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Diamagnetic cobalt(III)tris(o-ethylxanthate) and nickel(II)bis(o-ethylxanthate)

Abstract

Diamagnetic [Co(xanth)3] and [Ni(xanth)2] complexes have been prepared by reaction of Co(II) and Ni(II) salts with potassium O-ethyl xanthate (Kxanth). The isolated Co(III) and Ni(II) complexes have been characterized by single-crystal X-ray crystallography, UV-VIS and IR spectroscopy, computational methods, and magnetic measurements.

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The Influence of Mg(II) and Ca(II) Ions on Rutin Autoxidation in Weakly Alkaline Aqueous Solutions

Summary

Rutin (quercetin-3-O-rutinoside) is one of the most abundant bioflavonoids with various biological and pharmacological activities. Considering the ubiquitous presence of Mg(II) and Ca(II) ions in biological systems we decided to investigate their influence on the autoxidation of rutin in weakly alkaline aqueous solutions. Changes in UV-Vis spectra recorded during the rutin autoxidation in aqueous solution at pH 8.4 revealed that this process was very slow in the absence of metal ions. The presence of Mg(II) and, especially Ca(II) ion, increased the transformation rate of rutin. UV-Vis spectra recorded after prolonged autoxidation indicated the formation of humic acidlike products in the presence of Mg(II) and Ca(II) ions. Four new compounds formed during the initial stage of rutin autoxidation in the presence of Mg(II) and Ca(II) ions were detected by HPLCDAD. Based on the analysis of their DAD UV-Vis spectra and comparison of their retention times with the retention time value for rutin, we concluded that the initial rutin transformation products were formed by the water addition on double bond in ring C and hydroxylation of ring B. A very small decrease of the initial rutin concentration (4%) was observed by HPLC-DAD in the absence of metal ions for the period of 90 minutes. However, rutin concentration decrease was much larger in the presence of Mg(II) and Ca(II) ions (14% and 24%, respectively). The more pronounced effect of Ca(II) ion on the rutin autoxidation may be explained by the stronger binding of Mg(II) ion to rutin and thus greater stabilizing effect on reaction intermediates caused by its higher ionic potential (charge/ionic radius ratio) in comparison to Ca(II) ion. The results of this study may contribute to the better understanding of interactions of Mg(II) and Ca(II) ions with natural phenolic antioxidants which are important for their various biological activities.

Open access
UV-induced photodecomposition of 2, 2′, 4, 4′, 6, 6′-hexanitrostillbene (HNS)

Abstract

HNS (2, 2′, 4, 4′, 6, 6′-hexanitrostillbene) is a heat-resistant photosensitive explosive widely used in the booster charge. Investigation of the photodecomposition mechanism may provide important information for controlling and enhancing the detonation performance, also for the lifetime prediction. The UV-induced photodecomposition of HNS has been subjected to experimental studies. The UV-Vis spectra, X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance spectra (EPR) demonstrate the formation of NO2 free radicals and nitroso derivatives of HNS upon UV irradiation, which proves well known facts that C-NO2 breaking and removal of oxygen from the nitro group take part in the photodecomposition of HNS.

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Redetermination of Zero-Field Splitting in [Co(qu)2Br2] and [Ni(PPh3)2Cl2] Complexes

Abstract

A mononuclear CoII complex, [Co(qu)2Br2], and NiII complex, [Ni(PPh3)2Cl2], (qu = quinoline, PPh3 = triphenylphosphine) have been reinvestigated. Their crystal and molecular structures are reported along with IR and UV-Vis spectra. Magnetism of both complexes has been studied by using the DC SQUID magnetometry. These complexes exhibit a moderate magnetic anisotropy expressed by zero-field splitting parameter D. The D-value is positive for both complexes with D/hc = +5.94 cm−1 and D/hc = +12.76 cm−1, that is also confirmed by ab initio calculations.

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Green synthesis, characterization and antibacterial activities of silver nanoparticles from strawberry fruit extract

Abstract

Silver nanoparticles (AgNPs) have been synthesized in the presence of Strawberry fruit extract (SBFE) at room temperature. The synthesized AgNPs was characterized by UV-vis spectroscopy, SEM, EDS, XRD, TEM and FTIR. The UV-vis spectra of the AgNPs show SPR band at 450 nm. TEM results indicate that AgNPs are spherical in shape and size range between 7–65 nm. Antibacterial activity of the synthesized AgNPs has been assessed against Pseudomonas aeruginosa and Bacillus licheniformis. The results show that AgNPs exhibit inhibitory effect and effect is a function of AgNPs concentration. The antibacterial activity of the prepared AgNPs has been compared with two antibiotics, amoxicillin and ciprofloxacin. It is found that the antibiotics perform better than AgNPs.

Open access
Crystalline phase evolution in nanostructured copper sulfide thin films prepared by spray pyrolysis method: the effect of annealing

Abstract

In this study, physical properties of copper sulfide thin films deposited on glass substrates by spray pyrolysis method at different temperatures (260 °C, 285 °C and 310 °C) were investigated. The influence of annealing time on the physical properties of grown layers was also studied. According to FESEM images, the sizes of the compact copper sulfide grains were varied from about 100 nm to 60 nm. Hall effect and resistivity measurements confirmed that all samples had p-type conductivity. The XRD patterns showed that, together with the dominant digenite phase (Cu1.8S) in all samples, the copper-rich phases also appeared as a result of increasing substrate temperature. The optical UV-Vis spectra analysis showed that due to increasing the substrate temperature, the band gap of the layers was reduced from about 2.4 eV to 2.0 eV. We found that as a result of annealing at 400 °C for 1.5 h in Ar atmosphere, the sample which was initially grown at 310 °C with the highest copper content, totally transformed into the polycrystalline monoclinic chalcocite phase (Cu2S) with 3D nanoporous architecture.

