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311.
312.
Aslı Baysal Aslı Deniz Saatci Mehmet Kahraman Suleyman Akman 《Mikrochimica acta》2011,173(3-4):495-502
We report on the separation and preconcentration of lead(II) and copper(II) ions using silver-coated titanium dioxide nanoparticles modified with cysteamine, and their determination by slurry analysis via flame atomic absorption spectrometry. The ions were adsorbed via a conventional batch technique, and the ion-loaded slurry was separated and directly introduced into the spectrometer, thereby eliminating a number of drawbacks. The effects of pH, amount of sorbent, slurry volume, sample volume and other ions on the recovery were investigated. Under optimized experimental conditions, copper and lead can be recovered within the 95% confidence level in certificated waste water, but also in spiked sea water samples. The technique is fast, simple, and leads to complete elution. The limit of detection (3δ, at n?=?10) was 0.37 μg L?1 for Cu(II), and 0.38 μg L?1 for Pb(II). Figure
We report on the separation and preconcentration of lead(II) and copper(II) ions using silver-coated titanium dioxide nanoparticles modified with cysteamine (Fig. 1), and their determination by slurry analysis via flame atomic absorption spectrometry. Under optimized experimental conditions, copper and lead can be recovered within the 95% confidence level in certificated waste water and spiked sea water samples. The technique is fast, simple, and leads to complete elution. Figure 1. Schematic illustration of the preparation of TiO2@Ag–Cysteamine nanoparticles and inset shows the color of the nanoparticles. 相似文献
313.
Caglar M Ilican S Caglar Y Sahin Y Yakuphanoglu F Hür D 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,71(2):621-627
The optical properties of sulfonated polyaniline (SPAN) thin film prepared by electrochemical method have been investigated. Polychromic behavior of SPAN thin film (transparent yellow-green-dark blue) was observed when the cyclic voltammograms were taken between -0.25 V and +1.90 V (vs. Ag/AgCl, sat.) during the growth of polyaniline film. In situ UV-vis spectra of the polymers-indium tin oxide (ITO) glass electrode were taken during the oxidation of the polymers at different applied potentials. The direct band gap values of SPAN thin film changed from 3.771 eV to 3.874 eV with the applied potentials. From in situ UV-vis spectra, the optical constants such as refractive index and dielectric constant of the SPAN thin film were determined. The important changes in absorption edge, refractive index and the dielectric constant were observed due to the applied potentials. The refractive index dispersion curves of the film obey the single-oscillator model and oscillator parameters changed with the applied potentials. The most significant result of the present work is in situ spectroelectrochemical method, which can be used to modify the optical band gaps and constants. 相似文献
314.
Zeliha Gokmen Mehmet Erdi Onan Nahide Gulsah Deniz Didem Karakas Engin Ulukaya 《合成通讯》2013,43(21):3008-3016
1,4-Naphthoquinones (1,4-NQ) have been reported to possess a variety of pharma-cological properties including antibacterial, antifungal, antiviral, anti-inflammatory, anti-artherosclerotic, and anticancer effects. In this study, new N- and S,S-substituted-1,4-NQ derivatives were synthesized in excellent yields and were completely characterized by spectroscopic analysis IR, NMR (1H and 13C), MS and microanalysis. The cytotoxic activities of 1,4-NQ derivatives were examined against to A-549, DU145, HCT-116 and MDA-MB-231 cancer cells. Among these compounds, 2-[4-(2-furoyl)piperazine-1-yl]-3-chloro-1,4-NQ 5 and 2,3-bis(cyclobuthylsulfanyl)-1,4-NQ 17 were identified as the most potent anticancer agents with cytotoxic activity against three cell lines (breast (MDA-MB-231), prostate (DU145), colorectal (HCT-116). 相似文献
315.
316.
The swelling behavior of acrylamide (AAm)–based polyampholyte hydrogels in water and in aqueous salt (NaCl) solutions was investigated. [(Methacrylamido)propyl]trimethyl‐ammonium chloride (MAPTAC) and acrylic acid (AAc) were used as the ionic comonomer in the hydrogel preparation. Three sets of hydrogels containing 70 mol% AAm and 30 mol% ionic comonomers of varying mole ratios were prepared. The variations of the hydrogel volume in response to changes in pH, and salt concentration were measured. As pH increases from 1, the hydrogel volume V eq in water first increases and reaches a maximum value at a certain pH. Then, it decreases again with a further increase in pH and attains a minimum value around the isoelectric point (IEP). After passing the collapsed plateau region, the gel reswells again up to pH=7.1. The reswelling of the collapsed gels containing 10 and 4% MAPTAC occurs as a first‐order phase transition at pH=5.85 and 4.35, respectively, while the hydrogel with 1% MAPTAC reswells continuously beyond its IEP. Depending on pH of the solution, the hydrogels immersed in salt solutions exhibit typical polyelectrolyte or antipolyelectrolye behavior. The experimental swelling data were compared with the predictions of the Flory‐Rehner theory of swelling equilibrium including the ideal Donnan equilibria. It was shown that the equilibrium swelling theory qualitatively predicts the experimental behavior of polyampholyte hydrogels. 相似文献
317.
