Complete dechlorination of DDT and its metabolites in an alcohol mixture using NaOH and Pd/C catalyst

DDT (1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane) was dechlorinated in 2-propanol/methanol (99:1v/v) by means of stoichiometric reaction with NaOH and subsequent catalytic dechlorination over Pd/C catalyst. When DDT was treated with a molar excess of NaOH ([NaOH]/[DDT]=9) in the alcohol mixture at room temperature, DDT disappeared within 15min. The reaction of DDT produced an equimolar amount of HCl to yield DDE (1,1-bis(4-chlorophenyl)-2,2-dichloroethylene). The produced DDE was successfully dechlorinated to a chlorine-free product (1,1-diphenylethane, 97% yield) by addition of Pd/C to the alkaline solution and heating at 40 degrees C for 4h. DDD (1,1-bis(4-chlorophenyl)-2,2-dichloroethane) was also dechlorinated to 1,1-diphenylethane in a similar manner. Possible dechlorination pathways for DDT, DDE, and DDD were investigated by observation of the partially dechlorinated intermediates by means of gas chromatography/mass spectrometry (GC/MS).     

双酚A二环氧甘油醚的免疫检测方法研究

目的快速检测湖水中的双酚A二环氧甘油醚。方法试验设计一种新型双酚A二环氧甘油醚半抗原,并成功与载体蛋白偶联,经过小鼠免疫、细胞融合技术和三次亚克隆等方法,成功筛选出了可以稳定分泌BADGE单克隆抗体的杂交瘤细胞株。结果成功制备了高灵敏度高特异性的双酚A二环氧甘油醚单克隆抗体,可以用于针对双酚A二环氧甘油醚的间接竞争酶联免疫吸附测定(icELISA)。基于单克隆抗体,绘制了标准曲线,结果显示,单克隆抗体的IC50=1.15 ng/mL,检测线性范围IC20～IC80为0.16～8.15 ng/mL。通过加标回收实验,BADGE在湖水的添加回收率均在80%～120%之间。结论双酚A二环氧甘油醚单克隆抗体在实际湖水样品检测中的运用具有可行性。     

Reductive dechlorination of 3,3',4,4'-tetrachlorobiphenyl (PCB77) using palladium or palladium/iron nanoparticles and assessment of the reduction in toxic potency in vascular endothelial cells

Palladium-based nanoparticles immobilized in polymeric matrices were applied to the reductive dechlorination of 3,3',4,4'-tetrachlorobiphenyl (PCB77) at room temperature. Two different dechlorination platforms were evaluated using (1) Pd nanoparticles within conductive polypyrrole films; or (2) immobilized Fe/Pd nanoparticles within polyvinylidene fluoride microfiltration membranes. For the first approach, the polypyrrole film was electrochemically formed in the presence of perchlorate ions that were incorporated into the film to counter-balance the positive charges of the polypyrrole chain. The film was then incubated in a solution containing tetrachloropalladate ions, which were exchanged with the perchlorate ions within the film. During this exchange, reduction of tetrachloropalladate by polypyrrole occurred, which led to the formation of palladium nanoparticles within the film. For the second approach, the membrane-supported Fe/Pd nanoparticles were prepared in three steps: polymerization of acrylic acid in polyvinylidene fluoride microfiltration membrane pores was followed by ion exchange of Fe(2+), and then chemical reduction of the ferrous ions bound to the carboxylate groups. The membrane-supported iron nanoparticles were then soaked in a solution of tetrachloropalladate resulting in the deposition of Pd on the Fe surface. The nanoparticles prepared by both approaches were employed in the dechlorination of PCB77. The presence of hydrogen was required when the monometallic Pd nanoparticles were employed. The results indicate the removal of chlorine atoms from PCB77, which led to the formation of lower chlorinated intermediates and ultimately biphenyl. Toxicity associated with vascular dysfunction by PCB77 and biphenyl was compared using cultured endothelial cells. The data strongly suggest that the dechlorination system used in this study markedly reduced the proinflammatory activity of PCB77, a persistent organic pollutant.     

