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641.
Abbas Afkhami Tayyebeh Madrakian Reza Ahmadi Hasan Bagheri Masoumeh Tabatabaee 《Mikrochimica acta》2011,175(1-2):69-77
We have developed a solid phase extraction method for the determination of cadmium ions in aqueous samples. It is based on the adsorption of Cd(II) on alumina nanoparticles coated with sodium dodecyl sulfate and modified with a newly synthesized Schiff base. Analytical parameters such as pH value, amount of adsorbent, type and concentration of eluent, flow rates of the sample and eluent, sample volume and matrix effects were optimized. Desorption is accomplished with 2?mol?L?1 nitric acid. Cd(II) was then determined by flame atomic absorption spectrometry. The maximum enrichment factor is 75. Under the optimum experimental conditions, the detection limit is 0.14???g?L?1 in original solution. The adsorption capacity of the modified sorbent is 4.90?mg?g?1 for cadmium ions. The method was applied to the determination of trace quantities of Cd(II) in water, wastewater, and biological and food samples with satisfactory results. Figure
Schematic representation of the loading L on the alumina nanoparticles 相似文献
642.
Seyed Javad Ahmadi Sodeh Sadjadi Morteza Hosseinpour 《Monatshefte für Chemie / Chemical Monthly》2011,44(24):1163-1168
Abstract
An efficient method for the synthesis of 4-amino-5-pyrimidinecarbonitriles by the three-component reaction of malononitrile, aldehydes, and N-unsubstituted amidines under aqueous conditions using CuO microspheres as catalyst is reported. The catalyst exhibited remarkable reusable activity. 相似文献643.
Ali Ahmadi Mohammad Kamfiroozi Javad Beheshtian Nasser L. Hadipour 《Structural chemistry》2011,22(6):1261-1265
Our main objectives are to address the following fundamental issues: (1) A density functional theory study on the structural and electronic properties of the zigzag single-walled aluminum nitride nanotubes (AlNNTs) with various diameters, using B3LYP/6-31G* level of theory. (2) An ONIOM study on the curvature effect of AlNNTs on the NH3 adsorption process using B3LYP/6-31G* and semiempirical AM1 approaches. Furthermore, a potential energy surface is calculated for NH3 moving toward AlNNT surface. In contrast to semiconducting carbon nanotubes (Louie, Top Appl Phys 80:113, 2001) our calculations confirmed that the HOMO?CLUMO energy gap of AlNNTs increases with an increase of the tube diameter. Additionally, we showed that HOMO/LUMO interaction between NH3 and AlNNTs becomes stronger as the tube diameter decreases. 相似文献
644.
Shahin Ahmadi T. G. Deligeorgiev A. Vasilev M. Kubista 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2012,86(13):1974-1981
The thermodynamics of the monomer-dimer equilibrium of five cationic monomethine cyanine dyes has been studied by means of UV-vis spectroscopy and advanced chemometrics methods. The dimerization constants were determined by studying the dependence of their absorption spectra on temperature in the range 20?C75°C and were found to be: 1.91 × 103, 1.53 × 103, 6.81 × 103, 5.18 × 103, and 8.28 × 103 dm3 mol?1 for 1, 2, 3, 4, and 5 respectively. The absorption spectra of the monomer and dimer forms of the dyes were also determined, as well as the enthalpy and entropy of the dimerization. 相似文献
645.
Ali Ahmadi Peyghan Hamed Soleymanabadi Morteza Moradi 《Journal of Physics and Chemistry of Solids》2013
We have investigated energetic, geometric, electronic, and field emission properties of three recently synthesized fulleropyrrolidines based on the density functional theory method B3LYP/6-31G(d). Fulleropyrrolidines show higher conductivity, and solubility in water, and smaller work function in comparison with the pristine C60 fullerene. The functionalization of C60 with different pyrrolidines containing 3NH2, NO, or NO2 groups transforms it to an n-type semiconductor. The functionalization can also dramatically enhance the electrophilicity of the C60 about 23–37%. Moreover, it should be mentioned that the work function is mainly influenced by the pyrrolidine containing 3NO2 group whereas the conductivity is largely affected by the one containing 3NH2 functionality. 相似文献
646.
