Reactive blending of polypropylene and butadiene-acrylonitrile elastomer

Graft copolymer of polypropylene and butadiene-acrylonitrile random copolymer was prepared by reactive polymer blending in a melt without solvents. The process was performed by preliminary grafting of maleic anhydride groups to polypropylene and of isocyanate groups to butadiene-acrylonitrile copolymer, followed by blending of the modified polymers. The chemical reactions occurring in the process and the fraction composition of the copolymer were studied.     

Decay kinetics of aryloxy and semiquinone radicals in the presence of copper ions

The decay kinetics of aryloxy and semiquinone radicals in the presence of copper ions in aqueous solutions has been studied by means of the flash photolysis technique. The radicals are involved in electron transfer reactions and those leading to the formation of intermediate complexes with copper ions. The complexes of p-benzosemiquinone anion radicals and 2-hydroxyphenoxy radicals with cupric ions decay in bimolecular self-reactions at a much slower rate than the original radicals. The increased stability of the complexes compared with the initial radicals is attributed to partial delocalization of the unpaired electron over the electron shell of copper and to steric hindrances in the self-reactions of complexes.     

Electrode potential-controlled DNA damage in the presence of copper ions and their complexes.

Supercoiled (sc) DNA immobilized at the surface of a hanging mercury drop electrode was cleaved by reactive oxygen species generated by an electrochemically modulated reaction of copper ions, hydrogen peroxide and/or oxygen. The cleavage was observed in a certain potential region where redox cycling of DNA-bound Cu(II)/Cu(I) took place. In the presence of 1,10-phenanthroline the maximum efficiency of DNA cleavage was shifted to more negative potentials and the effect was enhanced.     

Formation of high nuclearity mixed-valent polyoxovanadates in the presence of copper amine complexes

Two new Müller-type clusters, a one-dimensional solid [Cu(en)]_{2 4}[Cl ⊂V₁₅O₃₆]−12H₂O1, and a three-dimensional solid [Cu(pn)]_{2 4}[Cl ⊂V₁₈O₄₂]·12H₂O2, have been synthesised by employing identical hydrothermal conditions e_xcept varying the nature of organic diamine.1 crystallised in a chiral space groupP2₁2₁2₁ witha = 12.757(1),b = 18.927(2) andc = 28.590(3) ?, andZ =4.2 crystallised in a tetragonal system with space groupP4/nnc,a = 15.113(1) andc = 18.542(3) ?, andZ = 2. Mixed-valent vanadium ions in structures1 and2 have been established both by magnetisation and bond-length bond-valence measurements. Chemistry of formation of high nuclearity polyoxovanadate clusters is discussed. Dedicated to Prof J Gopalakrishnan on his 62nd birthday.     

Effect of crystallization and annealing on polyacrylonitrile membranes for ultrafiltration

Polyacrylonitrile (PAN) membrane is known as one of the hydrophilic membranes for ultrafiltration. However, the membrane has been preventing from the versatile applications, because the semi-crystalline PAN membranes are so brittle that cannot reuse once the membrane has been dried. The effect of crystalline domains in asymmetric polyacrylonitrile membranes is investigated, when the membranes are annealed in hot water and when the membranes are dried. Asymmetric polyacrylonitrile membranes were prepared via phase inversion process in a water bath and the effect of additive, PVP to the casting solution on the morphology and the water flux and the rejection were investigated. When the membranes were annealed in hot water (80 °C), the size of pores have been reduced and the water flux also decreased. Using wide angle X-ray scattering (WAXS), the effect of absorbed water on PAN membranes was studied. The absorption of water in PAN membranes mainly occurred through amorphous phase like a plasticizer, and induced the change of crystalline structure. The size of crystallite and the degree of crystallinity have changed when the membrane were annealed in the hot water. When the asymmetric PAN membranes were dried, the moisture also plays a crucial role in transforming the crystalline structures. The kinetics of drying strongly influences the size of crystallite as well as the crystallinity.     

Infrared reflection-absorption spectroscopy of polyacrylonitrile on copper and aluminium surfaces

Infrared reflection-absorption spectroscopy has been used to study the chemical structure of thin films of pyrolyzed polyacrylonitrile (PAN) on copper and aluminium surfaces. The formation of a conjugated C? C?C backbone occurs at temperatures as low as 200°C for PAN on copper, whereas the same reaction on aluminium requires pyrolysis at 300°C in order to be completed. These temperatures are, respectively, about 200 and 100°C lower than those previously reported for bulk PAN. Pyrolysis of PAN on copper at 200°C also results in diffusion of copper atoms (ions) into the polymer network followed by Cu(I)? N°C complexing. Conclusive evidence is obtained for end-on coordination through nitrogen lone pair orbitals of the C?N groups. We propose a chemical structure of PAN on copper that is different to that in the bulk and on aluminium.     

