Current–Voltage Characteristics in Individual Polypyrrole Nanotube, Poly(3,4-ethylenedioxythiophene) Nanowire, Polyaniline Nanotube, and CdS Nanorope

In this paper, we focus on current–voltage (I–V) characteristics in several kinds of quasi-one-dimensional (quasi-1D) nanofibers to investigate their electronic transport properties covering a wide temperature range from 300 down to 2 K. Since the complex structures composed of ordered conductive regions in series with disordered barriers in conducting polymer nanotubes/wires and CdS nanowires, all measured nonlinear I–V characteristics show temperature and field-dependent features and are well fitted to the extended fluctuation-induced tunneling and thermal excitation model (Kaiser expression). However, we find that there are surprisingly similar deviations emerged between the I–V data and fitting curves at the low bias voltages and low temperatures, which can be possibly ascribed to the electron–electron interaction in such quasi-1D systems with inhomogeneous nanostructures.     

A Headspace–SPME–MS Method for Monitoring Rapeseed Oil Autoxidation

Headspace SPME–MS was used to analyze volatile compounds from rapeseed oil subjected to an accelerated storage test consisting of 0–12 days of storage at 60 °C. The SPME–MS data was compared with the data obtained by solid phase microextraction–gas chromatography/mass spectrometry (SPME–GC/MS). The SPME–GC/MS method allowed detection of 37 volatile compounds, of which 28 were identified. Predominant ones were hexanal, 2,4-heptadienal, 2-heptenal and 1-pentene-3-ol. Volatile compounds were not separated in SPME–MS—a single peak reflecting the total amount of volatiles was obtained. An increase in the abundance of characteristic ions in this peak could be used to detect of compounds characteristic for rapeseed oil autoxidation. These compounds (with their characteristic ions) were hexanal (m/z 56), 1-pentene-3-ol and 1-octene-3-ol (m/z 57), 2-pentenal and 2-heptenal (m/z 83 and 84), and 2,4-heptadienal (ions m/z 81 and 110). The SPME–MS peak area was correlated with peroxide value at 0.9779 and with Totox at 0.9841. Principal component analysis (PCA) of fatty acid volatile oxidation products from a model rapeseed oil indicated that SPME–MS was able to differentiate samples containing hexanal at a concentration of 0.2, 0.4, 0.6, 0.8 and 1.0 mg/L with proportional amounts of other compounds. Further, samples that were subjected to 0, 2, 4, 6, 8, 10 and 12 days of storage at 60 °C were differentiated using SPME–MS–PCA. PCA showed similarities in clustering of the data obtained by SPME–MS and sensory analysis.     

Antifeedants in the Feces of the Pine Weevil Hylobius abietis: Identification and Biological Activity

Egg-laying females of the pine weevil, Hylobius abietis (L.), regularly deposit feces adjacent to each egg. Egg cavities are gnawed in the bark of roots of recently dead conifer trees. After egg deposition, the cavity is sealed by feces and a plug of bark fragments. Root bark containing egg cavities with feces is avoided as food by pine weevils, which indicates the presence of natural antifeedants. Here we present the first results of the isolation and chemical analyses of antifeedant compounds in the feces of H. abietis. In feeding bioassays, methanol extracts of the feces revealed strong antifeedant properties. Methanol extracts were fractionated by medium-pressure liquid chromatography and the antifeedant effects were mainly found in the fractions of highest polarity. Volatile compounds in the active fractions were identified by gas chromatography–mass spectrometry (GC–MS) and the nonvolatile compounds were characterized by pyrolysis–GC–MS. Based on mass spectra, a number of compounds with various chemical structures were selected to be tested for their antifeedant properties. Antifeedant effects were found among compounds apparently originating from lignin: e.g., a methylanisol, guaiacol, veratrol, dihydroxybenzenes, and dihydroconiferyl alcohol. A weak effect by fatty acid derivatives was found. The types of naturally occurring antifeedant compounds identified in this study may become useful for the protection of planted conifer seedlings against damage by H. abietis.     

