Acetylcholine (ACh) and its precursor choline (Ch) play important roles in many biological processes. It is expected that Alzheimer's disease is occurred due to the reduction in synthesis of ACh. On ...the other hand, the increase in the level of ACh results in a depression of heart rate and over production of saliva. Therefore, the quantitative determination of Ch and ACh is very important in biological media. In the current work, sensitive and selective biosensors composed of choline oxidase (ChO) and/or acetylcholine esterase (AChE) on graphene oxide-ionic liquid (GO-IL)/ glassy carbon electrode (GCE) hyphenated with anodic differential pulse stripping voltammetry (ADPSV) were firstly established for the determination of ACh and Ch in human serum samples. The molecular bond of ionic liquid 1-allyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (AMIM TFSI) with GO was investigated by FT-IR and UV–Vis techniques. Furthermore, the surface topography of ChO/GO–IL and AChE-ChO/GO–IL composites was investigated by SEM and XRD. Then, the electron transfer features of biosensors ChO/GO-IL/GCE and AChE-ChO/GO-IL/GCE were characterized by the electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. The ADPSV was further used for the determination of Ch and ACh. The experimental parameters such as differential pulse working potential, differential pulse scan rate, equilibrium time and long-term stability were further optimized. Detection limits of 0.885 and 1.352 nmol L−1 with excellent linearity (R2 = 0.9996) over the range of 5–1000 nmol L−1 were obtained for Ch and ACh, respectively. The developed analytical methods showed excellent accuracy and precision for the determination of Ch and ACh in human serum samples avoiding their pretreatment or purification.
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•1-allyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid is first used along with graphene oxide.•Hyphenation of enzyme-based biosensors with anodic differential pulse stripping voltammetry.•Reliable detection of acetylcholine and its precursor choline in human serum.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The lithium-oxygen battery, of much interest because of its very high-energy density, presents many challenges, one of which is a high-charge overpotential that results in large inefficiencies. Here ...we report a cathode architecture based on nanoscale components that results in a dramatic reduction in charge overpotential to ~0.2 V. The cathode utilizes atomic layer deposition of palladium nanoparticles on a carbon surface with an alumina coating for passivation of carbon defect sites. The low charge potential is enabled by the combination of palladium nanoparticles attached to the carbon cathode surface, a nanocrystalline form of lithium peroxide with grain boundaries, and the alumina coating preventing electrolyte decomposition on carbon. High-resolution transmission electron microscopy provides evidence for the nanocrystalline form of lithium peroxide. The new cathode material architecture provides the basis for future development of lithium-oxygen cathode materials that can be used to improve the efficiency and to extend cycle life.
•Use of ionic liquids as micellar agents for trace analysis of acrylamide in bread.•Ecofriendly, inexpensive and reliable focusing of AA by ionic liquids micelle collapse.•Efficient ...ionic-liquid-based ultrasonic-assisted extraction of acrylamide from bread.•Robust ILUAE coupled with AFILMC is applicable to food safety.
Acrylamide (AA) is a known lethal neurotoxin and carcinogen. AA is formed in foods during the browning process by the Maillard reaction of glucose (GL) with asparagine (AS). For the first time, the simultaneous online preconcentration and separation of AA, AS and GL using analyte focusing by ionic liquid micelle collapse capillary electrophoresis (AFILMC) was presented. Samples were prepared in a 1-butyl-3-methylimidazolium bromide (BMIMBr) micellar matrix with a conductivity 4 times greater than that of the running buffer (12.5mmolL−1 phosphate buffer at pH 8.5). Samples were hydrodynamically injected into a fused silica capillary at 25.0mbar for 25.0s. Separations were performed by applying a voltage of 25.0kV and a detection at 200.0nm. To sufficiently reduce BMIMBr adsorption on the interior surface of capillary, an appropriate rinsing procedure by hydrochloric acid and water was optimized. AFILMC measurements of analytes within the concentration range of 0.05–10.0μmolL−1 achieved adequate reproducibility and accuracy with RSD 1.14–3.42% (n=15) and recovery 98.0–110.0%, respectively. Limits of detections were 0.71ngg−1 AA, 1.06ngg−1 AS and 27.02ngg−1 GL with linearity ranged between 2.2 and 1800ngg−1. The coupling of AFILMC with IL based ultrasonic assisted extraction (ILUAE) was successfully applied to the efficient extraction and determination of AA, AS and GL in bread samples. The structure of ILs has significant effects on the extraction efficiency of analytes. The optimal extraction efficiency (97.8%) was achieved by an aqueous extraction with 4:14 ratio of sample: 3.0molL−1 BMIMBr followed by sonication at 35°C. The proposed combination of ILUAE and AFILMC was simple, ecofriendly, reliable and inexpensive to analyze a toxic compound and its precursors in bread which is applicable to food safety.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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•Dynamics and thermodynamics of Cr6+ and Cd2+ adsorption on humic acid are studied.•The adsorption data are well modeled using the second-order kinetic equations.•The adsorption of ...Cr6+ and Cd2+ on HA was physical diffusion controlled reaction.•The experimental results well fit the Langmuir model.•The thermodynamics show endothermic, favorable and spontaneous sorption processes.