Doublely-doped Mg-Al-Ce-V_2O_7~(4-) LDH composite film on magnesium alloy AZ31 for anticorrosion

A doublely-doped layered double hydroxide(LDH)film was produced on an anodized magnesium alloy AZ31.The Ce-doped Mg-Al LDH film was prepared by in-situ hydrothermal treatment method,and the intercalation of vanadate was realized by ion-exchange reaction.The structure,morphology and composition of as-prepared LDH film were investigated by X-ray diffractometer,field-emission scanning electronic microscope and energy dispersive spectrometry.Results indicated that a uniform and compact LDH film was formed and the intercalation of Ce³⁺and vanadate would change the crystal structure of LDHs.The results of the potentiodynamic polarization,electrochemical impedance spectra,hydrogen evolution and corrosion weight loss tests showed the Ce³⁺and vanadate anions significantly improve the impedance of LDH film,and the active double-doped LDH film could effectively protect the magnesium substrate from corrosion.     

The color removal of dye wastewater by magnesium chloride/red mud (MRM) from aqueous solution

In this study, the MgCl₂/red mud system (MRM) was used to investigate the color removal efficiency of dye solutions. Parameters such as the effect of the dosage of red mud (RM) and MgCl₂ have been studied. The effect of pH on the conversion rate of Mg²⁺ has also been studied. The color removal efficiency of MRM was compared with that of PAC/RM and PAC/NaOH. Meanwhile, the color removal efficiency of RM was compared with that of NaOH. The results show that the MRM system can remove more than 98% of the coloring material at a dosage of 25 g RM/L dye solution and a volume of 1.5 mL MgCl₂/L dye solution in the decolorization process of reactive dye, acid dye and direct dye. The color removal efficiency was better than PAC/RM and PAC/NaOH system. The adsorption data have been analyzed using Langmuir and Freundlich isotherms. The results indicated that both models provide the best correlation of the experimental data. The decolorization mechanism of MRM was discussed, too. The MRM system was a viable alternative to some of the more conventional forms of chemical treatment of dye solutions and also provided another way to make use of industrial waste red mud.     

Surface poisoning in the nucleation and growth of palladium atomic layer deposition with Pd(hfac)2 and formalin

Palladium (Pd) atomic layer deposition (ALD) can be performed with Pd(hfac)₂ (hfac = hexafluoroacetyl-acetone) and formalin as the reactants. For Pd ALD on oxide surfaces, the nucleation of Pd ALD has been observed to require between 20 and 100 ALD cycles. To understand the long nucleation periods, this study explored the surface reactions occurring during Pd ALD nucleation and growth on hydroxylated Al₂O₃ substrates. In situ Fourier transform infrared (FTIR) spectroscopy on high surface area nanopowders was used to observe the surface species. The adsorption of Pd(hfac)₂ on hydroxylated Al₂O₃ substrates was found to yield both Pd(hfac)* and Al(hfac)* surface species. The identity of the Al(hfac)* species was confirmed by separate FTIR studies of hfacH adsorption on the hydroxylated Al₂O₃ substrates. Isothermal loss of the Al(hfac)* species revealed second-order kinetics at 448-523 K with an activation barrier of E_d = 39.4 kcal/mol. The lack of correlation between Al(hfac)* and AlOH* species during the loss of Al(hfac)* species suggested that the Al(hfac)* species may desorb as Al(hfac)₃. After Pd(hfac)₂ exposure and the subsequent formalin exposure on hydroxylated Al₂O₃ substrates, only hfac ligands from Pd(hfac)* species were removed from the surface. In addition, the formalin exposure added formate species. The Al(hfac)* species was identified as the cause of the long nucleation period because Al(hfac)* behaves as a site blocker. The surface poisoning by Al(hfac)* species was corroborated by adsorbing hfacH prior to the Pd(hfac)₂ exposures. The amount of Pd(hfac)* species after Pd(hfac)₂ exposures decreased progressively versus the previous hfacH exposure. Pd ALD occurred gradually during the subsequent Pd ALD cycles as the Al(hfac)* species were slowly removed from the Al₂O₃ surface. Ex situ transmission electron microscopy analysis revealed Pd nanoclusters that grew in size and dispersion with increasing number of Pd ALD cycles. These nanoclusters eventually coalesced to form a continuous Pd ALD film. Surface poisoning by the hfac ligands may help to explain the nucleation difficulties for metal ALD on oxide substrates using β-diketonate reactants.     