Surface characterization of zincated aluminium and selected alloys at the early stage of the autocatalytic electroless nickel immersion process

In this work the changing structure of nickel–phosphorus deposits on aluminium and its alloys at the early stage of electroless nickel phosphorus deposition using hypophosphite ion as reducing agent has been studied. Prior to electroless nickel deposition, zincating is used for pre-treatment of aluminium substrates. The surface morphology and structure of the electroless Ni–P layers were characterized by scanning electron microscopy and X-ray diffraction analysis. Results show that Ni–P deposition is closely related to the dissolution of the zincating layer, followed by progressive nickel nucleation. The nuclei serve as a catalytic surface for further Ni–P deposition which increases with deposition time. The growth and coalescence of the nuclei on the aluminium substrate results in crystalline layers of Ni–P.     

Electrodeposition of silver–tin alloys from pyrophosphate-cyanide electrolytes

Using cyclic-voltammetric techniques, a pyrophosphate-cyanide electrolyte for the electrodeposition of compact Ag–Sn alloy coatings is investigated. This electrolyte is suited to further investigations on the alloy composition, structure and properties. The electrodeposition of coatings with up to 40 wt% Sn is possible from the investigated complex electrolytes. The alloy surpasses the saturation limit of the silver lattice with Sn and allows the formation of coatings with phase heterogeneity. At high tin content an ordered spatial distribution of different alloy phases on the cathodic surface can be observed. The pattern formation in this system looks very similar to the phenomena and structures observed during electrodeposition of other silver alloys, such as Ag–Sb, Ag–Bi and Ag–In.     

Electrodeposition behavior of zinc–nickel–iron alloys from sulfate bath

The present work is directed at collecting the properties of Zn–Ni and Zn–Fe alloys in one alloy via the electrodeposition of Zn–Ni–Fe ternary alloy. Electrodeposition of ternary Zn–Ni–Fe alloy was investigated and compared with the characteristics of Zn–Ni electrodeposits. The electrodeposition was performed from a sulfate bath onto a steel substrate. Structural analysis by X-ray diffraction (XRD) method revealed that the Zn–Ni–Fe alloys consisted of a mixture of zinc, and (γ-Ni₂Zn₁₁) and (Fe₃Ni₂) phases. The study was carried out using electrochemical methods such as cyclic voltammetry and galvanostatic for electrodeposition, while anodic linear polarization resistance and anodic linear sweeping voltammetry techniques were used for the corrosion study. Surface morphology and chemical composition of the deposits were also examined by using scanning electron microscopy and atomic absorption spectroscopy, respectively. It was found that the obtained Zn–Ni–Fe alloy exhibited more preferred surface appearance and better corrosion resistance without adding any organic brighteners to the plating bath in comparison to Zn–Ni alloy that electrodeposited at similar conditions. Results obtained revealed that the increase in corrosion resistance of ternary deposits is not only attributed to the formation of (γ-Ni₂Zn₁₁) phase, but also to iron codeposition and formation of (Fe₃Ni₂) phase.     

Titanosilicate ETS-10 as a Lewis acid catalyst in the Meerwein–Ponndorf–Verley (MPV) reaction

The potential of ETS-10 as a Lewis acid catalyst was investigated using the MPV reaction at one atmosphere total pressure and 273 K. ETS-10 was hypothesized to be a potential Lewis acid catalyst as it has titanium in octahedral symmetry, which is the symmetry shown in zeolite Beta to be the most active site for the Lewis acid catalyzed Meerwein–Ponndorf–Verley (MPV) reaction. The MPV reaction is a hydrogen transfer reaction that can be used for obtaining information about the structure and performance of catalysts by comparing the product selectivities and catalytic activities. Due to their similar structures, the catalytic activity of ETS-10 was compared to zeolite Beta samples that were space-grown (flight, fewer defects) and to their earth-grown terrestrial controls. The higher tr-alcohol selectivity (i.e., trans-4-tert-butylcyclohexanol, ∼80% vs. 40%) observed over ETS-10 was attributed to a larger volume being available in the pores of ETS-10 compared to the zeolite Beta samples. By-product formation (i.e., 4-tert-butylcyclohexene) was significantly less over ETS-10 (∼5%) in comparison with the zeolite Beta samples (flight and control; ∼35%). These results reaffirm the octahedral symmetry as the Lewis active site for the MPV reaction, and illustrate that ETS-10 is a good catalyst for MPV type reactions.     

