An activated carbon with high capacitance from carbonization of a resorcinol–formaldehyde resin

A polymeric activated carbon (PAC) was synthesized from the carbonization of a resorcinol–formaldehyde resin with KOH served as an activation agent. The nitrogen adsorption–desorption at 77 K, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the prepared PAC. Compared with the commercial activated carbon (Maxsorb: Kansai, Japan), PAC shows superior capacitive performance in terms of specific capacitance, power output and high energy density as electrode materials for supercapacitors. PAC presents a high specific capacitance of 500 F g^?1 in 6 mol l^?1 KOH electrolyte at a current density of 233 mA g^?1 which remained 302 F g^?1 even at a high current density of 4.6 A g^?1. The good electrochemical performance of the PAC was ascribed to well-developed micropores smaller than 1.5 nm, the presence of electrochemically oxygen functional groups and low equivalent series resistance.     

Electrodeposition of hyaluronic acid and hyaluronic acid–bovine serum albumin films from aqueous solutions

Hyaluronic acid (HYH) films were prepared from aqueous sodium hyaluronate (HYNa) solutions by anodic electrodeposition. The film thickness was varied in the range of 0–20 μm by the variation of the deposition time and HYNa concentration. The deposition rate was low at HYNa concentration below 1 g L⁻¹ and increased significantly in the range of 3–5 g L⁻¹. The addition of bovine serum albumin (BSA) to the HYNa solutions resulted in increased deposition yield, which was attributed to the formation of composite HYH–BSA films. The thickness of the HYH–BSA films deposited by anodic electrodeposition was varied in the range of 0–80 μm. The HYH and composite HYH–BSA films were studied by scanning electron microscopy, thermogravimetric analysis, differential thermal analysis, Fourier transform infrared spectroscopy and circular dichroism spectroscopy. The deposition mechanism and kinetics of deposition are discussed.     

Cu determination in crude oil distillation products by atomic absorption and inductively coupled plasma mass spectrometry after analyte transfer to aqueous solution

Cu was determined in a wide range of petroleum products from crude oil distillation using flame atomic absorption spectrometry (FAAS), electrothermal atomic absorption spectrometry (ETAAS) and inductively coupled plasma mass spectrometry (ICP-MS). Different procedures of sample preparation were evaluated: (i) mineralization with sulfuric acid in an open system, (ii) mineralization in a closed microwave system, (iii) combustion in hydrogen–oxygen flame in the Wickbold's apparatus, (iv) matrix evaporation followed by acid dissolution, and (v) acidic extraction. All the above procedures led to the transfer of the analyte into an aqueous solution for the analytical measurement step. It was found that application of FAAS was limited to the analysis of the heaviest petroleum products of high Cu content. In ICP-MS, the use of internal reference method (with Rh or In as internal reference element) was required to eliminate the matrix effects in the analysis of extracts and the concentrated solutions of mineralized heavy petroleum products. The detection limits (in original samples) were equal to, respectively, 10, 86, 3.3, 0.9 and 0.4 ng g^− 1 in procedures i–v with ETAAS detection and 10, 78, 1.1 and 0.5 ng g^− 1 in procedures i–iii and v with ICP-MS detection. The procedures recommended here were validated by recovery experiments, certified reference materials analysis and comparison of results, obtained for a given sample, in different ways. The Cu content in the analyzed samples was: 50–110 ng g^− 1 in crude oil, < 0.4–6 ng g^− 1 in gasoline, < 0.5–2 ng g^− 1 in atmospheric oil, < 6–100 ng g^− 1 in heavy vacuum oil and 140–300 ng g^− 1 in distillation residue.     

Investigation of immiscible alloy system of Al–Sn thin films as anodes for lithium ion batteries

The Al–Sn, which is immiscible alloy, film was prepared by e-beam deposition to explore the possibility as anode material for lithium ion batteries for the first time. The film has a complex structure with tiny Sn particles dispersed homogeneously in the Al active matrix. The diffusion coefficients of Li⁺ in these Al–Sn alloy films were determined to be 2.1–3.2 × 10⁻⁸ cm²/s by linear sweep voltammetry. The film electrode with high Al content (Al–33wt%Sn) delivered a high initial discharge capacity of 972.8 mA h g⁻¹, while the film electrode with high Sn content (Al–64wt%Sn) with an initial discharge capacity of 552 mA h g⁻¹ showed good cycle performance indicated by retaining a capacity of about 381 mA h g⁻¹ after 60 cycles. Our preliminary results demonstrate that Al–Sn immiscible alloy is a potential candidate for anodic material of lithium ion batteries.     