Synthesis of an extremely stable ceramic in the system Si/B/C/N using 1-(trichlorosilyl)-1-(dichloroboryl)ethane as a single-source precursor

 A new material discovered in the Si/B/C/N system was found to remain in the amorphous state up to a very high temperature of 2000°C. This material, with the composition Si₂B₂N₅C₄, is the only material in this system which does not undergo any microstructural changes until such high temperatures. Furthermore, the substance shows an extremely high resistance to oxidation up to 1500°C. The synthesis of amorphous Si₂B₂N₅C₄ was achieved by using the novel single-source precursor 1-(trichlorosilyl)-1-(dichloroboryl)ethane (TSDE), which can be synthesized in high yields from inexpensive starting materials in a simple single pot reaction. Examination of the structural properties of the pyrolytic ceramic reveals a substructure consisting of tetrahedrally and trigonally-planar coordinated silicon and boron, respectively. Si-C- and B-C-bonds present in the molecular precursor could not be distinguished from Si-N- and B-N-bonds in the fully pyrolized ceramic. EDX and X-ray-diffraction showed the material to have a homogeneous elemental distribution, and no phase separation could be detected. Received: 15 August 1998 / Reviewed and accepted: 24 September 1998     

Monolayers, Langmuir-Blodgett films of bimetallic coordination polymers of 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine

Building blocks of coordination polymers have attracted much attention because of promising applications in porous materials, molecular engineering and devices. We report here an interfacial self-assembly of bimetallic coordination polymer of Cd-Fe(pyterpy)₂ (pyterpy: 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine). The surface pressure-area and area-time isotherms indicated that stable monolayers of Fe(pyterpy)₂(BF₄)₂ could be formed on the 0.1 mol/l CdCl₂ subphase surface after an interfacial coordination reaction over 12 h. By using the Langmuir-Blodgett (LB) method, monolayers of the Cd-Fe(pyterpy)₂ coordination polymer were transferred on the substrate surfaces, and characterized by using the UV-vis absorption and X-ray photoelectron spectroscopy, as well as transition electron microscopy. The spectral data revealed that the LB film was composed of C, Cl, Cd, N and Fe elements, which was in agreement with the composition of the coordination polymer. Reversible redox wave centered at about 500 mV (vs Ag/AgCl) was recorded for the electrode modified with the LB film of the coordination polymer. The present method could be developed to prepare two- and three-dimensional nanoporous building blocks containing two metal ions.     

Carbon and sulphur on Pd(111) and Pt(111): Experimental problems during cleaning of the substrates and impact of sulphur on the redox properties of CeOx in the CeOx/Pd(111) system

The X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and CO titration has been used to detect common impurities like carbon and sulphur on Pd(111) and Pt(111) surfaces. Different experimental problems are discussed and practical tips for the cleaning of Pd(111) and Pt(111) are given. A mechanism for the carbon oxidation on closed packed platinum group metals like Pt(111) and Pd(111) is presented. The bulk carbon concentration of Pd(111) was estimated based on the Langmuir-McLean theorem. Additionally it was shown that the titration with CO and subsequent XPS measurement is a powerful yet convenient method for quantitative detection of impurities and ceria coverage determination. A CeO_x/Pd(111) inverse model system was prepared by evaporation of cerium in an oxygen atmosphere. The comparative study has shown that sulphur contamination changes the redox properties of the CeO_x in the CeO_x/Pd(111) system.     

Solid phase growth and properties of Mg2Si films on Si(111)

Solid phase technology of growing of epitaxial and textured Mg₂Si films on Si(111) is developed. It includes fabrication of template layer, deposition of multiplayer sandwich structure Mg/Si/ and final annealing. Research results are presented on morphology, structure and optical properties of thin Mg₂Si films grown on Si(111) by the method of solid-phase annealing on a template layer.     

Physicochemical and catalytic properties of palladium supported on poly(o-methoxyaniline)