Open access
Synthesis and modification of reduced graphene oxide aerogels for biofuel cell applications

Abstract

We have carried out the preparation of reduced graphene oxide aerogels using eco-friendly method that is based on the Hummers method of graphite oxidation without the use of NaNO3 that produces toxic gases. To obtain a porous 3D structure of reduced graphene oxide, we performed the hydrothermal reduction at elevated temperature. We also prepared the rGO aerogel/CNT composite using multiwalled carbon nanotubes as linkers. The rGO aerogels are promising materials as they possess good electrical conductivity (up to 100 S/m) and high surface area and porous structure (~500 m2/g). The main goal was to obtain the material for electrodes in enzymatic biofuel cells. Thus, the proper modification was performed using free radical functionalization. It was shown that in order to synthesize rGO aerogels modified with anthracene, the proper order of reactions needs to be provided. The morphology of anthracene modified electrodes was analyzed using scanning electron microscopy, which confirmed their porous structure with non-uniform pore size distribution that ranged between few nanometers to microns. Data obtained by Raman spectroscopy confirmed the successful oxidation and reduction of analyzed materials. UV-Vis spectra revealed the presence of anthracene moieties in examined materials. We also recorded preliminary cyclic voltammograms that confirm an electric conductivity of the obtained structures.

Open access
High transparency and conductivity of heavily In-doped ZnO thin films deposited by dip-coating method

Abstract

Heavily In doped zinc oxide (IZO) thin films were deposited on glass substrates by dip-coating method with different concentrations of indium. The effect of heavy In doping on the structural, morphological, optical and electrical properties of ZnO was discussed on the basis of XRD, AFM, UV-Vis spectra and Hall effect measurements. The diffraction patterns of all deposited films were indexed to the ZnO wurtzite structure. However, high In doping damaged the films crystallinity. The highest optical transmittance observed in the visible region (>93 %) exceeded that of ITO: the absolute rival of the most commercial TCOs. The grain size significantly decreased from 140 nm for undoped ZnO to 17.1 nm for IZO with the greatest In ratio. The roughness decreased with increasing In atomic ratio, indicating an improvement in the surface quality. Among all synthesized films, the sample obtained with 11 at.% indium showed the best TCO properties: the highest transmittance (93.5 %) and the lowest resistivity (0.41 Ωcm) with a carrier concentration of 2.4 × 1017 cm−3. These results could be a promising solution for possible photonic and optoelectronic applications.

Open access
Treatment of produced water by induced air flotation: effect of both TWEEN 80 and ethanol concentrations on the recovery of PAHs

Abstract

The present study investigates the application of induced air flotation (IAF) technique on PAHs (PAHs) removal performance from a real oilfield produced water of a separator cell. The quantification of total PAHs (PAHtot) was done using ultraviolet-visible spectrometry (UV-Vis) according to the naphthalene calibration curve. The UV-Vis spectra of naphthalene dissolved in a mixture of the binary solvent (water-ethanol) and the Tween 80 showed stability in the molecular orbital of C10H8. The use of small concentration of Tween 80 was revealed to be discrete in the quantification of PAHtot. The flotation process was improved at the critical micelle concentration of Tween 80 (CMC) of 2 % and the critical coalescence concentration of ethanol (CCC) of 0.5 mL/L for the PAHtot recovery of 49.76 % and the PAHtot content in the pulp of 50.24 %. At these concentrations, half of PAHtot was removed from produced water PW. Above the CMC and the CCC, the PAHtot recovery decreased and the PAHtot content in the pulp increased. It was found that there is a collector concentration at which the amount of water carrying from the pulp to the concentrate was increased and in parallel, the PAHtot recovery increased and the PAHtot content in the pulp decreased. Both of the CMC and the CCC have promoted the decrease on the conditioning time from 30 to 10 min and the flotation time from 20 to 6 min. Since the impeller speed and air flow rate were constant, the flotation of PAHs was limited. The flotation kinetics of PAHtot was described by the Higuchi model.

Open access
Peat Humic Substances and Earthworm Biohumus Extracts for Agricultural Applications

Extracts for agricultural use were prepared using cavitation method at 45 oC and at 95 oC from peat and earthworm biohumus. Samples of all studied extracts had similar dry-matter content. Peat humic substances and earthworm biohumus extracts were analysed using UV-Vis, FT-IR, and fluorescence spectrometry. Trace element analysis was performed with atomic absorption spectrometry. Extracts were tested for acidity, conductivity, humic acid concentration, and carboxyl group concentration. Hydrophobicity was assessed using a water-polyethylene glycol twophase system and calculation of the partition coefficient. Total nitrogen and phosphorus concentration was determined. Concentration of the humic substances slightly changed during the heating process. Significant changes in total phosphorus concentration was observed both in earthworm humus and peat extract. Thermal treatment caused decrease of hydrophobicity and lower concentration of organic matter in extracts, while carboxyl group concentrations in isolated humic substances practically did not change. The calculated ratio from UV-Vis spectra showed significant difference in humification degree of samples.

Open access