Synthesis,structure and capacitive properties of cobalt hydroxide films on stainless steel substrates

Cobalt (hydro)oxide films on AISI 304 stainless steel and sintered metal fibre filter Bekipor ST 20AL3 were prepared using electrochemical deposition from neutral cobalt acetate solutions under galvanostatic conditions. Deposited films were structurally characterized using X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. All electrochemical measurements were performed in aqueous NaOH solution. Capacitive behavior of different films was evaluated using cyclic voltammetry data. The highest specific capacitance (965 F g^?1) was reached when Bekipor ST 20AL3 mesh was used as a support for electroactive substance.      

The effect of aluminium oxide on the reduction of cobalt oxide and thermostabillity of cobalt and cobalt oxide

During precipitation and calcination at 200°C nanocrystalline Co₃O₄ was obtained with average size crystallites of 13 nm and a well developed specific surface area of 44 m² g^?1. A small addition of a structural promoter, e.g. Al₂O₃, increases the specific surface area of the cobalt oxide (54 m² g^?1) and decreases the average size of crystallites (7 nm). Al₂O₃ inhibits the reduction process of Co₃O₄ by hydrogen. Reduction of cobalt oxide with aluminium oxide addition runs by equilibrium state at all the respective temperatures. The apparent activation energy of the recrystallization process of the nanocrystalline cobalt promoted by the aluminium oxide is 85 kJ mol^?1. Aluminium oxide improves the thermostability of both cobalt oxide and the cobalt obtained as a result of oxide phase reduction.      

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.      

The use of ultrasonic treatment for improvement of metrological performance of sorption atomic absorption determination of lead(II) and cadmium(II) traces

The optimal parameters for ultrasonic treatment (frequency 200–300 kHz, intensity 2–4 W cm^?2) were obtained to intensify Pb(II) and Cd(II) sorption concentration by carbon sorbent from apricot pit. The combined action of ultrasonic frequency of 18 kHz and 1 MHz on concentrate slurry increases its sedimentation stability from 3 to 180 minutes and decreases S_r value up to 7% at Pb(II), Cd(II) hybrid sorption atomic absorption determination in natural waters, brines, common salt.      

Sensitive and fast determination of papaverine by adsorptive stripping voltammetry on renewable mercury film electrode

The renewable mercury film electrode, applied for the determination of papaverine traces using differential pulse adsorptive stripping voltammetry (DP AdSV) is presented. The calibration graph obtained for papaverine is linear from 1.25 nM (0.42 µg L^?1) to 95 nM (32.2 µg L^?1) for a preconcentration time of 60 s, with correlation coefficient of 0.998. For the renewable mercury electrode (Hg(Ag)FE) with a surface area of 9.1 mm² the detection limit for a preconcentration time of 60 s is 0.7 nM (0.24 µg L^?1). The repeatability of the method at a concentration level of the analyte as low as 17 µg L^?1, expressed as RSD is 3.3% (n=5). The proposed method was successfully applied and validated by studying the recovery of papaverine from drugs, urine and synthetic solution.      

Interfacial behavior of water bound to nitrocellulose containing residual nitric and sulfuric acids

To prepare nitrocellulose (NC), microcrystalline cellulose was treated in a mixture of nitric and sulfuric acids. Prepared NC containing a small amount of acids was studied at a different hydration degree (h = 10–1000 mg g^?1) in different dispersion media (chloroform-d, acetone-d₆ or their mixtures) using low-temperature ¹H NMR spectroscopy. The hydration degree and the presence of residual acids affected the temperature dependence of the chemical shifts of proton resonance of water bound to NC. The Gibbs free energy of bound water became less negative with increasing hydration rate. The chloroform and acetone media affect the behavior of bound-to-NC water unfrozen at T<273 K differently. Quantum chemical calculations were performed using ab initio (HF/6-31G(d,p)), DFT (B3LYP/6-31G(d,p)) and semiempirical PM7 methods to analyze the interfacial behavior of water interacting with NC containing residual amounts of nitric and sulfuric acids.      