Behaviors and mechanisms of copper adsorption on hydrolyzed polyacrylonitrile fibers

Polyacrylonitrile fiber (PANF) was hydrolyzed in a solution of sodium hydroxide and the hydrolyzed polyacrylonitrile fiber (HPANF) was used as an adsorbent to remove copper ions from aqueous solution. Scanning electron microscopy (SEM) showed that the hydrolysis process made the surface of HPANF rougher than that of PANF. Fourier transform infrared (FTIR) spectroscopy revealed that the HPANF contained conjugated imine (-Cz=Nz-) sequences. Batch adsorption results indicated that the HPANF was very effective in adsorbing copper, and the adsorption equilibrium could be reached within 10-20 min. Atomic force microscopy (AFM) showed that some aggregates formed on the surface of the HPANF after copper ion adsorption and the average surface roughness (R(a)) value of the HPANF changed from 0.363 to 3.763 nm due to copper adsorption. FTIR analysis indicated that copper adsorption caused a decrease of the light adsorption intensity of the imine (-Cz=Nz-) groups at 1573 and 1406 cm(-1) wavenumbers, and X-ray photoelectron spectroscopy (XPS) showed that the binding energy (BE) of some of the nitrogen atoms in the HPANF increased to a greater value due to copper adsorption. The FTIR and XPS results suggest that the adsorption of copper ions to the HPANF is attributed to the imine groups on the surface of the HPANF.     

High flux nanofiltration membranes based on interfacially polymerized polyamide barrier layer on polyacrylonitrile nanofibrous scaffolds

Electrospun polyacrylonitrile (PAN) nanofibrous scaffold was used as a mid-layer support in a new kind of high flux thin film nanofibrous composite (TFNC) membranes for nanofiltration (NF) applications. The top barrier layer was produced by interfacial polymerization of polyamides containing different ratios of piperazine and bipiperidine. The filtration performance (i.e., permeate flux and rejection) of TFNC membranes based on electrospun PAN nanofibrous scaffold was compared with those of conventional thin film composite (TFC) membranes consisting of (1) a commercial PAN ultrafiltration (UF) support with the same barrier layer coating and (2) two kinds of commercial NF membranes (i.e., NF90 and NF270 from Dow Filmtec). The nanofiltration test was carried out by using a divalent salt solution (MgSO₄, 2000 ppm) and a cross-flow filtration cell. The results indicated that TFNC membranes exhibited over 2.4 times more permeate flux than TFC membranes with the same chemical compositions, while maintaining the same rejection rate (ca. 98%). In addition, the permeate flux of hand-cast TFNC membranes was about 38% higher than commercial NF270 membrane with the similar rejection rate.     

Adsorption and desorption of binary mixtures of copper and mercury ions on natural and crosslinked chitosan membranes

Copper and mercury ion adsorption on chitosan membranes was investigated in batch systems (with both single and binary solutions). The Langmuir model and its extensions (extended Langmuir, Jain-Snoeyink, and Langmuir-Freundlich models) were tested for the modeling of experimental data. Chitosan membranes presented more affinity for Hg ions than for Cu ions. The decrease of the amount of metal adsorbed on natural chitosan in binary systems (compared to single-metal solutions) showed the competition effects between the two metal ions. For glutaraldehyde-crosslinked chitosan and epichlorohydrin-crosslinked chitosan, the mixture effect was present, producing unexpected result such as higher adsorption capacities, when compared to the monocomponent solution of each metal. The desorption of the metals was also investigated, and copper and mercury ions could be selectively recovered using a combined process by using NaCl and H₂SO₄ as eluant.     

Triphenylene based copper ensemble for the detection of cyanide ions

The binding behavior of triphenylene based copper ensemble prepared in situ has been investigated toward various anions (F(-), Cl(-), Br(-), I(-), CH(3)COO(-), H(2)PO(4)(-), NO(3)(-), OH(-), ClO(4)(-), CN(-), CO(3)(-) and SO(4)(-)) by UV-vis and fluorescence spectroscopy. Among various anions tested, 1-Cu(2+) ensemble shows selective and sensitive response towards cyanide ions and responds to CN(-) ions even in the presence of bovine serum albumin and in blood serum milieu. Further, as practical application of compound 1, we utilized the TLC strips coated with THF solution of 1 for the solid state detection of copper and cyanide ions.     