Humic acids, HA represent a large portion of natural organic matter in soils, sediments and waters. They are environmentally important materials due to their extensive ubiquity and strong complexation ability, which can influence heavy metal removal and transportation in waters. The thermodynamics and kinetics of the adsorption of CdII and CrVI onto solid soil-derived HA have been investigated at optimum conditions of pH (5.5±0.1), metal concentration (10–100mmolL−1) and different temperatures (293–323K). The suitability of adsorption models such as Freundlich and Langmuir to equilibrium data was investigated. The adsorption was well described by Langmuir isotherm model in multi-detectable steps. Adsorption sites, i (i=A, B, C) with different capacities, νi are characterized. The stoichiometric site capacity is independent of temperature and equilibrium constant, Ki. Adsorption sites A and B are selectively occupied by CrVI cations while sites A and C are selectively occupied by CdII cations. The thermodynamic parameters of adsorption systems are correlated for each adsorption step. The adsorption is endothermic, spontaneous and favorable. Different kinetic models are applied and the adsorption of these heavy metals onto HA follows pseudo-second-order kinetics and equilibrium is achieved within 24h. The adsorption reaction is controlled by diffusion processes and the type of the adsorption is physical.
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•Precise protein-pharmaceutical binding measurements were achieved.•Temperature controlled hydrophilic IL aqueous two phase system combined with ACE was investigated.•A low ...concentration of 1-butyl-3-methylimidazolium chloride was the best IL.•Successful applications to precise binding between drugs and AGP were obtained.
Temperature controlled ionic liquid aqueous two phase system (ILATPS) was used to improve the precision of pharmaceutical-AGP (human alpha (α1)-acid glycoprotein) binding measurements by affinity capillary electrophoresis (ACE). The effect of different types of short-chain alkyl imidazolium ILs within the concentration range of 10.0–1000.0 μmol L−1 on a propranolol (PRO)-AGP model was firstly investigated by ILATPS/ACE system. Use of 100.0 μmol L−1 1-butyl-3-methylimidazolium chloride (BMImCl) in 67.0 mmol L−1 potassium phosphate buffer (pH 7.4) containing low concentrations of AGP (5.0–100.0 µmol L−1) gave the highest precision value (2.98 ± 0.14 × 105 L/mol) which is in concord with the reported one (3.00 × 105) under similar experimental conditions. The proposed BMImCl/phosphate solution was a unique temperature controlled system to preserve AGP activity during the pre-analysis and within ACE measurements under lab conditions for about 30 days. This period could be prolonged by converting the one-phase solution into biphasic solution at 4 °C storage temperature and again it could get rapidly back into one-phase by raising the temperature with gentle shaking. This behavior could be attributed to the electrostatic interaction and π–π interaction between BMIm cations and negatively charged AGP ions (pI = 2.7). Moreover, the compatibility of ILATPS with ACE has been the critical factor to avoid precipitation of salts formed by anion exchange in the running buffer. The current ILATPS/ACE system was further used to rapidly and precisely estimate the binding constants of anticancer drugs methotrexate (MTX) and vinblastine (VBL) with human AGP. The obtained binding values have been in good agreements with their findings by high performance affinity chromatography (HPAC). This ILATP/ACE system could similarly be applied to improve the precision of other proteins binding measurements with consuming a small amount of protein and with shortening ACE analysis time.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Hydrogen production is produced for future green energy. The radiation–chemical yield for seawater without a catalyst, with Zr, and with Zr1%Nb (Zr = 99% Nb = 1%) were (G(H2) = 0.81, 307.1, and 437.4 ...molecules/100 eV, respectively. The radiation–thermal water decomposition increased in γ-radiation of the Zr1%Nb + SW system with increasing temperature. At T = 1273 K, it prevails over radiation processes. During the radiation and heat radiation heterogeneous procedures in the Zr1% Nb + SW system, the production of surface energetic sites and secondary electrons accelerated the accumulation of molecular hydrogen and Zr1%Nb oxidation. Thermal radiation and thermal processes caused the metal phase to collect thermal surface energetic sites for water breakdown and Zr 1%Nb oxidation starting at T = 573 K.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The presence of triclosan in water is toxic to human beings, hazardous to the environment and creates side effects and problems because this is an endocrine-disturbing water pollutant. Therefore, ...there is a great need for the separation of this notorious water pollutant at an effective, economic and eco-friendly level. The interface sorption was achieved on synthesized ionic liquid-based nanocomposites. An N-methyl butyl imidazolium bromide ionic liquid copper oxide nanocomposite was prepared using green methods and characterized by using proper spectroscopic methods. The nanocomposite was used to remove triclosan in water with the best conditions of time 30 min, concentration 100 µg/L, pH 8.0, dose 1.0 g/L and temperature 25 °C, with 90.2 µg/g removal capacity. The results obeyed Langmuir, Temkin and D-Rs isotherms with a first-order kinetic and liquid-film-diffusion kinetic model. The positive entropy value was 0.47 kJ/mol K, while the negative value of enthalpy was −0.11 kJ/mol. The negative values of free energy were −53.18, −74.17 and −76.14 kJ/mol at 20, 25 and 30 °C. These values confirmed exothermic and spontaneous sorption of triclosan. The combined effects of 3D parameters were also discussed. The supramolecular model was developed by simulation and chemical studies and suggested electrovalent bonding between triclosan and N-methyl butyl imidazolium bromide ionic liquid. Finally, this method is assumed as valuable for the elimination of triclosan in water.