Prnová Anna Valúchová Jana Mutlu Nurshen Parchovianský Milan Klement Róbert Plško Alfonz Galusek Dušan 《Journal of Thermal Analysis and Calorimetry》2020,142(1):129-138
Journal of Thermal Analysis and Calorimetry - Yttrium aluminate glasses (76.8 mol% of Al2O3, 23.2 mol% of Y2O3) doped with Er3+ and Nd3+ ions at different concentration levels... 相似文献
318.
Using Markov models to simulate electron spin resonance spectra from molecular dynamics trajectories
Simulating electron spin resonance (ESR) spectra directly from molecular dynamics simulations of a spin-labeled protein necessitates a large number (hundreds or thousands) of relatively long (hundreds of nanoseconds) trajectories. To meet this challenge, we explore the possibility of constructing accurate stochastic models of the spin label dynamics from atomistic trajectories. A systematic, two-step procedure, based on the probabilistic framework of hidden Markov models, is developed to build a discrete-time Markov chain process that faithfully captures the internal spin label dynamics on time scales longer than about 150 ps. The constructed Markov model is used both to gain insight into the long-lived conformations of the spin label and to generate the stochastic trajectories required for the simulation of ESR spectra. The methodology is illustrated with an application to the case of a spin-labeled poly alanine alpha helix in explicit solvent. 相似文献
319.
Lokman Uzun Deniz Türkmen Erkut Ylmaz Sema Bekta Adil Denizli 《Colloids and surfaces. A, Physicochemical and engineering aspects》2008,330(2-3):161-167
The aim of this study was to investigate the performance of monoliths composed of hydroxyethyl methacrylate (HEMA) to which N-methacryloyl-(L)-cysteine methyl ester (MAC) was polymerized for removal of heavy metal ions. Poly(HEMA-MAC) monolith was produced by bulk polymerization. Poly(HEMA-MAC) monolith was characterized by FTIR and scanning electron microscopy (SEM). The poly(HEMA-MAC) monolith with a swelling ratio of 89%, and containing 69.4 μmol MAC/g were used in the adsorption studies. Adsorption capacity of the monolith for the metal ions, i.e., Cu2+, Cd2+, Zn2+, Hg2+, and Pb2+ were investigated in aqueous media containing different amounts of the ions (10–750 mg/L) and at different pH values (3.0–7.0). The maximum adsorption capacities of the poly(HEMA-MAC) monolith were 68.2 mg/g for Zn2+, 129.2 mg/g for Cu2+, 245.8 mg/g for Pb2+, 270.2 mg/g for Hg2+, and 284.0 mg/g for Cd2+. pH significantly affected the adsorption capacity of MAC incorporated monolith. The competitive adsorption capacities were 587 μmol/g for Zn2+, 1646 μmol/g for Cu2+, 687 μmol/g for Pb2+, 929 μmol/g for Hg2+, and 1993 μmol/g for Cd2+. The chelating monolith exhibited the following metal ion affinity sequence on molar basis: Cd2+ > Cu2+ > Hg2+ > Pb2+ > Zn2+. The formation constants of MAC–metal ion complexes have been investigated applying the method of Ruzic. The calculated values of stability constants were 5.28 × 104 L/mol for Cd2+, 4.16 × 104 L/mol for Cu2+, 2.27 × 104 L/mol for Hg2+, 1.98 × 104 L/mol for Pb2+, and 1.25 × 104 L/mol for Zn2+. Stability constants were increased with increasing binding affinity. The chelating monoliths can be easily regenerated by 0.1 M HNO3 with higher effectiveness. These features make poly(HEMA-MAC) monolith a potential adsorbent for heavy metal removal. 相似文献
320.
Ertugrul Altuntas Tufan Salan Eyyup Karaogul Deniz Aydemir 《International Journal of Polymer Analysis and Characterization》2018,23(1):89-98
The aim of this study was to investigate the effects of maleic anhydride-graft-polypropylene (MA-g-PP) as a compatibilizer and wood fiber as a lignocellulosic filler on technical properties of poly(l-lactic acid) (PLLA)/polypropylene composites. The obtained composites were characterized through mechanical tests, thermogravimetric analysis, differential scanning analyzer, and chemical analysis via Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM). The obtained results showed that the mechanical properties of the composites containing MA-g-PP were higher than those of the composites without MA-g-PP. SEM images revealed that the morphological properties of the composites including PP and PLLA were improved. The chemical interactions between PP and PLLA were demonstrated through FTIR results of composites with MA-g-PP. 相似文献