Copper(II)–neocuproine reagent for spectrophotometric determination of captopril in pure form and pharmaceutical formulations

A simple, rapid, sensitive and accurate spectrophotometric method for the determination of captopril in pure form and pharmaceutical formulations is developed. The procedure is based on the reaction of copper(II) with captopril in the presence of neocuproine (NC) (2,9-dimethyl-1,10-phenanthroline) reagent in acetate buffer at pH 5.0. Copper(II) is reduced easily by captopril to Cu(I)–neocuproine complex, which shows an absorption maximum at 448 nm. Beer’s law was obeyed in the concentration range 0.3–3.0 μg mL^?1 with a minimum detection limit (LOD) of 0.039 μg mL^?1 and a quantification limit (LOQ) of 0.129 μg mL^?1. For more accurate results, Ringbom optimum concentration ranges was 0.5–2.7 μg mL^?1. The apparent molar absorbtivity and Sandell sensitivity were calculated. The validity of the proposed method was tested by analyzing the pure and pharmaceutical formulations and compared well with those obtained by the official method and demonstrated good accuracy and precision.     

Electrodeposited PbO2 thin film on Ti electrode for application in hybrid supercapacitor

PbO₂ thin films were prepared by pulse current technique on Ti substrate from Pb(NO₃)₂ plating solution. The hybrid supercapacitor was designed with PbO₂ thin film as positive electrode and activated carbon (AC) as negative electrode in the 5.3 M H₂SO₄ solution. Its electrochemical properties were determined by cyclic voltammetry (CV), charge–discharge test and electrochemical impedance spectroscopy (EIS). The results revealed that the PbO₂/AC hybrid supercapacitor exhibited large specific capacitance, high-power and stable cycle performance. In the potential range of 0.8–1.8 V, the hybrid supercapacitor can deliver a specific capacitance of 71.5 F g^?1 at a discharge current density of 200 mA g^?1(4 mA cm^?2) when the mass ratio of AC to PbO₂ was three, and after 4500 deep cycles, the specific capacitance remains at 64.4 F g^?1, or 32.2 Wh Kg^?1 in specific energy, and the capacity only fades 10% from its initial value.     

Structural characterization of dodecyltrimethylammonium (DTMA) bromide modified sepiolite and its adsorption isotherm studies

In this study, dodecyltrimethylammonium (DTMA) bromide was used to modify natural sepiolite via an ion exchange reaction to form DTMA-sepiolite. Sepiolite and DTMA-sepiolite were then characterized by using Brunauer–Emmett–Teller (BET), elemental analysis, XRD, FT-IR, thermogravimetric (TG) and zeta potential analysis techniques. The BET surface area of sepiolite significantly decreased from 152.14 m² g^–1 to 88.63 m² g^–1, after the modification, due to the coverage of the pores of sepiolite. DTMA was located onto sepiolite according to the differential thermogravimetric (dTG) peaks of DTMA-sepiolite. XRD results confirmed the interaction between DTMA⁺ cations and sepiolite. FT-IR spectra indicated the existence of DTMA functional groups on sepiolite surface. After the characterization was accomplished, adsorption isotherm studies of naphthalene, which is the first member of the polycyclic aromatic hydrocarbons (PAHs), were carried out. The maximum adsorption capacity of DTMA-sepiolite for naphthalene was determined from Langmuir isotherm equation at pH 6 and 20 °C as 1.88 × 10^–4 mol g^?1 or 24.09 mg g^?1.     

Determination of triclosan,triclocarban and methyl-triclosan in aqueous samples by dispersive liquid–liquid microextraction combined with rapid liquid chromatography

In this study, dispersive liquid–liquid microextraction (DLLME) combined with ultra-high-pressure liquid chromatography (UHPLC)–tunable ultraviolet detection (TUV), has been developed for pre-concentration and determination of triclosan (TCS), triclocarban (TCC) and methyl-triclosan (M-TCS) in aqueous samples. The key factors, including the kind and volume of extraction solvent and dispersive solvent, extraction time, salt effect and pH, which probably affect the extraction efficiencies were examined and optimized. Under the optimum conditions, linearity of the method was observed in the range of 0.0500–100 μg L^?1 for TCS, 0.0250–50.0 μg L^?1 for TCC, and 0.500–100 μg L^?1 for M-TCS, respectively, with correlation coefficients (r²) > 0.9945. The limits of detection (LODs) ranged from 45.1 to 236 ng L^?1. TCS in domestic waters was detected with the concentration of 2.08 μg L^?1. The spiked recoveries of three target compounds in river water, irrigating water, reclaimed water and domestic water samples were achieved in the range of 96.4–121%, 64.3–84.9%, 77.2–115% and 75.5–106%, respectively. As a result, this method can be successfully applied for the rapid and convenient determination of TCS, TCC and M-TCS in real water samples.     

