Development of nanomaterial chemosensors for toxic metal ions sensing

Heavy metal ions are harmful to aquatic life and humans owing to their high toxicity and non‐biodegradability, so their removal from wastewater is an important task. Therefore, this work focuses on designing suitable, simple and economical nanosensors to detect and remove these metal ions with high selectivity and sensitivity. Based on this idea, different types of mesoporous materials such as hexagonal SBA‐15, cubic SBA‐16 and spherical MCM‐41, their chloro‐functionalized derivatives, as well as 4‐(4‐nitro‐phenylazo)‐naphthalen‐1‐ol (NPAN) azo dye have been synthesized, with the aim of designing some optical nanosensors for metal ions sensing applications. The mentioned azo dye has been anchored into the chloro‐functionalized mesoporous materials. The designed nanosensors were characterized using scanning and transmission electron microscopy as well as Fourier transform infrared and UV–visible spectral analysis, nitrogen adsorption–desorption isotherms, low‐angle X‐ray diffraction and thermogravimetric analyses. Their optical sensing to various toxic metal ions such as Cd (II), Hg (II), Mn (II), Fe (II), Zn (II) and Pb (II) at different values of pH (1.1, 4.9, 7 and 12) was investigated. The optimization of experimental conditions, including the effect of pH and metal ion concentration, was examined. The experimental results showed that the solution pH had a major impact on metal ion detection. The optical nanosensors respond well to the tested metal ions, as reflected by the enhancement in both absorption and emission spectra upon adding different concentrations of the metal salts and were fully reversible on adding ethylene diamine tetra acetic acid or citric acid to the formed complexes. High values of the binding constants for the designed nanosensors were observed at pHs 7 and 12, confirming the strong chelation of different metals to the nanosensor at these pHs. Also, high binding constants and sensitivity were observed for NPAN‐MCM‐41 as a nanosensor to detect the different metal ions. From the obtained results, we succeeded in transforming the harmful azo dye into an environmentally friendly form via designing of the optical nanosensors used to detect toxic metal ions in wastewater with high sensitivity.     

Geometry of the common dynamics of Pisot substitutions with the same incidence matrix

Any Pisot substitution can be associated with a bounded set with interesting properties, called the Rauzy fractal. This set is obtained by projection of the broken line associated with an infinite fixed point. Two substitutions having the same incidence matrix can have different Rauzy fractals. We show that under weak conditions, the intersection of these two fractals has strictly positive measure, and can also be generated by a substitution.     

Novel Uncatalyzed Hydrocyanation of Ketones utlizing Tetrachlorosilane–Potassium Cyanide Reagent

A combination of tetrachlorosilane and potassium cyanide (in situ trichlorosilyl cyanide) was found to work efficiently for hydrocyanation of ketones to afford the corresponding cyanohydrins in high yield under mild conditions.     

Molecularly Imprinted Impedimetric Sensor for Determination of Mycotoxin Zearalenone

The mycotoxin zearalenone (ZEA) prompts reproductive toxicity due to its strong estrogenic effects. In this work, an electrochemical sensor for determination of ZEA was developed by electropolymerization of a molecularly imprinted poly (o‐phenylenediamine) (PPD) film on screen‐printed gold electrode (SPGE) surface. The sensor was examined by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) using K₃[Fe(CN)₆]/K₄[Fe(CN)₆] as redox probe. The molecularly imprinted polymer (MIP) sensor showed a wide determination range from 2.50 to 200.00 ngmL^?1 for ZEA. The Limit of detection (LOD) was calculated to be 0.20 ngmL^?1, based on the signal to noise (S/N) ratio equal to 3.0. The sensor displayed good repeatability, with RSD values≤4.6 %, and maintained 93.2 % of its initial response after storage for 10 days in air at room temperature. The developed method was successfully applied for the determination of ZEA in corn flakes with mean recoveries ranged from 96.2 % to 103.8 % and RSDs within the interval of 2.1 % to 3.8 %.     

Study of the usability of sinusoidal function heat flux based on enthalpy-porosity technique for PCM-related applications

Journal of Thermal Analysis and Calorimetry - The present study summarizes a two-dimensional (2D) numerical simulation of a phase change material (PCM) melting/solidification processes in a square...     