Palladium was introduced into a conjugated polymer poly(o-methoxyaniline) (POM) by reacting the powdered polymer with aqueous solution of PdCl₂ of low acidity (PdCl₂: 2.3 × 10⁻³ mol/dm³, HCl: 0.66 × 10⁻³ mol/dm³). Various Pd²⁺ complexes with Cl⁻, H₂O, OH⁻ ligands coexisted in this solution but predominated [PdCl₂(H₂O)₂] ones. Several techniques like X-ray powder diffraction, scanning electron microscopy, X-ray photoelectron and Raman spectroscopy, extended X-ray absorption fine structure have been used to characterize the poly(o-methoxyaniline)-Pd systems. In particular, the state of Pd species in the Pd/POM of various content of palladium (2-8 wt.% Pd) and chemical changes in the polymer matrix induced by insertion of palladium were studied. The protonation and redox reactions involved on palladium incorporation resulted in palladium ions and Pd metal in the final samples. Metallic Pd produced due to spontaneous reduction of palladium ions by the polymer formed large crystalline particles 200-1000 nm in size. The Pd²⁺ species in the form of anionic complexes like [PdCl₄]²⁻ acted as the counterions at low content of palladium (2-4 wt.% Pd). At high palladium content (8 wt.% Pd), several atoms like Cl, N and/or O were identified by extended X-ray absorption fine structure (EXAFS) technique in the nearest environment of Pd atoms. The structural groups of POM (like N groups and/or OCH₃) as well as H₂O, OH⁻ molecules are, therefore, considered as probable species in the coordination sphere of palladium. The catalytic properties were studied for the as-prepared Pd/POM and the samples additionally reduced with aqueous solution of NaH₂PO₂. They were used in the hydrogenation of CC bonds in maleic acid (MAC) and CO groups in 2-ethylanthraquinone (eAQ) at 60 °C and atmospheric pressure of hydrogen using xylene-octanol-2 or water medium. The correlation between Pd/POM activities and the content of Pd metal was found. Activation of the as-prepared Pd/POM with NaH₂PO₂ improved their catalytic properties. Much higher and much stable activities were then obtained in both MAC and eAQ hydrogenation reactions.     

Preliminary investigations about effects of Zr, Sc and Ce additions on as-cast microstructure and mechanical properties of Mg-3Sn-1Mn (wt.%) magnesium alloy

In this paper, the effects of Zr, Sc and Ce additions on the as-cast microstructure and mechanical properties of Mg-3Sn-1Mn (wt.%) magnesium alloy were preliminarily investigated and compared. The results indicate that adding 0.36 wt.% Sc and 0.87 wt.% Ce to the Mg-3Sn-1Mn alloy, respectively leads to the formation of the extra phases of Mg-Sn-Sc and Mg₁₂Ce while adding 0.43 wt.% Zr does not cause the formation of any new phases. At the same time, adding 0.43 wt.% Zr or 0.87 wt.% Ce can refine the grains while adding 0.36 wt.% Sc coarsens the grains. Among the Zr- and Ce-containing alloys, the grains of the latter are relatively finer than those of the former. In addition, adding 0.43 wt.% Zr, 0.36 wt.% Sc and 0.87 wt.% Ce to the Mg-3Sn-1Mn alloy can improve the tensile and/or creep properties of the alloy. However, the addition of 0.43 wt.% Zr is not beneficial to the creep properties. Among the Zr-, Sc- and Ce-containing alloys, the alloy with the addition of 0.87 wt.% Ce exhibits the optimal tensile and creep properties.     

Surface morphology and structure of ultra-thin magnesium oxide grown on (100) silicon by atomic layer deposition oxidation

Ultra-thin magnesium oxide layers were elaborated by atomic layer deposition and oxidation process on silicon (100) starting from (2 × 1) thermally-reconstructed or hydrogen-terminated Si surfaces. Low-energy electron diffraction experiments show (2 × 3) and (3 × 3) reconstructions while depositing a magnesium monolayer on Si clean surfaces, and a 3-dimentional growth of the oxide as confirmed by ex-situ atomic force microscopy. For hydrogen-terminated or clean surfaces previously physisorbed by oxygen, uniform cobalt/magnesium-oxide/silicon stacks of layers are observed by transmission electron microscopy. Annealing above 150 °C leads to MgO dissolution and formation of an interfacial complex compound by inter-diffusion of Si and Co.     

AuCl4 ions-assisted fabrication of bimetallic {Poly(ethylenimine)-Ag/Au} multilayer polyelectrolyte film and application in electrocatalysis

Bimetallic {Poly(ethylenimine) (PEI)-Ag/Au} multilayer film was in situ simultaneously fabricated by alternating immersions of a substrate in PEI-Ag⁺ and AuCl₄⁻ solutions followed by chemical reduction with NaBH₄ solution. In the process, the AuCl₄⁻ ions not only play an important role of a reaction reagent, but also served as an assembly reagent. Au, Ag nanoparticles (NPs) were observed with a spherical morphology and well-dispersed in the composite multilayer film, and the size of Au NPs in the bimetallic {PEI-Ag/Au} multilayer film was smaller than that of the single Au NPs formed in {PEI/Au} multilayer films. It was also very interesting to observe that this bimetallic {PEI-Ag/Au} multilayer film exhibited more efficient electrocatalytic activity for the oxidation of ascorbic acid than the multilayer film containing only single Au or Ag NPs. These results indicated that this bimetallic composite multilayer film may be potentially applied in electrochemical biosensors.     

