A simple,rapid and sensitive method based on modified multiwalled carbon nanotube for preconcentration and determination of lead ions in aqueous media in natural pHs

In this study, multiwalled carbon nanotube (MWCNT) was modified by the pyridine group using a silane agent and characterized by infrared spectroscopy (IR), thermal analysis (TG/DTA), and elemental analysis (CHN) and scanning electron microscopy (SEM). The application of this sorbent was investigated in determination of lead ions in aqueous samples, using flame atomic absorption spectrometry (FAAS). Through this study, different parameters such as pH and sample flow rate on adsorption process and eluent concentration, volume and flow rate were optimized. The limit of detection (LOD), the relative standard deviation and the recovery of the method were 2 ng mL^?1, 1.3% and 99.7%, respectively. Two standard reference materials (NIST 1571 and NIST 1572) were used to verify accuracy of this method. Finally, the sorbent was successfully applied for extraction and determination of low levels of Pb(II) ions in aqueous samples.     

Preparation of an efficient catalyst through injection of CuI on modified poly (styrene-co-maleic anhydride) and theoretical investigation of the structural and electronic properties of catalyst

A novel polymer supported [poly (styrene-co-maleic imide) (SMI)]Cu(I) nano-particles was prepared via in situ reaction of 4-amino-5-methyl-4H-1,2,4-triazole-3-thione with [poly (styrene-co-maleic anhydride)] (SMA) along with immobilization of CuI. These nano-particles were fully characterized by using scanning electron microscopy (SEM), energy dispersive spectroscopy analysis, Xray (EDAX), inductively coupled plasma (ICP) analysis, ¹H NMR and FT-IR techniques. Moreover, the structural and electronic features of metal–ligand interactions in the complex model of polymer-supported copper nanocatalyst were assessed using density functional theory calculations. The catalytic activity of these supported Cu(I) nonoparticles was examined in one of the classiest name reaction so–called “click reaction” which is coined K. B Sharpless for the regioselective synthesis of 1,2,3-triazole derivatives using a multicomponent reaction (MCR) involving benzyl halides, sodium azide and terminal alkynes in water as a green solvent. This heterogeneous catalyst showed excellent catalytic activity and was separated by simple filtration and was used at least in five consecutive runs without a significant decrease in its activity.     

A microextraction procedure based on a task‐specific ionic liquid for the separation and preconcentration of lead ions from red lipstick and pine leaves

First, the extraction and preconcentration of ultratrace amounts of lead(II) ions was performed using microliter volumes of a task‐specific ionic liquid. The remarkable properties of ionic liquids were added to the advantages of microextraction procedure. The ionic liquid used was trioctylmethylammonium thiosalicylate, which formed a lead thiolate complex due to the chelating effect of the ortho‐positioned carboxylate relative to thiol functionality. So, trioctylmethylammonium thiosalicylate played the roles of both chelating agent and extraction solvent simultaneously. Hence, there is no need to use a ligand. The main parameters affecting the efficiency of the method were investigated and optimized. Under optimized conditions, this approach showed a linear range of 2.0–24.0 ng/mL with a detection limit of 0.0010 ng/mL. The proposed method was applied to the extraction and preconcentration of lead from red lipstick and pine leaves samples prior to electrothermal atomic absorption spectroscopic determination.     

Computational Study on the Structural and Electronic Properties of Multi-Nuclear Palladium and Nickel Silyl Complexes via DFT and QTAIM Approaches

In this research, we have concentrated on the survey of ability of density functional methods and also modern semi-empirical approaches to reproduce the crystal structure of a binuclear silyl nickel complex and a trinuclear palladium silyl complex. In the structural analysis of the aforesaid nickel and palladium complexes, we have also interested to investigate the possibility of Si-Si bond formation between SiH₂ and μ-SiH moieties from the structural and electronic viewpoints. Comparison of our calculated structural parameters of aforementioned complexes with the available X-ray crystallographical data reveals that both functionals (B3LYP and M062X) can well reproduce X-ray structure of the complex with a near accuracy while the PM6-D2 semi-empirical calculated values are not in a reliable agreement with the crystallographical data. In the next step, we assessed the nature of interactions between palladium and nickel metal ions with silyl ligands via Quantum Theory of Atoms in Molecule (QTAIM) computations. Furthermore, we have analyzed the possibility of Si-Si bond formation in the aforementioned complexes by means of topological electronic indices. Strictly speaking, QTAIM calculations have been performed to explore the electronic density, its laplacian and electronic energy density at some key bond critical points to interpret the structural features of aforesaid complexes from the electronic point of view.     