Facile synthesis of new imidazoles from direct reaction of 2,3‐diamino‐1,4‐naphthoquinone with aldehydes

New imidazoles were easily prepared from 2,3‐diamino‐1,4‐naphthoquinone and stoichiometric quantities of the appropriate aldehydes in dimethyl sulfoxide as a solvent. The reaction proceeded for few hours. The procedure can be generalized to different classes of aldehydes. 2‐Methyl‐1H‐naphtho[2,3‐d]imidazole‐4,9‐dione was also obtained in good yield during refluxing of 2,3‐diaminonaphthoquinone in acetic acid. The structure of the newly synthesized imidazoles was extensively investigated using NMR experiments. J. Heterocyclic Chem., (2011).     

Effect of mordenite dealumination on the structure of encapsulated molybdenum catalysts

A series of dealuminated mordenites treated under various conditions of acid leaching was impregnated in an aqueous solution of ammonium heptamolybdate to achieve a loading of 12 wt% Mo. These samples were characterized by XRD, UV-DRS, N(2) adsorption, TGA, and FTIR techniques. Special attention was given to the far-IR measurements and IR study of surface hydroxyl groups before and after dealumination. A polymolybdate species was recognized by the appearance of bands at 344, 319, and 236 (229) cm(-1) due to the vibrational modes of delta(Mo-O) and delta(Mo-O-Mo), respectively. The disappearance of the 236 cm(-1) band as well as that at 344 cm(-1) in favor of the 319 cm(-1) band, with the dealumination, was related to the high dispersion of Mo species in the produced mesopore surface assessed by the N(2) adsorption at 77 K. No bands due to bulk MoO(3) were detected from the IR and XRD results. A strong interaction between Mo species and dealuminated mordenite surfaces (OH groups) was recognized by a decrease in intensity and a marked shift of the band at 3745 to 3727 cm(-1) as well as the appearance of a new band at 3668 cm(-1). The latter band was produced by the interaction of the framework Al-OH with Mo species. The BET surface areas of Mo-dealuminated mordenite samples were higher than the corresponding Mo-free ones. The diffuse reflectance measurements suggested that Mo cations are predominantly present as an octahedrally coordinated Mo(6+), along with some tetrahedral Mo(6+). New spectral features as a consequence of dealumination events in the far-IR range were evaluated and discussed.     

Highly selective reduction of acyclic beta-alkoxy ketones to protected syn-1,3-diols

[reaction: see text] The conversion of 1-(2-methoxyethoxy)ethyl-protected beta-hydroxy ketones to syn-1,3-ethylidene acetals is effected by Et(3)SiH and SnCl(4). This reaction is proposed to proceed via a cyclic oxocarbenium ion intermediate and provides the products in yields that range from 69 to 94% and with diastereoselectivities that are >200:1.     

Inversion of guided-wave dispersion data with application to borehole acoustics

The problem of inferring unknown geometry and material parameters of a waveguide model from noisy samples of the associated modal dispersion curves is considered. In a significant reduction of the complexity of a common inversion methodology, the inner of two nested iterations is eliminated: The approach described does not employ explicit fitting of the data to computed dispersion curves. Instead, the unknown parameters are adjusted to minimize a cost function derived directly from the determinant of the boundary condition system matrix. This results in an efficient inversion scheme that, in the case of noise-free data, yields exact results. Multimode data can be simultaneously processed without extra complications. Furthermore, the inversion scheme can accommodate an arbitrary number of unknown parameters, provided that the data have sufficient sensitivity to these parameters. As an important application, we consider the sonic guidance condition for a fluid-filled borehole in an elastic, homogeneous, and isotropic rock formation for numerical forward and inverse dispersion analysis. We investigate numerically the parametric inversion with errors in the model parameters and the influence of bandwidth and noise, and examine the cases of multifrequency and multimode data, using simulated flexural and Stoneley dispersion data.     

A matrix formulation for the dynamic analysis of planar mechanisms using point coordinates and velocity transformation

This paper presents a matrix formulation for the dynamic analysis of planar mechanisms consisting of interconnected rigid bodies. The formulation initially uses the rectangular Cartesian coordinates of an equivalent constrained system of particles to define the configuration of the mechanical system. This results in a simple and straightforward procedure for generating the equations of motion. The equations of motion are then derived in terms of relative joint coordinates through the use of a velocity transformation matrix. The velocity transformation matrix relates the relative joint velocities to the Cartesian velocities. For the open-loop case, this process automatically eliminates all of the non-working constraint forces and leads to an efficient integration of the equations of motion. For the closed-loop case, suitable joints should be cut and few cut-joints constraint equations should be included for each closed loop. Two examples are used to demonstrate the generality and efficiency of the proposed method.