Novel luminescent nanoparticles for DNA detection

Highly luminescent LaF₃:Ce³⁺/Tb³⁺ nanocrystals were successfully prepared and surface functionalized via Layer-by-Layer technology. These as-prepared nanocrystals are highly resistant to photobleaching and pretty dispersible in aqueous solution. Due to the efficient luminescence quenching of the nanocrystals by nucleic acids, a facile fluorescence quenching method was developed for the detection of trace amount of nucleic acids. Under optimal conditions, the fluorescence intensity was proportional to the DNA concentration over the range of 0.60–25.0 μg mL^?1 for calf thymus DNA (ct-DNA) and 0.60–30.0 μg mL^?1 for herring sperm DNA (hs-DNA), respectively. The corresponding detection limit is 0.21 μg mL^?1 for ct-DNA and 0.31 μg mL^?1 for hs-DNA, respectively. The results indicated that the reported method is simple and rapid with wide linear range. Also, the recovery and relative standard deviation of this method are reasonable and satisfactory.     

Mucin 4 detection with a label-free electrochemical immunosensor

Mucin 4 (MUC4) is a useful biomarker for endometriosis and cancers of the pancreas, esophagus and breast. The very first electrochemical immunosensor for the detection of MUC4 is reported, using carbon-based screen-printed electrodes modified by reaction with the diazonium salt of p-aminophenylacetic acid. Electrochemical impedance spectroscopy and cyclic voltammetry were used to characterize and optimize the electrografting process. The in situ surface modification through diazotation with phenylacetic groups enables the chemical binding of the specific antibody, followed by its affinity reaction with MUC4. The immunosensor was optimized with respect to several parameters and is very promising for clinical applications, having a limit of detection of 0.33 μg mL^− 1 and a linear domain between 1 and 15 μg mL^− 1 obtained by electrochemical impedance spectroscopy measurements.     

Formation and characterization of magnetic barium ferrite hollow fibers with high specific surface area via sol–gel process

The magnetic barium ferrite (BaFe₁₂O₁₉) hollow fibers with a high specific surface area about 22–38 m² g^?1, diameters around 1 μm and a ratio of the hollow diameter to the fiber diameter estimated about 1/2–2/3 have been prepared by the gel-precursor transformation process. The precursor and resulting ferrite hollow fibers were analyzed by thermo-gravimetric and differential scanning calorimetry, infrared spectroscopy, scanning electron microscopy and X-ray diffraction. The specific surface area was measured by the Brunauer–Emmett–Teller method. The gel formed at pH 5.5 has a good spinnability. A pure barium ferrite phase is formed after calcined at 750 °C for 2 h and fabricated of nanograins about 38 nm with a hexagonal plate-like morphology, which are increased to about 72 nm with the calcination temperature increased up to 1050 °C. The barium ferrite hollow fibers obtained at 750 °C for 2 h have a specific surface area 38.1 m² g^?1 and average pore size 6.5 nm and then the specific surface area and average pore size show a reduction tendency with the calcination temperature increasing from 750 to 1050 °C owing to the particle growth and fiber densification. These barium ferrite hollow fibers exhibit typical hard-magnetic materials characteristics and the formation mechanism for hollow structures is discussed.     

Contribution enthalpic in the interaction of activated carbon with polar and apolar solvents

A method is presented for calculating the contribution that enthalpies make for every component of mixtures of activated carbon–water and activated carbon–hexane to the immersion enthalpy using the concepts that are used in the solution enthalpies. The immersion enthalpies of microporous activated carbon in water and in hexane have values from ?18.97 to ?27.21 and ?25.23 to ?47.89 J g^?1, respectively. From the immersion enthalpies and mass relation of the activated carbon in each of the solvents, the differential enthalpies are calculated for the activated carbon in water, Hw_DIFac, with values between ?15.95 and ?26.81 J g^?1, as are the differential enthalpies for the activated carbon in hexane, ΔHh_DIFac, with values between ?6.86 and ?46.97 J g^?1. For a low mass relation of the mixture components the contributions to the immersion enthalpy of the activated carbon and water differ by 3.20 J g^?1, while the difference between the contributions of the activated carbon and hexane is 19.41 J g^?1.     