基于金纳米棒刻蚀比色法检测铁、铜离子

采用种子生长法制备金纳米棒(AuNRs)以构建光学传感器,用于Fe³⁺和Cu²⁺的高选择性快速可视化检测。在酸性环境中,Fe³⁺和Cu²⁺通过与KI溶液反应,将I-氧化成I2。I2刻蚀AuNRs,导致其纵向表面等离子体共振(LSPR)吸收峰蓝移,从而实现对Fe³⁺和Cu²⁺的检测。结果表明,反应温度为50℃时,添加0.8 mL 0.1 mol·L^-1 HCl、2 mL AuNRs生长液和20 mmol·L^-1 KI溶液,与2 mL 500 μmol·L^-1 Fe³⁺或30 μmol·L^-1 Cu²⁺反应25或90 min,可将AuNRs刻蚀至LSPR吸收峰消失。该方法对Fe³⁺和Cu²⁺检测具有高选择性和准确性,对于Fe³⁺、Cu²⁺共存体系的检测,可通过加入适量F-与Fe³⁺生成配合物[FeF₆]^3-完成对Fe³⁺的化学掩蔽,消除Fe³⁺的干扰,实现共存体系中Cu²⁺的准确检测。     

基于金纳米棒刻蚀比色法检测铁、铜离子

采用种子生长法制备金纳米棒(AuNRs)以构建光学传感器,用于 Fe³⁺和 Cu²⁺的高选择性快速可视化检测。在酸性环境中,Fe³⁺和 Cu²⁺通过与 KI溶液反应,将 I^-氧化成 I₂。I₂刻蚀 AuNRs,导致其纵向表面等离子体共振(LSPR)吸收峰蓝移,从而实现对Fe³⁺和Cu²⁺的检测。结果表明,反应温度为50℃时,添加0.8 mL 0.1 mol·L^-1 HCl、2 mL AuNRs生长液和20 mmol·L^-1 KI溶液,与 2 mL 500 μmol·L^-1 Fe³⁺或 30 μmol·L^-1 Cu²⁺反应 25或 90 min,可将 AuNRs刻蚀至 LSPR 吸收峰消失。该方法对 Fe³⁺和 Cu²⁺检测具有高选择性和准确性,对于 Fe³⁺、Cu²⁺共存体系的检测,可通过加入适量 F-与 Fe³⁺生成配合物[FeF₆]3^-完成对 Fe³⁺的化学掩蔽,消除Fe³⁺的干扰,实现共存体系中Cu²⁺的准确检测。     

Cyclization and carbonization of anionic polyacrylonitrile in the presence of carbon nanofibers

Composites based on anionic polyacrylonitrile and carbon nanofibers were studied by X-ray diffraction, differential scanning calorimetry, thermal gravimetric analysis, and electron microscopy. The effect of carbon nanofibers on the specific features of cyclization and carbonization of anionic polyacrylonitrile at temperatures of to 550°C was studied.     

Microanalysis of oligodeoxynucleotides by cathodic stripping voltammetry at amalgam-alloy surfaces in the presence of copper ions

The application of gold amalgam-alloy electrode (AuAE) for a sensitive voltammetric detection of different oligodeoxynucleotides (ODNs) containing the purine units within the ODN-chains in the presence of copper is described. The detection of ODNs is based on the following procedure: (i) the first step includes an acidic hydrolysis of the ODN (ahODN) samples performing the release of the purine bases from ODN-chain; (ii) the second step includes an electrochemical accumulation of the complex of the purine base residues released from ODN-chain with copper ions Cu(I) (ahODN-Cu(I) complex) at the potential of reduction of copper ions Cu(II) on the amalgam-alloy electrode surfaces; (iii) finally followed the cathodic stripping of the electrochemically accumulated ahODN-Cu(I) complex from the electrode surface. The proposed electrochemical method was used for: (a) detection of different ODN lengths containing only adenine units (the number of adenine units within the ODN-chains was changed from 10 to 80), and (b) determination of the number of purine units within the 30-mer ODNs containing a random sequence segments involving both the purine and pyrimidine units. The intensity of the cathodic stripping current density peak (j_CSP) of the electrochemically accumulated ahODN-Cu(I) complex increased linearly with the increasing number of purine units within the ODN-chains. We observed a good correlation between the percentage content of purine units to the whole length of different 30-mer ODNs and the percentage content of the intensity of the j_CSP of the electrochemically accumulated 30-mer ahODN-Cu(I) complexes. The detection of acid hydrolysed 80-mer (A₈₀) in the bulk solution and in a 20-μl volume is possible down to 200 pM and 2 nM at the AuAE, respectively. For the shortest 10-mer (A₁₀) a detectable value of 5 nM in the bulk solution on the AuAE was observed. The sensitive detection of different ODNs containing the purine units in their chains in the presence of copper can be also performed at the platinum amalgam-alloy (PtAE) and copper amalgam-alloy (CuAE) contrary to a lower sensitivity at the silver amalgam-alloy (AgAE) electrode.     

