Silver selenide modification of polyamide fabric

Formation of a silver selenide layer on silicone coated polyamide cloth was investigated. Fabric samples were selenized in potassium selenotrithionate (K₂SeS₂O₆) solution then treated with AgNO₃ solution. Formation of a silver selenide particle layer on the surface was confirmed by a change in appearance, X-ray diffraction, and EDX analysis. XRD revealed two phases: orthorhombic naumannite (Ag₂Se) and monoclinic selenium (Se₈). SEM showed that the fabric macrostructure and the multifilament yarn microstructure was preserved. The silver selenide particles ranged from 100 nm to more than 20 µm.      

Spectral properties and photophysical behaviour of water soluble cationic Mg(II) and Al(III) phthalocyanines

Peripherally and non-peripherally tetrasubstituted-[(N-methyl-2-pyridylthio)]phthalocyaninato magnesium (II) (5 and 6) and chloro aluminium (III) (7 and 8) tetraiodide have been synthesized and characterized. The photophysical properties of the complexes in dimethyl sulfoxide (DMSO) and aqueous medium in the presence and absence of cremophore EL have been studied. These complexes show high solubility in aqueous medium though they were aggregated. The triplet state quantum yields (F_T) and the triplet lifetimes (t_T) were found to be higher in DMSO with Φ_T ranging from 0.32 to 0.51, while t_T ranged from 282 to 622 ms in DMSO, compared to aqueous medium (pH 7.4 buffer) where Φ_T ranged from 0.15 to 0.19 and t_T from 26 to 35 ms. Addition of cremophore EL in aqueous solution resulted in partial disaggregation and increased photoactivity. The fluorescence lifetimes of the complexes showed strong dependence on their immediate environment. The ionic magnesium(II) and aluminium(III) phthalocyanines strongly bind to bovine serum albumin (BSA).      

Salutaridine and its derivatives as thebaine-equivalents in the synthesis of aporphines

Here we report the transformation of tetracyclic morphinan salutaridine (1) into 2,3,10,11-tetrasubstituted (R)-aporphines. This method serves as another chemical proof of the previously verified biosynthetic connection with pentacyclic morphinan-6,8-diene-type thebaine. In the presence of nucleophiles, this procedure could lead to pharmacologically interesting new tetrasubstituted aporphinoids. The enantioselective synthesis of 7S-salutaridinol (2) has been also achieved in order to investigate the acid-catalyzed reactions of this natural morphinan.      

Physical-chemical transformations in the system V2O5/(NH4)2Mo2O7 under hydrothermal conditions

Modified compositions in the system V₂O₅/(NH₄)₂Mo₂O₇ have been prepared by means of mechanochemical, hydrothermal, microwave and ultrasonic treatments in aqueous medium. Chemical and phase transformations occurring on the stages of modification and following calcinations have been studied with the help of XRD, DTA-TG, FTIR and UV-Vis spectroscopy, nitrogen adsorption, and SEM. It has been established that precursors of catalytically active phases possessing meso-macroporous structure have been formed during modification. The comparison of the properties of compositions prepared via different methods has been carried out. Particularly, precursors modified via various procedures possess different morphology.      

Addition of boranes to (E)-(η5-C5H5)2Zr(CH=CHPh)Cl

In this study, the addition of boranes to (E)-(η⁵-C₅H₅)₂Zr(CH=CHPh)Cl (3) has been examined in order to investigate the regioselectivity of these ‘hydroboration’ reactions. We have found that these additions proceed with remarkable selectivity to give exclusive formation of a saturated organic molecule where one carbon atom has both the boron and the zirconium fragments. These reactions do not proceed via a conventional hydroboration reaction, but instead go through an initial transmetalation step to generate (E)-(η⁵-C₅H₅)₂Zr(H)Cl (1) and the corresponding alkenyl boron intermediate, whereupon subsequent hydrozirconation of this latter species gives the geminal products. An x-ray diffraction study has been conducted on gem-(η⁵-C₅H₅)₂Zr(CH(Bpin)CH₂Ph)Cl (pin = 1, 2-O₂C₂Me₄) (2). Crystals of 2 were orthorhombic with a = 18.545(3) Å, b = 15.713(3) Å, c = 16.157(3) Å in the space group Pccn. An x-ray diffraction study has also been conducted on the trinuclear zirconium oxide species (η⁵-C₅H₅)₂ZrO₂[ZrCl(η⁵-C₅H₅)₂]₂ (4). Crystals of 4 were orthorhombic with a = 13.6000(8) Å, b = 14.2252(8) Å, c = 17.6500(10) Å in the space group P2(1)2(1)2(1).      

