Effect of Fe/Pb molar ratio on the structure,magnetic and dielectric properties of PbFe12O19 nanoparticles

In this paper, lead hexaferrite (PbFe₁₂O₁₉) nanoparticles were synthesized by sol-gel method. In order to prepare PbFe₁₂O₁₉ nanoparticles, the metal nitrates with Fe/Pb?=?8, 10, 11, 12, 14 ratios and citric acid were used. The structure, morphology, magnetic, and dielectric properties of PbFe₁₂O₁₉ nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), vibrating sample magnetometer (VSM) and LCR meter. XRD results revealed that the samples with Fe/Pb?≤?10 and Fe/Pb?>?10 have single-phase hexaferrite and hematite (α- Fe₂O₃) structures, respectively. As a result, the sample with Fe/Pb?=?10 is single-phase and shows the highest values of the saturation magnetization and remanence magnetization. We found that the values of dielectric constant (ε′) and dielectric loss (ε″) increase with an increase in the Fe/Pb molar ratio from 8 to 12 and then decreases with an increase of Fe/Pb molar ratio to 14. The variation of ac conductivity (σ_ac) with frequency ranging from 1?kHz to 200?kHz showed that electrical conductivity in these ferrites is mainly due to the electron hopping mechanism.     

Isoclinism between pairs of n-Lie algebras and their properties

In this paper, we investigate the notion of isoclinism on a pair of n-Lie algebras, which forms an equivalence relation. In addition, we prove that each equivalence class contains a stem pair of n-Lie algebras, which has minimal dimension amongst the finite dimensional pairs of n-Lie algebras. Finally, some more results are obtained when two isoclinic pairs of n-Lie algebras are given.     

Ultrasound assisted dispersive micro solid-phase extraction of four tyrosine kinase inhibitors from serum and cerebrospinal fluid by using magnetic nanoparticles coated with nickel-doped silica as an adsorbent

Nanoparticles (NPs) consisting of a magnetic Fe₃O₄ core and a nickel(II)-doped silica shell were prepared and are shown to be viable materials for selective magnetic extraction of trace quantities of the tyrosine kinase inhibitors (TKIs) imatinib, nilotinib, erlotinib and sunitinib. The NPs were characterized by scanning electron microscopy, transmission electron microscopy, DLS and XRD analysis, and the results revealed a uniform in size (with a typical diameter of 40 nm) and a core-shell structure. The magnetic nanoadsorbent displays good affinity of the TKIs, probably because of the affinity between the Ni(II) ions of the NPs with the nitrogen atoms in the TKIs. The magnetism of the NPs enables them to be quickly separated from serum and cerebrospinal fluid samples. Imidazole, with its higher affinity for Ni(II) than that of the TKIs, was used for desorption of the TKIs from the NPs prior to their quantification by HPLC with UV detection. The detection limits are as low as 200, 480, 130, and 250 ng·L￣¹ for imatinib, sunitinib, erlotinib, and nilotinib, respectively. The intra-day precisions (RSDs) were lower than 4.0 %. The method displays a wide linear range. It was applied to the determination of TKIs in (spiked) human serum and cerebrospinal fluid and gave recoveries in the range from 94.6 to 98.6 %.     

Innovative separation and preconcentration technique of coagulating homogenous dispersive micro solid phase extraction exploiting graphene oxide nanosheets

A uniquely novel, fast, and facile technique is introduced for the first time in which a scant amount of graphene oxide (GO), without modification, has been utilized in dispersive mode of solid phase extraction (SPE) for an efficient yet simple separation. The proposed method of coagulating homogenous dispersive micro solid phase extraction (CHD-µSPE) is based on coagulation of homogeneous GO solution with the aid of polyetheneimine (PEI). CHD-µSPE use full adsorption capacity of GO because in this method was used GO solution obtained from synthesis process without drying step and stacking nanosheets. In optimized condition, 30 µL GO solution (7 mg mL⁻¹), obtained in synthesis process, was injected into 1.5 mL the sample solution followed by immediate injection of 53 µL PEI solution (1 mg mL⁻¹). After inserting PEI, GO sheets aggregate and can be readily separated by centrifugation. PEI not only cause aggregation of GO, but also form three-dimensional network of GO with easy handling in following separation steps. Lead, cadmium, and chromium were selected as model analytes and the effecting parameters including the amount of GO, concentration of PEI, sample pH, extraction time, and type of desorption solvent were investigated and optimized. The results indicate that the proposed CHD-µSPE method can be successfully applied GO in dispersive mode of SPE without effecting on good capability adsorption of GO. The novel method was applied in determination of lead, cadmium, and chromium in water, human saliva, and urine samples by electrothermal atomic absorption spectrometry. The detection limits are as low as 0.035, 0.005, and 0.012 µg L⁻¹ for Pb, Cd, and Cr respectively. The intra-day precisions (RSDs) were lower than 3.8%. CHD-µSPE method showed a good linear ranges of 0.24–15.6, 0.015–0.95 and 0.039–2.33 µg L⁻¹ for Pb, Cd and Cr respectively. Method performance was investigated by determination of mentioned metal ions in river water, human urine and saliva sample with good recoveries in range of 94.2–103.0%. The accuracy of the method was underpinned by correct analysis of a standard reference material (SRM: 2668 level I, Urine).     