L-alaninium perrhenate: crystal structure and non-linear optical properties

The crystal structure and non-linear optical properties of L-alaninium perrhenate, C₃H₈NO²⁺ ReO₄ ^?, are reported. The protonated amino acid and the perrhenate anion have their usual geometries. The three-dimensional hydrogen-bonded network can be seen as a stacking of layers parallel to the (100) planes. Each layer is formed by chains of alternating positive and negative ions along the b and c axes. Hydrogen bonding of adjacent layers forms alternating chains along the a axis. A high damage threshold and a second-harmonic generation efficiency three times that of KDP make this new material potentially useful in non-linear optics.      

Aerobic oxidation of cumene catalysed by 4-alkyloxycarbonyl-N-hydroxyphthalimide

4-Hexyloxycarbonyl-, 4-dodecyloxycarbonyl- and 4-hexadecyloxycarbonyl-N-hydroxyphthalimides were synthesised using trimellitic anhydride chloride as the starting material. The obtained lipophilic derivatives of N-hydroxyphthalimide were applied as catalysts of the cumene oxidation reaction with oxygen performed in polar acetonitrile, in non-polar tert-butylbenzene and in the absence of a solvent. The courses of reactions catalysed by N-hydroxyphthalimide and its derivatives were compared.      

Determination of vitamin B6 (pyridoxine hydrochloride) based on a novel BZ oscillating reaction system catalyzed by a macrocyclic complex

This paper reports a new method for determination of VB₆ (pyridoxine hydrochloride) by its perturbation effects on a novel Belousov-Zhabotinskii (BZ) oscillating system. This novel BZ system, in which malic acid serves as the substrate, contains an enzyme-like complex, macrocyclic complex {[CuL](ClO₄)₂}, as catalyst. The ligand L in the complex is 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene. Results show that the addition of pyridoxine hydrochloride can perturb the oscillation amplitude and period, and the change of the oscillation amplitude is linearly proportional to the concentration of pyridoxine hydrochloride in the range of 5×10^?7?2.5×10^?4 M. The obtained RSD with seven samples is 3.073%. An assay of pharmaceutical tablets of vitamin B₆ was evaluated. Some foreign ions were studied with respect to their possible influence on the determination of pyridoxine hydrochloride. The factors which influence this reaction include the concentration of reactant, the temperature of the reaction, property of catalyst, etc. Furthermore, the possible reaction mechanism has been proposed using the Field-Körös-Noyes (FKN) model.      

Stereoselective (exo-specific) synthesis, dynamic 1H NMR and quantum chemical conformational and configurational analysis of norbornene-aziridine-E-imidoyl system

Stereoselective (exo-specific) synthesis, dynamic ¹H NMR and computational analysis of exo-N??-{3-azatricyclo[3.2.1.0.^2,4]oct-3-yl)mesithyloxy)methylene}-1-benzensulfunamide (3) were investigated. Aziridine nitrogen inversion gives rise to two sets of configurations where the N-substituent is Syn (S) or Anti (A) to C7 of the norbornyl ring. At lower temperature, the proton signals of aziridine exo-E-3 decoalesces to show two syn conformers and one anti conformer (exo-E-3 ^{1 S} ? $ \leftrightharpoons $ ?exo-E-3 ^{2 S} ? $ \leftrightharpoons $ ?exo-E-3 ^{3 A} ) with ratio of 60:20:20, respectively. Experimentally, the Gibbs free energy of activations [??G ^? (kcal/mol) ?±?0.08] were calculated 11.96, 12.45 for 3 isomerizations. The standard Gibbs free energy (??G ^o kcal/mol) 0.174, 0, 0.174, and 0.298 at 213?K and energy minimum 6.64, 4.77 and 1.78 were calculated for 3 ^1S? $ \leftrightharpoons $ ?3 ^2S, 3 ^2S? $ \leftrightharpoons $ ?3 ^{3 A} , 3 ¹ S? $ \leftrightharpoons $ ?3 ^{3 A} isomerizations, respectively. The enthalpy (??H ^?, kcal/mol) and entropy (??S ^?, cal?mol^?1?K^?1) of activation for the nitrogen inversion of aziridine of 3 were calculated 11.2 and ?0.80, respectively.     