Electrochromic behavior of poly(3,5-bis(4-bromophenyl)dithieno[3,2-b;2′,3′-d]thiophene)

Electropolymerization of 3,5-bis(4-bromophenyl)dithieno[3,2-b;2′,3′-d]thiophene, having a mild electron-withdrawing bromine atom attached to the para position of the two phenyl groups of dithienothiophene, was performed, utilizing a potentiodynamic method. The resultant homopolymer was characterized by cyclic volyammetry, fourier transform infrared and ultraviolet-visible spectroscopy. Spectroelectrochemical and electrochromic properties were investigated and a device was constructed with polyethylenedioxythiophene to understand the characteristics in detail, which had the potential range of 0.0-2.0 V for operating the device between green and blue colors. It had a good optical contrast of 18% with a switching time of less than a second. Moreover, open circuit memory and stability of the device were investigated.     

Studies of structural and electrical properties of Pb(Li1/4Eu1/4Mo1/2)O3 ceramics

Polycrystalline sample of Pb(Li_1/4Eu_1/4Mo_1/2)O₃ was prepared by usual ceramic route. X-ray diffraction, SEM and EDAX were used to check the formation, homogeneity and elements present in the compound. The measurement of dielectric constant (ɛ), dielectric loss (tanδ), hysteresis loop parameters (e.g. spontaneous polarization) as function of frequency and temperature suggest that the compound is a ferroelectric one and has a ferro-paraelectric phase transition at 112 ± 2°C. The measurement of dc resistivity both as function of biasing electric field and temperature of the compound suggests that the compound has negative temperature coefficient (NTC) of resistance above 100°C.     

Synthesis of nanocrystalline magnesium aluminate (MgAl2O4) spinel powder by the urea-formaldehyde polymer gel combustion route

Nanocrystalline MgAl₂O₄ spinel powder was synthesized by the urea-formaldehyde (UF) polymer gel combustion route. A transparent gel formed from magnesium nitrate, aluminium nitrate and UF after drying underwet self-sustained combustion when initiated with a burning splinter. The combustion product on calcinations at 850 °C formed MgAl₂O₄ spinel. Calcination of the combustion product resulted in particle coarsening. The powder obtained by planetary ball milling of the spinel had a median particle size of 1.58 μm. The spinel particles are agglomerates of nanocrystallites of size in the range 10-30 nm. The compacts prepared by uni-axial pressing of the spinel powder sintered to >99% TD at 1600 °C.     

Enhanced Ferroelectric Properties of Predominantly (100)-oriented Ca_(0.4)Sr_(0.6)Bi_4Ti_4O_(15) Thin Films on Pt/Ti/SiO_2/Si Substrates

Predominantly (100)-oriented Ca0.4Sr0.6Bi4Ti4O15 (C0.4S0.6BTi) thin films were prepared on Pt (111)/Ti/SiO2/Si substrates by a sol-gel method at annealing temperatures ranging from 650 to 850 ℃.The growth mode of the predominantly (100)-oriented C0.4S0.6 BTi thin films fabricated by the sequential layer annealing was discussed based on the structure evolution with the annealing temperature.The remnant polarization and coercive field of the C0.4S0.6 BTi film annealed at 800 ℃ are 16.1 μC/cm 2 and 85 kV/cm,re...     

AZ31/7A52复合材料爆炸焊接工艺研究

对材料组合为AZ31/7A52的镁合金/铝合金进行了爆炸焊接的工艺性研究.分析了其结合界面的金相组织和硬度,测量了爆炸焊接界面的波形参数,探讨了不同爆炸焊接工艺对爆炸复合效果(界面波形和复合率)的影响.结果表明,镁合金AZ31塑性差,爆炸复合困难,复合率＜10%;复合界面为波纹状结合,波长约2.20mm,波高约0.40...