A strategy to enhance the thermal stability of a nanostructured polypyrrole-based coating for solid phase microextraction

We report on a nanostructured self-doped polypyrrole (SPPy) film that was prepared by an electrochemical technique in an electrolyte containing fluorosulfonic acid as the sulfonation reagent. The film was applied as a new fiber material for solid-phase microextraction (SPME) of the pesticides lindane, heptachlor, aldrin, endosulfans I and II prior to their quantitation by GC with electron capture detection. The SPPy nanoparticles have a diameter of <100?nm. The introduction of covalently bound sulfo groups into the backbone of the polymer resulted in improved temperature resistance (~350?°C) and satisfactory extraction efficiency. The thermal stability of the SPPy fiber is superior to common polypyrrole fibers. Extraction was optimized by means of the Taguchi orthogonal array experimental design with an OA₁₆ (4⁵) matrix including extraction temperature, extraction time, salt concentration, stirring rate, and headspace volume. The method displays good repeatability (RSD?<?6%) and linearity (in the range from 0.78 to 100?ng?mL^?1; with an R² of >0.998. The detection limits are <0.23?ng?mL^?1. The method was successfully applied to the analysis of the pesticides in skimmed milk and fruit juice samples, and recoveries are from 84?±?1 to 105?±?1%.

Thermodynamic study of triclosan adsorption from aqueous solutions on activated carbon

The change in the thermodynamic properties of triclosan adsorption on three activated carbons with the different surface chemistry was studied through immersion calorimetry and equilibrium data; the amount adsorbed of triclosan (Q) during calorimetry was determined and correlated with the energy associated with adsorbate–adsorbent interactions in the adsorption process. It was noted that triclosan adsorption capacity decreases with an increase in oxygenated surface groups. For an activated carbon oxidized with HNO₃ (OxAC), the amount adsorbed was 8.50?×?10^?3 mmol g^?1, for a activated carbon without modification (GAC) Q?=?10.3?×?10^?3 mmol g^?1 and for a activated carbon heated at 1073 K (RAC1073) Q?=?11.4?×?10^?3 mmol g^?1. The adsorbed amounts were determined by adjusting the isotherms to the Sips model. For the activated carbon RAC1073, the immersion enthalpy (ΔH_imm) was greater than those of the other two activated carbons due to the formation of interactions with the solvent (ΔH_immOxAC?=?? 27.3 J g^?1?<?ΔH_immGAC?=?? 40.0 J g^?1?<?ΔH_imm RAC1073?=???60.7 J g^?1). The changes in the interaction enthalpy and Gibbs energy are associated with adsorbate–adsorbent interactions and side interactions such as the adsorbate–adsorbate and adsorbate–solvent interactions.

     

LC-QTOF/MS metabolomic profiles in human plasma after a 5-week high dietary fiber intake

The objective was to investigate the alterations of plasma metabolome profiles to identify exposure and effect markers of dietary fiber intake. Subjects (n?=?25) aged 58.6 (1.1)?years (mean and SD) with a body mass index of 26.6 (0.5)?kg/m² were given a high fiber (HF) and a low fiber (LF) diet, in a 5-week randomized controlled crossover intervention. The HF diet consisted of oat bran, rye bran, and sugar beet fiber incorporated into test food products, whereas the LF diet was made of equivalent food products to the HF diet, but without adding fibers. Blood plasma samples were collected at the start and end of each intervention period and analyzed by LC-QTOF/MS. In total, 6 features in positive mode and 14 features in negative mode were significantly different between the HF and the LF diet (p?<?0.01, q?<?0.05). Two markers, 2,6-dihydroxybenzoic acid and 2-aminophenol sulfate, were increased after HF diet, along with a tentatively identified saponin derived from oat avenacosides. The untargeted metabolomics approach enabled the identification of two new markers of dietary fiber intake in human plasma. Further studies will be needed to verify if these markers could serve as compliance markers of fiber intake.     