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Transition metal dichalcogenides (TMD), analogue of graphene, could form various dimensionalities. Similar to carbon, one-dimensional (1D) nanotube of TMD materials has wide application in hydrogen ...storage, Li-ion batteries, and supercapacitors due to their unique structure and properties. Here we demonstrate the feasibility of tungsten disulfide nanotubes (WS2-NTs)/graphene (GS) sandwich-type architecture as anode for lithium-ion batteries for the first time. The graphene-based hierarchical architecture plays vital roles in achieving fast electron/ion transfer, thus leading to good electrochemical performance. When evaluated as anode, WS2–NTs/GS hybrid could maintain a capacity of 318.6 mA/g over 500 cycles at a current density of 1A/g. Besides, the hybrid anode does not require any additional polymetric binder, conductive additives, or a separate metal current-collector. The relatively high density of this hybrid is beneficial for high capacity per unit volume. Those characteristics make it a potential anode material for light and high-performance lithium-ion batteries.
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IJS, KILJ, NUK, PNG, UL, UM
A novel polyaniline-modified CNT and graphene-based nanocomposite (2.32–7.34 nm) was prepared and characterized by spectroscopic methods. The specific surface area was 176 m2/g with 0.232 cm3/g as ...the specific pore volume. The nanocomposite was used to remove zinc and lead metal ions from water; showing a high removal capacity of 346 and 581 mg/g at pH 6.5. The data followed pseudo-second-order, intraparticle diffusion and Elovich models. Besides this, the experimental values obeyed Langmuir and Temkin isotherms. The results confirmed that the removal of lead and zinc ions occurred in a mixed mode, that is, diffusion absorption and ion exchange between the heterogeneous surface of the sorbent containing active adsorption centers and the solution containing metal ions. The enthalpy values were 149.9 and 158.6 J.mol−1K−1 for zinc and lead metal ions. The negative values of free energies were in the range of −4.97 to −26.3 kJ/mol. These values indicated an endothermic spontaneous removal of metal ions from water. The reported method is useful to remove the zinc and lead metal ions in any water body due to the high removal capacity of nanocomposite at natural pH of 6.5. Moreover, a low dose of 0.005 g per 30 mL made this method economical. Furthermore, a low contact time of 15 min made this method applicable to the removal of the reported metal ions from water in a short time. Briefly, the reported method is highly economical, nature-friendly and fast and can be used to remove the reported metal ions from any water resource.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
•Emphasize the role of long chain ionic liquid in enhancing the sensitivity of CE.•Sweeping-MEKC making up to 183-fold sensitivity enhancement.•Investigation of simple and fast CE method for the ...analysis of catechins.•Reliable application to determine unchanged catechins in human plasma.
Determination of tea catechins in human plasma might provide a means of better evaluation of their benefits. The main difficulty in their analysis is the low catechins concentrations in plasma and their susceptible to oxidation during sample pretreatment. In the current work, a sweeping-micellar electrokinetic chromatography (sweeping-MEKC) by long alkyl chain ionic liquid was investigated for the simultaneous determination of seven principal naturally-occurring tea catechins in human plasma under acidic conditions after the intake of green tea beverage. The effects of type and concentration of three 1-tetradecyl-3-methylimidazolium ionic liquids, namely bromide, acetate and hydrogen sulfate salts were studied. The seven catechins were successfully separated within 5min by micellar running buffer of 5mmolL−1 1-tetradecyl-3-methylimidazolium bromide and 15mmolL−1 phosphate buffer at pH 4.5 under optimal parameters of 50mbar injection for 150s, 10kV, 25°C and 200nm. To prevent the possibility of IL adsorption, an appropriate rinsing protocol was established. The method has analytical ranges from 0.5, 1, 0.5, 1, 2, 1 and 1 to 500ngmL−1 for GC, C, EC, EGCG, GCG, ECG and EGC, respectively (r ranged from 0.995 to 0.999). The intraday precision and accuracy were 0.1–0.9% RSD (n=10) and 97–106% recovery, respectively. Limits of detections of analytes were ranged from 0.2 to 1.2ngmL−1. The current sweeping-MEKC achieved sensitivity enhancement factor (SEF) up to 183-fold of analytes concentrations compared to other hitherto published CE reports that is suitable to find out the trace amounts of catechins in plasma.
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