Redox‐Active Nickel in Carbon Nanotubes and Its Direct Determination

The presence of residual metal‐catalyst impurities in carbon nanotubes is responsible for their toxicity. It is important to differentiate between the total amount of impurities and the redox‐active (bioavailable) amount of such impurities because only the bioavailable impurities exhibit toxic effects. Herein, we report a simple and specific method for quantifying the amount of redox‐active Ni present in various commercial samples of CNTs. It is based on the electrochemical oxidation of Ni(OH)₂ that is formed in alkaline solutions when Ni impurities are opened to the surrounding environment. Metallic Ni impurities play an extremely active role in toxicological assays as well as in undesired catalytic processes, and thus a method to rapidly quantify the amount of redox‐active Ni is of great importance.     

Direct determination of bioavailable molybdenum in carbon nanotubes

Bioavailable residual metallic impurities within carbon nanotubes (CNTs) are responsible for the toxicity of CNTs. Herein we present a method for fast, sensitive determination of bioavailable molybdenum residual catalyst impurities within CNTs by using electrochemical oxidation in neutral pH buffers at low potentials. This method is unique because no other method can rapidly distinguish between bioavailable/mobilizable impurities from defects in CNTs and between the total amounts of impurities. This method will be indispensable for future toxicological studies of CNTs.     

Molecular Engineering of Quinone-Based Nickel Complexes and Polymers for All-Organic Li-Ion Batteries

All-organic Li-ion batteries appear to be a sustainable and safer alternative to the currently-used Li-ion batteries but their application is still limited due to the lack of organic compounds with high redox potentials toward Li⁺/Li⁰. Herein, we report a computational design of nickel complexes and coordination polymers that have redox potentials spanning the full voltage range: from the highest, 4.7 V, to the lowest, 0.4 V. The complexes and polymers are modeled by binding low- and high-oxidized Ni ions (i.e., Ni(II) and Ni(IV)) to redox-active para-benzoquinone molecules substituted with carboxyl- and cyano-groups. It is found that both the nickel ions and the quinone-derived ligands are redox-active upon lithiation. The type of Ni coordination also has a bearing on the redox potentials. By combining the complex of Ni(IV) with 2-carboxylato-5-cyano-1,4-benzoquinones as a cathode and Ni(II)-2,5-dicarboxylato-3,6-dicyano-1,4-benzoquinone coordination polymer as an anode, all-organic Li-ion batteries could be assembled, operating at an average voltage exceeding 3.0 V and delivering a capacity of more than 300 mAh/g.     

Simple and rapid detection of Alternaria alternata using an excreted redox-active species

Airborne fungi pose a serious threat to public health. Alternaria alternata (A. alternata) is a fungus that has been associated with the development of asthma. Detection using redox-active species excreted from fungi is an effective method for a simple electrochemical fungal biosensor. The achievable electrochemical signal in most fungi, however, is exceptionally low because of the low amount of excreted redox-active species and their slow excretion rates. Herein, we report that A. alternata excretes an exceptionally large amount of a redox-active species that can be used for sensitive and selective detection of A. alternata. The excretion rate is enhanced in Tris buffer, and the electrochemical-chemical redox cycling involving excreted redox-active species significantly increases the electrochemical signals. Only A. alternata among five common airborne fungi provides large electrochemical signals, which allows selective detection of A. alternata. The calculated detection limit for A. alternata is ~20 spores/mL with an incubation period of 10 min, indicating that the detection method is highly sensitive and rapid. The detection method does not require complicated procedures or harsh pretreatment and is optimal for point-of-care testing of A. alternata.     

Direct Voltammetric Determination of Redox‐Active Iron in Carbon Nanotubes

With the advances in nanotechnology over the past decade, consumer products are increasingly being incorporated with carbon nanotubes (CNTs). As the harmful effects of CNTs are suggested to be primarily due to the bioavailable amounts of metallic impurities, it is vital to detect and quantify these species using sensitive and facile methods. Therefore, in this study, we investigated the possibility of quantifying the amount of redox‐available iron‐containing impurities in CNTs with voltammetric techniques such as cyclic voltammetry. We examined the electrochemistry of Fe₃O₄ nanoparticles in phosphate buffer solution and discovered that its electrochemical behavior could be affected by pH of the electrolyte. By utilizing the unique redox reaction between the iron and phosphate species, the redox available iron content in CNTs was determined successfully using voltammetry.     

Determination of metallic impurities in a silicon wafer by local etching and electrothermal atomic absorption spectrometry.