Adsorption of S2− and HS− ions on the (111) face of coinage metals: A quantum-chemical study

The interactions of S^2? and HS^? ions with gold, silver, and copper were studied by density functional theory using the cluster model of the metal surface. The geometrical and energy characteristics of the interactions of these ions with the surface metal atoms were evaluated. The S^2? ions form stronger chemical bonds with the surface metal atoms than HS^? ions. A significant charge transfer from anion to metal occurs during the adsorption. The adsorbability increased in the series Ag < Cu < Au for both anions. The HS^? ion showed greater ability to be transferred to the surface during the electrochemical adsorption due to the strong hydration of the S^2? ion. In alkaline media, however, the dissociation of the adsorbed HS^? leads to its conversion to S^2?.     

Blinded predictions of standard binding free energies: lessons learned from the SAMPL6 challenge

In the context of the SAMPL6 challenges, series of blinded predictions of standard binding free energies were made with the SOMD software for a dataset of 27 host–guest systems featuring two octa-acids hosts (OA and TEMOA) and a cucurbituril ring (CB8) host. Three different models were used, ModelA computes the free energy of binding based on a double annihilation technique; ModelB additionally takes into account long-range dispersion and standard state corrections; ModelC additionally introduces an empirical correction term derived from a regression analysis of SAMPL5 predictions previously made with SOMD. The performance of each model was evaluated with two different setups; buffer explicitly matches the ionic strength from the binding assays, whereas no-buffer merely neutralizes the host–guest net charge with counter-ions. ModelC/no-buffer shows the lowest mean-unsigned error for the overall dataset (MUE 1.29?<?1.39?<?1.50 kcal mol^?1, 95% CI), while explicit modelling of the buffer improves significantly results for the CB8 host only. Correlation with experimental data ranges from excellent for the host TEMOA (R² 0.91?<?0.94?<?0.96), to poor for CB8 (R² 0.04?<?0.12?<?0.23). Further investigations indicate a pronounced dependence of the binding free energies on the modelled ionic strength, and variable reproducibility of the binding free energies between different simulation packages.     

Tritium in water bodies around the Kaiga generating station

Tritium concentration was monitored in different water sources collected around Kaiga Nuclear Power plant, India. The concentration was in the ranges?<?1.9–27.4 Bq L^?1 (GM?=?4.0 Bq L^?1) for groundwater,?<?1.9–42.1 Bq L^?1 (GM?=?3.5 Bq L^?1) for surface water and in 12.4–42.0 Bq L^?1 (GM?=?24.07 Bq L^?1) for reservoir water. The concentration values observed in this study are similar to those reported for other PHWR stations of the world. The radiation dose to the public due to ingestion of Tritium through groundwater was computed to be 0.08 μSvy^?1.

     

Biomimetic approach towards the preparation of hydroxyapatite and hydroxyapatite/chitosan/β-cyclodextrin nanoparticles: application to controlled drug release

Hydroxyapatite (HAp) and hydroxyapatite/chitosan/β-cyclodextrin (HAp/CS/β-CD) nanoparticles were successfully prepared in the modified simulated body fluid (SBF) solution at the physiological conditions (pH 7.4, temperature?=?37 °C). CS/β-CD nanoparticles acted as templates for the synthesis of HAp/CS/β-CD nanoparticles to improve the nanoarchitecture of HAp and its crystallinity.The nanoparticles were characterized by FT-IR spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Kneading and coprecipitation methods were applied to prepare the inclusion complex involving β-CD and p-THPP (5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin), a photosensitizer for anti-cancer drugs. The 1:1 stoichiometric ratio of the formed inclusion complex was characterized by a formation constant of 7.216?×?10² mol^?1 dm³ and analyzed by ¹H NMR, FTIR, and UV–Vis. The p-THPP delivery release in vitro was in this order: HAp/CS/β-CD?<?CS/β-CD?<?<?HAp/β-CD?<?β-CD, hinting at a better controlled release by HAp/CS/β-CD nanoparticles.     

