Application of a new nanoporous sorbent for extraction and pre-concentration of lead and copper ions

The authors describe a method for the trace determination of copper (II) and lead (II) in water and fish samples using solid-phase extraction via siliceous mesocellular foam functionalised by dithizone. Siliceous mesocellular was functionalised with dithizone, and the resulting sorbent was characterised by scanning electron microscopy, surface area analysis, thermogravimetric/differential thermal analysis and FTIR. Following solid-phase extraction of target ions by the sorbent, copper and lead ions were quantified by flame atomic absorption spectrometry. Factors affecting the sorption and desorption of target ions by the sorbent were evaluated and optimised. The calibration plot is linear in the 1 – 500 μg L^?1 copper (II) and 3–700 μg L^?1 lead (II) concentration range. The relative recovery efficiency in real sample analysis is in the range from 96 to 102%, and precision varies between 1.7 and 2.8%. It is should be noted that the limits of detection for the copper and lead analysis were 0.8 and 1.6 μg L^?1, respectively. Also, the adsorption capacities for copper and lead ions were 120 and 160 mg g^?1, respectively. The obtained pre-concentration factor for the lead and copper ions by the proposed solid-phase extraction was 75. The method was successfully applied to the determination of low levels of copper (II) and lead (II) in tap, Caspian sea, Persian gulf and lake water and also their detection in fish samples.     

Synthesis and characterization of novel polymeric organic–inorganic complex framework based on sodium 2,4-dioxo-6-aryl-3-oxa-bicyclo[3.1.0]hexane-1,5-dicarboxylate (SDAOBDC) with three-dimensional hybrid networks

Synthesis and characterization of novel polymeric organic–inorganic complex based on sodium 2,4-dioxo-6-aryl-3-oxa-bicyclo[3,1,0]hexane-1,5-dicarboxylate with three-dimensional hybrid networks were reported. The polymeric complex was crystallizing in the triclinic, space group P1. As determined by X-ray single-crystal analysis, in this compound each Na ion is coordinated by six O atoms: two from different carbonyl oxygen atom of carboxylic acid groups, two from bridged carbonyl oxygen atom of carboxylic acid groups, one from the carbonyl oxygen atom of cyclic anhydride and one from water molecule. The structure characterization was done by means of IR, ¹H, ¹³C NMR, UV–Vis spectroscopies, Tg, flame photometry and X-ray crystallographic analysis.     

An investigation on ordered algebraic hyperstructures

In this paper, we present some basic notions of simple ordered semihypergroups and regular ordered Krasner hyperrings and prove some results in this respect. In addition, we describe pure hyperideals of ordered Krasner hyperrings and investigate some properties of them. Finally, some results concerning purely prime hyperideals are proved.     

Expedient Catalytic Access to Knöevenagel Condensation Using Sr<Subscript>3</Subscript>Al<Subscript>2</Subscript>O<Subscript>6</Subscript> Nanocomposite in Room Temperature

Sr₃Al₂O₆ nanocomposite was prepared by sol gel method using aluminum isopropoxide, strontium nitrate, acetylacetone and polyethylene glycol as template, followed by calcination at 900 °C. This nanocomposite was characterized by various techniques including X-ray powder diffraction, infrared spectroscopy, elemental analysis, scanning transmission microscope and transmission electron microscope. It was found that Sr₃Al₂O₆ nanocomposite successfully catalyzes the Knöevenagel condensation of aromatic aldehydes with malononitrile in room temperature in ethanol. Expedient access to the corresponding Knöevenagel adducts in moderate to high yields within 6 min is promising. The recovered catalyst was reused for three times without significant loss of activity.     

Synthesis of poly(2‐hydroxyethyl methacrylate)‐based molecularly imprinted polymer nanoparticles containing timolol maleate: morphological,thermal, and drug release along with cell biocompatibility studies