Kinetic parameters of urease immobilized on modified acrylonitrile copolymer membranes in the presence and absence of Cu(II) ions

Poly(acrylonitrile-methylmethacrylate-sodium vinylsulfonate) membranes were subjected to seven different chemical modifications and the amount of the newly formed groups was measured for each membrane. Urease was then covalently immobilized onto the modified membranes and the amount of bound protein was determined. The kinetic parameters V(max) and K(m) of the immobilized urease were studied under static and dynamic conditions. Results showed that the rate of the enzyme reaction was higher for the membranes modified with NH(2)OH . H(2)SO(4), NH(2)NH(2) . H(2)SO(4), NaOH + EDA and NaOH + GA + EDA. It was confirmed that the reaction rate, measured under dynamic conditions, was higher than that one determined under static conditions. The influence of Cu(II) ions, as inhibitors, on the enzyme reaction kinetics (V(i) and K(i)) was also investigated. It turned out that the most sensitive membranes towards Cu(II) were those modified with NH(2)NH(2) . H(2)SO(4), NaOH + EDA and H(2)O(2). The results initiated further investigations on the influence of other heavy metal ions (Cd(II), Zn(II), Ni(II) and Pb(II)) over urease bound to a NH(2)OH . H(2)SO(4)-modified membrane. It was found that the inhibition effect of the heavy metal ions over immobilized urease decreases in the order: Cu(II) > Cd(II) > Zn(II) > Ni(II) > Pb(II). [Diagram: see text]     

Site-directed cleavage of DNA by an oligonucleotide conjugate with o-bromobenzoic acid in the presence of copper ions

Site-directed cleavage of single- and double-stranded DNAs by an oligonucleotide conjugate with 5-[N-(3-aminopropyl)sulfamoyl]-2-bromobenzoic acid was investigated. When forming duplex complexes with a single-stranded DNA and triplex complexes with a double-stranded DNA, this conjugate cleaves DNA near the binding site in the presence of copper ions and free o-bromobenzoic acid. The efficacy and specificity of DNA cleavage by this conjugate and other oligonucleotide conjugates bearing tetracarboxyphthalocyanine Co^II and bleomycin A5 as reactive groups were compared.     

The determination of copper ions based on sensitized chemiluminescence of silver nanoclusters

We report on the first application of novel, water-soluble and fluorescent silver nanoclusters (Ag NCs) in a chemiluminescent (CL) detection system. A method has been developed for the determination of copper(II) ion that is based on the fact that the weak CL resulting from the redox reaction between Ce(IV) ion and sulfite ion is strongly enhanced by the Ag NCs and that the main CL signals now originate from Ag NCs. UV-visible spectra, CL spectra and fluorescent (FL) spectra were acquired to investigate the enhanced CL mechanism. It is proposed that the electronic energy of the excited state intermediate SO₂* that originates from the CL reaction is transferred to Ag NCs to form an electronically excited NC whose emission is observed. In addition, it is found that copper(II) is capable of inhibiting the CL of the nanoclusters system, but not if other common metal ions are present. The detection of copper(II) is achieved indirectly by measuring the CL intensity of Ag NCs. Under the optimized experimental conditions, a linear relationship does exist between the intensity of CL and the concentrations of copper(II) in the range of 0.2?nM to 0.1?m??. The detection limit is 0.12?nM. The method is applied to the determination of copper(II) ion in tap water with satisfactory results.

Formation of dibromo-, bromochloro-, and dichlorocarbenes in the cathodic electrolysis of tetrabromomethane in the presence of chloride ions

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, p. 2183, September, 1988.     

Discharge of nickel ions in presence of zinc ions

Summary The present results confirm conclusively the inference drawn earlier [2] regarding the role of adsorption of zinc ions on the basis of galvanostatic studies on solid substrates which is also the conclusion drawn by Yurev and Volkov [3] by their recent work on solid substrates.

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Zusammenfassung Bei galvanostatischen Untersuchungen an festen Medien über die Bedeutung der Adsorption von Zinkionen konnten die Ergebnisse einer früheren eigenen Arbeit [2] sowie der Arbeit von Yurev u. Volkov [3] bestätigt werden. Aufgrund potentiodynamischer und potentiostatischer Versuche mit der Quecksilber-Tropfelektrode konnte festgestellt werden, daß die Abscheidungsgeschwindigkeit von Nickel aus Nickelbädern durch Zusatz von Zinkionen herabgesetzt wird. Die Vorteile einer Quecksilber-Tropfelektrode für solche Untersuchungen werden aufgezeigt und interessante Besonderheiten im Verhalten der Strom-Zeit-Kurve während des Wachstums des Tropfens diskutiert.

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Dedicated to Prof. Dr. M. von Stackelberg on his 70th birthday.