Potentiometric back titration as a robust and simple method for specific surface area estimation of lignocellulosic fibers

The specific surface area (SSA) of cellulosic or lignocellulosic fibers is seldom reported in the recent literature on papermaking, despite its close relation with the degree of refining and other key pulp properties. Amidst outdated assays (Pulmac permeability test) and methods that, while accurate, are of doubtful usefulness for papermaking purposes (N₂ adsorption–desorption), we suggest a methodology based on the cationic demand. A commonly used cationic polyelectrolyte, poly(diallyldimethylammonium chloride) (PDADMAC), became adsorbed onto thermomechanical pulp samples. Then, a potentiometric back titration with an anionic polyelectrolyte measured the cationic demand, expressed as microequivalents of PDADMAC per gram of pulp. Multiplying this value by the surface area of a microequivalent of polymer, considering rod-like conformation in the case of minimum ionic strength, yielded the SSA of the lignocellulosic pulp. Our system assumes that the quaternary ammonium groups were anchored through electrostatic and ion–dipole interactions. Measuring the carboxyl content allowed for discriminating between both kinds of forces. Finally, the model could be validated by plotting the estimated SSA values against the Schopper-Riegler degree, attaining high correlation coefficients (R²?~?0.98). Owing to the high molecular weight of the polyelectrolyte of choice (107 kDa), and more particularly in the case of fine-free pulps, SSA values estimated from the cationic demand were consistently lower than those from dye (Congo red) sorption. Instead of being a drawback, the limited diffusion of PDADMAC through fibers can enable papermakers to attain a more helpful quantification of the available surfaces in operations with low residence times.

     

Occurrence of synthetic hormones in sewage effluents and Langat River and its tributaries,Malaysia

This study investigated for the first time the occurrence of selected synthetic hormones including 17α-ethinylestradiol, levonorgestrel, norethindrone and cyproterone acetate in Malaysian tropical waters. Samples were collected from the effluents of five sewage treatment plants (STPs) and at seven stations along the Langat River in Selangor, Malaysia, and its main tributaries. Samples were extracted by solid phase extraction (SPE) and analyzed by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). In Langat river samples, only levonorgestrel and cyproterone acetate were found at 50% and 3.3% frequency. The concentrations detected for levonorgestrel ranged from less than the method detection limit (<MDL) to 213?ng?L^?1 and from?<?MDL to 76?ng?L^?1 for cyproterone acetate. For the STP effluent samples, levonorgestrel was <MDL in all samples and the concentrations detected were in the range?<?MDL – 262?ng?L^?1 for cyproterone acetate,?<?MDL ?11336?ng?L^?1 for norethindrone and?<?MDL – 1898?ng?L^?1 for 17α-ethinylestradiol.     

Sensitive spectrophotometric detection of dopamine,levodopa and adrenaline using surface plasmon resonance band of silver nanoparticles

A simple and effective procedure is proposed for spectrophotometric determination of catecholamines; Dopamine (1), L-Dopa (2) and Adrenaline (3). It was found that the reduction of Ag⁺ to silver nanoparticles (Ag-NPs) by these catecholamines in the presence of polyvinylpyrrolidone (PVP) as a stabilizing agent produced very intense surface plasmon resonance peak of Ag-NPs. The plasmon absorbance of the Ag-NPs allows the quantitative spectrophotometric detection of the catecholamines. The calibration curves derived from the changes in absorbance at λ = 440 nm were linear with concentration of Dopamine, Levodopa and Adrenaline in the range of 3.2×10^?6? 2.0×10^?5 M, 1.6×10^?7 ? 1.0×10^?5 M, 1.5×10^?6? 4.0×10^?5 M, respectively. The detection limits (3σ) were 1.2×10^?6 M, 8.6 ×10^?8 M, 9.7 ×10^?7 M for the Dopamine, L-Dopa and Adrenaline, respectively. The method was applied successfully to the determination of catecholamines in Ringer’s injection serum.     