This work was aimed to synthesize and characterize poly(2‐hydroxyethyl methacrylate) [poly (HEMA)]‐based molecularly imprinted polymer nanoparticles (MIP NPs) containing timolol maleate (TM) via precipitation polymerization. The molecular structures of the MIP and non‐imprinted polymer (NIP) NPs were compared by means of Fourier transform infrared spectroscopy. The morphological observations by using scanning electron microscopy and transmission electron microscopy confirmed the formation of MIP NPs as small as 128 nm in average diameter with appropriate synthesis conditions. Thermal behaviors of the samples were also studied by the use of thermogravimetric analysis and differential scanning calorimetry. By considering a series of key factors such as monomer : template ratio, cross‐linker type, pH, and temperature, the sample with promising characteristics was found to be that of HEMA : TM ratio of 10:1, 40 mmol of ethylene glycol dimethacrylate as cross‐linker, and polymerization temperature of 60°C in acetonitrile as porogenic solvent. Furthermore, the ultraviolet‐visible (UV‐vis) spectrophotometry results proved a controlled release of TM from the MIP NP samples compared with NIP ones at extended periods. Moreover, the cytotoxicity of the MIP and NIP NPs samples was evaluated on mesenchymal stem cells, and the obtained observations showed that they had no adverse side effect on the living cells; especially the surface of the MIP NPs sample depicted highly cell's biocompatibility. Finally, the outcomes from designed different experiments conducted us that the HEMA‐based MIP NPs have great potential as an ocular nanocarrier for TM delivery. Copyright © 2016 John Wiley & Sons, Ltd.     

Selective and Sensitive Determination of Uranyl Ions in Complex Matrices by Ion Imprinted Polymers‐Based Electrochemical Sensor

We report on the design of a UO₂²⁺‐selective electrode based on the use of UO₂²⁺ imprinted polymer nanoparticles (IP‐NPs), and its application for the differential pulse adsorptive cathodic stripping voltammetry determination of uranyl ions. A carbon paste electrode was modified with the IP‐NPs, and differential pulse adsorptive cathodic stripping voltammetry was applied as the detection technique after open‐circuit sorption of UO₂²⁺ ions. The modified electrode responses to UO₂²⁺ was linear in the 0.1 µg L^?1 to 10 µg L^?1 and in the 0.01 mg L^?1 to 10 mg L^?1. The method detection limit of the sensor was 0.03 µg L^?1.     

Universal adjacency matrices with two eigenvalues

Consider a graph Γ on n vertices with adjacency matrix A and degree sequence (d₁,…,d_n). A universal adjacency matrix of Γ is any matrix in Span {A,D,I,J} with a nonzero coefficient for A, where and I and J are the n×n identity and all-ones matrix, respectively. Thus a universal adjacency matrix is a common generalization of the adjacency, the Laplacian, the signless Laplacian and the Seidel matrix. We investigate graphs for which some universal adjacency matrix has just two eigenvalues. The regular ones are strongly regular, complete or empty, but several other interesting classes occur.     

The influence of processing parameters on the fabrication of Si3N4 wires

Silicon nitride (Si₃N₄) wires have been prepared by means of carbothermal reduction followed by the nitridation (CTRN) of silica gel containing ultrafine decomposed saccharose. The influence of temperature of reaction and mass ratio of carbon to silicon $ \left( \frac{C}{Si} \right) $ on the synthesis of Si₃N₄ wires were studied. The presence of nitrogen gas in the pores of gel at high temperature starts the CTRN reaction leading to the formation of Si₃N₄ wires. The results show that the Si₃N₄ was fully formed with two kinds of morphologies including globular and wire with a width of 100–500 nm and length of several microns at sintering temperature of 1,400 °C by employing the mass ratio of $ \frac{C}{Si} \; = \;0.5 $ . The infrared adsorption of the wires exhibits absorption bands related to the absorption peaks of Si–N bond of Si₃N₄. The thermal analysis results reveal that carbothermal nitridation reaction was completed at temperature of 1,400 °C.     

Beam propagation analysis of a multi beam FSO system with partially flat-topped laser beams in turbulent atmosphere

In this paper, the propagation properties of partially coherent flat-topped (PCFT) laser beams in multi-beam FSO communication links are analyzed. Analytical expressions for the average intensity and beam width of PCFT multi beams are derived based on extended Huygens–Fresnel principle by considering the effects of turbulent atmosphere. Also power in bucket (PIB) is calculated numerically based on analytical expression of average intensity. It is revealed that PCFT multi beams can be converted into a Gaussian beam after sufficiently large propagation distance. It is found that correlation length, order of flatness and beams’ separation distances in the source plane have strong effects on minimum distance required for this conversion as well as beam width and PIB. Obtained results are confirmed and illustrated with numerical examples and resulted graphs.