytic degradation of polystyrene with modified nano-TiO2 catalyst

A novel photodegradable polystyrene-grafted-TiO₂ (PS-g-TiO₂) nanocomposite was prepared by embedding the grafted-TiO₂ into the commercial polystyrene. Solid-phase photocatalytic degradation of the PS-g-TiO₂ nanocomposite was carried out in ambient air at room temperature under ultraviolet lamp and/or sunlight irradiation. The properties of composite film were compared with those of the pure PS film by methods such as weight loss measurement, scanning electron microscope (SEM), gel permeation chromatogram (GPC), X-ray photoelectron spectroscopy (XPS), FT-IR spectroscopy, and UV-vis spectroscopy. The results show that the photo-induced degradation of PS-g-TiO₂ composite film is significantly higher than that of pure PS film. The weight loss of composite film reached 31.9%, average molecular weight (M_w) of composite film decreased by 53.1%, and the number average molecular weight (M_n) decreased by 73.2% after 396 h of UV-light irradiation. FT-IR analysis and weight loss indicated that the benzene rings in PS-matrix of composite film were cleaved during UV-light irradiation. The photocatalytic degradation mechanism of the films is briefly discussed.     

Does Vitamin D Work Synergistically with Anti-Asthmatic Drugs in Airway Remodeling?

Vitamin D is commonly known for its properties of airway remodeling inhibition. Due to this, we decided to analyze the action of calcitriol with anti-asthmatic drugs in airway remodeling. The HFL1 cell line was treated with calcitriol, beclomethasone 17-propionate, montelukast sodium, LTD4 and TGF-β in different combinations. Real-time PCR was used to analyzed the expression of ACTA2, CDH-1, Vimentin, ADAM33, MMP-9 and CysLTR1 on the mRNA level, whereas Western blot was used to analyze gene expression on the protein level. One-way analysis variants, the Kruskal-Wallis test, Student’s t-test or Welch’s t-test were used for statistical analysis. Concerning the results, pre-treatment with calcitriol increased the inhibitory effect of beclomethasone 17-propionate and montelukast sodium on the expression of ACTA2 (p = 0.0072), Vimentin (p = 0.0002) and CysLTR1 (p = 0.0204), and 1,25(OH)₂D₃ had an influence on the effects of beclomethasone 17-propionate and montelukast sodium and of CDH1 expression (p = 0.0076). On the protein level, pre-treatment with calcitriol with beclomethasone 17-propionate and montelukast sodium treatment decreased ACTA2 expression in comparison to the LT (LTD4 and TGF-β) control group (p = 0.0191). Hence, our study not only confirms that vitamin D may inhibit airway remodeling, but also shows that vitamin D has a synergistic effect with anti-asthmatic drugs.     

Reversibility of the l-cysteine/l-cystine redox process at physiological pH on graphite electrodes modified with coenzyme B12 and vitamin B12

We report on the electrocatalytic activity of immobilized coenzyme B₁₂ and vitamin B₁₂ (as aquocobalamin) for the electrooxidation of l-cysteine and their effects on the electrochemical reversibility of the l-cysteine/l-cystine redox couple, a crucial biological system. Cyclic voltammograms of coenzyme B₁₂ adsorbed on a graphite electrode show that upon the reductive elimination of the 5′-deoxyadenosyl group from the cobalt center, at approximately −1.1 V, the electrochemical response of the modified electrode becomes similar to that of aquocobalamin. The electrochemically pretreated coenzyme B₁₂ shows a high electrocatalytic activity for the electro-oxidation of l-cysteine at physiological pH that has never been observed before with the commonly used metallophthalocyanine catalysts. Also, its activity is slightly higher than that exhibited by aquocobalamin.     

High-temperature hydrogenation behaviour of bulk titanium silicon carbide

Thermal stability of Ti₃SiC₂ was investigated at 1200–1400°C in hydrogen atmosphere for 3 hours. The hydrogenation mechanism was clarified by a combination of X-ray diffraction, scanning electron microscope, Raman spectroscopy and first principles calculation. At 1200°C, a dense and uniform TiSi₂ layer formed on the sample surface, which originated from both the preferable lose of silicon from the Ti₃SiC₂ substrate and the dissociation of Ti₃SiC₂. As temperature increased to 1300°C, TiSi₂ layer began to scale off and presented laminated Ti₃SiC₂ grains beneath this layer, which indicated preferential hydrogenation occurred along the basal planes. This phenomenon was ascribed to the fact that the introduction of H interstitial atom weakened the combination between titanium and silicon interface layer, which was confirmed by first principles calculations. In addition, the formation of TiSi₂ owing to the dissociation of Ti₃SiC₂ caused the volume expansion after hydrogenation, resulting in that majority of TiSi₂ layer spelled off at 1400°C.     

Electrocatalytic degradation of 4-chlorophenol on F-doped PbO2 anodes

PbO₂ and F-doped PbO₂ (F-PbO₂) anodes have been prepared by a standard thermal decomposition-electrodeposition technique. The electrochemical stability of these anodes has been investigated by the accelerated life tests in sulphuric acid solution. The results show that the service life of the F-PbO₂ anodes is almost three times longer than that of the PbO₂ anodes. Furthermore, in the degradation of 4-chlorophenol (4-CP), the F-PbO₂ anodes give a higher degradation rate than that observed for the PbO₂ anodes. The influence of F⁻ anion doping on the stability and activity of PbO₂ anodes has been discussed. With the F-PbO₂ anodes, the degradation of 4-CP is investigated according to the results of high-performance liquid chromatograph (HPLC), ionic chromatograph (IC) and cyclic voltammetry (CV). In addition, the electron spin resonance (ESR) technique using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as the spin-trap reagent has been applied to detect free radical intermediates generated during in situ the electrocatalytic degradation of aqueous 4-CP on the F-PbO₂ anodes. ESR measurements give the direct evidence that the active species (OH) are responsible for the decomposition of 4-CP over F-PbO₂ under anodic bias potential, strongly suggesting that the electrocatalytic degradation of most organic compounds on F-PbO₂ anodes proceed via surface intermediates of water oxidation, not via direct oxidation at electrode surface. The formation mechanism of surface intermediates is also discussed.