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1.
The oxidant‐free dehydrogenation of n‐pentanol over copper based catalysts was investigated in this paper. The effect of metal modification on the activity and stability of the copper catalyst supported on γ‐Al2O3 and La2O3 (Cu/γ‐Al2O3‐La2O3) was clarified and a Cr modified Cu/Al2O3‐La2O3 (Cu‐Cr/γ‐Al2O3‐La2O3) showed the best catalytic performance. The conversion of n‐pentanol was 70.0% and the selectivity for n‐pentanal increased to 97.1% over Cu‐Cr/γ‐Al2O3‐La2O3. X‐ray diffraction and temperature programmed reduction of H2 indicated that the addition of Cr favors the formation and reduction of the copper oxide, and the dispersion of the active Cu0 species, accounting for the good activity and stability of this catalyst. Furthermore, the lower amount of acidic sites in Cu‐Cr/γ‐Al2O3‐La2O3 is suggested to suppress the dehydration in oxidant‐free dehydrogenation of n‐pentanol, accounting for the higher selectivity for n‐pentanal.  相似文献   

2.
Electrocatalytic conversion of carbon dioxide (CO2) has recently received considerable attention as one of the most feasible CO2 utilization techniques. In particular, copper and copper‐derived catalysts have exhibited the ability to produce a number of organic molecules from CO2. Herein, we report a chloride (Cl)‐induced bi‐phasic cuprous oxide (Cu2O) and metallic copper (Cu) electrode (Cu2OCl) as an efficient catalyst for the formation of high‐carbon organic molecules by CO2 conversion, and identify the origin of electroselectivity toward the formation of high‐carbon organic compounds. The Cu2OCl electrocatalyst results in the preferential formation of multi‐carbon fuels, including n‐propanol and n‐butane C3–C4 compounds. We propose that the remarkable electrocatalytic conversion behavior is due to the favorable affinity between the reaction intermediates and the catalytic surface.  相似文献   

3.
A method was developed to determine 2‐mercaptobenzimidazole in water and urine samples using dispersive liquid–liquid microextraction technique coupled with ultraviolet–visible spectrophotometry. It was essential to peruse the effect of all parameters that can likely influence the performance of extraction. The influence of parameters, such as dispersive and extraction solvent volume and sample volume, on dispersive liquid–liquid microextraction was studied. The optimization was carried out by the central composite design method. The central composite design optimization method resulted in 1.10 mL dispersive solvent, 138.46 μL extraction solvent, and 4.46 mL sample volume. Under the optimal terms, the calibration curve was linear over the range of 0.003–0.18 and 0.007–0.18 μg/mL in water and urine samples, respectively. The limit of detection and quantification of the proposed approach for 2‐mercaptobenzimidazole were 0.013 and 0.044 μg/mL in water samples and 0.016 and 0.052 μg/mL in urine samples, respectively. The method was successfully applied to determination of 2‐mercaptobenzimidazole in urine and water samples.  相似文献   

4.
The increased global concern on environmental protection has made researchers focus their attention on new and more efficient methods of pollutant removal. In this research, novel nanocomposite adsorbents,i.e., magnetic hydroxyapatite (Fe3O4@HA) and magnetic hydroxyapatite β‐cyclodextrin (Fe3O4@HA‐CD) were synthesized and used for heavy metal removal. The adsorbents were characterized by FTIR, XRD, TGA, VSM, and SEM. In order to investigate the effect of β‐cyclodextrin (β‐CD) removal efficiency, adsorption results of nine metal ions were compared for both adsorbents. β‐CD showed the most increasing effect for Cd2+ and Cu2+ removal, so these two ions were selected for further studies. The effect of diverse parameters including pH, contact time, initial metal ion concentration and adsorbent dosage on the adsorption process was discussed. The optimum pH was 6 and adsorption equilibrium was achieved after 1 hr. Adsorption kinetic data were well fitted by pseudo‐second‐order model proposing that metal ions were adsorbed via chemical reaction. Adsorption isotherm was best described by the Langmuir model, and maximum adsorption capacity for Cd2+ and Cu2+ was 100.00 and 66.66 (mg/g), respectively. Desorption experiment was also done, and the most efficient eluent used for desorption of metal ions was EDTA (0.001 M) with 91% and 88% of Cd2+ and Cu2+ release, respectively. Recyclability studies also showed a 19% decrease in the adsorption capacity of the adsorbent after five cycles of regeneration. Therefore, the synthesized adsorbents were recognized as potential candidates for heavy metal adsorption applications.  相似文献   