Cobalt electrodeposition onto polycrystalline gold from ammoniacal solutions

In the present work, the cobalt electrodeposition onto polycrystalline gold electrodes from aqueous solutions containing 0.01M CoSO₄ + 1 M (NH₄)₂SO₄ at pH=7 was analyzed. Linear voltammetry results suggested a change in the kinetic of the cobalt electrodeposition. In all cases, the nucleation rate (A), the number of active nucleation sites (N ₀) and the saturation number of nuclei (N _s ) values were potential dependent. The calculated Gibbs free energy (ΔG) for this system was 1.88×10^?20 J nuclei^?1 and the transfer coefficient for the Hydrogen Electroreduction Reaction (HER) was 0.47.      

Complexes of platinum and palladium with 4-nitrobenzoic hydrazide: synthesis and cytotoxic activity

New complexes of platinum and palladium were isolated with 4-nitrobenzoic hydrazide (4-NH) and characterized by spectroscopic techniques. Results show that the ligand is coordinated to metallic ions by the basic nitrogen of NH₂ group and have the general structure cis-[M(4-NH)₂X₂] where M= Pt or Pd and x = Cl or I. The compound III, [Pt(4-NH)₂I₂], was found to display cytotoxicity (IC₅₀ = 0.96 μmol L^?1) against the K562 tumoral cell line. This complex is significantly more cytotoxic than cisplatin.      

Synthesis and characterization of nanosized NiO2 and NiO using Triton® X-100

Nanosized NiO₂ particles with an average diameter of 15 nm are prepared by treating of Ni(NO₃)₂ · 6H₂O with an aqueous solution of KClO in the presence of Triton® X-100. This black fine powder of nickel peroxide was characterized by XRD diffraction, energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). The as-prepared NiO₂ can be easily transformed to nanosized NiO merely by washing it with acetone. The obtained NiO has an average diameter of 40 nm and was characterized by the same means used for NiO₂. The nanoparticles of NiO₂ and NiO were obtained in high yields and purities.      

Agglomeration of ZnS nanoparticles without capping additives at different temperatures

ZnS nanoparticles were precipitated in diluted aqueous solutions of zinc and sulphide ions without capping additives at a temperature interval of 0.5–20°C. ZnS nanoparticles were arranged in large flocs that were disaggregated into smaller agglomerates with hydrodynamic sizes of 70–150 nm depending on temperature. A linear relationship between hydrodynamic radius (R _a ) and temperature (T) was theoretically derived as R _a =652 - 2.11 T. The radii of 1.9–2.2 nm of individual ZnS nanoparticles were calculated on the basis of gap energies estimated from their UV absorption spectra. Low zeta potentials of these dispersions of ?5.0 mV to ?6.3 mV did not depend on temperature. Interactions between individual ZnS nanoparticles were modelled in the Material Studio environment. Water molecules were found to stabilize ZnS nanoparticles via electrostatic interactions.      

The effect of steel modifying with zinc oxyethylidenediphosphonate on its passivation in solutions of certain inhibitors

It is shown that a solution of zinc complex of 1-hydroxyethane-1,1-diphosphonic acid can be used for modifying the surface of low-carbon steel in order to enhance its passivation by aqueous solutions of other inhibitors (1,2,3-benzotriazole, sodium alkylcarboxylate, and their mixture). The results of accelerated tests of protectability of nanosized passivating coatings are compared. To assess the efficiency of steel protection by electrochemical tests, the difference in pit formation potentials ΔE = E _pt ⁱⁿ ? E _pt ^sup are determined from polarization curves in borate buffer solutions containing NaCl in the absence (E _pt ^sup ) and in the presence (E _pt ⁱⁿ ) of the inhibitor. The direct corrosion tests are carried out in cells and in the G-4 humidity chamber (GOST (State Standard) 9.054–75) where the time of the appearance of first indications of corrosion on samples τ_cor serves as the criterion of efficient protection. Three groups of coatings can be distinguished: with weak protectability characterized by ΔE < 0.20 V and τ_cor < 6.25 days; with medium protectability and ΔE = 0.20–0.40 V with τ_cor reaching 9 days; and the with high protecting efficiency and ΔE > 0.40 V where τ_cor can be even longer than 25 days.     