Surface characterization and electrical property of carbon fibers modified by air oxidation

Polyacrylonitrile‐based carbon fibers were modified by oxidation in air, and a systematic study of surface groups and surface resistance at different treated temperatures was made. Progressive fiber weight loss occurred with increasing extents of air oxidation, and it was approximately proportional to the extent of air oxidation from the onset of oxidation up to 400 °C. At this point 4.4% of the initial fiber weight had been lost. A faster loss of weight occurred as the extent of air oxidation increased from 400 °C to 700 °C. X‐ray photoelectron spectroscopy studies (C 1s and O 1s) indicated that the oxygen/carbon atomic ratio rose rapidly from 2.64% (as‐received carbon fiber) to 42.83% as the oxidation temperature was increased to 400 °C. Fourier transform infrared spectra showed the relative intensity of the peaks at about 3440 cm^?1 from ―OH stretching vibrations and at 1634 cm^?1 from ―C?O stretching vibrations increased significantly at 400 °C. FESEM micrographs showed that as‐received fibers show relatively smooth surface. With oxidation temperature increasing, the fiber surface was rougher. The surface resistance of treated carbon fibers decreased obviously with increasing oxidation temperatures. The most decrease was about 100% at 400 °C. Copyright © 2014 John Wiley & Sons, Ltd.     

Preparation and Properties of Chitosan/Konjac Glucomannan Blend Fibers

Chitosan and konjac glucomannan (KGM) blend fibers were prepared by spinning their solution through a viscose‐type spinneret into a coagulating bath containing aqueous sodium hydroxide and ethanol. The structure and properties of the blend fibers were studied with the aids of infrared spectra (IR), scanning electron micrography (SEM) and X‐ray diffraction (XRD). The structure analysis indicated that there were strong interaction and good miscibility between the chitosan and KGM molecule which resulted from intermolecular hydrogen bonds. Mechanical properties and water‐retention properties were measured. Through controlling blend conditions, blend fibers can obtain better mechanical properties than the pure chitosan fiber. The water‐retention values (WRV) of blend fibers increase as the amount of KGM is raised. The fibers treated with alcoholic solution of acetic acid have good antibacterial activity to Staphylococcus aureus.     

DFT and kinetics study of O/O2 mixtures reacting over a graphite (0001) basal surface

Spin-polarized density functional calculations were used to investigate the interaction of atomic and molecular oxygen on the basal graphite surface at several atomic coverages. Two carbon layers were enough to represent the graphite surface. Oxygen atoms bind mainly over C?CC bridge sites forming an epoxide-like structure with a two carbon puckering and with adsorption energies in the 0.95?C1.28?eV range, depending on the atomic coverage. Molecular oxygen only shows a very weak physisorption. Atomic adsorption and diffusion along with atomic recombination via Eley?CRideal and Langmuir?CHinshelwood mechanisms were studied. All surfaces processes were activated with energy barriers that decreased for lower atomic coverages. Relaxation effects were non-negligible. A microkinetic model with six elementary surface processes was proposed to see the overall behaviour of several initial O/O₂ mixtures flowing over a graphite surface at 300?C1,000?K. Thermal rate constants were derived from Density Functional Theory data and standard Transition State Theory. A very low steady-state atomic coverage (??_???<?0.5%) was predicted, and also very low atomic recombination coefficients were observed (??_O?<?5?×?10^?4). The Eley?CRideal together with the adsorption and desorption processes was much more important than the Langmuir?CHinshelwood reaction.     

Homogeneous Solid‐State Titanium Phosphate Potentiometric Sensor and its Application; Sorption of Iron (III) by Modified Chitosan in Two Modes of Operations

Abstract

A solid state iron (III) potentiometric sensor based on a pure tablet of titanium phosphate (TP) ion exchanger as sensitive membrane is elaborated. A homogeneous sensor prepared by this exchanger displays a useful analytical response with a super Nernestian cationic response (slope 22.5±1 mV/decade), excellent reproducibility and applicability over a wide range of iron (III) concentration (1×10^?6 ?1× 10^?2 mol l^?1). It also offers the advantages of fast response time (<1 min.), low cost, and simple construction. The proposed potentiometric sensor was successfully used in direct potentiometry as a low cost monitoring in sorption of iron (III) using modified chitosan in two modes of operations. Langmuir and Freundlich constants have been determined. In continuous flow system, the influences of varying parameters such as bed depth and solution flow rate have been studied. In a new approach (low cost monitoring/low cost treatment), the feasibility of the proposed potentiometric sensor in monitoring and the modified chitosan as sorbent in treatment of iron (III) from liquid waste streams were addressed.     

