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Abstract  

The objective of this study is to evaluate the use of titanium dioxide nanoparticles which were prepared by novel sonochemical method as an ion exchange material for the removal of Sr from aqueous solution. The pH effect on the Sr2+ sorption was investigated. The data obtained have been correlated with Freundlich, Temkin and Dubinin–Radushkevich (D–R) isotherm models. Thermodynamic parameters fort he sorption system have been determined at four temperatures. Simple kinetic models have been applied to the rate and isotherm sorption data and the relevant kinetic parameters were determined from the graphical presentation of these models at 298°K. Results explained that the pseudo second-order sorption mechanism is predominant and the overall rate constant of sorption process appears to be controlled by chemical sorption process. The value of sorption energy E = 13 kJ/mol at 298°K and the value of Gibbs free energy ∆G° = 3,222 kJ/mol at 298°K prove that the sorption of strontium on titanium dioxide nanoparticles is an endothermic and non-spontaneous process.

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The real-time monitoring of the adsorption kinetic of antibody onto polyethylene terephthalate (PET) modified with gold nanoparticles (NPs) is performed into a dielectric flow microchannel. The principle is based on the microelectrode–dielectric interface excitation by a modulated voltage excitation through the dielectric layer with high frequency range. The set-up configuration using a homemade current-to-voltage converter has been developed for fast monitoring of biomolecule adsorption without direct electrical contact of microelectrodes with the microchannel flow. The change in the interfacial admittance, related to the output voltage measured through the microchip, during antibody incubation, gives information on the kinetics involved while antibodies are adsorbed at the interface. An example of adsorption on PET modified with gold NPS was taken. Experimental data were fit with the Langmuir equation and a good correlation was obtained with this latter, where the equilibrium constant, K, was found as 1.55 × 108 M−1 with a limit of detection for antibody concentration without depletion equal to 8.25 nM.

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devoted to the characterization of elastomer compounds containing NZnO particles. For example, Sahoo and Bhowmick [ 12 ] synthesized rod-shaped ZnO nanoparticles and studied the effect of prepared nanoparticles on cure characteristics besides static and

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Journal of Thermal Analysis and Calorimetry
Authors: J. González-Irún Rodríguez, P. Carreira, A. García-Diez, D. Hui, R. Artiaga, and L. Liz-Marzán

Abstract  

The effect of silica nanofiller on the glass transition of a polyurethane was studied by DSC. The pristine polymer exhibits a single glass transition at about –10C. Uniform SiO2 spheres with different average sizes and narrow size distributions were synthesized in solution by the Stber method [1]. Both the effects of silica content within the polymer and particle size were investigated, as well as two different surface treatments. Scanning electron microscopy (SEM) clearly confirms the presence of the particles within the polymer matrix, showing uniform distribution and no agglomeration. While shifting of the glass transition has been reported by many authors, we have not seen any noticeable shift in this polymer. Surprisingly, we found no relevant effects when either increasing the filler content or changing the particle size. Different amounts of particles with average diameters of 175, 395 and 730 nm did not affect the glass transition temperature of the pristine polymer.

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Figure 7 shows the transmission electron images of the PbTiO 3 nanoparticles obtained from pyrolysis complex 1 at 773 K for 2 h. It was found that PbTiO 3 powders only consisted of the nano-scale crystallites with the crystalline size of 60–100 nm

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Biotransformation of l-phenylalanine (l-1a) and five unnatural substrates (rac-1bf) by phenylalanine ammonia-lyase (PAL) was investigated in a novel microfluidic device (Magne-Chip) that comprises microliter volume reaction cells filled with PAL-coated magnetic nanoparticles (MNPs). Experiments proved the excellent reproducibility of enzymecatalyzed biotransformation in the chip and the excellent reusability of the enzyme layer during 14 h continuous measurement (>98% over 7 repetitive measurements with l-1a). The platform also enabled fully automatic multiparameter measurements with a single biocatalyst loading of about 1 mg PAL-MNP. Computational fluid dynamics (CFD) calculations were used to study the flow field in the chambers and the effect of unintended bubble formation. Optimal flow rate for l-1a reaction and specific activities for rac-1bf under these conditions were determined.