Tuning the textural and surface properties of carbon xerogels to be used as supports for gold catalysts

Carbon xerogels (CXs) synthesized from resorcinol and formaldehyde under different pH conditions were investigated. Both the textural and surface properties of the CXs depend closely on the pH used in the synthesis procedure. Concerning the texture, the mesoporous surface area (S_meso) increases and the micropore volume (V_micro) decreases as the pH increases; concerning the surface chemistry, surface oxygen functional groups were easier to be created (by O₂) on CX synthesized at lower pH. Application of these CXs as support of gold catalysts was also studied. Results showed that the oxygen activated CX that was synthesized at moderate pH (i.e., pH 6.0) was the most favorable support for gold catalysts used in selective oxidation of benzyl alcohol by molecular oxygen in liquid phase, due to the adequate amounts of surface oxygen functional groups created on the surface.      

Synthesis and spectral characterization of stannocanes of the type [O(CH2CH2S)2SnR2](R=Me1,Bun2,Ph3)

The stannocanes of the type [O(CH₂CH₂S)₂SnR₂](R=Me1,Buⁿ 2,Ph3) have been synthesized in an improved method by the reaction of R₂SnCl₂ with 2, 2′-oxydiethanethiol O(CH₂CH₂SH)₂ in molar ratio of 1:1 at the presence of sodium ethoxide in anhydrous ethanol. The reactions are carried out under inert atmosphere. These compounds have been extensively characterized by FT-IR, UV-Vis spectrophotometry, multi-nuclear (¹H, ¹³C, ¹¹⁹Sn) NMR, elemental analysis and mass spectrometry. The obtained data clearly indicates that, there is a strong interaction between oxygen atom of the ligand as a donor and Sn atom of the organotin species as a Lewis acid acceptor. Therefore, the resulted dithiostannocanes possess a transannular secondary bonding and hypervalency at the central Sn atom which leads to an increase in the coordination number of tin from four to five-coordinated tin.      

Stereoselective preparation of mono- and bis-derivatives of pentacyclo[6.3.0.02,6.03,10.05,9] undecane (D 3-trishomocubane)

The rearrangement of easily accessible Cookson’s diketone with chlorosulfonic acid in chloroform followed by the acidic hydrolysis gave 6-chloro-7-hydroxy-dichloropentacyclo[6.3.0.0^2,6.0^3,10.0^5,9]undecane-4-one, whose syn-stereochemistry was assigned through the X-ray crystal structure analysis. This key structure was used for the stereoselective synthesis of the D ₃-trishomocubane derivatives as well as for the preparation of potential drugs bearing hydroxy- and amino-functional groups. A new multigram preparative synthesis of D ₃-trishomocubane was developed.      

Spectral variational principle for Green's functions

For a suitable approximation \(\tilde K\) (q, q′, τ) to the Dirac-Feynman Green's function of a quantummechanical system, the parameter \({\mathcal{L}\tilde K}\) is defined, where ?≡i?/?τ??. It is shown thatΔ≧0 andΔ→0 asK→K, the exact Green's function, thus providing a criterion on approximate Green's functions analogous in its role to the variational principle for wavefunctions. A second somewhat weaker criterion is also proposed, based on \(\Sigma \equiv \left[ {tr\tilde K*tr\mathcal{L}^2 \tilde K - |tr\mathcal{L}\tilde K|^2 } \right]_{\tau avg} \geqq 0\) . Recipes are given for projecting out continuum contributions toΔ or∑ and for analyzing for the discrete eigen-value spectrum.     

Characterization of the citrate precursor, used for synthesis of nanosized Mg-Zn ferrites

The citrate precursor has been used to synthesize nanocrystalline Mg-Zn-ferrites. The nature of the prepared precursor is characterized and compared with those of the precursors studied earlier, prepared by the same process. The study has been performed by inorganic and organic elemental analyses, Fourier Transformed Infrared Spectroscopy (FTIR), Mössbauer spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Electron Paramagnetic Resonance (EPR), Electronic absorption spectrometry in the UV-VIS region, Differential Thermal analysis/ Thermogravimetry (DTA-TG) analyses, and X-ray diffraction (XRD) analysis. The collected results determined the precursor as a coordination polymer with monomer unit (NH₄)₄{M [Fe(C₆H₅O₇)₂]₂}, where M=Zn or Mg.      

