固载于 Al-MCM-41 纳米孔道中的钒离子催化氧化烷基芳基硫化物

 VOSO₄ immobilized within nanoreactors of Al-MCM-41 (VO²⁺/Al-MCM-41) was synthesized and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, nitrogen adsorption-desorption, and chemical analysis techniques. The prepared VO²⁺/Al-MCM-41 successfully catalyzes the oxidation of aryl alkyl sulfides and up to 99% conversion and 90% selectivity for the corresponding sulfoxides were obtained with H₂O₂ as oxidant in acetonitrile at room temperature in 30 min.     

Wetting and superhydrophobic properties of PECVD grown hydrocarbon and fluorinated-hydrocarbon coatings

Wetting characteristics of micro-nanorough substrates of aluminum and smooth silicon substrates have been studied and compared by depositing hydrocarbon and fluorinated-hydrocarbon coatings via plasma enhanced chemical vapor deposition (PECVD) technique using a mixture of Ar, CH₄ and C₂F₆ gases. The water contact angles on the hydrocarbon and fluorinated-hydrocarbon coatings deposited on silicon substrates were found to be 72° and 105°, respectively. However, the micro-nanorough aluminum substrates demonstrated superhydrophobic properties upon coatings with fluorinated-hydrocarbon providing a water contact angle of ∼165° and contact angle hysteresis below 2° with water drops rolling off from those surfaces while the same substrates showed contact angle of 135° with water drops sticking on those surfaces. The superhydrophobic properties is due to the high fluorine content in the fluorinated-hydrocarbon coatings of ∼36 at.%, as investigated by X-ray photoelectron spectroscopy (XPS), by lowering the surface energy of the micro-nanorough aluminum substrates.     

Laser induced thermal lens spectrometry for cobalt determination after cloud point extraction

A new approach, employing cloud point extraction (CPE) in combination with thermal lens spectrometry (TLS), has been developed for the determination of cobalt. The CPE and TLS methods have good matching conditions for combination because TLS is suitable for low volume samples obtained after CPE and for organic solvents, which are used for dissolving the remaining analyte phase.1-(2-Pyridylazo)-2-naphthol (PAN) was used as a complexing agent and octylphenoxypolyethoxyethanol (Triton X-114) was added as a surfactant; then the pH of solution was adjusted. After phase separation at 50 °C based on the cloud point extraction of the mixture, the surfactant-rich phase was dried and the remaining phase was dissolved using 20 μL of carbon tetrachloride. The obtained solution was introduced into the quartz micro cell and the analyte was determined by thermal lens spectrometry. The He-Ne laser (632.8 nm) was used as both the probe and the excite source.Under optimum conditions, the analytical curve was linear for the concentration range of 0.2-40 ng mL⁻¹ and the detection limit was 0.03 ng mL⁻¹. The enhancement factor of 470 was achieved for a 10 mL sample. Relative standard deviations were lower than 5%.The method was successfully applied to the extraction and determination of cobalt in tap, river and sea water.     

Synthesis of salicylaldehyde-modified mesoporous silica and its application as a new sorbent for separation, preconcentration and determination of uranium by inductively coupled plasma atomic emission spectrometry

A new functionalized mesoporous silica (MCM-41) using salicylaldehyde was utilized for the separation, preconcentration and determination of uranium in natural water by inductively coupled plasma atomic emission spectrometry (ICP-AES).Experimental conditions for effective adsorption of trace levels of U(VI) were optimized. The preconcentration factor was 100 (1.0 mL of elution for a 100 mL sample volume). The analytical curve was linear in the range 2-1000 μg L⁻¹ and the detection limit was 0.5 ng mL⁻¹. The relative standard deviation (R.S.D.) under optimum conditions was 2.5% (n = 10). Common coexisting ions did not interfere with the separation and determination of uranium at pH 5. The sorbent exhibited excellent stability and its sorption capacity under optimum conditions has been found to be 10 mg of uranium per gram of sorbent. The method was applied for the recovery and determination of uranium in different water samples.     

Backward substitution method based on Müntz polynomials for solving the nonlinear space fractional partial differential equations

A computational technique based on the Müntz polynomials and meshless method has been presented for the solution of nonlinear and linear space fractional partial differential equations (PDEs). The meshless method that is used in this study is the new version of backward substitution method (BSM). First, the time-derivative term is discretized by the Crank-Nicolson method. Then, the approximate solution is given as the separation of the approximation of the boundary data and the correcting functions using the Müntz polynomials. In general form, this approximate solution that does not necessarily satisfy the original equation is shown as the sum of the system basics in which it consists free parameters. Finally, these parameters are determined by the BSM method inside the domain. The main advantage of the method is efficiency and reliability that is examined by six numerical experiments.     

Extraction and preconcentration of ultra trace amounts of beryllium from aqueous samples by nanometer mesoporous silica functionalized by 2,4-dihydroxybenzaldehyde prior to ICP OES determination

A new functionalized nanometer mesoporous silica (MCM-41) using 2,4-dihydroxybenzaldehyde (4-OHsal) was applied as an effective sorbent for solid phase extraction (SPE) of beryllium ions from aqueous solution followed by inductively coupled plasma optical emission spectrometric detection (ICP OES). The influences of some analytical parameters on the quantitative recoveries of the analyte ion were investigated in batch method. In order to perform the batch mode of SPE, known amount of sorbent was added to a test tube containing sample solution buffered at pH 7.2. After manual shaking and centrifugation the aqueous phase was decanted and beryllium was desorbed by adding 1.0 mL of 1.0 mol L^?1 HNO₃ to the sedimented sorbent. The sorbent was separated by centrifugation and the concentration of beryllium in the supernatant was determined by ICP OES. The maximum sorption capacity of the modified MCM-41 was found to be 34 mg g^?1. The sorbent exhibited good stability, reusability and fast rate of equilibrium for sorption/desorption of beryllium ions. The present method was used for preconcentration and determination of beryllium for water samples. Under optimal conditions, the limit of detection (LOD) obtained was 0.3 ng L^?1. The accuracy of the procedure was evaluated by analysis of the certified reference material (NIST 1640).     

Solid phase microextraction with gas chromatography-mass spectrometry: a very rapid method for identification of volatile organic compounds emitted by Carum copticum

The investigation of flower scent represents an important field of modern biological research which is directed towards special theories of biological recognition. The headspace solid phase microextraction coupled with gas chromatography-mass spectrometry was used to identify the volatile components of Carum copticum (C. copticum) cultivated in Iran. The compounds were identified according to their retention indices and mass spectra (EI, 70 eV). The effects of different parameters, such as the desorption time, the extraction temperature, the sample mass, the addition of salt, the pre-equilibration time and the extraction time, on the extraction efficiency were investigated. The optimized conditions were: the desorption time, 2 min; the extraction temperature, 58 degrees Celsius; the sample mass, 1.000 g in 4.0 mL 2.0 M NaCl solution; the pre-equilibration time, 25 min; the extraction time, 20 min. Finally, ten components were identified in the volatile components of C. copticum. The major components of C. copticum were thymol (68.2%), gamma-terpinene (13.9%), p-cymene (11.6%), myrcene (1.0%) and beta-pinene (0.6%). Precision of the proposed method is good and %RSD less than 14 was obtained.