Structural and electrochemical properties of a porous nanostructured SnO2 film electrode for lithium-ion batteries

A B₂O₃-doped SnO₂ thin film was prepared by a novel experimental procedure combining the electrodeposition and the hydrothermal treatment, and its structure and electrochemical properties were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis, energy dispersive X-ray (EDX) spectroscopy and galvanostatic charge–discharge tests. It was found that the as-prepared modified SnO₂ film shows a porous network structure with large specific surface area and high crystallinity. The results of electrochemical tests showed that the modified SnO₂ electrode presents the largest reversible capacity of 676 mAh g^?1 at the fourth cycle, close to the theoretical capacity of SnO₂ (790 mAh g^?1); and it still delivers a reversible Li storage capacity of 524 mAh g^?1 after 50 cycles. The reasons that the modified SnO₂ film electrode shows excellent electrochemical properties were also discussed.     

Fabrication and electrochemical properties of the Sn–Ni–P alloy rods array electrode for lithium-ion batteries

A new ternary Sn–Ni–P alloy rods array electrode for lithium-ion batteries is synthesized by electrodeposition with a Cu nanorods array structured foil as current collector. The Cu nanorods array foil is fabricated by heat treatment and electrochemical reduction of Cu(OH)₂ nanorods film, which is grown directly on Cu substrate through an oxidation method. The Sn–Ni–P alloy rods array electrode is mainly composed of pure Sn, Ni₃Sn₄ and Ni–P phases. The electrochemical experimental results illustrate that the Sn–Ni–P alloy rods array electrode has high reversible capacity and excellent coulombic efficiency, with an initial discharge capacity and charge capacity of 785.0 mAh g^?1 and 567.8 mAh g^?1, respectively. After the 100th discharge–charge cycling, capacity retention is 94.2% with a value of 534.8 mAh g^?1. The electrode also performs with an excellent rate capacity.     

The determination of trace lead in drinking water by flow injection spectrophotometry

Lead is the non-essential trace element in the human body, and it has been confirmed that drinking water is one of the sources of lead in human body. In the research, based on the sensitive colour reaction of lead with I^?–EV⁺–PVA, a simple, sensitive, accurate and portable method for the determination of trace lead in drinking waters was proposed. Chemicals and physicals had been optimized in detail. The apparent molar absorption coefficient was up to 7.4 × 10⁵ mol L^?1 cm^?1. The developed method provided a linearity range over 5–80 μg L^?1. The regression deviation was between 0.71% and 2.33%. The 3σ detection limit was 0.9 μg L^?1. Close to the quantitation limit for the analyte the relative standard deviation was 1.10% (n = 10) at 40 μg L^?1. The method developed here for analysis of lead yielded results that were comparable with those of the GFAAS.     

On the electrodialysis of aqueous H2SO4–CuSO4 electrolytes with metallic impurities

This work aims to contribute to the characterization of the electrodialysis (ED) of aqueous sulfuric acid–copper sulfate solutions. The presence of impurities such as As and Sb, typical of copper electrorefining electrolytes, is also studied. Results from kinetic studies carried out in ED cells with and without re-circulation are presented. The concentrations were: 3–9 g l⁻¹ copper, 50 g l⁻¹ sulfuric acid, 3 g l⁻¹ arsenic and 0.025 g l⁻¹ antimony; the temperatures, 22 and 44 °C; the transport rates, depending on experimental conditions, 0.2–0.6 mol h⁻¹ m⁻²of membrane for copper, 0.65–2.8 for sulfate, and 0.016–0.03 for arsenic. A speciation model has been developed and applied in order to interpret the experimental results and the performance of the studied cells has been evaluated. The main conclusion is that ED can be applied to the separation and concentration of chemical species in these systems.     

Net-structured NiO–C nanocomposite as Li-intercalation electrode material

Net-structured NiO was prepared by urea-mediated homogeneous hydrolysis of Ni(CH₃COO)₂ under microwave radiation followed by a calcination at 500 °C. NiO–C nanocomposite was prepared by dispersing the as-prepared net-structured NiO in glucose solution and subsequent carbonization under hydrothermal conditions at 180 °C. The carbon in the composite was amorphous by the X-ray diffraction (XRD) analysis, and its content was 15.05 wt% calculated according to the energy dispersive X-ray spectroscopy (EDX) result. Transmission electron microscopy (TEM) image of the NiO–C nanocomposite showed that the NiO network was homogeneously filled by amorphous carbon. The reversible capacity of NiO–C nanocomposite after 40 cycles is 429 mAh g⁻¹, much higher than that of NiO (178 mAh g⁻¹). These improvements are attributed to the carbon, which can enhance the conductivity of NiO, suppress the aggregation of active particles, and increase their structure stability during cycling.     