An etching technique for the determination of the metallic impurities distribution in silicon wafers has been developed. An area of 10 mmphi and 10 microm depth was etched by 100 microL of an etching solution with a HF and HNO3 mixture. The acid matrix was evaporated on the wafer surface by IR lamp illumination and vacuum exhaust. Metallic impurities remaining on the wafer surface were redissolved into the collection solution, which was measured by electrothermal atomic absorption spectrometry (ET-AAS). The recovery invested by local etching/ET-AAS was within 95 - 112% for Fe, Cu and Ni. The detection limit (3sigma) for Fe, Cu and Ni in silicon was 1 x 10(13) atoms/cm3. To confirm the applicability, local etching was applied to evaluate the effects of metallic impurities in a gettering study and the electronic properties of semiconductor devices. It was found that local etching is a useful sample preparation technique for the analysis of metallic impurities in a specific area on a silicon wafer.     

Characterization of Metallo Bis(terpyridine) Diblock Polymers by Nonaqueous Capillary Zone Electrophoresis

A method of nonaqueous capillary zone electrophoresis (CZE) has been developed to characterize block (co)polymers of poly(ethylene oxide) and poly(styrene) containing metallo bis(terpyridine) complexes as bridging units. Specific CZE separation conditions had to be applied, with barium perchlorate dissolved in N-methylformamide (NMF) as background electrolyte and OV-1701-OH deactivated capillaries. For detection UV absorption was measured at a wavelength of 316 nm. Metallo diblock polymers with molecular weights up to 30,000 Da could be analyzed by the proposed nonaqueous CZE method. Experiments performed with polymeric compounds containing Fe, Ni or Ru as central metal ions showed that their electrophoretic mobilities were independent of the type of metal ion. Therefore, the data on the size of the polymeric compounds could be obtained using just one set of calibration standards. Polydispersities of the samples calculated from the experimental results were in correlation with the polydispersities of the polymers used in the synthesis of the metallo diblock polymers. Several polymeric samples contained metallo mono(terpyridine) complexes as impurities. These by-products could be separated from the main product. With symmetrical diblock polymers only one by-product was detected, while with an asymmetric diblock polymer two types of mono-complexes were found. The amount of the mono-complexes present as impurities was dependent on the type of central metal ion (Ni > Fe >> Ru).     

Non-destructive determination of trace elements in tungsten by helium-3 activation analysis

A non-destructive method is described for the determination of trace impurities at sub-p.p.m. levels in a tungsten matrix by 14-MeV ³He activation analysis. A Ge(Li) spectrometer and a multichannel analyzer were used to determine V, Fe, Ni, Zn and Mo impurities. Interfering reactions are discussed in detail.     

Assessment of chemical purity of 10B-enriched p-boronophenylalanine by high-performance liquid chromatography coupled on-line with inductively coupled plasma optical emission spectrometry

A dual-detection technique, consisting of a combination of reversed-phase high-performance liquid chromatography and on-line detection of elemental boron in the column effluents by inductively coupled plasma optical emission spectrometry, was tested for drug analysis. The method was applied to assessing the chemical purity of p-boronophenylalanine (BPA), isotopically enriched in ¹⁰B. This compound is employed as a fructose complex solution for biodistribution studies in laboratory and clinical trials of boron neutron capture therapy. Besides the determination of the content of BPA, required for chemical quality controls of solutions of the complex used for infusions, resolution of mixtures of BPA and two usually accompanying residual impurities (phenylalanine and tyrosine) was achieved with UV detection. The limits of detection (in solution) were 1.5 and 0.6 ng ml⁻¹, respectively. In addition, by monitoring a sensitive-element emission wavelength it was possible to jointly observe the elution of boron-containing compounds that may be transparent to UV radiation or to confirm the presence of boron in potential impurities accompanying the drug. Those impurities may arise from the BPA synthesis or may be produced by degradation during the aging of the solutions. Chromatographic peaks corresponding to the amino acids and also to a related inorganic compound were detected in BPA–fructose complex solutions that were stored for different times and under different conditions. An increase in the areas of the peaks attributed to tyrosine and phenylalanine was observed for BPA–fructose solutions stored refrigerated for 1 month to 1 year, suggesting that degradation processes able to reduce the amount of bioavailable BPA could be active. In memoriam Dr. Daniel Batistoni.     

