High-performance supercapacitors based on an ionic liquid-derived nanofibrillated mesoporous carbon

This article reports the superior specific capacitance, energy, and power density of a nanofibrillated mesoporous carbon derived from an ionic liquid source (IFMC). It was concluded that high specific capacitance and good electrical conductivity were originated from contribution of nitrogen content of IFMC, also the interesting nanofibrillated structure. A specific capacitance of 235 F g^?1 at a high discharge current of 5 A g^?1 was estimated for IFMC-based electrode which is higher than the most reported capacitance for carbon materials. An excellent performance of the nanofibrillated mesoporous carbon along with proper concentration of nitrogen constituent in the carbonaceous framework is indicative for important effects of tuning the carbon nanostructure for energy storage applications.     

Desirability function approach for the optimization of an in‐syringe ultrasound‐assisted emulsification‐microextraction method for the simultaneous determination of amlodipine and nifedipine in plasma samples

In the present study, an in‐syringe ultrasound‐assisted emulsification‐microextraction using a low‐density organic solvent was developed for simultaneous extraction and pre‐concentration of amlodipine besylate and nifedipine from plasma samples. The extracts were analyzed by high‐performance liquid chromatography with UV detection. Central composite design combined with desirability function was applied to find out the optimal experimental conditions providing the highest global extraction efficiency. The optimal conditions identified were volume of the extracting solvent 45 μL, ionic strength 18.95% w/v, sonication time 2.58 min, and centrifugation time 3 min. Under the optimal conditions, the proposed method was evaluated, and applied to the analysis of amlodipine besylate and nifedipine in plasma samples. The validation results of the method indicated a wide linear range (2–1200 ng/mL) with a good linearity (r² >0.9991) and low detection limits (0.17 ng/mL for amlodipine besylate and 0.15 ng/mL for nifedipine) with RSD less than 5.2% for both components, both in intra‐ and inter‐day precision studies. The applicability of the proposed in‐syringe ultrasound‐assisted emulsification‐microextraction coupled to high‐performance liquid chromatography with UV detection method was demonstrated by analyzing the drugs in spiked plasma samples.     

Conductive polymer-based microextraction methods: A review

Conductive polymers (CPs) are classified as materials which exhibit highly reversible redox behavior and the unusual combined properties of metal and plastics. CPs, due to their multifunctionality, ease of synthesis and their stability, have attracted more attentions in different fields of research, including sample preparation. CPs along with several commercial hydrophilic sorbents, are alternative to the commercially available hydrophobic sorbents which despite their high specific surface areas, have poor interactions and retentions in the extraction of polar compounds. This review covers a general overview regarding the recent progress and new applications of CPs toward their synthesis and use in novel extraction and microextraction techniques including solid phase microextraction (SPME), electrochemically controlled solid-phase microextraction (EC-SPME) and other relevant techniques. Furthermore the contribution of nano-structured CPs in these methodologies is also reviewed.     

A novel magnetic poly(aniline-naphthylamine)-based nanocomposite for micro solid phase extraction of rhodamine B

A novel Fe₃O₄–poly(aniline-naphthylamine)-based nanocomposite was synthesized by chemical oxidative polymerization process as a magnetic sorbent for micro solid phase extraction. The scanning electron microscopy images of the synthesized nanocomposite revealed that the copolymer posses a porous structure with diameters less than 50 nm. The extraction efficiency of this sorbent was examined by isolation of rhodamine B, a mutagenic and carcinogenic dye, from aquatic media in dispersion mode. Among different synthesized polymers, Fe₃O₄/poly(aniline-naphthylamine) nanocomposite showed a prominent efficiency. Parameters including the desorption solvent, amount of sorbent, desorption time, sample pH, ionic strength, extraction time and stirring rate were optimized. Under the optimum condition, a linear spiked calibration curve in the range of 0.35–5.00 μg L⁻¹ with R² = 0.9991 was obtained. The limits of detection (3S_b) and limits of quantification (10S_b) of the method were 0.10 μg L⁻¹ and 0.35 μg L⁻¹ (n = 3), respectively. The relative standard deviation for water sample with 0.5 μg L⁻¹ of RhB was 4.2% (n = 5) and the absolute recovery was 92%. The method was applied for the determination of rhodamine B in dishwashing foam, dishwashing liquid, shampoo, pencil, matches tips and eye shadows samples and the relative recovery percentage were in the range of 94–99%.     

