Fe+3-Montmorillonite K10, as effective,eco-friendly,and reusable catalyst for the synthesis of bis(1H-indol-3-yl)methanes under grinding condition

Russian Journal of General Chemistry - Bis(indoyl)methanes have been synthesized via electrophilic reaction of indole and aldehydes in excellent yields under mild reaction conditions in the...     

Biomimetic Sensor for Dobutamine Employing Nano‐ TiO2/Nafion/Carbon Nanoparticles Modified Electrode

A novel voltammetric biosensor based on nano‐TiO₂/nafion/carbon nanoparticles modified glassy carbon electrode (TiO₂/N/CNP/GCE) was developed for the determination of dobutamine (DBA). Characterization of the surface morphology and property of TiO₂/N/CNP layer was carried out by the scanning electron microscopy and atomic force microscopy. The electrochemical performance of the modified electrode was investigated by means of the cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy techniques. Effective experimental variables, such as the scan rate, pH of the supporting electrolyte, drop size of the casted modifier suspension and accumulation conditions of DBA on the surface of TiO₂/N/CNP/GCE were optimized. Under the optimized conditions, a significant electrochemical improvement was observed toward the electro‐oxidation of DBA on the surface of TiO₂/N/CNP/GCE compared to the bare GCE. Under the optimized conditions, a wide linear dynamic range (6 nM–1 µM) with a low detection limit of 2 nM for DBA was resulted. The prepared modified electrode shows high sensitivity, stability and good reproducibility in the determination of DBA concentrations. Satisfactory results were obtained for DBA analysis in the pharmaceutical and clinical preparations using TiO₂/N/CNP/GCE.     

KAl(SO4)2 · 12H2O as a Recyclable Lewis Acid Catalyst for Synthesis of Some Amidoalkyl Naphthols Under Solvent-Free Conditions

A general and practical one-pot synthesis of amidoalkyl naphthols derivatives using KAl(SO₄)₂ · 12H₂O as catalyst is described. This method provides several advantages such as short reaction times, good yields, and simple workup procedure.     

Nickel-aluminum layered double hydroxide as a nanosorbent for selective solid-phase extraction and spectrofluorometric determination of salicylic acid in pharmaceutical and biological samples

The nickel-aluminum layered double hydroxide (Ni-Al LDH) was synthesized by a simple co-precipitation method and used as a solid-phase extraction (SPE) sorbent for separation and pre-concentration of trace levels of salicylic acid (SA) from aqueous solutions. Extraction of analyte is based on the adsorption of salicylate ions on the Ni-Al (NO₃⁻) LDH and/or their exchanging with LDH interlayer NO₃⁻ ions. The retained analyte on the LDH was stripped by 3 mol L⁻¹ NaOH solution and its concentration was subsequently determined spectrofluorometrically at λ_em = 400 nm with excitation at λ_ex = 270 nm. Various parameters affecting the extraction efficiency of SA on the Ni-Al (NO₃⁻) LDH, such as pH, amount of nano-sorbent, sample loading flow rate, elution conditions, sample volume and matrix effects were investigated. In the optimum experimental conditions, the limit of detection (3 s) and enrichment factor were 0.12 μg L⁻¹ and 40, respectively. The relative standard deviation (RSD) for six replicate determinations of 10 μg L⁻¹ SA was 2.3%. The calibration graph using the pre-concentration system was linear in the range of 0.3-45 μg L⁻¹ with a correlation coefficient of 0.9985. The optimized method was successfully applied to the determination of SA in blood serum, willow leaf and aspirin tablet.     

Electrodeposition of Copper Oxide Nanoparticles on Precasted Carbon Nanoparticles Film for Electrochemical Investigation of anti‐HIV Drug Nevirapine

This work describes the development of a novel electrochemical sensor based on electrodeposition of copper oxide nanoparticles onto carbon nanoparticle (CNP) film modified electrode for the analysis of the anti‐HIV drug, nevirapine (NEV). The electrochemical experiments were performed using linear sweep and cyclic voltammetry. Atomic force microscopy was applied for surface characterization of the deposited modifier film (CuO‐CNP) on glassy carbon electrode (GCE). No oxidation peak was observed for NEV on the bare GCE, but both CNP‐GCE and CuO‐CNP‐GCE showed a distinctive anodic response towards NEV with considerable enhancement (276‐fold and 350‐fold, respectively) compared to CuO‐GCE. The mechanism of the electrocatalytic process on the modified electrode surface was investigated by cyclic and linear sweep voltammetry at various potential sweep rates and pHs of the buffer solutions. The modified electrode exhibited linear dynamic range in three concentration intervals (0.1–0.8, 1–10 and 10–100 µM) with a detection limit of 66 nM. The stability, reproducibility, and repetitive usability exhibited by the proposed modified electrode are good enough to make it a suitable sensor for the determination of NEV in real samples with complex matrices such as human blood serum.     

Numerical evaluation of various levels of singular integrals, arising in BEM and its application in hydrofoil analysis

The sound implementation of the boundary element method (BEM) is highly dependent on an accurate numerical integration of singular integrals. In this paper, a set of various types of singular domain integrals with three-dimensional boundary element discretization is evaluated based on a transformation integration technique. In the BEM, the integration domain (body surface) needs to be discretized into small elements. For each element, the integral I(x^p, x) is calculated on the domain dS. Several types of integrals IB_α and IC_α are numerically and analytically computed and compared with the relative error. The method is extended to evaluate singular integrals which arise in the solution of the three-dimensional Laplace’s equation. An example of the elliptic hydrofoil is performed to study the physical accuracy. The results obtained using both numerical and analytical methods are shown in good agreement with the experimental data.