Synthesis and application of glutaric dihydrazide modified multiwalled carbon nanotubes for selective solid-phase extraction and preconcentration of Cu(II), Zn(II), Ni(II), and Fe(III)

An SPE method for selective separation-preconcentration of Cu(ll), Zn(II), Ni(II), and Fe(III) on multiwalled carbon nanotubes (MWCNTs) modified by glutaric dihydrazide prior to flame atomic absorption spectrometric determination was investigated. The adsorption was achieved quantitatively on MWCNTs at pH 5.0, and then the retained metal ions on the adsorbent were eluted with 1 M HNO3. The effects of analytical parameters including pH of the solution, eluent type, sample volume, and matrix ions were investigated for optimization of the presented procedure. The adsorption capacity of the adsorbent at optimum conditions was found to be 33.6, 29.2, 22.1, and 36.0 mg/g for Cu(ll), Zn(ll), Ni(ll), and Fe(lll), respectively. The LOD values of the method were 0.21, 0.11, 0.24, and 0.27 microg/L for Cu(ll), Zn(ll), Ni(ll), and Fe(lll), respectively. The RSDs were lower than 3.01%. The method was applied for the determination of analytes in soil, river water, and wastewater samples with satisfactory results.     

Theoretical study of the effects of substitution,solvation, and structure on the interaction between nitriles and methanol

We report an investigation on intermolecular interactions in R? CN ··· H? OCH₃ (R = H, CH₃, F, Cl, NO₂, OH, SH, SCH₃, CHO, COCH₃, CH₂Cl, CH₂F, CH₂OH, CH₂COOH, CF₃, SCOCH₃, SCF₃, OCHF₂, CH₂CF₃, CH₂OCH₃, and CH₂CH₂OH) complexes using density functional theory. The calculations were conducted on B3LYP/6‐311++G** level of theory for optimization of geometries of complexes and monomers. An improper hydrogen bonding (HB) in the H₃CO? H ··· NC? R complexes was observed in that N atom of the nitriles functions acts as a proton acceptor. Furthermore, quantum theory of “Atoms in Molecules” (AIM) and natural bond orbital (NBO) method were applied to analyze H‐bond interactions in respective complexes. The electron density (ρ) and Laplacian (?²ρ) properties, estimated by atoms in molecules calculations, indicate that H ··· N bond possesses low ρ and positive ?²ρ values, which are in agreement with partially covalent character of the HBs, whereas O? H bonds have negative ?²ρ values. In addition, the weak intermolecular force due to dipole–dipole interaction (U) is also considered for analysis. The examination of HB in these complexes by quantum theory of NBO method fairly supports the ab initio results. Natural population analysis data, the electron density, and Laplacian properties, as well as, the ν(O? H) and γ(O? H) frequencies of complexes, calculated at the B3LYP/6‐311++G** level of theory, are used to evaluate the HB interactions. The calculated geometrical parameters and conformational analysis in water phase solution show that the H₃CO? H ··· NC? R complexes in water are more stable than that in gas phase. The obtained results demonstrated a strong influence of the R substituent on the properties of complexes. Numerous correlations between topological, geometrical, thermodynamic properties, and energetic parameters were also found. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

A vertically aligned carbon nanotube-based impedance sensing biosensor for rapid and high sensitive detection of cancer cells

A novel vertically aligned carbon nanotube based electrical cell impedance sensing biosensor (CNT-ECIS) was demonstrated for the first time as a more rapid, sensitive and specific device for the detection of cancer cells. This biosensor is based on the fast entrapment of cancer cells on vertically aligned carbon nanotube arrays and leads to mechanical and electrical interactions between CNT tips and entrapped cell membranes, changing the impedance of the biosensor. CNT-ECIS was fabricated through a photolithography process on Ni/SiO(2)/Si layers. Carbon nanotube arrays have been grown on 9 nm thick patterned Ni microelectrodes by DC-PECVD. SW48 colon cancer cells were passed over the surface of CNT covered electrodes to be specifically entrapped on elastic nanotube beams. CNT arrays act as both adhesive and conductive agents and impedance changes occurred as fast as 30 s (for whole entrapment and signaling processes). CNT-ECIS detected the cancer cells with the concentration as low as 4000 cells cm(-2) on its surface and a sensitivity of 1.7 × 10(-3)Ω cm(2). Time and cell efficiency factor (TEF and CEF) parameters were defined which describe the sensor's rapidness and resolution, respectively. TEF and CEF of CNT-ECIS were much higher than other cell based electrical biosensors which are compared in this paper.     

DFT investigation of endohedral boron oxide nanocapsules: Encapsulation of He, Ne, Ar, H, N, and Cl atoms

The electronic structure and stabilization energy of spherical and pyramidal shapes of boron oxide nanocapsules (X@B₂₀O₃₀, X = He, Ne, Ar, H, N, Cl) were investigated by long-range and dispersion corrected density functional theory (DFT + Disp) including CAM-B3LYP, B3LYP-D3, ωB97X-D and B2PLYP-D methods. Based on these calculations, the formation of nanocapsules is an exothermic process (except for Cl@B₂₀O₃₀). The spherical boron oxide nanocapsules are mainly stabilized by dispersion, while the stability of pyramidal complexes is mainly due to monomer relaxation energy. The theoretical results obtained in this work show that the boron oxide capsule is a good potential candidate for gas storage.     