Column solid phase extraction and determination of ultra-trace Au,Pd and Pt in environmental and geological samples

A new sorbent based on cysteine modified silica gel (SiG-cys) was prepared and studied for preconcentration and separation of noble metals Au(III), Pd(II), Pt(II), Pt(IV). Its extraction efficiency was examined by batch and column solid phase extraction procedures. Laboratory experiments performed showed that sorbent is characterized with high selectivity, permiting quantitative sorption (93–97%) of noble metals Au, Pd and Pt from acidic media 0.1–2 mol L^? 1 HCl and unsignificant sorption (less than 2%) for common base metals like Cu, Fe, Mn and Zn. The analytes retained on the sorbent are effectively eluted with 0.1 mol L^? 1 thiourea in 0.1 mol L^? 1 HCl and measured by ETAAS or ICP OES under optimal instrumental parameters. The sorbent showed high mechanical and chemical stability and extraction efficiency was not changed after 500 cycles of sorption/desorption. The sorbent was successfully applied in analyticals procedures for preconcentration and determination of Au, Pd and Pt in geological and soil samples. Detection limits (3σ criteria) achieved, depending on the instrumental methods used are: ETAAS (0.005 μg L^? 1 for Au in river and sea water, 0.002 μg g^? 1 for Au in copper ore and copper concentrate); ICP OES (0.03 μg L^? 1 for Pd and 0.06 μg L^? 1 for Pt in river and sea water, 0.006 μg g^? 1 for Pd in copper ore and copper concentrate and 0.002 μg g^? 1 for soluble Pt in soil). The accuracy of the procedures developed was confirmed by added/found method for sea and river water; by the analysis of national certified materials (copper ore and copper concentrate for Au and Pd) and by determination of the sum of soluble Pt(II) + Pt(IV) in spiked soil samples.     

Cellulose-g-PDMAam copolymers by controlled radical polymerization in homogeneous medium and their aqueous solution properties

Water-soluble cellulose-graft-PDMAam copolymers were prepared by single-electron-transfer living radical polymerization (SET-LRP). Cellulose based macroinitiator for SET-LRP with a degree of substitution DS ≈ 2 was synthesized from softwood dissolving pulp in a homogeneous LiCl/DMAc solution. The macroinitiator was then grafted using N,N-dimethyl acrylamide (DMAam) in DMSO. Formation of cellulose-g-DMAam copolymers were confirmed by ATR–FTIR, ¹H and ¹³C NMR spectroscopy and SEC analyses. Light scattering and steady–shear viscosity measurements revealed that the studied chain length of grafts (DP_graft) had only minor effects on the solution properties of cellulose-g-PDMAam copolymers. SLS studies suggested a loose, solvent-draining architecture of the cellulose-g-PDMAam copolymer particles in H₂O.     

Investigation of Mg modified mesoporous silicas and their CO2 adsorption capacities

CO₂ adsorption properties on Mg modified silica mesoporous materials were investigated. By using the methods of co-condensation, dispersion and ion-exchange, Mg²⁺ was introduced into SBA-15 and MCM-41, and transformed into MgO in the calcination process. The basic MgO can provide active sites to enhance the acidic CO₂ adsorption capacity. To improve the amount and the dispersion state of the loading MgO, the optimized modification conditions were also investigated. The XRD and TEM characteristic results, as well as the CO₂ adsorption performance showed that the CO₂ adsorption capacity not only depended on the pore structures of MCM-41 and SBA-15, but also on the improvement of the dispersion state of MgO by modification. Among various Mg modified silica mesoporous materials, the CO₂ adsorption capacity increased from 0.42 mmol g⁻¹ of pure silica SBA-15 to 1.35 mmol g⁻¹ of Mg–Al–SBA-15-I1 by the ion-exchange method enhanced with Al³⁺ synergism. Moreover, it also increased from 0.67 mmol g⁻¹ of pure silica MCM-41 to 1.32 mmol g⁻¹ of Mg–EDA–MCM-41-D10 by the dispersion method enhanced with the incorporation of ethane diamine. The stability test by 10 CO₂ adsorption/desorption cycles showed Mg–urea–MCM-41-D10 possessed quite good recyclability.