Volumetric properties of a stoichiometric mixture of K+ and Br− ions in H/D isotope-substituted aqueous methanol at 278.15–318.15 K: I. The H2O-CH3OH-KBr system

The densities of potassium bromide solutions in aqueous methanol mixtures have been measured with an error of at most ±(1 × 10^?5) g/cm³ for methanol mole fractions x ₂ of 0.06, 0.1, 0.3, or 0.6 and for the potassium bromide mole fractions up to about 2.65 × 10^?2 at 278.15, 288.15, 298.15, 308.15, and 318.15 K. Limiting partial molar volumes $\overline V _3^\infty $ , excess molar volumes $\overline V _3^{E, \infty } $ , and expansibilities $\overline E _{p, 3}^\infty $ have been calculated for a stoichiometric mixture of solvated K⁺ and Br^? ions in the mixed solvents. In the region of x ₂ ≈ 0.25, $\overline E _{p, 3}^\infty $ changes its sign from positive to negative. The $\overline V _3^{E, \infty } $ (x ₂) trend, on the whole, reflects the topologic features of the molecular structure of aqueous methanol associated through H-bonding.     

Kinetics investigation on the combustion of waste capsicum stalks in Western China using thermogravimetric analysis

The combustion kinetics of waste capsicum stalk (WCS) in Western China is investigated through thermogravimetric analysis compared with sawdust and coal, and co-combustion of WCS with coal is also investigated. Results show that the ignition characteristics of WCS is better than that of sawdust and coal, and the activation energy E of WCS-volatile combustion and WCS-char combustion are 78.55?kJ?mol^?1 and 44.59?kJ?mol^?1. However, integrating the characteristics of ignition and burnout, the combustion characteristic factor (S _N) of WCS is lower than that of sawdust. With the increasing in the heating rate, the ignition of WCS is delayed. Oxygen concentration $ C_{{{\text{O}}_{2} }} $ affects E and k ₀ of volatile combustion largely under rich-oxygen condition, when $ C_{{{\text{O}}_{2} }} $ increases from 0.2 to 0.8, E has increased threefold and k ₀ also intensively increases from 10⁶ to 10¹³?C10²². Oppositely, effect of $ C_{{{\text{O}}_{2} }} $ on the E and k ₀ of char combustion is little, and there is an exponential relationship $ S_{\text{N}} = 7. 1 2 8 \times 10^{ - 9} \times { \exp }(C_{{{\text{O}}_{2} }} /0. 3 6 8) - 6. 1 2 6 \times 10^{ - 9} $ between S _N and $ C_{{{\text{O}}_{2} }} $ . For the tests of co-combustion, all the experimental and weighted-average curves coincide well, and there is no remarkable synergistic effect. With the increase of mixing ratio that WCS added, E and k ₀ of volatile combustion increase, but correspondingly E and k ₀ of char combustion decrease.     

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.      

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.      

Debromination of 2,4,6-tribromophenol coupled with biodegradation

The application effect of aluminium and their alloys and mixtures with nickel was studied for the complete hydrodebromination of 2,4,6-tribromophenol (TBP) to phenol in aqueous NaOH solution at room temperature. It was found that the Raney Al-Ni alloy can rapidly transform TBP to phenol. Removal efficiency of 25 mM TBP solution in aqueous NaOH (15 g L^?1) solution at the end of 1h reaction was 100% using 4 g L^?1 Al-Ni. The hydrodebromination is accompanied by the dissolution of aluminium and formation of soluble Al(OH)₄ ^?1 anions under these reaction conditions. After completion of the hydrodebromination reaction removal of the dissolved metals was achieved by precipitation of appropriate hydroxides by adjustment of the pH value and filtration, the filtrate was treated with Pseudomonas or Rhodococcus bacterial strains to degrade dissolved phenol. The combined application of both (chemical-biological) treatments produced degradations of 100% of aromatic compounds.      

