Czochralski method for crystal growth of reactive intermetallics

Czochralski method of crystallization allows obtaining single crystals of many intermetallic compounds. New series Gd7NixPd3x (x = 2, 3) intermetallics was grown by the modi ed Czochralski method using a levitated melt in protective argon atmosphere. Preliminary studies of magnetic properties have shown that all crystals of the series order ferromagnetically. It was found that Gd7Ni2Pd shows magnetic transition to the ferromagnetic state at 225 K while Gd7Ni3 orders at 145 K

Surface properties of particles emitted from selected coal-fired heating plants and electric power stations in Poland : preliminary results

The surface properties of particles emitted from six selected coal-fi red power and heating plants in Poland have been studied in this work for the fi rst time. Samples were collected beyond the control systems. Surface composition of the size-distributed particles was obtained by photoelectron spectroscopy (XPS). The refl ection of the smallest, submicron particles was also measured to calculate their specifi c/mass absorption. The surface layer of the emitted particles was clearly dominated by oxygen, followed by silicon and carbon. The sum of the relative concentration of these elements was between 85.1% and 91.1% for coarse particles and 71.8–93.4% for fi ne/submicron particles. Aluminum was typically the fourth or fi fth, or at least the sixth most common element. The mass absorption of the submicron particles emitted from the studied plants ranged from 0.02 m2g-1 to 0.03 m2g-1. Only specifi c absorption obtained for the “Nowy Wirek” heating plant was signifi cantly higher than in other studied plants probably because the obsolete fi re grate is used in this heating plant. The obtained results suggest that the power/heating-plant-emitted fi ne particles contain less carbonaceous material/elemental carbon on their surfaces than those that are typical in urban air

Preconcentration of Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Pb(II) with ethylenediamine-modified graphene oxide

We describe a novel solid phase sorbent that was synthesized by coupling graphene oxide (GO) to ethylenediamine (EDA). This nanomaterial (referred to as GO-EDA) is capable of adsorbing the ions of iron, cobalt, nickel, copper, zinc and lead. The ethylenediamine-modified graphene oxide was characterized by X-ray photoelectron spectroscopy, scanning electron microscopy and Fourier transform infrared spectroscopy. The analytical procedure relies on (a) sorption of metal ions on GO-EDA dispersed in aqueous samples; (b) filtering, and (c) direct submission of the filter paper to energy-dispersive X-ray fluorescence spectrometry. This kind of dispersive micro-solid phase extraction was optimized with respect to pH values, concentration of GO-EDA, contact time, and the effects of interfering ions and humic acid on recovery of determined elements. Under optimized conditions, the recoveries of spiked samples range from 90 to 98 %. The detection limits are 0.07, 0.10, 0.07, 0.08, 0.06 and 0.10 ng mL−1 for Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Pb(II), respectively. The method has a relative standard deviation of <6 %, and its accuracy was verified by analysis of two standard reference materials [LGC6016 (estuarine water) and BCR-610 (groundwater)]. It was successfully applied to the determination of trace amounts of these metal ions in water samples

Influence of Yttrium Substitution on the Electronic Structure and Magnetic Moment of Gd7-xYxPd3 (x=0, 1, 2, 3, 4)

The electronic structure and magnetic properties of Gd7¡xYxPd3 (x = 0, 1, 2, 4) single crystals were examined. These compounds crystallized in the same crystal structure type (Th7Fe3) with the same c=a ratio of 0.63. A strongly anisotropic behavior of the magnetic and transport properties was found. Magnetic frustration and spin °uctuations on the palladium atoms are responsible for the complex magnetic properties of this ternary compound. As a part of current research we presented further characteristic of the Gd7¡xYxPd3 (x = 0, 1, 2, 4) single crystal

Quantification of active pharmaceutical ingredients in commercially available poly pharmaceutical tablets by means of DSC

Differential scanning calorimetry is the first line technique indispensable for industrial quality controllaboratories and, next to many routine applications, could be used in quantitative assays. For this purpose, a relationship between the signal value of analyte (enthalpy change ΔH) and its concentration in the matrix isused. However, there are several limitations of its application, concerning solid state interactions between APIs, other APIs and/or coexisting excipients. With respect to their physical properties, it is known that amorphization state and/or permanent particle deformation can produce relatively large areas of interparticle contact and thus high particle-particle bonding forces. Finally, it may affect the DSC quantitative measurements. The problem was shown using commercially available, different poly component tablets containing ibuprofen in the presence of pseudoephedrine hydrochloride or paracetamol and coexisting excipients

Studies of the bacterial surfaces by XPS and SEM methods

This work presents the results of studies on bacteria Bacillus subtilis which was grown at di erent temperatures. The experiments were carried out using X-ray photoelectron spectroscopy and scanning electron microscope equipped with cryo-chamber , which gives the possibility of testing biological samples in a frozen state. These methods enabled receiving images of surface topography of the bacteria and demarcated their chemical composition. After deconvolution of the lines C 1s and O 1s information concerning the intensity of the various functional groups in the bindings presented in the cell walls surface of tested strain and reallocation in relation to the temperaturę of incubation was obtained. These changes are visible in the form of an additional peak in both the C 1s and O 1s in bacteria cultured in suboptimum temperature

Selective adsorption and determination of hexavalent chromium ions using graphene oxide modified with amino silanes