New method for determining the concentration of ionic impurities in solvent polymeric membranes

A new method is proposed for ascertaining the amount of ionic impurities in solvent polymeric membranes of ion-selective electrodes. The method is based on determining the selectivity coefficient for ions of different valences as a function of the concentration of a lipophilized tetraphenylborate salt added to the membrane phase. Thus, the concentration of anionic impurities in commercially available poly(vinyl chloride) and of cationic ones in Tecoflex® (a polyurethane) was obtained as 0.063 ± 0.016 and 0.044 ± 0.006 mmol/kg, respectively.     

Flame AAS determination of dopants and trace metal impurities in single crystals of potassium titanylphosphate

A flame AAS method is used for the determination of dopants and impurities in potassium titanylphosphate (KTP) single crystals. Sample digestion using sulphuric acid and hydrofluoric acid is proposed as being the most appropriate procedure. The effect of major and minor components in the sample solution on the analytical signal is studied. The content of the dopants Cr, Mn and Ni (at a level of about 1 mg g(-1)) as well as the content of the impurities Fe, Na, Mg, W and Al (from 4 mug g(-1), depending on the trace metal) in the KTP single crystals is determined. The precision of the method is characterized by a relative standard deviation of 3-10%. The accuracy is checked by comparison with ICP-AES data for the trace element content in the KTP single crystals.     

Depth profiling of ultra trace metal impurities in polytetrafluoroethylene wares by surface scraping and acid-vapor extraction followed by ICP-MS analysis.

This paper describes the development of the depth profiling method of ultra trace metal impurities in polytetrafluoroethylene (PTFE) wares based on contamination-free sampling followed by acid-vapor extraction and its application to evaluate the washing method for PTFE wares. A contamination-free sampling process was achieved by scraping the surface of PTFE wares with the cleft face of a silicon wafer followed by exposing the PTFE scraped to highly pure acid-vapor. The concentration of metal impurities in extractants was determined by ICP-MS equipped with an electrothermal vaporizer (ETV-ICP-MS). The blank values of Al, Cr, Fe, Ni and Cu by the depth profiling method were 0.006, 0.004, 0.005, 0.002 and 0.003 ng, respectively. By analyzing the depth profile of beakers, the distributions of ultra trace (ng g(-1) level) metal impurities were clarified. An examination of the washing methods by the depth profiling method also clarified that exposing to acid-vapor was more effective than the acid-dipping method for the elimination of metal impurities.     

One-dimensional bromo-bridged Ni III complexes [Ni(S,S-bn)2Br]Br2 (S,S-bn=2S,3S-diaminobutane): synthesis, physical properties, and electrostatic carrier doping

A new bromo-bridged Ni III compound has been synthesized. This compound displayed a strong antiferromagnetic interaction between spins located on Ni III species (J=(2350+/-500) K) that result from the strong covalency of the Ni--Br bond and the spin-Peierls transition below 150 K. This was shown by the results of magnetic susceptibility and 81Br nuclear quadrupole resonance spectroscopy analysis. We succeeded in the electrostatic carrier doping of a single crystalline sample by using a field-effect transistor device. This compound also showed n-type semiconductor behavior, which can be reasonably rationalized by the existence of a small amount of Ni II impurities.     

Persistent metal bis(hexafluoroacetylacetonato) complexes featuring a 2,2'-bipyridine substituted triarylamminium radical cation

Herein, we describe the preparation of a 2,2'-bipyridine derivative containing a redox-active N,N'-(4,4'-dimethoxydiphenylamino) substituent (1), which readily coordinates M(hfac)(2) salts [M = Mn (2), Ni (3), Cu (4)] to generate stable, neutral, and pseudo-octahedral coordination complexes, which have been fully characterized. Cyclic voltammetry and spectroelectrochemical measurements on complexes 2-4 indicate stable one-electron oxidation processes, and the formation of persistent radical cation complexes. The neutral complexes (M = Mn or Ni) were subject to one-electron oxidation with NOPF(6) in acetonitrile, and magnetic moments of the resulting solutions were obtained using the Evans method at different temperatures. Our experimental results suggest that the first reported ferromagnetically coupled metal-triarylamminum radical cation complex is obtained when M = Mn(2+), and antiferromagnetic coupling results when M = Ni(2+). These results are supported by results from density functional theory calculations, which indicate that a π spin polarization mechanism for magnetic exchange coupling is operative in singly oxidized complexes, 2-4.     