Surface active sites present in the orthorhombic M1 phases: low energy ion scattering study of methanol and allyl alcohol chemisorption over Mo–V–Te–Nb–O and Mo–V–O catalysts

The outermost surface compositions and chemical nature of active surface sites present on the orthorhombic (M1) Mo–V–O and Mo–V–Te–Nb–O phases were determined employing methanol and allyl alcohol chemisorption and surface reaction in combination with low energy ion scattering (LEIS). These orthorhombic phases exhibited vastly different behavior in propane (amm)oxidation reactions and, therefore, represented highly promising model systems for the study of the surface active sites. The LEIS data for the Mo–V–Te–Nb–O catalyst indicated surface depletion for V (−23%) and Mo (−27%), and enrichments for Nb (+55%) and Te (+165%) with respect to its bulk composition. Only minor changes in the topmost surface composition were observed for this catalyst under the conditions of the LEIS experiments at 400 °C, which is a typical temperature employed in these propane transformation reactions. These findings strongly suggested that the bulk orthorhombic Mo–V–Te–Nb–O structure is terminated by a unique active and selective surface layer in propane (amm)oxidation. Moreover, direct evidence was obtained that the topmost surface VO _x sites in the orthorhombic Mo–V–Te–Nb–O catalyst were preferentially covered by chemisorbed allyloxy species, whereas methanol was a significantly less discriminating probe molecule. The surface TeO _x and NbO _x sites on the Mo–V–Te–Nb–O catalyst were unable to chemisorb these probe molecules to the same extent as the VO _x and MoO _x sites. These findings suggested that vastly different catalytic behavior exhibited by the Mo–V–O and Mo–V–Te–Nb–O phases is related to different surface locations of V⁵⁺ ions in the orthorhombic Mo–V–O and Mo–V–Te–Nb–O catalysts. Although the proposed isolated V⁵⁺ pentagonal bipyramidal sites in the orthorhombic Mo–V–O phase may be capable of converting propane to propylene with modest selectivity, the selective 8-electron transformation of propane to acrylic acid and acrylonitrile may require the presence of several surface VO _x redox sites lining the entrances to the hexagonal and heptagonal channels of the orthorhombic Mo–V–Te–Nb–O phase. Finally, the present study strongly indicated that chemical probe chemisorption combined with low energy ion scattering (LEIS) is a novel and highly promising surface characterization technique for the investigation of the active surface sites present in the bulk mixed metal oxides.     

Synthesis and characterization of poly-(allylbenzene p-sulphonate) films incorporating electrolessly deposited Ni–P

The preparation of a novel electrode material is described. The ionic exchange properties of polymer films electrochemically prepared from the allyl ether of the p-benzenessulphonic acid monomer were explored with an incorporated ion of metallic crystallites in the polymeric matrix. The autocatalytic activity of the pristine and modified polymer for the electroless deposition of Ni–P from a hypophosphite containing solution was analyzed and conditions for the use of the deposition method to modify the nature and the size of the metal particles established. The performance of typical electrodes prepared by this route, e.g., polymer/Cu/Ni–P, towards the proton reduction reaction in buffer solution, when contrasted to polymer/Ni, revealed promising electrocatalytic activity. This behaviour, along with the simplicity of the preparation route makes these modified electrodes strong candidates to replace other systems for electrohydrogenation purposes.     

