Study of kinetic,thermodynamic, and isotherm of Sr adsorption from aqueous solutions on graphene oxide (GO) and (aminomethyl)phosphonic acid–graphene oxide (AMPA–GO)

Journal of Radioanalytical and Nuclear Chemistry - In this work, graphene oxide (GO) and (aminomethyl)phosphonic acid–Graphene oxide (AMPA–GO) adsorbents were prepared by the modified...     

Analytical Formulation for ϕ 4 Field Potential Dynamics

An analytical model for adding a space-dependent potential to the ? ⁴ field equation of motion is presented, by constructing a collective coordinate system for the solitary solutions of this model. The interaction of ? ⁴ solitons with a delta function potential barrier and also delta function potential well is investigated. Most of the characters of interaction are derived analytically while they are calculated by other models numerically. We will find that the behaviour of a solitary solution is like a point particle which is moved under the influence of a complicated effective potential. The effective potential is a function of the field initial conditions and also of parameters of the added potential.     

ZnO thin film characterization by X-ray reflectivity optimization using genetic algorithm and Fourier transformation

Zinc oxide (ZnO) thin film was fabricated by sol-gel spin coating method on glass substrate. X-ray reflectivity (XRR) and its optimization have been used for characterization and extracting physical parameters of the film. Genetic algorithm (GA) has been applied for this optimization process. The model independent information was needed to establish data analyzing process for X-ray reflectivity before optimization process. Independent information was exploited from Fourier transform of Fresnel reflectivity normalized X-ray reflectivity. This Fourier transformation (Auto Correlation Function) yields thickness of each coated layer on substrate. This information is a keynote for constructing optimization process. Specular X-ray reflectivity optimization yields structural parameters such as thickness, roughness of surface and interface and electron density profile of the film. Acceptable agreement exists between results obtained from Fourier transformation and X-ray reflectivity fitting.     

Enhanced Kerr nonlinearity in a quantized four-level graphene nanostructure

In this paper, a new model is proposed for manipulating the Kerr nonlinearity of right-hand circular probe light in a monolayer of graphene nanostructure. By using the density matrix equations and quantum optical approach, the third-order susceptibility of probe light is explored numerically. It is realized that the enhanced Kerr nonlinearity with zero linear absorption can be provided by selecting the appropriate quantities of controllable parameters, such as Rabi frequency and elliptical parameter of elliptical polarized coupling field. Our results may be useful applications in future all-optical system devices in nanostructures.     

Nitrite‐Selective Electrode Based On Cobalt(II) tert‐Butyl‐Salophen Ionophore

A series of polymeric nitrite‐selective electrodes containing a new lipophilic ionophore Co(II) tert‐butyl‐salophen is reported. The stability of Co(II) ionophores within a PVC‐based membrane was investigated by leaching experiments. Different membrane compositions were explored in order to reach the lowest possible limit of detection for a PVC‐based nitrite selective polymeric membrane electrode containing this ionophore. The optimal electrode showed a limit of detection of 2×10^?6 M and exhibited four orders of magnitude of discrimination over nitrate, chloride and bromide. The electrodes were evaluated in undiluted human urine and attest to the robustness of the ionophore.     

Thin‐Layer Chemical Modulations by a Combined Selective Proton Pump and pH Probe for Direct Alkalinity Detection

We report a general concept based on a selective electrochemical ion pump used for creating concentration perturbations in thin layer samples (～40 μL). As a first example, hydrogen ions are released from a selective polymeric membrane (proton pump) and the resulting pH is assessed potentiometrically with a second membrane placed directly opposite. By applying a constant potential modulation for 30 s, an induced proton concentration of up to 350 mM may be realized. This concept may become an attractive tool for in situ titrations without the need for sampling, because the thin layer eventually re‐equilibrates with the contacting bulk sample. Acid–base titrations of NaOH and Na₂CO₃ are demonstrated. The determination of total alkalinity in a river water sample is carried out, giving levels (23.1 mM ) comparable to that obtained by standard methods (23.6 mM ). The concept may be easily extended to other ions (cations, anions, polyions) and may become attractive for environmental and clinical applications.     