Differential thermal analysis- studies on the crystallization of strontium tungstate from sodium tungstate melts

The kinetics of strontium tungstate crystallization from sodium tungstate melts in platinum crucibles were studied by differential thermal analysis at crystallization temperaturesT ₀=800, 900 and 1000° by continuous cooling at ratesR _T=40, 120 and 200° per hour. Heterogeneous nuclei that first formed on the metal platinate particles in the solution during the induction periods (t) grew to small crystallites (¯l). The main crystal growth started after the development of some excess solute concentration (Δ¯C) at the end of the induction temperatures (¯T). For the first 80% crystallization, the average crystal lengths (l _τ ) varied with the growth time (τ) according to the relation \(l_\tau ^2 = (\bar l)^2 + + 4\bar k_{D_1 } M\Delta \bar C\) where \(\bar k_{D1} \) is the diffusion rate constant at temperatures nearT, andM is the metal salt molecular weight. The initial growth rates and the ratiosl _τ ² /τ depended onΔ¯C instead ofR _T The last 20% growth was controlled only by the rate of development of the excess solute concentration.     

Lead and cadmium atomic absorption determination in solid carbonized food samples using flame-furnace atomizer

Direct atomic absorption solid sampling analysis using flame-furnace atomizer enables a significant decrease in the analysis duration, to avoid sample pollution and to exclude toxic reagents. The selection of the chemical modifiers decreasing the detection limit and improving the results repeatability is based on the analyte’s free atoms formation mechanism. The developed kinetic approach has allowed to determine pre-exponential factors k₀ and apparent activation energies E_a of atomization processes for Pb(II) and Cd(II) compounds and to propose effective chemical modifiers sodium N,N-diethyldithiocarbamate and urea for food samples. The express and precision technique for lead and cadmium determination in food, using proposed chemical modifiers and carbonization techniques was developed.      

Syntheses, characterization and crystal structures of new mono- and bis-Schiff base compounds derived from 1,2,4-triazine and the silver(I) complexes containing mono-Schiff base ligands

Some new Schiff bases, (Z)-4-amino-3-((E)-(R-methoxybenzylidene)hydrazono)-6-methyl-3,4-dihydro-1,2,4-triazin-5(2H)-one (R?=?2 (L2), R?=?3 (L3) and R?=?4 (L4)), were synthesized by the condensation reactions of 4-amino-3-hydrazinyl-6-methyl-1,2,4-triazin-5(4H)-one (L1) and corresponding methoxybenzaldehyde in a molar ratio 1:1.5 in high yields. The reaction of L2 and L4 with an excess amount of the corresponding aldehydes gave the unsymmetrical bis-Schiff bases (E)-3-((E)-(R-methoxybenzylidene)hydrazono)-4-((E)-R-methoxybenzylideneamino)-6-methyl-3,4-dihydro-1,2,4-triazin-5(2H)-one (R?=?2 (L22) and R?=?4 (L44)), respectively. Furthermore, the reaction of L2?CL4 with silver(I) nitrate in a molar ratio 2:1 led to the silver(I)-complexes with the general formula [Ag(Lx)₂]NO₃ (Lx?=?L2 (2), L3 (3) and L4 (4)). All synthesized Schiff base compounds and complexes were characterized by a combination of IR-, ¹H-NMR spectroscopy, mass spectrometry and elemental analyses. In addition, the structures of L2, L4·CH₃CN, L22·CH₃OH and L44·CH₃OH and complexes 2 and 4 were determined by X-ray diffraction studies.     

Biogenic iron compounds: XRD, Mossbauer and FTIR study

Materials based on biogenic iron oxides, which are a product of the metabolic activities of the neutrophilic iron-oxidizing bacteria (NIOB) from Sphaerotilus-Leptothrix group, were investigated. Natural microbial probes were collected from freshwater flow from Vitosha Mountain (Bulgaria) and cultivated under laboratory conditions in respect to select suitable cultures and conditions (nutrition media) for biomaterial accumulation of biogenic oxides. Samples were studied by physicochemical methods: X-ray diffraction, Mossbauer spectroscopy and IR spectroscopy. Their phase composition and physicochemical properties were obtained. Presence of both amorphous and crystal phase (ultra- and highly dispersed particles) was proved. Iron-containing compound in the natural biomass consists of α-FeOOH. The cultivated materials have more complex composition with iron-containing ingredients as α-FeOOH, Γ-FeOOH, Γ-Fe₂O₃ and Fe₃O₄. The sample of natural biomass was tested in reaction of CO oxidation and it showed potential to be used as catalyst support.