Spectrophotometric Determination of Thorium with Disodium Salt of Arsenazo-III in Perchloric Acid

A rapid and sensitive spectrophotometric method has been developed for the determination of thorium using 0.04% Arsenazo-III in a 2M perchloric acid solution. Absorbance was measured in 1 cm cell and the complex has a sensitive absorption peak at 654 nm. The complex is formed instantly in perchloric acid and remains stable for 45 minutes with constant absorbance. Beer's law is obeyed in the range 1–60 g·g^–1 of thorium concentration with a molar absorptivity at 654 nm = 3.07·10⁵ M^–1·cm^–1 at 24±2°C. The foreign ions interference in thorium determination have been checked. The cations were tested at >60-fold excess of thorium, Mn(II), Fe(III), Co(II) and Ni(II) interfere negatively, whereas only Ce(III) has increased the absorbance. Among the anions, cyanide, phosphate, thiocyanate and acetate at 150-fold excess of thorium cause significant interference. However, thorium can bedetermined in the presence of nitrate, chloride, oxalate, tartrate, ascorbate, thiosulphate and citrate. The method has been applied on certified reference material for thorium determination after extractive separation and the result was found in good agreement with the certified value. The method has been also applied successfully to determine thorium at g·g^–1 level in local ore samples with a precision of ±0.04%.     

A new route to trinuclear carbocyanines

Amides or vinylogous amides react with tosyl chloride-pyridine to form activated intermediates which condense with Fischer's base or their vinylogs to give carbocyanine structures. Under the same conditions formylated Fischer's base reacts with vinylogous Fischer's bases to give trinuclear carbocyanines in good yields. Their structure and the limitations of this route are discussed.     

A novel ion selective membrane potentiometric sensor for direct determination of Fe(III) in the presence of Fe(II)

A new PVC membrane potentiometric sensor that is highly selective to Fe(III) ions was prepared by using 2-[(2-hydroxy-1-propenyl-buta-1,3-dienylimino)-methyl]-4-p-tolylazo-phenol [HPDTP] as a suitable carrier. The electrode exhibits a linear response for iron(III) ions over a wide concentration range (3.5 × 10⁻⁶ to 4.0 × 10⁻²) with a super Nernstian slope of 28.5 (±0.5) per decade. The electrode can be used in the pH range from 4.5 to 6.5. The proposed sensor shows fairly a good discriminating ability towards Fe³⁺ ion in comparison to some hard and soft metals such as Fe²⁺, Cd²⁺, Cu²⁺, Al³⁺ and Ca²⁺. It has a response time of <15 s and can be used for at least 2 months without any measurable divergence in response characteristics. The electrode was used in the direct determination of Fe³⁺ in aqueous samples and as an indicator electrode in potentiometric titration of Fe(III) ions.     

Determination of the curie temperature of a single Ni nanowire from the analysis of current-voltage characteristics

A new method of measuring the Curie temperature of a single nanowire located on the surface of an insulating substrate has been proposed. The method is based on the analysis of the current-voltage characteristics of the nanowire obtained at different initial temperatures of the sample. A maximum is observed on the dependence of the first derivative of the resistance on the applied power, the position of which is shifted to lower powers with increasing initial temperature. The Curie temperature is determined graphically as the temperature at zero power. The Curie temperature of a nickel nanowire formed on a SiO₂/Si surface by the scanning probe lithography method has been measured. The critical current density at which the transition from the ferromagnetic to the paramagnetic state occurs has been determined.     

Magnetization Distribution in Particles with Configuration Anisotropy,Prepared via Microsphere Lithography

Technical Physics - The arrays of permalloy particles with shape anisotropy, prepared via microsphere lithography, have been characterized using atomic force microscopy and magnetic force...     

Kinetics and mechanism of base-catalyzed hydrolysis of Cu(II)-salicylamide complex

The kinetics of hydrolysis of Cu(II)-salicylamide complex have been studied in sodium hydroxide solution (0.5 to 2.5M). The observed pseudo-first-order rate constants vary according to the empirical equation 1/??_obs = B₁ + B₂/[ōH] up to 2.0 M sodium hydroxide concentration. The mechanism of base-catalyzed hydrolysis has been proposed and it is concluded that the reaction proceeds by the interaction of complex with the nucleophile, forming tetrahedral intermediate which then breaks down to products. The rate equation has been derived. Thermodynamic parameters have also been reported.     