Synthesis of molecularly imprinted polymer as a sorbent for solid phase extraction of bovine albumin from whey,milk, urine and serum

This study describes the synthesis of molecularly imprinted polymers (MIPs) using bovine albumin as a template, 2-VP as a functional monomer, EGDMA as a cross-linker and AIBN as an initiator by radical polymerization. Non-imprinted polymers (NIPs) were prepared and treated with the same method, but in the absence of bovine albumin. The synthesized MIPs and NIPs were characterized on the basis of FTIR, TGA and DTA. An adsorption process (solid phase extraction, SPE) for the removal of bovine albumin using the fabricated MIPs and NIPs was evaluated under various conditions. Effective parameters on bovine albumin retention for example, pH, flow rate, nature of the eluent, the ionic strength, selectivity coefficient, and retention capacity were studied. Competition test implicates that the MIP adsorbents have the strongest specific retention and enrichment for bovine albumin respect to NIPs. The maximum adsorption of bovine albumin by the fabricated MIPs was 24 mg/g. The calibration curves were linear in the range of 20–200 mg/L of bovine albumin. The limit of detection (LOD), the calibration sensitivity, the relative standard deviation (RSD) and preconcentration factor under optimal experimental conditions were 2.44 and 25, respectively. The extraction of bovine albumin from blood serum, urine, whey and milk samples had a selectivity and enrichment property. In the actual experiment for real samples, recovery of ~ 80% was achieved.     

High‐Selective Tramadol Sensor Based on Modified Molecularly Imprinted Polymer?Carbon Paste Electrode with Multiwalled Carbon Nanotubes

We report here a novel carbon paste electrode (CPE) which is able to quantitatively sense tramadol under physiological conditions without sample preparation step. The selectivity of CPE is modified by applying molecularly imprinted polymer (MIP) technology. Multiwalled carbon nanotubes (MWCNTs) are incorporated in the structure of CPE to improve the conductivity and the ion‐to‐electron transduction. The electrode shows a wide dynamic linear range for tramadol from 10^?7 to 10^?3 M. The observed limit of detection and % RSD are 5×10^?7 M and 1.8 %, respectively. Finally, the proposed method is applied to determine tramadol in urine and medicinal tablets.     

Incorporation of Fe in mixed CoCu-alkoxide hollow sphere for enhancing the electrochemical water oxidation performance

The promotion of water electrolysis performance heavily relies on the development of affordable and efficient electrocatalytic materials for the oxygen evolution reaction (OER). In this study, ternary Fe-substituted CoCu-glycerate microspheres (CoCuFe(X)-Gly) with cobalt (Co):copper (Cu):iron (Fe) atomic ratio of 2:1-X:X (X = 0.15, 0.3, 0.5, 0.8) have been prepared through facile template-free solvothermal method to examine their performance as alkaline OER catalyst. The results suggested that Fe incorporation could enhance the OER activity, and all Fe-modified samples showed lower overpotential with faster kinetic, as revealed by their Tafel slope and electrochemical impedance spectroscopy (EIS) analysis. Among the fabricated samples, CoCuFe(0.5)-Gly possessed the smallest overpotential of 317 mV at 10 mA/cm² with 3.58-fold higher current density than that of Fe-free CoCu-Gly at the overpotential of 350 mV. Cyclic voltammetry (CV) disclosed that Fe incorporation imposed strong electronic interactions that facilitate the transformation of metal-glycerate surface into active oxyhydroxide species under anodic condition prevalent before oxygen evolution reaction. Using various characterization techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) method of surface area analysis, and thermogravimetric analysis (TGA), the physiochemical traits of samples have been carefully elucidated to determine the changes applied upon Fe substitution. Also, through Fe introduction, owing to the outward diffusion of ions to replace 2-propanol with glycerol, the solid microspheres partly become hollow which results in higher BET surface area and increase in accessible active sites. However, the evaluation of current density normalized by electrochemical active surface area (ECSA) indicates that the promotional effect of Fe was not solely related to the higher surface area but also because the intrinsic activity of Fe-modified samples has also been enhanced. The durability of optimal CoCuFe(0.5)-Gly catalyst has been examined using chronopotentiometry, chronoamperometry and potential cycling methods the findings of which suggest the good short-term and long-term stability of catalyst.