The mutual effect of metal sample and turboflame in LIBS signal enhancement

The main aim of the present study is to evaluate the mutual effect of copper sample and turboflame in laser induced breakdown spectroscopy (LIBS) signal enhancement. The use of copper sample leads to a signal enhancement in CN (B²Σ⁺–X²Σ⁺) 384.2–388.4 nm molecular transition, N_742nm, N_744nm, N_746nm (a triplet generated by the fine splitting of the 2s²2p²(³P)3s–2s²2p²(³P)3p transition) and H_{α, 656.3 nm} (as a flame inductor) atomic lines analysis. Additionally, increase in copper sample temperature with flame can enhance the Cu atomic line intensities (as copper sample inductors). Moreover, in this paper, the comparison between turboflame and alcohol flame on LIBS analysis was studied. LIBS signal intensity variation in a turboflame and turboflame coupled with copper sample at different laser pulse energies indicated that the low laser pulse energy could be compensated by using a copper sample that is coupled with turboflame and improved LIBS signal enhancement. For flames analysis, the use of metal sample in LIBS method is demonstrated to be costeffective, compact, and capable of signal enhancement.     

Electro-optical Kerr effect of azo-dye-doped liquid crystals using nulled intensity method

ABSTRACT

The electro-optical Kerr effect and pre-transition behavior have been investigated for different concentration of dimethyl-aminoazobenzene dye-doped nematic liquid crystal by using the nulled intensity method. Measurement results have showed that the molecular reorientation of liquid crystals induced by photoisomerization of azo dyes come about to increase an amount of Kerr constant at low percentages of dye concentration. Additionally, the results of pre-transition temperature which were obtained by extrapolating the invers Kerr constant as a function of temperature have been found to be in good agreement with predictions of the Landau-De Gennes model.     

Application of dispersive liquid–liquid microextraction followed by gas chromatography/mass spectrometry as effective tool for trace analysis of organochlorine pesticide residues in honey samples

A dispersive liquid–liquid microextraction (DLLME) method followed by gas chromatography/mass spectrometry (GC/MS) was applied for the trace determination of organochlorine pesticides in honey samples. The type and volume of organic extraction and disperser solvents, pH, effect of added salt content and centrifuging time and speed were optimized to find the appropriate extraction conditions. In DLLME, 30 µL of 1,2-dibromomethane (serving as extractant) and 1.5 mL of acetonitrile (serving as disperser) were applied. The limit of detection (3 s) and limit of quantification (10 s) for all the analytes of interest (organochlorine pesticides) varied from 0.004 to 0.07 and from 0.02 to 0.3 ng g^?1, respectively. The extraction recovery ranged from 91 to 100 %, and the enrichment factors ranged from 171 to 199. The relative standard deviation was <6 % for intraday (n = 6) and <8 % interday (n = 4) measurements. The proposed DLLME–GC/MS method was confirmed to be fast, simple to perform, friendly to environment and suitable for analysis of organochlorine pesticide residues at trace levels in honey samples.     

Electrocatalytic oxidation of glucose at a Ni-curcumin modified glassy carbon electrode

The electrocatalytic oxidation of glucose was investigated on a nickel-basedchemically modified electrode (Ni(II)-curcumin) prepared by electropolymerization of Ni-curcumin complex (curcumin=1,7-bis[4-hydroxy-3-methoxyphenyl]-1,6-heptadiene-3,5-dione) in alkaline solution. Reaction kinetic and mechanism were investigated by using cyclic voltammetry (CV) and chronoamperometry (CA) techniques and steady-state polarization measurements. Cyclic voltammetry studies indicated that in the presence of glucose the anodic peak current of surface redox mediator was increased, followed by decrease in the corresponding cathodic current. This indicates that glucose was oxidized at the surface of this modified electrode. The results were explained based on the concept of electrocatalytic reactions that occur in this chemically modified electrode. The diffusion coefficient of glucose and the rate constant of the catalytic oxidation of glucose were found to be 6.7×10⁻⁶ cm² s⁻¹ and 6.5×10³ M⁻¹ s⁻¹, respectively. It has shown that by using the Ni-curcumin modified electrode, glucose can be determined with good response and low detection limit.     

Dynamic modelling of milk ultrafiltration by artificial neural network

Artificial neural networks (ANNs) have been used to dynamically model crossflow ultrafiltration of milk. It aims to predict permeate flux, total hydraulic resistance and the milk components rejection (protein, fat, lactose, ash and total solids) as a function of transmembrane pressure and processing time. Dynamic modelling of ultrafiltration performance of colloidal systems (such as milk) is very important for designing of a new process and better understanding of the present process. Such processes show complex non-linear behaviour due to unknown interactions between compounds of a colloidal system, thus the theoretical approaches were not being able to successfully model the process. In this work, emphasis has been focused on intelligent selection of training data, using few training data points and small network. Also it has been tried to test the ANN ability to predict new data that may not be originally available. Two neural network models were constructed to predict the flux/total resistance and rejection during ultrafiltration of milk. The results showed that there is an excellent agreement between the validation data (not used in training) and modelled data, with average errors less than 1%. Also the trained networks are able to accurately capture the non-linear dynamics of milk ultrafiltration even for a new condition that has not been used in the training process.     

Potentiometric membrane sensors based on zirconyl(IV) phthalocyanine for detection of sulfosalicylic acid

A metallophthalocyanine complex with zirconium(IV) ion in the center (as an oxo-zirconium, Zr=O, group) was used in poly vinyl chloride (PVC) membranes for the selective detection of 5-sulfosalicylic acid (SSA). The resulting electrodes demonstrate Nernstian responses over a wide range of sulfosalicylic acid concentration (10⁻⁶ to 10⁻¹ mol dm⁻³) with a slope of about −29 mV per decade. The influence of lipophilic ion-exchanger sites on the response properties of the electrodes was investigated. The optimal potentiometric response was observed for the electrode in the presence of about 150 mol% of cationic additive (relative to ionophore) in the phase membrane. The electrodes have a fast response time, micromolar detection limit and good long-term stability (more than 2 months). The feasibility of the application of these sensors for the potentiometric titration of iron in solutions that were prepared from magnetite samples was investigated.