Electrochemical study of the codeposition of Mg–Li–Al alloys from LiCl–KCl–MgCl<Subscript>2</Subscript>–AlCl<Subscript>3</Subscript> melts

This work presents a novel electrochemical study on the codeposition of Mg, Li and Al on a molybdenum electrode in LiCl–KCl–MgCl₂–AlCl₃ melts at 943 K to form Mg–Li–Al alloys. Cyclic voltammograms (CVs) showed that the underpotential deposition (UPD) of magnesium on pre-deposited aluminum leads to the formation of a liquid Mg–Al solution, and the succeeding underpotential deposition of lithium on pre-deposited Mg–Al leads to the formation of a liquid Mg–Li–Al solution. Chronopotentiometric measurements indicated that the codeposition of Mg, Li and Al occurs at current densities lower than −0.47 A cm⁻² in LiCl–KCl–MgCl₂ (0.525 mol kg⁻¹) melts containing 0.075 mol kg⁻¹ AlCl₃. Chronoamperograms demonstrated that the onset potential for the codeposition of Mg, Li and Al is −2.100 V, and the codeposition of Mg, Li and Al is formed when the applied potentials are more negative than −2.100 V. The diffusion coefficient of aluminum ions in the melts was determined by different electrochemical techniques. X-ray diffraction and inductively coupled plasma analysis indicated that α, α + β and β Mg–Li–Al alloys with different lithium and aluminum contents were obtained via potentiostatic and galvanostatic electrolysis.     

Selective area deposition of Tin–Nickel alloy coating – an alternative for decorative chromium plating

Sn–Ni alloy coatings on mild steel substrates produced by selective area deposition process with layer thickness of about 14 μm were investigated with regard to the structural and corrosion properties. X-ray diffraction analysis revealed that the selective area plated Sn–Ni alloy was heterogeneous and composed of NiSn, Ni₃Sn₂ and Ni₃Sn₄ phases. Uniform surface coverage of the substrate by granular morphology was observed from SEM and AFM. The alloy composition was determined by X-ray fluorescence (XRF). The corrosion protection performance of Sn–Ni alloy on mild steel was assessed using salt-water immersion and electrochemical corrosion tests. A sharp decrease in I _corr and high charge transfer resistance indicated improved corrosion resistant behavior of the selective area deposited Sn–Ni alloy.     

Gas Phase Hydrogenation of Maleic Anhydride to γ-Butyrolactone by Cu–Zn–Ce Catalyst in the Presence of n-Butanol

A series of Cu–Zn–Ce catalysts were prepared by coprecipitation method and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, temperature programmed reduction, and N₂ adsorption. The catalytic activities of the Cu–Zn–Ce catalysts in gas phase hydrogenation of maleic anhydride in the presence of n-butanol were studied at 220–280 °C and 1 MPa. The conversion of maleic anhydride was more than 97%. After reduction, CuO species present in the calcined Cu–Zn–Ce catalysts were converted to metallic copper (Cu°). The presence of ZnO in the Cu–Zn–Ce catalysts was beneficial to stabilizing the catalytic activity in maleic anhydride hydrogenation to γ-butyrolactone. At the same time, n-butanol was dehydrogenated to butyl aldehyde, then to butyl butyrate via reactions, such as disproportionation and esterification. Cu–Zn–Ce catalysts are beneficial to the H₂ compensation in the coupling process of hydrogenation and dehydrogenation.     

Electrochemical investigation of the passive behaviour of biomaterials based on Ag–Sn and Cu–Zn–Al in carbonate buffer in the absence and presence of chloride

The electrochemical behaviour of biomaterials based on Cu–Zn–Al (cubic Cu₃Zn phase) and Ag–Sn (orthorhombic Ag₃Sn and hexagonal Ag₄Sn phases) alloys was investigated in carbonate buffer solutions (pH 9.66) in the absence and presence of chloride, using different electrochemical techniques. Analyses of the open circuit potential and the potentiodynamic polarisation curves showed that the passivation domain and the corrosion parameters depend on alloy composition and chloride concentration. Chronoamperometric studies showed that passivation kinetics and corrosion of the passive film are both well described by a linear ln(i) versus ln(t) relation. The passive film formed on the Ag–Sn alloy is less susceptible to corrosion when compared to the Cu–Zn–Al system. The impedance data obtained in the passive region for the Cu–Zn–Al alloy showed that the passive layer is compact. In contrast, the impedance data obtained for the Ag–Sn alloy showed that the passive layer is formed by a compact oxide layer covered by a porous oxide gel layer. Mott–Schottky analysis showed that the passive film formed on the Cu–Zn–Al alloy behaves as a p-type semiconductor.     