Electrical double layer and adsorption of iodide ions at the Bi | acetonitrile interface

The adsorption of I^? ions on the Bi(111) single crystal plane from solutions in acetonitrile has been investigated by impedance measurement method. The ionic charge due to the specific adsorption has been obtained using the mixed electrolyte method applied for both electrode charge and electrode potential as the independent electrical variables. The Gibbs energy of ions adsorption has been calculated using the virial adsorption isotherm. It was found that under comparable conditions the results obtained at constant electrode potential and at constant electrode charge are coincident and the Gibbs energy of I^? anion adsorption increases in the sequence of solvents: methanol < ethanol < propylene carbonate < acetonitrile. The electrosorption valency has been calculated and it was found that this parameter increases in the sequence propylene carbonate < ethanol < methanol < acetonitrile.     

Characterization of wood fibers modified by phenol-formaldehyde

Wood-fiber phenol-formaldehyde-resin (PFR) modified surfaces, obtained from the adsorption of a PFR/water solution, are investigated as a function of the nature and the amount of PFR adsorbed. Surface are measurements are performed by using krypton adsorption at 77 K. Chemical modification is monitored by the electron spectroscopy for chemical analysis (ESCA) technique and the surface energy by the inverse phase gas chromatography (IPGC) method at infinite dilution. The London dispersive componentγ _S ^L of the surface energy shows a relationship to the concentration of carbon and oxgen at the fiber surface.γ _S ^L increases from 27.5 mN·m⁻¹ for the untreated fiber to 42.5 mN·m⁻¹ for the fibers treated with 20% high molecular-weight-grade phenol-formaldehyde. The surface atomic ratio O/C determined using the ESCA technique exhibits a decrease from 44% for untreated to 31% for treated samples. Surface area also decreases from 2.09 m²/g to 1.50 m²/g. The PFR adsorbed by wood fibers is observed as the dispersive component of surface energy starts to increase, as the surface oxygen concentration decreases, and on the surface area of the wood fiber.     

Effects of pre-oxidation temperature on coal secondary spontaneous combustion

The hydrodynamic force (drag) on spherical and irregularly shaped particles significantly increases when the particles move close to solid and permeable boundaries. The overall effect of the increased hydrodynamic drag is to hinder the particle movement in the vicinity of boundaries and this includes the Brownian movement and electrophoresis. The Monte Carlo simulation method is used to model the Brownian movement, the resulting diffusion, and the electrophoresis of spherical particles in narrow, cylindrical pores, filled with Newtonian fluids. It is observed that the effect of the pore walls is a significant reduction of the space-averaged electrophoretic velocity of the particles, which implies reduced particle flux through the pores. The hindered electrophoresis is primarily a geometric phenomenon, caused by the increased drag and depends on the size of the particles and the pore-to-particle diameter ratio. The temperature of the fluid slightly affects the hindered electrophoresis through its effect on the viscosity, which is a determinant of the Brownian force, the diffusivity and the electrophoretic velocity. The hindered electrophoresis is almost independent of the other fluid and particle properties, such as density. Based on the simulation results a non-linear correlation for the flux of particles is derived, valid in the ranges 5?<?R/α?<?120, 5 nm?<?α?<?100 nm and 273 K?<?T?<?355 K.

