Use of the diffusion gradient thin film method to measure trace metals in fresh waters at low ionic strength

The diffusion gradients in thin films (DGT) method was investigated and used to measure trace metal concentrations in river water. The principle of DGT is that trace metal ions diffuse through a thin polyacrylamide gel film (the diffusion gel layer) and are subsequently immobilised and concentrated on a layer of Chelex-100 resin embedded in another polyacrylamide gel film (the resin gel layer). These layers are mounted in a plastic holder, which exposes a fixed area of the diffusion gel layer to the water being monitored. Replacement of the normal agarose cross-linked diffusion gel with bisacrylamide cross-linked gel altered the ion uptake properties of DGT. The bisacrylamide cross-linked gel weakly, and with little selectivity, bound metal ions prior to their irreversible binding to Chelex-100. Trace metal ion uptake by these DGT devices was thus dependent on ionic strength and temperature, although the ionic strength effect is relatively small for most natural waters and negligible in sea water. The concentrations of Cd, Co, Cu, Ni, Pb, and Zn in the Water of Leith, an urban stream in Dunedin, New Zealand, were measured by DGT and the results compared with total dissolved concentrations of these metals measured in conventional (bottle) samples collected in parallel with the DGT monitoring. Greater than 90% of the total dissolved Cd and Zn; 20-40% of the total dissolved Co, Ni, and Pb; and 5% of the total dissolved Cu was available to the DGT method.     

A new green method for the synthesis of silver nanoparticles and their antibacterial activities against gram‐positive and gram‐negative bacteria

This study aims to evaluate the capability of Ageratum conyzoides and Mikania micrantha extracts to synthesize silver nanoparticles (AgNPs) and their antibacterial capability against gram‐positive and gram‐negative bacteria. Several properties of the synthesized AgNPs, including plasmonic, biomolecule bonding, shape, size, and antibacterial, were investigated. Ultraviolet–visible (UV–vis) spectroscopy was employed for characterizing their plasmonic properties. Functional groups on the produced AgNPs were investigated by Fourier‐transform infrared (FT‐IR) spectroscopy. The size and shape of the AgNPs were identified using the field‐emission scanning electron microscopy (FESEM). Inhibition zone measurement was carried out for evaluating the antibacterial capability. This study showed that the extracts of A. conyzoides and M. micrantha were able reducing agents as evidenced by the formation of the spherical AgNPs. UV–vis spectroscopy, FT‐IR spectroscopy, and FESEM confirmed the physicochemical characteristics of AgNPs. AgNPs that were synthesized using M. micrantha were slightly smaller than those produced using A. conyzoides. In general, the present work establishes that the synthesized AgNPs have antibacterial capability depending on their size and synthesis procedure.     

A Simple and Efficient Process for the Synthesis of Novel Heterocycles Containing Benzofuran Moiety Using Thiocarbohydrazide as a Precursor

A simple and efficient process for the synthesis of novel heterocycles starting from thiocarbohydrazide was reported. Reaction of 2‐acetylbenzofuran ( 1 ) and thiocarbohydrazide ( 2 ) in ethanol containing acetic acid produced the corresponding thiocarbohydrazone 3 in 86% yield. Reaction of 3 and isatin ( 4 ) gave N,2‐bis(2‐oxoindolin‐3‐ylidene)hydrazine‐1‐carbothiohydrazine ( 6 ) in 65% yield, rather than the expected product, 3‐[(1‐methyl‐1‐benzofur‐2‐ylmethylidene)amino]‐1‐{[(3Z)‐2‐oxo‐2,3‐dihydro‐1H‐indol‐3‐ylidene]amino}thiourea ( 5 ). Reaction of 2‐((3‐(benzofuran‐2‐yl)‐1‐phenyl‐1H‐pyrazol‐4‐yl)methylene)hydrazine carbothioamide ( 9 ) and chloroacetic acid or hydrazonoyl chloride 11 in basic medium gave (Z)‐2‐((E)‐((3‐(benzofuran‐2‐yl)‐1‐phenyl‐1H‐pyrazol‐4‐yl)methylene)hydrazono)thiazolidin‐4‐one ( 10 ) or 2‐((E)‐2‐((3‐(benzofuran‐2‐yl)‐1‐ phenyl‐1H‐pyrazol‐4‐yl)methylene)hydrazinyl)‐4‐((E)‐(4‐fluorophenyl)diazenyl)‐5‐methylthiazole ( 12 ) in 62% or 74%, respectively.     

DFT and TD-DFT calculations on thieno[2,3-b]indole-based compounds for application in organic bulk heterojunction (BHJ) solar cells

Research on Chemical Intermediates - Eight novel organic compounds with donor–π–acceptor (D–π–A) structure were designed for use as donors in organic bulk...     