In situ–Directed Growth of Organic Nanofibers and Nanoflakes: Electrical and Morphological Properties

Organic nanostructures made from organic molecules such as para-hexaphenylene (p-6P) could form nanoscale components in future electronic and optoelectronic devices. However, the integration of such fragile nanostructures with the necessary interface circuitry such as metal electrodes for electrical connection continues to be a significant hindrance toward their large-scale implementation. Here, we demonstrate in situ–directed growth of such organic nanostructures between pre-fabricated contacts, which are source–drain gold electrodes on a transistor platform (bottom-gate) on silicon dioxide patterned by a combination of optical lithography and electron beam lithography. The dimensions of the gold electrodes strongly influence the morphology of the resulting structures leading to notably different electrical properties. The ability to control such nanofiber or nanoflake growth opens the possibility for large-scale optoelectronic device fabrication.     

The Meerwein–Ponndorf–Verley–Oppenauer reaction between 2-hexanol and cyclohexanone on magnesium phosphates

Various magnesium phosphates were tested as catalysts for the vapour-phase Meerwein–Ponndorf–Verley–Oppenauer (MPVO) reaction between 2-hexanol and cyclohexanone. Some of the solids studied are as selective as MgO in this reaction. Others are also active in the dehydration of the alcohols. The activity and selectivity of the catalysts are related to their structure and surface chemical properties. This revised version was published online in July 2006 with corrections to the Cover Date.     

Preparation of Mesoporous Ni–alumina Catalyst by One-step Sol–gel Method: Control of Textural Properties and Catalytic Application to the Hydrodechlorination of o-dichlorobenzene

Mesoporous Ni–alumina catalysts (Ni–alumina-pre and Ni–alumina-post) were synthesized by one-step sol–gel method using micelle complex comprising lauric acid and nickel ion as a template with metal source and using aluminum sec-butoxide as an aluminum source. The Ni–alumina catalysts showed relatively high surface areas (303 m²/g for Ni–alumina-pre and 331 m²/g for Ni–alumina-post) and narrow pore size distributions centered at ca. 4 nm. Highly dispersed Ni particles were observed in the Ni–alumina catalysts (ca. 5.2 nm for Ni–alumina-pre and ca. 6.8 nm for Ni–alumina-post) after reduction at 550 °C, while a catalyst prepared without a template (NiAl-comp) exhibited inferior porosity with large metal particles (ca. 12.3 nm). Mesoporous Ni–alumina catalysts with different porosity were obtained by employing different hydrolysis step of aluminum source. When aluminum source was hydrolyzed under the presence of micelle complex, a supported Ni catalyst with highly developed framework mesoporosity was obtained (Ni–alumina-post). On the other hand, when aluminum source was pre-hydrolyzed followed by mixing with micelle solution, the resulting catalyst (Ni–alumina-pre) retained high portion of textural porosity. It was revealed that the hydrolysis method employed in this research affected not only textural properties but also metal-support interaction in the Ni–alumina catalysts. It was also found that the Ni–alumina-pre catalyst exhibited weaker interaction between nickel and alumina than the Ni–alumina-post, leading to higher degree of reduction in the Ni–alumina-pre catalyst. In the hydrodechlorination of o-dichlorobenzene, the Ni–alumina catalysts exhibited better catalytic performance than the NiAl-comp catalyst, which was attributed to higher metal dispersion in the Ni–alumina catalysts. In particular, the Ni–alumina-pre catalyst showing 1.5 times higher degree of reduction and larger amounts of o-dichlorobenzene adsorption exhibited better catalytic performance than the Ni–alumina-post catalyst.     

Electroless deposition of ternary Ni–P alloy coatings containing tungsten or nano-scattered alumina composite on steel

The performance of ternary electroless deposited Ni–P–W and Ni–P–alumina composite coatings on low carbon steel substrates was studied. The effect of experimental parameters, such as temperature, pH, nickel sulfate concentration, sodium hypophosphite concentration, sodium citrate concentration, and deposition time on the deposition rate were investigated. The coating brightness, coherence, and uniform surface distribution were improved due to addition of W and alumina. The coating performance was evaluated based on the wear-resistance, micro-hardness, and corrosion resistance. The Ni–P–W ternary alloy coatings showed the highest micro hardness, wear-resistance, brightness, and corrosion resistance. The improvement in the performance of Ni–P–W coatings can be explained by the formation of a tungsten phosphide phase.     