Prussian Blue Nanoparticles Self Assembling on Electrochemically Reduced Graphene Oxide Modified GC Electrode for Sensitive Hydrogen Peroxide Detection

A facile, fast, and convenient route was suggested for the fabrication of Prussian blue nano particles (PBNPs) assembled on reduced graphene oxide (RGO) modified glassy carbon electrode (PBNPs|RGO|GCE). RGO was electrodeposited on the surface of GCE and the prepared RGO|GCE was immersed into a ferric‐hexacyanoferrate(III) solution and PBNPs were assembled on the RGO|GCE for a certain period of time. The PBNPs film thickness can be easily controlled by adjusting the assembling duration. The developed PBNPs|RGO|GCE was successfully used for determining hydrogen peroxide, with a linear response over the concentration range 0.5‐400 μM, a good accuracy and precision, detection limit 0.44 μM, and sensitivity 1168 mA M^?1 cm^?2.     

Asymptotical stability analysis of Riemann‐Liouville q‐fractional neutral systems with mixed delays

This paper investigates the asymptotical stability of Riemann‐Liouville q‐fractional neutral systems with mixed delays (constant time delay and distributed delay). By constructing some appropriate Lyapunov‐Kravsovskii functionals, some sufficient conditions on delay‐dependent and delay‐independent asymptotical stability are obtained in terms of linear matrix inequality (LMI). Our employed method is based on the direct calculation of quantum derivatives of the Lyapunov‐Kravsovskii functionals. Finally, two examples are presented to demonstrate the availability of our obtained results.     

Quantum Lévy Laplacian and associated heat equation

As a non-commutative extension of the Lévy Laplacian for entire functions on a nuclear space, we define the quantum Lévy Laplacian acting on white noise operators. We solve a heat type equation associated with the quantum Lévy Laplacian and study its relation to the classical Lévy heat equation. The solution to the quantum Lévy heat equation is obtained also from a normal-ordered white noise differential equation involving the quadratic quantum white noise.     

Interferometric Sensor for Electrochemical Studies of Metallic Alloys in Aqueuos Solution

In a previous study a mathematical model relating surface and bulk behaviors of metals in aqueous solution was developed. The model was established based on principles of holographic interferometry for measuring microsurface dissolution, i.e., mass loss, and on those of electrochemistry for measuring the bulk electronic current, i.e., corrosion current. In the present work, an interferometric sensor was built based on the above model, and the corrosion current density of coated copper and brass in seawater were obtained using this sensor. The interferometric sensor was also utilized for the first time to measure the initial stage of the anodization process (oxidation) of aluminium samples in aqueous solution. This was carried out chemically in different acid concentrations (3.125–25% H₂SO₄) at room temperature. The sensor was further used for observation of catalytic activities, i.e., pitting corrosion, which occurred subsequent to the anodization of the aluminium samples in aqueous solutions, after an oxide film had been formed.     

Measurement of the double layer capacitance of aluminium samples by holographic interferometry

In the present investigation, holographic interferometry was utilized for the first time to measure the double layer capacitance of aluminium samples during the initial stage of anodization processes in an aqueous solution without any physical contact. The anodization process (oxidation) of the aluminium samples was carried out chemically in different sulphuric acid concentrations (0.5–3.125% H₂S0₄) at room temperature. In the meantime, a method of holographic interferometry was used to measure the thickness of anodization (oxide film) of the aluminium samples in aqueous solutions. Along with the holographic measurement, a mathematical model was derived in order to correlate the double layer capacitance of the aluminium samples in solutions to the thickness of the oxide film of the aluminium samples which forms due to the chemical oxidation. The thickness of the oxide film of the aluminium samples was measured by real-time holographic interferometry. Consequently, holographic interferometry is found to be very useful for surface finish industries, especially for monitoring the early stage of anodization processes of metals, in which the thickness of the anodized film as well as the double layer capacitance of the aluminium samples can be determined in situ. In addition, a comparison was made between the obtained data of the double layer capacitance from the holographic measurements and the double layer capacitance data obtained from measurements of electrochemical impedance spectroscopy. The comparison indicates that there is good agreement between the data from both techniques.     

Kinetics of ion-exchange on montmorillonite clays

The kinetics for the exchange of Li⁺, K⁺, Rb⁺, and Cs⁺ for Na⁺ as the exchangeable cation on bentonite and montmorillonite K10 and KSF have been studied using conductimetric stoppedflow. Dilute aqueous suspensions of the clays, of particle sizes of a few micrometers, were used, so that diffusion was fast and the rate-determining step was the substitution of one cation by another on the lattice surface. The kinetics were treated in terms of relaxation from equilibrium. Relaxation times ranged from 100 to 250 ms, and forward rate constants from 30 to 500 M^?1 s^?1. The reactions had very low activation enthalpies (7–25 kJ mol^?1) and were only slow enough to be studied by the stopped-flow technique because of the large negative entropies of activation (?120 to ?170 J K^?1 mol^?1). © 1993 John Wiley & Sons, Inc.