A direct and reagent free procedure for simultaneous determination of sodium lauryl ether sulfate (SLES), coconut diethanol amide (CDEA) and linear alkylbenzene sulfonate (LABS) in undiluted samples of hand dishwashing liquids has been developed. This determination was carried out by using attenuated total reflectance Fourier transform infrared spectrometry (ATR-FTIR) and multivariate analysis. An implementation of the PLS statistical approach to quantitative analysis of one nonionic and two anionic surfactants was applied to a set of mid-infrared spectra (1305-990 cm(-1)) recorded for commercial detergent samples and ternary standard solutions. An orthogonal calibration design for three components and five levels for standards were employed. Number of factors and scans and also the resolution were optimized. The statistical parameters such as the root mean square error of calibration (RMSEC), root mean square error of cross-validation (RMSECV), standard error of prediction (SEP) and relative standard deviation (R.S.D.) were evaluated. These parameters were obtained as: RMSEC 0.13, 0.20 and 0.14, RMSEV 0.09, 0.17 and 0.04 and SEP 0.12, 0.39 and 0.18 (g per 100 g) for SLES, CDEA and LABS, respectively. R.S.D. for five independent analyses were 1.69 for SLES, 3.76 for CDEA and 1.76 for LABS. The component linear correlation coefficients comparing actual and predicted concentrations of SLES, CDEA and LABS in some real samples were 0.9995, 0.9915 and 0.9974, respectively. 相似文献
647.
Fast Quantitation of Target Analytes in Small Volumes of Complex Samples by Matrix‐Compatible Solid‐Phase Microextraction Devices
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Dr. Hamed Piri‐Moghadam Fardin Ahmadi MSc. German Augusto Gómez‐Ríos Dr. Ezel Boyacı MSc. Nathaly Reyes‐Garcés Dr. Ali Aghakhani Dr. Barbara Bojko Prof. Janusz Pawliszyn 《Angewandte Chemie (International ed. in English)》2016,55(26):7510-7514
Herein we report the development of solid‐phase microextraction (SPME) devices designed to perform fast extraction/enrichment of target analytes present in small volumes of complex matrices (i.e. V≤10 μL). Micro‐sampling was performed with the use of etched metal tips coated with a thin layer of biocompatible nano‐structured polypyrrole (PPy), or by using coated blade spray (CBS) devices. These devices can be coupled either to liquid chromatography (LC), or directly to mass spectrometry (MS) via dedicated interfaces. The reported results demonstrated that the whole analytical procedure can be carried out within a few minutes with high sensitivity and quantitation precision, and can be used to sample from various biological matrices such as blood, urine, or Allium cepa L single‐cells. 相似文献
648.
The construction and general performance of four novel potentiometric membrane sensors for the determination of fluoxetine have been described. The sensors are based on the formation of the ion association complex of fluoxetine with sodium tetraphenylborate and phosphotungstic acid as electroactive materialles, dispersed in a PVC matrix with dibuthyl sebacate (or diethyl sebacate) as a plasticizer. These sensors exhibit fast, stable and near-Nernstian response for the monocharged fluoxetine cation over wide concentration range from 3.0 × 10?6 to 1.2 × 10?2 M and pH 4.0–7.5. No interferences are caused by many inorganic and organic species. Direct potentiometric determinations of 5–100 μg/mL of fluoxetine in drug and urine samples show good recovery of fluoxetine. The developed membrane electrodes have been used as an end point indicator electrode; the potentiometric titration of fluoxetine with sodium tetraphenylborate as a titrant has been monitored. 相似文献
649.
In this paper, the effect of etching time on light emitting porous silicon has been studied by using Raman scattering. Enhancement of Raman intensity by increasing the porosity is observed. Also there is a red shift, about 4 cm−1, from the Raman peak of crystalline silicon to that of porous silicon. The phonon confinement model suggests the existence of spherical nanocrystalline silicon with diameter around 7 nm. But SEM images show that the samples have a sheetlike structure that confines phonons in one dimension. This should not cause any shift in their Raman spectra. It is suggested that the observed Raman peak shift is due to the spherical nanocrystals on the surface of these sheets. 相似文献
650.
Two-Phase Inertial Flow in Homogeneous Porous Media: A Theoretical Derivation of a Macroscopic Model
The purpose of this article is to derive a macroscopic model for a certain class of inertial two-phase, incompressible, Newtonian
fluid flow through homogenous porous media. Starting from the continuity and Navier–Stokes equations in each phase β and γ, the method of volume averaging is employed subjected to constraints that are explicitly provided to obtain the macroscopic
mass and momentum balance equations. These constraints are on the length- and time-scales, as well as, on some quantities
involving capillary, Weber and Reynolds numbers that define the class of two-phase flow under consideration. The resulting
macroscopic momentum equation relates the phase-averaged pressure gradient to the filtration or Darcy velocity in a coupled nonlinear form explicitly given by
or equivalently
In these equations, and are the inertial and coupling inertial correction tensors that are functions of flow-rates. The dominant and coupling permeability tensors and and the permeability and viscous drag tensors and are intrinsic and are those defined in the conventional manner as in (Whitaker, Chem Eng Sci 49:765–780, 1994) and (Lasseux
et al., Transport Porous Media 24(1):107–137, 1996). All these tensors can be determined from closure problems that are to
be solved using a spatially periodic model of a porous medium. The practical procedure to compute these tensors is provided. 相似文献