Surface texturing of Mo–V–Te–Nb–O x selective oxidation catalysts

The paper concentrates on the study of Mo–V–Te–Nb oxide mixtures by electron microscopy combined with catalytic investigation of these materials in the partial oxidation of propane. Surface texturing of catalyst particles composed of two phases referred to in the literature as M1 and M2 is revealed by high-resolution transmission electron microscopy of high performing catalysts. The chemical composition of the catalyst surface is modified by treatment in water to obtain a significant increment in yield of acrylic acid. A chemical realization of the site isolation concept recurring on a supramolecular arrangement of catalyst and reactant rather than on atomic site isolation is suggested. A complex Mo–V–Te–Nb–O _x precursor phase carries nanoparticles made from a network of oxoclusters active as catalyst for the conversion of propane to acrylic acid. The designed synthesis of the multi-element oxide bulk and of the surface structure with a different composition than the precursor phase improved the performance by a factor of 4.     

Electroless deposition of copper in acidic solutions using hypophosphite reducing agent

A new bath formulation was developed, which allowed deposition of copper-rich Cu–Ni–P alloys in electroless acidic solutions in the absence of formaldehyde. The reducing agent was sodium hypophosphite. Though cupric ions do not catalyse the oxidation of hypophosphite, we show that, in the presence of a low concentration of Ni(II) species, it is possible, even at low pHs, to induce the reduction of the cupric species. A very strong preferential deposition of copper was observed, which gives Cu–Ni–P layers with copper content up to 97 wt%. The phosphorus content decreased from 13% to 1% with increasing copper content. The plating rate decreased when the copper sulfate concentration in the solution increased. It increased with increasing pH or temperature, but the influence was less pronounced than in alkaline solutions. Compact layers were obtained with a nodular morphology which did not markedly changed with composition.     

Biocompatible Nanocomplexes for Molecular Targeted MRI Contrast Agent

Accurate diagnosis in early stage is vital for the treatment of Hepatocellular carcinoma. The aim of this study was to investigate the potential of poly lactic acid–polyethylene glycol/gadolinium–diethylenetriamine-pentaacetic acid (PLA–PEG/Gd–DTPA) nanocomplexes using as biocompatible molecular magnetic resonance imaging (MRI) contrast agent. The PLA–PEG/Gd–DTPA nanocomplexes were obtained using self-assembly nanotechnology by incubation of PLA–PEG nanoparticles and the commercial contrast agent, Gd–DTPA. The physicochemical properties of nanocomplexes were measured by atomic force microscopy and photon correlation spectroscopy. The T₁-weighted MR images of the nanocomplexes were obtained in a 3.0 T clinical MR imager. The stability study was carried out in human plasma and the distribution in vivo was investigated in rats. The mean size of the PLA–PEG/Gd–DTPA nanocomplexes was 187.9 ± 2.30 nm, and the polydispersity index was 0.108, and the zeta potential was −12.36 ± 3.58 mV. The results of MRI test confirmed that the PLA–PEG/Gd–DTPA nanocomplexes possessed the ability of MRI, and the direct correlation between the MRI imaging intensities and the nano-complex concentrations was observed (r = 0.987). The signal intensity was still stable within 2 h after incubation of the nanocomplexes in human plasma. The nanocomplexes gave much better image contrast effects and longer stagnation time than that of commercial contrast agent in rat liver. A dose of 0.04 mmol of gadolinium per kilogram of body weight was sufficient to increase the MRI imaging intensities in rat livers by five-fold compared with the commercial Gd–DTPA. PLA–PEG/Gd–DTPA nanocomplexes could be prepared easily with small particle sizes. The nanocomplexes had high plasma stability, better image contrast effect, and liver targeting property. These results indicated that the PLA–PEG/Gd–DTPA nanocomplexes might be potential as molecular targeted imaging contrast agent.