Solvent selection in ultrasonic-assisted emulsification microextraction: Comparison between high- and low-density solvents by means of novel type of extraction vessel

There are numerous published reports about dispersive liquid phase microextraction of the wide range of substances, however, till now no broadly accepted systematic and purpose oriented selection of extraction solvent has been proposed. Most works deal with the optimization of available solvents without adequate pre-consideration of properness. In this study, it is tried to compare the performances of low- and high-density solvents at the same conditions by means of novel type of extraction vessel with head and bottom conical shape. Extraction efficiencies of seven basic pharmaceutical compounds using eighteen common organic solvents were studied in this work. It was much easier to work with high-density solvents and they mostly showed better performances. This work shows that although exact predicting the performance of the solvents is multifaceted case but the pre-consideration of initial selection of solvents with attention to the physiochemical properties of the desired analytes is feasible and promising. Finally, the practicality of the method for extraction from urine and plasma samples was investigated.     

Isocyanide-based four-component synthesis of ferrocenyl 1,5-disubstituted tetrazoles

A convenient four-component synthesis of ferrocenyl tetrazoles by the reaction of ferrocenecarboxaldehyde, isocyanides, azidotrimethylsilane and alkyl or aryl amines in CH₂Cl₂ at room temperature is reported.     

Isocyanide‐Based Three‐Component Synthesis of Pyrano‐pyrido‐quinoxalines

Pyrano‐pyrido‐quinoxaline derivatives were synthesized in good yields by a three‐component reaction of isocyanides, dialkyl acetylenedicarboxylates, and pyrido[1,2‐a]quinoxaline‐triones in DMF at 100°.     

A DFT study on the complexation of La3+ ion with malonamide and diglycolamide ligands

The main goal of this research is to investigate the structural and thermochemical aspects of complexation between La³⁺ with tetrapropyl malonamide (TPMA) and tetrapropyl diglycolamide (TPDGA) ligands via density functional theory (DFT) methods. In this respect, the structural parameters of [La-TPMA]³⁺ and [La-TPDGA]³⁺ complexes have been calculated and compared with the available X-ray crystallographic data. These comparisons revealed that both calculated structural values using B3LYP and M06 are in a reliable agreement with X-ray crystal structure with a near accuracy. In the next step, the more efficiency of diglycolamides in comparison with malonamides in the extraction of La³⁺ have been analyzed by calculating thermochemical properties of the complexation. It should be stated that this issue has been observed in many experimental elucidations. In the next step, the inclusion of solvent effects on thermodynamical properties of complexation has been evaluated via polarized continuum model (PCM) calculations. In this context, enthalpy and Gibbs free energy changes have been determined in the presence of three solvents, chloroform, toluene and n-hexane. Our obtained results demonstrate that using n-hexane as solvent is more favorable thermodynamically than chloroform and toluene that confirms the previously observed experiments. Finally, the bond orders of some selected key bonds in TPMA and TPDGA ligands and their corresponded La³⁺ complexes have been evaluated comparatively to analyze the electronic features of coordination in [La-TPMA]³⁺ and [La-TPDGA]³⁺ complexes.     

Fe3O4@SiO2‐PANI‐Au Nanocomposite Prepared for Electrochemical Determination of Quercetin in Food Samples and Biological Fluids

A new electrochemical sensor based on Fe₃O₄@SiO₂‐PANI‐Au nanocomposite was fabricated for modification of glassy carbon electrode (Fe₃O₄@SiO₂‐PANI‐Au GCE). The Fe₃O₄@SiO₂‐PANI‐Au nanocomposite was characterized by TEM, FESEM‐EDS‐Mapping, XRD, and TGA methods. The Fe₃O₄@SiO₂‐PANI‐Au GC electrode exhibited an acceptable sensitivity, fast electrochemical response, and good selectivity for determination of quercetin. Under optimal conditions, the linear range for quercetin concentrations using this sensor was 1.0×10^?8 to 1.5×10^?5 mol L^?1, and the limit of detection was 3.8×10^?9 mol L^?1. The results illustrated that the offered sensor could be a possible alternative for the measurement of quercetin in food samples and biological fluids.