     

Acute kidney injury caused by the intraperitoneal injection of Bothrops jararaca venom in rats

Abstract

We examined the ability of Bothrops jararaca venom (12.5?mg/kg) injected intraperitoneally (i.p.) to cause acute kidney injury (AKI) in rats. Blood urea and creatinine (AKI biomarkers, in g dL^?1) were elevated after 2?h in venom-treated rats (urea: from 0.41?±?0.1 to 0.7?±?0.03; creatinine from 46.7?±?3.1 to 85?±?6.7; p?<?0.05; n?=?3 each), with no change in circulating reduced glutathione. Venom-treated rats survived for ～6?h, at which point platelets were reduced (×10³ µL^?1; from 763.8?±?30.2 to 52.5?±?18.2) whereas leukocytes and erythrocytes were slightly increased (from 4.7?±?0.3 to 6.6?±?0.1?×?10³?µL^?1 and from 8.38?±?0.1 to 9.2?±?0.09?×?10⁶?µL^?1, respectively; p?<?0.05); blood protein (5.2?±?0.4?g dL^?1) and albumin (2.7?±?0.1?g dL^?1) were normal, whereas blood and urinary urea and creatinine were increased. All parameters returned to normal with antivenom given 2?h post-envenomation. The i.p. injection of venom caused AKI similar to that seen with other routes of administration.     

Magnetothermal Microfluidic‐Assisted Hierarchical Microfibers for Ultrahigh‐Energy‐Density Supercapacitors

Chemical architectures with an ordered porous backbone and high charge transfer are significant for fiber‐shaped supercapacitors (FSCs). However, owing to the sluggish ion kinetic diffusion and storage in compacted fibers, achieving high energy density remains a challenge. An innovative magnetothermal microfluidic method is now proposed to design hierarchical carbon polyhedrons/holey graphene (CP/HG) core–shell microfibers. Owing to highly magnetothermal etching and microfluidic reactions, the CP/HG fibers maintain an open inner‐linked ionic pathway, large specific surface area, and moderate nitrogen active site, facilitating more rapid ionic dynamic transportation and accommodation. The CP/HG FSCs show an ultrahigh energy density (335.8 μWh cm^?2) and large areal capacitance (2760 mF cm^?2). A self‐powered endurance application with the integration of chip‐based FSCs is designed to profoundly drive the durable motions of an electric car and walking robot.     

CoMnO2-Decorated Polyimide-Based Carbon Fiber Electrodes for Wire-Type Asymmetric Supercapacitor Applications

In this work, we report the carbon fiber-based wire-type asymmetric supercapacitors (ASCs). The highly conductive carbon fibers were prepared by the carbonized and graphitized process using the polyimide (PI) as a carbon fiber precursor. To assemble the ASC device, the CoMnO₂-coated and Fe₂O₃-coated carbon fibers were used as the cathode and the anode materials, respectively. Herein, the nanostructured CoMnO₂ were directly deposited onto carbon fibers by a chemical oxidation route without high temperature treatment in presence of ammonium persulfate (APS) as an oxidizing agent. FE-SEM analysis confirmed that the CoMnO₂-coated carbon fiber electrode exhibited the porous hierarchical interconnected nanosheet structures, depending on the added amount of APS, and Fe₂O₃-coated carbon fiber electrode showed a uniform distribution of porous Fe₂O₃ nanorods over the surface of carbon fibers. The electrochemical properties of the CoMnO₂-coated carbon fiber with the concentration of 6 mmol APS presented the enhanced electrochemical activity, probably due to its porous morphologies and good conductivity. Further, to reduce the interfacial contact resistance as well as improve the adhesion between transition metal nanostructures and carbon fibers, the carbon fibers were pre-coated with the Ni layer as a seed layer using an electrochemical deposition method. The fabricated ASC device delivered a specific capacitance of 221 F g⁻¹ at 0.7 A g⁻¹ and good rate capability of 34.8% at 4.9 A g⁻¹. Moreover, the wire-type device displayed the superior energy density of 60.2 Wh kg⁻¹ at a power density of 490 W kg⁻¹ and excellent capacitance retention of 95% up to 3000 charge/discharge cycles.