A New Trend on Biosensor for Neurotransmitter Choline/Acetylcholine—an Overview

Technology always has been an indispensible part in the development of biosensors. The performance of biosensors is being tremendously improved using new materials as transducer as well as binding material in their construction. The use of new materials allowed innovation on transduction technology in biosensor preparations. Because of the submicron dimensions of these sensors, simple and rapid analyses in vitro as well as in vivo are now possible. Portable instruments capable of analysing multiple components are becoming available, too. Sensors that provide excellent temporal and spatial resolution for in vivo monitoring such as for measurement of neurotransmitters have become prominent. The interest to improve the stability, sensitivity and selectivity of the sensors is paramount. This study tries to give an overview of the present status of the material-based biosensor design and new generation of choline/acetylcholine neurotransmitter biosensors.     

Study on a novel thermoset nanocomposite form DGEBA–cycloaliphatic diamine and metal nanoparticles

The thermo-physical properties of diglycidyl ether of bisphenol A (DGEBA)/isophoronediamine (IPDA) with iron nanoparticles were investigated using DSC, DMT, and TG analysis. Because of the higher values of the glass transition, it is recognized that the optimum behavior of the three-component system corresponds to the 10% loading level of iron nanoparticles. The addition of iron nanoparticles into the epoxy matrix resulted in a significant increment in the storage modulus and crosslink density. Also, the DGEBA/IPDA/10% iron nanoparticles showed an enhanced thermal stability owing to the introduction of iron nanoparticles as reinforcing filler. Curing reaction of DGEBA/IPDA with 10% iron nanoparticles was investigated by DSC at dynamic mode. Activation energy was calculated based on Kissinger method (66.52 kJ mol^?1). Also, the advanced isoconversional method is utilized to describe the curing reaction process. In the dynamic DSC analyses, the curing kinetics could be successfully described with the two-parameter autocatalytic model (Sěsták–Berggren equation) and the overall reaction order was about 2.78.     

Radical copolymerization of acrylonitrile with 2,2,2‐trifluoroethyl acrylate for dielectric materials: Structure and characterization

Radical copolymerization based on acrylonitrile (AN) and 2,2,2‐Trifluoroethyl acrylate (ATRIF) initited by AIBN was investigated in acetonitrile solution. The resulting poly(AN‐co‐ATRIF) copolymers were characterized by ¹H, ¹³C, and ¹⁹F NMR and IR spectroscopy, and size exclusion chromatography (SEC). Their compositions were assessed by ¹H NMR. The kinetics of radical copolymerization of AN with ATRIF was investigated from sereval experiments achieved at 70 °C from initial [AN]₀/[ATRIF]₀ molar ratios ranging between 20/80 and 80/20 and was enabled to determine the reactivity ratios of both comonomers. From the monomer—polymer copolymerization curve, the Fineman–Ross and Kelen–Tüdos laws enabled to assess the reactivity ratios (r_AN= r₁ = 1.25 ± 0.04 and r_ATRIF = r₂ = 0.93 ± 0.05 at 70 °C) while the revised patterns scheme led to r₁₂ = r_AN = 1.03, and r₂₁ = r_ATRIF = 0.78 at 70 °C. In all cases, r_AN x r_ATRIF product was close to unity, which indicates that poly(AN‐co‐ATRIF) copolymers exhibit a random structure. This was also confirmed by the Igarashi's and Pyun's laws which revealed the presence of AN‐ATRIF, AN‐AN, and ATRIF‐ATRIF dyads. The Q and e values for ATRIF were also assessed (Q₂ = 0.62 and e₂ = 0.93). The glass transition temperature values, T_g, of these copolymers increased from 17 to 61 °C as the molar percentage of ATRIF decreased from 77 to 16% in the copolymer. Thermogravimetry analysis of poly(AN‐co‐ATRIF) copolymers showed a good thermal stability compared to that of poly(ATRIF) homopolymer due to incorporation of AN comonomer. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3856–3866     

Microwave-assisted synthesis,antimicrobial, antiquorum-sensing and cytotoxic activities of a new series of isatin-β-thiocarbohydrazones

Abstract

New isatin-β-thiocarbohydrazone hybrids 4-17 were designed relied on isatin scaffold to generate various analogs with expected antimicrobial activity. The new hybrids were estimated for antibacterial effectiveness over S. aureus, B. cereus and E. coli, and antifungal efficacy over C. albicans and A. fumigatus. Compound 14 evinced the highest efficacy over A. fumigatus and C. albicans. In addition, 5 and 12 showed eminent efficacy toward A. fumigatus, where compounds 4, 7, 9, 11, 13, 15 and 16 exhibited moderate activity over the same fungus. Moreover, 6 and 9 displayed moderate activity over C. albicans. The new compounds were also estimated for antiquorum-sensing effectiveness against C. violacium, where compound 17 showed interesting activity. In vitro cytotoxicity assay of the new analogs was done over Hela and COS-7 cancer cell lines. All analogs have IC₅₀ values >50?μM toward both cell lines.     

Room Temperature Catalytic Aromatization of Hantzsch 1,4-Dihydropyridines by Sodium Nitrite in the Presence of Acidic Silica Gel

Summary. Various alkyl, aryl, and heterocyclic Hantzsch 1,4-dihydropyridines were converted to the corresponding pyridines in excellent yields and short times using sodium nitrite in the presence of a catalytic amount of acidic silica gel at room temperature.