Polymer conjugates with potential biological activity based on new derivatives of 2-mercaptobenzoxazole-synthesis and characterization

New potentially biologically active compounds derived from 2-mercapto-benzoxazole were synthesized and coupled on polymeric support of poly (maleic anhydride-alt-vinyl acetate) for the preparation of polymer-drug conjugates with controlled drug release. All compounds were characterized by elemental and spectroscopy (FT-IR, ¹H-NMR) analysis. The toxicological tests recommend the products for further laboratory screening.      

Thermodynamic protonation constants of vardenafil by the nonlinear regression of multiwavelength pH-spectrophotometric titration data

pH-spectrophotometric titration data were used to determine protonation constants of vardenafil at different ionic strengths I and temperatures of 25°C and 37°C. The use of two different multiwavelength and the multivariate treatment of spectral data, SPECFIT32 and SQUAD(84) nonlinear regression analyses and INDICES factor analysis is presented. The reliability of the protonation constants of the drug was proven with goodness-of-fit tests of the pH-spectra. The thermodynamic protonation constants log K _T ⁱ were estimated by a nonlinear regression of (log K, I) data using the Debye-Hückel equation, yielding log K ₄ ^T = 3.59(1) and 3.26(1), log K ₃ ^T = 5.64(1) and 5.81(1), log K ₂ ^T = 9.41(1) and 8.59(2), log K ₁ ^T = 10.92(2) and 10.05(1) at 25°C and 37°C, where the figure in brackets is the standard deviation in last significant digit. Concurrently, the experimental determination of four thermodynamic protonation constants was combined with the computational prediction of the MARVIN program based on knowledge of the chemical structures of the drug and was in good agreement with its experimental value. The factor analysis of spectra in the INDICES program predicts the correct number of light-absorbing components when the instrument error is known and when the signal-to-error ratio SER is higher than 10.      

Self-assembly of acetylcholinesterase on gold nanoparticles electrodeposited on graphite

The immobilisation of AChE enzyme through chemisorption on Au-modified graphite was examined with view of its prospective application in the design of membraneless electrochemical biosensors for the assay of enzyme inhibitors. The developed immobilisation protocol has been based on a two-stage procedure, comprising i) electrodeposition of gold nanostructures on spectroscopic graphite; followed by ii) chemisorption of the enzyme onto gold nanoparticles. Both the coverage of the electrode surface with Au nanostructures and the conditions for enzyme immobilisation were optimised. The proposed electrode architecture together with the specific type of enzyme immobilisation allow for a long-term retaining of the enzyme catalytic activity. The extent of inhibition of the immobilised acetylcholinesterase enzyme by the organophosphorous compound monocrotophos has been found to depend linearly on its concentration over the range from 50 to 400 nmol mL^?1 with sensitivity 77.2% inhibition per 1 µmol mL^?1 of monocrotophos.      

Biodegradation of Benzo[a]Pyrene through the use of algae

In this work for disposal of the biologically hard decomposed pollutant Benzo[a]Pyrene (BaP) photooxidation Chlorella kessleri was used. The simulation model system under the different experimental conditions (varying biomass and light intensity) was evaluated. For quantitative analysis of the decrease in BaP, GC/MS technique was used. The highest degradation efficiency was achieved in the case of biomass from the culture of live algae (29%) and light intensity at level of 13.5 W m^?2. When the dry biomass was used, degradation under the same conditions was lower because of lack of enzymatic activity in the system.