Speciation and determination of chromium ions by dispersive micro solid phase extraction using magnetic graphene oxide followed by flame atomic absorption spectrometry

A selective, simple and fast dispersive micro solid phase extraction method using magnetic graphene oxide (GO) as an efficient sorbent has been developed for the extraction, separation and speciation analysis of chromium ions. The method is based on different adsorption behaviour of Cr(VI) and Cr(III) species onto magnetic GO in aqueous solutions which allowed the selective separation and extraction of Cr(VI) in the pH range of 2.0–3.0. The retained Cr(VI) ions by the sorbent were eluted using 0.5 mL of 0.5 mol L^?1 nitric acid solution in methanol and determined by ?ame atomic absorption spectrometry. Total chromium content was determined after the oxidation of Cr(III) to Cr(VI) by potassium permanganate. All effective parameters on the performance of the extraction process were thoroughly investigated and optimised. Under the optimised conditions, the method exhibited a linear dynamic range of 0.5–50.0 µg L^?1 with a detection limit of 0.1 µg L^?1 and pre-concentration factor of 200. The relative standard deviations of 3.8% and 4.6% (n = 8) were obtained at 25.0 µg L^?1 level of Cr(VI) for intra- and inter-day analysis, respectively. The method was successfully applied to the speciation and determination of Cr(VI) and Cr(III) in environmental water samples.     

Pt–NiO–Al2O3/G derived from graphene-supported layered double hydroxide as efficient catalyst for p-nitrophenol reduction

Research on Chemical Intermediates - The present work reports the synthesis of a Pt-modified NiO–Al2O3 nanocomposite derived from graphene-supported layered double hydroxide (Pt–NiO/G)...     

新型吡咯烷键合反相高效液相色谱固定相的制备与研究（英文）

正A new ionic liquid-based high-performance liquid chromatography stationary phase is reported.A derivative of N-methyl pyrrolidinium tetrafluoroborate was covalently immobilized on the surface of silica particles to prepare silica-based N-methyl pyrrolidinium tetrafluoroborate(SilprMP BF4)stationary phase.The obtained ionic liquid-modified silica was evaluated and confirmed by elemental analysis,infrared spectroscopy,and thermogravimetric analysis.A column was packed with the modified particles.The retention behavior of aromatic compounds,alkyl benzenes,and acidic and basic compounds on the SilprMP BF4 stationary phase was studied under reversed-phase liquid chromatography conditions.The effect of the eluent pH on the separation of the acidic and basic compounds was also studied.The new stationary phase involves multiple retention mechanisms,such as electrostatic,hydrophobic,ion-dipole,and anion-exchange interactions,which might lead to multipurpose separation media.     

H2 adsorption on Ag‐nanocluster/single‐walled carbon nanotube composites: A molecular dynamics study on the effects of nanocluster size,diameter, and chirality of nanotube

The H₂ physisorption on Ag_N (with N = 32, 108, 256, 500, and 864)/carbon nanotube (CNT; in armchair and zigzag structures with diameters between 0.54 and 2.98 nm) composites were studied by molecular dynamic simulation to investigate the effect of nanocluster size, diameter, and chirality of nanotube on the adsorption phenomena. The calculations indicate that the effects of nanocluster properties are more important than those of the nanotube, in such a way that increase of nanocluster size, decreases the H₂ adsorption. Also, the diameter and chirality of CNTs have considerable influence on the adsorption phenomena. As the diameter of nanotube is increased, the amount of adsorption is decreased. Moreover, H₂ molecules have more tendencies to those nanoclusters located on the armchair nanotubes than the zigzag ones. Another important result is the reversibility of H₂ adsorption on these materials in which the structure of composite in vacuum and after reduction of H₂ pressure to zero, is not changed, considerably. © 2015 Wiley Periodicals, Inc.     

Synthesis of 2,3-dihydroquinazolin-4(1H)-ones catalyzed by zirconium (IV) chloride as a mild and efficient catalyst

2, 3-Dihydroquinazolin-4 (1H)-ones have been synthesized in the high to excellent yields via condensation of 2-aminobenzamide with aldehydes and ketones in the presence of catalytic amount of ZrCl₄ in EtOH at room temperature. Mild reaction conditions, clean reaction media, simple workup and easy purification are advantages of this methodology.     

Isocyanide-based four-component synthesis of 1,3-indandionylamidinium betaines

An efficient approach for the synthesis of novel 1,3-indandionylamidinium betaines via four-component reaction of 1,3-indandione, aldehydes, amines, and isocyanides, without assistance of any catalyst and under mild reaction conditions has been reported. The structures of these compounds were confirmed by IR, mass spectroscopic, ¹H NMR, ¹³C NMR, and single-crystal X-ray diffraction studies.     

Synthesis and Crystal Structure Study of Diethyl Aryl(benzo[d]thiazol‐2‐ylamino)methyl Phosphonates

A three‐component synthesis of α‐aminophosphonate is described from a reaction between aldehydes, 2‐aminobenzothiazole, and triethyl phosphite in the presence of InCl₃ as a catalyst under solvent‐free conditions for the generation of the particular α‐aminophosphonates. These products have two potentially biologically active parts, aminophosphonate and benzothiazole. This method offers advantages such as short reaction times, good yields, solvent‐free conditions, and easy workup with the green aspects by avoiding toxic catalysts and solvents. The crystal structure of 4b has been determined by X‐ray crystallography. This compound crystallizes in the monoclinic space group C2/c with cell parameters a = 21.9285(5) Å, b = 10.3221(2) Å, c = 18.5979(5) Å, β = 108.759(3)°, V = 3985.99(18) ų, D_calc = 1.301 mg m⁻³, and Z = 8. The final R value is 0.0501 for 3741 reflections. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 24:58–65, 2013; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21063     

Permutation entropy and detrend fluctuation analysis for the natural complexity of cardiac heart interbeat signals

We compute fractal dimension and permutation entropy for healthy and people who have experienced heart failure. Our result shows that permutation entropy is a suitable approach as well as detrend fluctuation analysis (DFA). The result of DFA shows that the fractal dimensions for healthy and heart failure are different as well as the permutation entropy result. The fluctuation value for permutation entropy for an individual who has experienced heart failure is bigger than for a healthy person. There is some specific change in the interbeat signal of a person who has experienced heart failure, but there is not previous trend for a healthy person.     

Theoretical study of CuxAg1−xI alloys

We have performed first-principles calculations using full potential linearized augmented plane wave (FP-LAPW) method within density functional theory (DFT) to investigate the fundamental properties of Cu_xAg_1−xI alloys. We used both GGA96 [J.P. Perdew, K. Burke, M. Ernzerhof, Phys. Rev. Lett. 77 (1996) 3865.] and EVGGA [E. Engel, S.H. Vosko, Phys. Rev. B. 47 (1993) 13164.] generalized gradient approximations of the exchange-correlation energy that are based on the optimization of total energy and corresponding potential. Quantities such as lattice constants, bulk modulus, band gap, density of occupied states and effective mass were calculated as a function of copper molar fraction x. These parameters were found to depend non-linearly on alloy composition x, except the lattice parameter, which follows Vegard's law. The microscopic origins of the gap bowing were explained using the approach of Zunger and co-workers; we have concluded that the band-gap energy bowing was mainly caused by the chemical charge-transfer effect and the volume deformation , while the structural relaxation contribute to the gap bowing parameter at smaller magnitude. The calculated phase diagram shows a broad miscibility gap for this alloy with a high critical temperature.