Computational studies on optoelectronic and charge transfer properties of some perylene‐based donor‐π‐acceptor systems for dye sensitized solar cell applications

We report DFT studies on some perylene‐based dyes for their electron transfer properties in solar cell applications. The study involves modeling of different donor‐π‐acceptor type sensitizers, with perylene as the donor, furan/pyrrole/thiophene as the π‐bridge and cyanoacrylic group as the acceptor. The effect of different π‐bridges and various substituents on the perylene donor was evaluated in terms of opto‐electronic and photovoltaic parameters such as HOMO‐LUMO energy gap, λ_max, light harvesting efficiency(LHE), electron injection efficiency (Ø_inject), excited state dye potential (E^dye*), reorganization energy(λ), and free energy of dye regeneration (). The effect of various substituents on the dye–I₂ interaction and hence recombination process was also evaluated. We found that the furan‐based dimethylamine derivative exhibits a better balance of the various optical and photovoltaic properties. Finally, we evaluated the overall opto‐electronic and transport parameters of the TiO₂‐dye assembly after anchoring the dyes on the model TiO₂ cluster assembly.     

Magnetic,Electrical and Thermal Studies of Polypyrrole-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> Nanocomposites

This research paper comprises of the synthesis of polypyrrole (PPy)-Fe₂O₃ nanocomposites by employing the in situ chemical oxidative polymerization method. The concentration of the filler material was adjusted between 10–50 wt % of PPy. The synthesized nanocomposites were characterized by using X-ray diffraction (XRD). Magnetic analysis and DC electrical conductivity of the samples were carried out using vibrating sample magnetometer (VSM) and two probe DC conductivity method, point towards magnetically active and electrically conductive samples. The magnetic parameters under applied magnetic field demonstrated that the values of coercivity (H _c ), saturation magnetization (M _s ) and remanence (M _r ) can be tailored by carefully controlling the amount of dopant material into the nanocomposites indicating their suitability for controllable switching devices and microwave absorption applications. The DC electrical conductivity showed an increase up to 20 wt % of filler material and thereafter a decrease in the conductivity of nanocomposites with increase in filler content is observed. Thermogravimetric analysis (TGA) showed an increase in thermal stability with an increase in ferrite content in nanocomposites.     

Thermal Decomposition Kinetics of Some Di‐ and Triorganotin(IV) Carboxylates Derived from para‐Nitrophenylethanoic Acid

Thermogravimetric (TG) investigations of organotin(IV) carboxylates with the general formula R_mSnL_4−m (where R=CH₃, C₂H₅, n‐C₄H₉, C₆H₅, cyclo‐C₆H₁₁, n‐C₈H₁₇, m=2, 3, and L=para‐nitrophenylethanoate anion) have been performed. Derivative thermogravimetry (DTG) and differential thermal analysis (DTA) techniques, Horowitz‐Metzger method and the fundamental thermodynamic relations are used to evaluate the thermokinetic parameters of each thermal degradation pattern. Results reveal that the thermal stability is functional to Sn C and Sn O bonds. In the case of R₂SnL₂, activation energy, reaction order and pre‐exponential factor associated with the bulk degradation processes increase as the alkane chain length increases. Hence, Oct₂SnL₂ is thermally more stable than Bu₂SnL₂, which in turn is more resistant to thermal dissociation than Et₂SnL₂. The same phenomenon is not observed for R₃SnL compounds because their degradation is highly irregular. Furthermore, R₂SnL₂ has larger values of kinetic parameters than those of corresponding triorganotin(IV) para‐nitrophenylethanotes. Thermodynamic parameters of these compounds also reinforce the above facts.     

Two new sesquiterpenes derivatives from marine fungus Leptosphaerulina Chartarum sp. 3608

Two new sesquiterpenes, leptoterpenes A (1) and B (2) were isolated from the fungus Leptosphaerulina Chartarum sp. 3608, derived from a crinoid. It was the first chemical study on this species. The structures of these compounds were elucidated by spectroscopic methods including NMR and MS spectrometry. The absolute configurations of the new compounds were determined on the basis of the single-crystal X-ray diffraction and electronic circular dichroism data analysis. All compounds were tested for their anti-inflammatory activity and the inhibitory effects on Tyrosyl DNA phosphodiesterase II (TDP2).