5.
《Electroanalysis》2003,15(14):1177-1184
The metal binding properties of glutathione (GSH) and their fragments γ‐Glu‐Cys and Cys‐Gly are of biological and environmental interest. In this work a differential pulse polarographic study of the Zn2+/γ‐Glu‐Cys and Zn2+/Cys‐Gly systems was carried out for a better understanding of the results obtained in previous studies on the Zn2+‐GSH system. In the case of γ‐Glu‐Cys, complexation with Zn2+ was not detected. In the case of Cys‐Gly, the parallel analysis, by multivariate curve resolution with alternating least squares, of data from the titration of peptide with metal and of metal with peptide suggested the presence of two types of bound Zn2+. This could be attributed to Zn2+ strongly bound to two sulfur atoms of two peptides, to form a complex of 1 : 2 stoichiometry, and to Zn2+ weakly bound to carboxylate and/or amino groups.  相似文献   

6.
In this study, a novel organic–inorganic hybrid adsorbent for single‐step detection and removal of Pb(II) ions based on dithizone (DZ) anchored on mesoporous SBA‐15 was fabricated. The designed solid optical sensor revealed rapid colorimetric responses and high selectivity. Central composite design (CCD) combined with desirability function (DF) was applied to evaluate the interactive effects and optimization of important variables such as pH value, mesoporous SBA‐15 dosage, contact time and initial concentration of Pb(II) ions and optimum conditions for each of the factors were obtained 6.0, 25 mg, 30 min and 20 μg ml− 1, respectively. This adsorbent or solid optical chemo sensor exhibited a linear range of 1.0 to 100.0 μg ml−1 of Pb(II) ion concentration with a detection limit of 0.07 μg ml−1. This adsorbent was applied to determine and remove the Pb(II) in spiked samples. Various isotherm models such as Langmuir, Freundlich, Temkin and Dubinin–Radushkevich were studied for fitting the experimental equilibrium data. Langmuir model was chosen as an efficient model. Various kinetic models such as pseudo‐first, second order intraparticle, diffusion models were studied for analysis of experimental adsorption data and the pseudo second order model was chosen as an efficient model.  相似文献   

7.
We describe ultrasonic‐assisted dispersive solid‐phase extraction based on ion‐imprinted polymer (UA‐DSPE‐IIP) nanoparticles for the selective extraction of silver ions. Ultrasound is a good and robust method to facilitate the extraction of target ions in the sorption step and elution of the target ions in the desorption step. The IIP nanoparticles used in the UA‐DSPE‐IIP were prepared by precipitation polymerization. To prepare the IIP nanoparticles, 2‐vinylpyridine, ethylene glycol dimethacrylate, 2,2′‐azobisisobutyronitrile, 2‐picolinic acid, silver and chloroform–methanol (50:50) solution were used as functional monomer, cross‐linker, initiator, silver‐binding ligand, template ion and porogen, respectively. The IIP nanoparticles were characterized using Fourier transformed infrared spectroscopy, thermogravimetric and differential thermal analysis, X‐ray diffraction and scanning electron microscopy. A Box–Behnken design was used for optimization of sorption and desorption steps in UA‐DSPE‐IIP. In the sorption step: pH of solution, IIP amount (mg), sonication time for sorption (min); in the desorption step: concentration of eluent (mol l−1), volume of eluent (ml), sonication time (min) for desorption were investigated and optimized by Box–Behnken design. The optimum conditions for the method were: pH of solution, 7; sonication time for sorption, 7 min; IIP amount, 17 mg; type and concentration of eluent, HCl 1.5 mol l−1; volume of eluent, 2 ml; sonication time for desorption, 140 s. Under the optimized conditions the limit of detection and relative standard deviation for the detection of silver ions using UA‐DSPE‐IIP were found to be 0.09 μg l−1 and <3%, respectively.  相似文献   

8.
A simple, efficient and eco‐friendly procedure has been developed using Cu(II) immobilized on guanidinated epibromohydrin‐functionalized γ‐Fe2O3@TiO2 (γ‐Fe2O3@TiO2‐EG‐Cu(II)) for the synthesis of 2,4,5‐trisubstituted and 1,2,4,5‐tetrasubstituted imidazoles, via the condensation reactions of various aldehydes with benzil and ammonium acetate or ammonium acetate and amines, under solvent‐free conditions. High‐resolution transmission electron microscopy analysis of this catalyst clearly affirmed the formation of a γ‐Fe2O3 core and a TiO2 shell, with mean sizes of about 10–20 and 5–10 nm, respectively. These data were in very good agreement with X‐ray crystallographic measurements (13 and 7 nm). Moreover, magnetization measurements revealed that both γ‐Fe2O3@TiO2 and γ‐Fe2O3@TiO2‐EG‐Cu(II) had superparamagnetic behaviour with saturation magnetization of 23.79 and 22.12 emu g?1, respectively. γ‐Fe2O3@TiO2‐EG‐Cu(II) was found to be a green and highly efficient nanocatalyst, which could be easily handled, recovered and reused several times without significant loss of its activity. The scope of the presented methodology is quite broad; a variety of aldehydes as well as amines have been shown to be viable substrates. A mechanism for the cyclocondensation reaction has also been proposed.  相似文献   