Spectrochemical Determination of Metallic Pollutants At Sub Ppm Levels In Fresh Water Samples

Abstract

A quantitative method to analyse fresh water samples for ultratrace pollutants such as Cd, Cr, Fe, Mn, Ni, Pb, V and Zn has been developed. the impurities in the water sample were preconcentrated by the method of slow evaporation and collected on specpure graphite which was subsequently analysed by d.c. are excitation using NaF as the carrier. the mean relative standard deviation of the method employed is + 15%. the accuracy of the method reported has been found to be quite satisfactory as borne out by the results of the Intercomparison Run conducted by the International Atomic Energy Agency, Vienna for the determination of trace elements in water. the detection limits for the various elements are as follows: Ni, Pb, V : 1 ng/ml; Cd, Cr, Mn: 2 ng/ml; Fe: 15 ng/ml and Zn : 20 ng/ml. Some of these detection limits have been compared with those obtained in some of the recent techniques such as AAS, Laser Induced Fluorescence (LIF) and Laser Enhanced Ionization (LEI) or Opto-Galvanic Spectrometry(òGS). It has been found that there is a tenfold increase in sensitivity for Pb in the present method as compared to the above techniques except LEI while the detection limits obtained for other elements are comparable with those in other techniques.     

Mechanism of nickel extraction from sulfuric acid medium by synthesized α‐aminophosphonate derivative

A new compound, α‐aminophosphonate derivative containing pyridine ring (PPDE), was designed and synthesized as an extractant for the separation of nickel from metal impurities. Over 94.5% of Ni (II) extraction from sulfuric acid solution was achieved by using PPDE with an equilibrium pH of 4.02. Meanwhile, high separation coefficients of 23.8 for Ni to Co, 84.9 for Ni to Mn, 254.1 for Ni to Ca and 696.7 for Ni to Mg, respectively, were obtained. It was noted that PPDE exhibited an excellent regenerability, and the extraction of Ni with the recycled organic phase ranged from 92.5% to 93.9% during six circulations. The extracted nickel complex was determined as [Ni (PPDE)₂(DNNSA^?)₂(H₂O)₄], which was supported by the data obtained from Fourier transform‐infrared, UV–Vis and electrospray ionization‐mass spectrometry spectra.     

添加钠对低镍甲烷化催化剂结构性能的影响

用活性测试、XRD和EXAFS方法研究了一系列含Ni 6wt％、添加不同量Na助剂的γ-Al_2O_3担载Ni甲烷化催化剂的结构性能。结果表明:Ni与Al_2O_3有较强的相互作用。添加不同量的Na助剂能增强或削弱这种作用,从而影响催化剂宏观性能,Na在Al_2O_3上是高度分散的。它的影响是通过改变载体表面性能从而改变Ni的状态及其分布,Ni的分散度和Ni-Al_2O_3相互作用而完成的。适量Na可提高Ni的分散度,优化Ni-Al_2O_3相互作用,从而提高催化剂活性。过量Na则会加强Ni-Al_2O_3相互作用,或者造成NiO自身聚集形成NiO晶相,从而降低Ni利用率,使催化剂活性降低。     

Ni掺杂的Cu-ZnO催化剂甘油加氢反应性能

采用浸渍法制备了Ni掺杂的Cu-ZnO催化剂,采用多种物理化学手段研究了其化学物理性质及甘油加氢制取1,2-丙二醇反应催化性能。结果发现,金属Ni助剂的引入可以进一步优化Ni-Cu-ZnO催化剂的甘油加氢生成1, 2-丙二醇的反应活性。少量金属Ni的加入,Ni-Cu-ZnO催化剂的甘油转化率变化不大,生成1, 2-丙二醇的选择性明显增加。而进一步增加Ni含量到n_Ni/n_Cu=0.5,Ni含量过高会导致Ni-Cu-ZnO催化剂中实际Cu原子的量减少,从而导致甘油转化率下降。Ni掺杂的Cu-ZnO催化剂甘油加氢性能稳定性较好,在反应102 h后没有明显变化。     

Characterisation of a Cu selective resin and its application to the production of <Superscript>64</Superscript>Cu

Cu isotopes (e.g. ⁶⁴Cu) increasingly find use in radiopharmaceutical applications, accordingly fast and reliable methods for the production of these isotopes are needed. The aim of the presented project is the characterization of a Cu selective extraction chromatographic resin for the fast and selective separation of Cu radionuclides, e.g. from irradiated targets. The characterisation of the resin includes the determination of weight distribution factors D _w of Cu, Ni, Zn and other potentially interfering elements and impurities for varying acids and pH values, the influence of macro amounts of Ni and Zn on the extraction of Cu as well as the influence of other potential interferents. Based on the obtained results, a method for the separation of Cu and its purification from irradiated Ni or Zn targets was developed and tested on simulated Ni and Zn targets.