Novel adsorbents are described for the preconcentration of chromium(VI). Graphene oxide (GO) was modified with various amino silanes containing one, two, or three nitrogen atoms in the molecule. These include 3-aminopropyltriethoxysilane (APTES), N-(3-trimethoxysilylpropyl)ethylenediamine (TMSPEDA), and N1-(3-trimethoxysilylpropyl)diethylenetriamine (TMSPDETA). The resulting GO derivatives were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and energy-dispersive X-ray fluorescence spectrometry (EDXRF). Adsorption studies show that these GO based sorbents are highly selective for Cr(VI) in the presence of Cr(III) at pH 3.5. Although the amino silanes applied in modification of GO contain different numbers of nitrogen atoms, the maximum adsorption capacities of GO derivatives are very similar (13.3–15.1 mg·g−1). Such results are in accordance with spectroscopy studies which show that the amount of amino silanes attached to GO decreases in the order of APTES > TMSPEDA > TMSPDETA. The APTES-modified GO was applied to selective and sensitive extraction of Cr(VI) ions prior to quantitation by low-power EDXRF using the Cr Kα line. The Cr(VI) ions need not be eluted from the solid adsorbent. The method has a 0.17 ng·mL−1 detection limit, and the recovery is 99.7 ± 2.2% at a spiking level of 10 ng·mL−1. The method was successfully applied to the determination of Cr(VI) in water samples

Nano-bismuth sulfide based dispersive micro-solid phase extraction combined with energy dispersive X-ray fluorescence spectrometry for determination of mercury ions in waters

A selective method for the determination of mercury ions in different types of water samples by energy dispersive X-ray fluorescence spectrometry (EDXRF) was developed. Quantification of Hg(II) by EDXRF was preceded by ultra-sound assisted dispersive micro-solid phase extraction (USA-DMSPE) on nano-bismuth sulfide (nano-Bi2S3) as a solid sorbent. At pH 1 nano-Bi2S3 selectively adsorbs Hg(II) ions from aqueous samples with an adsorption capacity of 499.1 mg g -1. The experimental data fitted well with the Langmuir isotherm model, which confirms the chemical character of the adsorption process. Under optimized preconcentration conditions, i.e. a sample pH of 1, adsorbent mass of 1 mg, sample volume of 50 mL and sonication time of 15 min, the linear response between fluorescence radiation intensity and the metal concentration was obtained within 1–200 ng mL -1 range with a correlation coefficient of 0.9988. The method allows the detection of mercury ions at a concentration of only 0.06 ng mL -1. The determination of Hg(II) ions after the nano-Bi2S3 based USA-DMSPE-EDXRF procedure is possible even in the presence of a high concentration of anions and cations typically coexisting in surface waters. The described method was applied to the determination of Hg(II) ions in mineral, spring, river, and artificial sea waters. The correctness of the procedure was confirmed by analysis of the certified reference material (Seawater QC3163)

Impact of D2O on peptidization of L‑proline

This is our follow-up study carried out in an order to collect experimental evidence regarding the impact of heavy water (D2O) on the spontaneous oscillatory peptidization of l-proline (l-Pro). Our earlier studies have been focused on the two sulfurcontaining proteinogenic α-amino acids, i.e., l-cysteine (l-Cys) and l-methionine (l-Met), and it seemed interesting to assess the effect induced by D2O on one more proteinogenic α-amino acid, i.e., l-Pro. It needs to be added that unlike l-Met, but similar to l-Cys, the oscillatory peptidization of l-Pro dissolved in the organic-aqueous solvent characterizes with the circadian rhythm. As analytical techniques, we used high-performance liquid chromatography with the evaporative light-scattering detection (HPLC-ELSD), mass spectrometry (MS), scanning electron microscopy (SEM), and turbidimetry. The obtained results can in certain sense be viewed as analogous to those earlier reported for l-Cys and l-Met by demonstrating that heavy water considerably hampers the oscillatory peptidization of l-Pro. However, an unexpected observation was also made than unlike the cases with l-Cys and l-Met, the observed hampering effect of D2O on the oscillatory peptidization of l-Pro is not monotonously dependent on the concentration of D2O in the system, but it is the strongest pronounced for 10% (v/v) D2O in the employed binary methanol–water solvent (with the investigated proportions of D2O in this solvent changing from 0 to 30%). Although we have no rational explanation for this striking effect, we believe that it should not pass unnoticed and therefore it is emphasized in this study. Maybe this firm quantitative result will prove an inspiration for future researchers interested in getting a deeper insight into the role of D2O in life processes, and more specifically in the kinetic and the mechanistic aspects thereof

Dielectric properties of BiFeO3 ceramics obtained from mechanochemically synthesized nanopowders

Dielectric behaviour of BiFeO3 ceramics,obtained by hot-pressing of nanopowders produced by mechanochemical synthesis from Bi2O3 and Fe2O3 oxides (weight ratio 2:1), was studied in the temperature range 125–575 K. The ceramics was found to exhibit step-like dielectric response ε*(T) with high permittivity values, similar to the behaviour of materials with giant dielectric permittivity. Three overlapping relaxation processes contribute to the dielectric response: i) relaxation in the lowtemperature range (220–420 K), characterized by activation energy of 0.4 eV, ii) relaxation in the temperature range 320–520 K with activation energy of 1.0 eV and iii) broad dielectric anomaly in the vicinity of 420 K, which disappears after 1 h annealing at 775 K. The lowtemperature relaxation is ascribed to the carrier hopping process between Fe2+ and Fe3+ ions. The presence of mixed valence of the Fe ions was proved by X-ray photoelectron spectroscopy. Dielectric relaxation in the middle-temperature range is considered as a result of grain boundary effect and internal barrier layers related to Bi25FeO40 phase as verified by X-ray diffraction. The high-temperature dielectric anomaly we relate to short-range hopping of ordered oxygen vacancies