9.
Two routes have been developed inorder to prepare an inclusion complex of polyaniline (PANI) and β‐cyclodextrin (βCyD). The first route was to in situ polymerize N‐phenyl‐1,4‐phenylenediamine (PPD) which was encapsulated in βCyD in advance. The formation of an inclusion complex was confirmed by UV‐vis, circular dichroism (CD), and NMR spectra. It was found that the synthesized complex was readily dissolved in a range of solvents due to the solubility of βCyD. In these solvents, PANI was well encapsulated by βCyD with some conformation change in the chain of PANI, which was proved by the CD spectra of PANI. The second route involved preparing the inclusion complex by post‐encapsulation of PANI emeraldine base (EB) into βCyD in aqueous solution at room temperature. The encapsulation of EB into βCyD was confirmed by FT‐IR and UV‐vis spectra. The band shift in UV‐vis spectra indicated that the inclusion complexation was a gradual process, and the change in the chain conformation of PANI was also observed after it was encapsulated into βCyD. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

10.
An extraction method based on dispersive nanomaterial ultrasound‐assisted microextraction was used for the preconcentration of carbofuran and propoxur insecticides in water samples prior to high‐performance liquid chromatography with UV detection. ZnS:Ni nanoparticles were synthesized based on the reaction of the mixture of zinc acetate and nickel acetate with thioacetamide in aqueous media and then loaded on activated carbon (ZnS:Ni‐AC). Different methods were used for recognizing the properties of ZnS:Ni‐AC and then this nanomaterial was used for extraction of carbamate insecticide as new adsorbent. The influence of variables on the extraction method (such as amount of adsorbent (mg: NiZnS‐AC), pH and ionic strength of sample solution, vortex and ultrasonic time (min), ultrasound temperature and desorption volume (mL) was investigated by a screening 27–4 Plackett–Burman design. Then the significant variables were optimized by using a central composite design combined with a desirability function. At optimum conditions, this method had linear response >0.0060–10 μg/mL with detection limit 0.0015 μg/mL and relative standard deviations <5.0% (n = 3).  相似文献   

11.
In this work, cross‐linked poly(1‐vinylimidazole) (PVIm) and poly(1‐vinylimidazole‐co‐acrylic acid) [poly(VIm‐co‐AA)] polyampholytes microgel were synthesized by precipitation polymerization in supercritical carbon dioxide at 14 and 20 MPa. The obtained products were characterized by Fourier transform infrared spectroscopy and Energy‐dispersive X‐ray spectroscopy. The results indicate that the functional monomers including 1‐VIm and AA were cross‐linked in polymers successfully. Aggregate particles with diameters of approximately 200 nm were observed by scanning electron microscopy and particle size distribution. Surface area analysis showed that the surface area of microgel prepared at a pressure of 14 MPa are 40.28 m2/g. The swelling behavior of polyampholytes microgel was studied. The cross‐linking degrees of PVIm and copolymers can reach 92.6% and 98.1%. The effect of pH values of solution, contact time, adsorbent dosage, initial Cr(VI) concentration on adsorption capacity were also investigated. The results revealed that cross‐linked polymer has a high adsorption capacity of 306.0 mg/g for Cr(VI) in 130 mg/l solution at pH 2 and cross‐linker ratio of 27.3%. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

12.
A method for the trace determination of cadmium ions in water, human urine and human blood serum samples using ultrasonic‐assisted dispersive micro‐solid‐phase extraction (UA‐D‐μSPE) was developed. Silica‐coated magnetic nanoparticles were coated with polythiophene, and the resulting sorbent was characterized using thermogravimetry, differential thermal analysis, scanning electron microscopy, Fourier transform infrared spectrometry and X‐ray diffraction. Following UA‐D‐μSPE, cadmium ions were quantified using graphite furnace atomic absorption spectrometry. A Box–Behnken design was used for optimization of important sorption and desorption parameters in UA‐D‐μSPE: in the sorption step, pH of solution, sorption amount and sonication time for sorption; in the desorption step, concentration of eluent, volume of eluent and sonication time. The optimum conditions for the method were: pH of solution, 7.5; sonication time for sorption, 3 min; sorption amount, 35 mg; type and concentration of eluent, HCl and 1.1 mol l?1; volume of eluent, 360 μl; sonication time for desorption, 110 s. Under the optimized conditions the limit of detection and relative standard deviation for the detection of cadmium ions by UA‐D‐μSPE were found to be 0.8 ng l?1 and <6%, respectively.  相似文献   