A Simple,Mild and Efficient One‐Pot Synthesis of 2‐Substituted Benzimidazoles in the Presence of H2O2/HCl under Microwave Irradiation

A simple, fast and efficient method for the preparation of several 2‐substituted benzimidazole derivatives is reported. Compounds were synthesized through a rapid one‐pot synthesis via microwave irradiation, starting from aldehydes and o‐phenylenediamine, in the presence of H₂O₂/HCl system in acetonitrile. The significant features of this method are short reaction times, high yields, easy and quick isolation of the products.     

Extraordinarily water permeable sol-gel formed nanocomposite nanofibrous membranes

Electrospun nanofibrous membranes (ENMs) are considered as a state of the art in water filtration technology mainly owing to their high interconnected porosity and tunable pore size assumed to offer a very high permeability also selectivity. However, the extremely high surface area makes the ENMs prone to mechanical breakdown and lack of wettability lowering the filtration efficiency. Hence, any attempt to enhance both the mechanical properties and hydrophilicity of the ENMs is highly recommended. In the current study, the structural and transport properties of polyethersulfone (PES) ENMs were modified through incorporation of titania (TiO(2)) nanoparticles via a sol-gel approach. Presence of titania precursor increased the conductivity of the electrospun solution thereby optimized the structural features of the electrospun mat in terms of formation of very thin beadless nanofibers, a higher porosity and smaller pore size. Moreover, a significant rise in mechanical properties, thermal stability and switching from a highly hydrophobic membrane to a superhydrophilic one occur simultaneously. The combination of a more optimum porosity, very high mechanical properties and hydrophilicity leads to a significantly higher water permeability in the TiO(2)/PES ENMs encouraging us to propose it as a water filtration membrane with longer life span and lower energy consumption.     

Chemical composition analysis of the essential oil of Melissa officinalis L. from Kurdistan, Iran by HS/SPME method and calculation of the biophysicochemical coefficients of the components

The volatile constituents of the essential oil of wild Melissa officinalis L. obtained from the Kurdistan province of Iran were extracted by headspace/solid-phase micro-extraction and were analysed by gas chromatography and gas chromatography/mass spectrometry. Of a total of 14 compounds in the oil, 12 (85.7%) were identified. The main components were as follows: (E)-citral (37.2%), neral (23.9%) and citronellal (20.3%). Some physicochemical properties, such as the logarithm of calculated octanol-water partitioning coefficients (log?K (ow))(,) total biodegradation (TB (d) in mol?h(-1) and g?h(-1)), water solubility (S (w), mg?L(-1) at 25°C) and median lethal concentration 50 (LC(50)), were calculated for compounds 1-14 from M. officinalis L.     

One Dimensional Hydrogen Bonded Arrangement in New Schiff-Base Compound (<Emphasis Type="Italic">E</Emphasis>)-2-(2,5-dimethoxybenzylideneamino)phenol (1): Synthesis,Characterization, Crystal Structure and Conformational Studies

Abstract  

New Schiff-base compound (E)-2-(2,5-dimethoxybenzylideneamino)phenol (1) was synthesized and characterized by elemental analyses, FT-IR and ¹H-NMR spectroscopy and single crystal X-ray diffraction. Molecular orbital calculation has been carried out for 1 by using HF method at 6-31G basis set. The title compound 1 crystallizes in monoclinic system, space group C2/c, with a = 19.4581(13) ?, b = 9.5805(5) Ǻ, c = 13.8431(7) Ǻ, β = 93.471(2)°, V = 2575.9(3) Ǻ³ and Z = 8. In the crystal structure two molecules are stabilized by a pair of intermolecular O1–H1···N1ⁱ hydrogen bonds. The dimeric units are further linked via C6–H6···O3ⁱⁱ hydrogen bond.     

Effects of Final State Interactions in Pure Annihilation Decay of B^{0}_{s}\rightarrow\pi^{0}\pi^{0}

We investigate the effects of final state interactions (FSI) contributions in the nonleptonic two body $B^{0}_{s} \rightarrow \pi^{0}\pi^{0}$ decay. The short distance interaction amplitude is calculated by using the annihilation diagrams and a tiny branching ratio is obtained, then the long distance amplitude is considered and calculated within FSI effects. For contributions of FSI, the ρ ⁰ ρ ⁰, π ⁺ π ^?(ρ ⁺ ρ ^?), K ⁺ K ^?(K ^+? K ^??) and $K^{0}\bar{K}^{0}(K^{0*}\bar{K}^{0*})$ are produced for intermediate states, in this case the π ⁰, π ^?(ρ ^?), K ^?(?) and $\bar{K}^{0(*)}$ mesons are exchanged. The absorptive part of the diagrams is directly calculated and the dispersive part of the rescattering amplitude can be obtained from the absorptive part via the dispersion relation. The imaginary and real parts of the amplitudes are summed over all intermediate states. The predicted branching ratio of $B^{0}_{s} \rightarrow \pi^{0}\pi^{0}$ is 0.69×10^?8 in the absence of FSI effects and it becomes 1.86×10^?4 when FSI contributions are taken into account, while the experimental result is less than 2.1×10^?4.