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Gold nanoparticles (AuNPs) and l-cysteine (l-cys), in order, as first and second layer were coated on the surface of a commercial thin-layer chromatography (TLC) plate. This assemble has been used as a new substrate for direct resolution of propranolol enantiomers based on the ordinary TLC technique. The effect of concentrations of the involved chemicals, time periods of the required processes, pH of the sample solutions, as well as the effects of different coating protocols on the resolution of the enantiomers, were investigated in order to find the optimized separation conditions. The results showed that 10.0 mM copper(II) acetate, in 70% ethanol-water adjusted at pH = 6.3, was suitable for being used as the mobile phase. The AuNPs with the average size of 15 nm and l-cys solution with a concentration of 10.0 mM and pH = 8.1 had been chosen for impregnating TLC plates.

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Summary

Formaldehyde in aquatic products was determined by micellar electrokinetic capillary chromatography (MEKC) after derivatization with 2,4-dinitrophenylhydrazine. Separation was carried out at 25 °C and 25 kV, using a fused silica capillary (75 µ internal diameter; 50.5 cm effective length) and an ultraviolet detector set at 360 nm. The optimal background electrolyte was 20 mM sodium tetraborate and 20 mM sodium dodecyl sulfate at pH 9.0 with 3 s hydrodynamic injection at 30 mbar. Electrophoretic analysis took approximately 6.5 min. The correlation coefficient of the calibration curve was 0.999 over the concentration range 2.0–100.0 mg L−1, and the LOD and LOQ values were 0.57 and 1.89 µg mL−1, respectively. The recoveries were from 83.7% to 97.2% with steam distillation as the sample pretreatment method.

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Summary

A new, specific, sensitive, selective, precise, and reproducible high-performance thin-layer chromatographic (HPTLC) method has been established for study of the stability of 3-acetyl-11-keto-β-boswellic acid (AKBA). HPTLC was performed on aluminium foil plates coated with 200 μm silica gel 60F254. Linear ascending development with toluene-ethyl acetate 7:3 (v/v) was performed at room temperature (25 ± 2°C) in a twin-trough glass chamber saturated with mobile phase vapour. Compact bands (R F 0.52 ± 0.02) were obtained for AKBA. Spectrodensitometric scanning was performed in absorbance mode at 250 nm. Linear regression analysis of the calibration plots showed there was a good linear relationship (r 2 = 0.9989 ± 0.0002) between peak area and concentration in the range 200–1200 ng band−1. The method was validated for precision, recovery, robustness, specificity, and detection and quantification limits, in accordance with ICH guidelines. The limits of detection and quantification were 3.06 and 9.29 ng band−1, respectively. The recovery of the method was 99.35–100.21%. AKBA was subjected to various stress test conditions — acid and alkali hydrolysis, oxidation, photodegradation, and dry and wet heat treatment. Degradation products were well resolved from the pure drug with significantly different R F values. Statistical analysis showed the method could be successfully applied for the estimation of AKBA in herbal extract and in nanoparticles. Because the method could effectively separate the drug from its degradation products, it can be regarded as stability-indicating.

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Abstract  

In this research, for the first time Nb and Ge were doped into titanosilicate nanoparticles up to 25% simultaneously. Crystalline phases and morphology of the synthesized samples were studied by X-ray diffraction (XRD) method and scanning electron microscope (SEM), respectively. Elemental analysis of the samples was performed using X-ray fluorescence (XRF) and Energy dispersive X-ray (EDX) techniques. Surface area of the samples was measured by BET method. Ion exchange potential of the synthesized samples for Sr2+ and Cs+ and effective parameters such as concentration, temperature, time, and pH were investigated. In addition,137Cs and 90Sr radio nuclides absorption in the best appropriate sample was examined. The selectivity of the samples for absorption of 137Cs and 90Sr was studied by gamma spectroscopy, liquid scintillation spectrometry, and atomic absorption spectroscopy methods. The obtained results showed that the prepared samples had good potential for absorption of 137Cs and 90Sr from the model solution. The sample containing equal amount of niobium and germanium, removed completely the 137Cs within the waste water of Tehran nuclear reactor and 90Sr in the desired solution.

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