13.
Copper is an indispensable trace element for human health. Too much or too little intake of copper ion (Cu2+) can lead to its own adverse health conditions. Therefore, detection of Cu2+ is always of vital importance. In this work, a simple sensor was developed for rapid detection of trace Cu2+ in water, in which L‐cysteine (Cys) as a molecular probe was self‐assembled on a gold interdigital electrode to form a monolayer for specific capture of Cu2+. The interfacial capacitance of interdigital electrode was detected to indicate the target adsorption level under an AC signal working as the excitation to induce directed movement and enrichment of Cu2+ to the electrode surface. This sensor reached a limit of detection of 4.14 fM and a satisfactory selectivity against eight other ions (Zn2+, Hg2+, Pb2+, Cd2+, Mg2+, Fe2+, As3+, and As5+). Testing of spiked tap water was also performed, demonstrating the sensor's usability. This sensor as well as the detection method shows a great application potential in fields such as environmental monitoring and medical diagnosis.  相似文献   

14.
Novel Cu 2+ and Fe 3+ chelates derived from L 1 were synthesized and characterized by single crystal X‐ray diffraction. The results indicate that the Fe (III) crystal, [Fe(L1‐H)Cl2], has an orthorhombic structure of the type pc2b while the dimeric Cu (II) crystal, [Cu(L1‐H)Cl … ClCu(L1‐H)], has a monoclinic with space group Cc. X‐ray diffraction and spectroscopic studies revealed that L 1 acts as monobasic tetradentate with octahedral geometry in Fe (III) crystal while it behaves as dibasic tetradentate with distorted‐octahedral in the Cu (II) crystal. Also, the two chelates were characterized by spectral, magnetic and thermal analyses. DFT parameters were used to prove the liberation of a proton from COOH rather than NH groups. The kinetic and thermodynamic parameters of Fe (III) chelate were determined by Coats‐Redfern and Horowitz‐Metzger methods. Cyclic voltammogram provides information about the oxidation states of Cu (II) and Fe (III) chelates. Antitumor activity against Epitheliod carcinoma (Hela), breast cancer (MCF‐7) and antibacterial activities of chelates were investigated.  相似文献   

15.
We report an eco‐friendly synthesis of α‐Cr2O3 nanoparticles (NPs) using Callistemon viminalis (Bottle Brush) flower extracts as an efficient reducing and capping agent. NPs of sizes 15 nm and 17 nm were synthesized by annealing them at 400°C and 500°C, respectively, which were characterized by X‐ray diffraction, UV–Vis, Fourier transform‐infrared, high‐resolution‐transmission electron microscopy/scanning electron microscopy, SAED, energy‐dispersive X‐ray spectroscopy and SQUID. Microplate‐based assay was used for examining antibacterial potential against 12 pathogenic bacterial strains, and their minimum inhibitory concentrations were calculated. MTT cytotoxic assay was accomplished on Leishmania tropica amastigotes and promastigotes, which revealed IC50 values of 44 μg/ml and 10.56 μg/ml, respectively. An IC50 value of 46.32 μg/ml was obtained for HepG2 cancer cells. Enzyme inhibition studies indicated good acetylcholinesterase, moderate butyrylcholinesterase and low alpha‐glucosidase inhibition. Hemolytic assay indicated hemocompatibility at low concentration. In addition, good DPPH radical scavenging and moderate reducing power and total antioxidant potential was revealed by α‐Cr2O3 NPs.  相似文献   

16.
Detection and the simultaneous removal of mercury ions are of vital importance. In this study, fluorescent monomers, small molecular sensors, were first synthesized using 4‐bromo‐naphthalic anhydride as precursor. These double bond bearing sensors were then grafted to polystyrene (PS) microspheres through dispersion polymerization. The sensors still retained their detecting ability when they were anchored on the surfaces of PS microspheres. Upon the addition of Hg2+ ions to the PS microspheres, both the color and the fluorescence intensity changed, which could be employed to detect Hg2+ ions. The absorption capacity of the two kinds of PS microspheres reached 0.557 mg g?1 and 0.628 mg g?1 respectively. The PS microspheres still remain their fluorescence and absorption even used for five times. These polymeric highly sensitive chemosensors may see their applications in purification of polluted environments. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4592–4600  相似文献   

17.
A novel Cu–Zn β‐cyclodextrin (CuZn/β‐CD) model compound was synthesized under ultrasound irradiation to mimic the functionality of copper zinc superoxide dismutase (CuZnSOD). For comparison, Cu/β‐CD and Zn/β‐CD complexes were also synthesized via a sonochemical approach. The obtained complexes were characterized by FTIR, ICP‐OES, UV–vis and Scanning electron microscopy‐Energy dispersive X‐ray (SEM‐EDX) techniques. The SOD activity of the complexes was evaluated by a pyrogallol autoxidation method. These enzyme‐mimetic materials scavenge ambient free radicals, with the potential to provide significant antioxidant protection (scavenging ability > 70%).  相似文献   

18.
From previous reports, graphitic carbon nitride (g‐C3N4) can be used as a photocatalyst, although the low efficiency of solar energy utilization, small specific surface area and high recombination rate of photogenerated electron–hole pairs limit its practical application. For the purpose of increasing photocatalytic activity, especially under irradiation of visible light, we successfully synthesized a new composite, namely porous g‐C3N4/Ag/Cu2O, through chemical adsorption of Ag‐doped Cu2O on porous g‐C3N4, which has not been investigated carefully worldwide. The composition, morphology and optical properties of the composite were investigated through methods including X‐ray diffraction, energy‐dispersive X‐ray, Fourier transform infrared, UV–visible and photoluminescence spectroscopies and transmission electron microscopy. Using rhodamine B as organic pollutant to be degraded under the irradiation of visible light, different mass ratios of Ag/Cu2O doped on porous g‐C3N4 led to enhanced photocatalytic performance of the composite compared to pure porous g‐C3N4. When the mass ratio of Ag/Cu2O is 15%, porous g‐C3N4/Ag/Cu2O exhibits a degradation rate 2.015 times higher than that of pure porous g‐C3N4. The reasons for this phenomenon may be attributed to the increased utilization efficiency of visible light, high‐speed separation of photogenerated electron–hole pairs, accelerated interfacial transfer process of electrons and increased surface area of the composite. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

19.
A rapid and sensitive LC–MS/MS method with good accuracy and precision was developed and validated for the pharmacokinetic study of quercetin‐3‐O‐β‐d ‐glucopyranosyl‐7‐O‐β‐d ‐gentiobioside (QGG) in Sprague–Dawley rats. Plasma samples were simply precipitated by methanol and then analyzed by LC–MS/MS. A Venusil® ASB C18 column (2.1 × 50 mm, i.d. 5 μm) was used for separation, with methanol–water (50:50, v/v) as the mobile phase at a flow rate of 300 μL/min. The optimized mass transition ion‐pairs (m/z) for quantitation were 787.3/301.3 for QGG, and 725.3/293.3 for internal standard. The linear range was 7.32–1830 ng/mL with an average correlation coefficient of 0.9992, and the limit of quantification was 7.32 ng/mL. The intra‐ and inter‐day precision and accuracy were less than ±15%. At low, medium and high quality control concentrations, the recovery and matrix effect of the analyte and IS were in the range of 89.06–92.43 and 88.58–97.62%, respectively. The method was applied for the pharmacokinetic study of QGG in Sprague–Dawley rats. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

20.
Herein, the α‐Fe2O3@carboxyl‐functionalized yeast composite (α‐F@CFYC) was synthesized by direct oxidation of yeast with K2FeO4 and used as a novel adsorbent/heterogeneous Fenton catalyst for removal of methylene blue (MB). The obtained α‐F@CFYC was fully characterized by scanning electron microscopy, EDX, X‐ray diffraction analysis, Fourier‐transform infrared, thermogravimetry, and X‐ray photoelectron spectroscopy, respectively, and the corresponding results showed that α‐Fe2O3 nanoparticles were successfully obtained and deposited on yeast surface, as well as more functional groups were introduced/exposed on yeast surface. Furthermore, various influence parameters (eg, contact time, initial pH, and MB concentration) on the adsorption/catalysis ability of α‐F@CFYC for MB have been investigated in detail under ambient conditions. As a result, owing to the synergetic effect of the loaded α‐Fe2O3 and the introduced/exposed functional groups on yeast surface, the as‐obtained α‐F@CFYC exhibited high adsorption capacities and good catalysis degradation properties for MB.  相似文献   

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