Synthesis and photocatalytic activity assessing of the TiO<Subscript>2</Subscript> nanocomposites modified by some lanthanide ions and tin-derivative sandwich-type polyoxometalates

New nanocomposites containing sandwich-type polyoxometalate of [(PW₉O₃₄)₂(HOSn^IVOH)₃]^12? (P₂W₁₈Sn₃) loaded onto Ln-doped TiO₂ (Nd, Sm, Dy, Tb) nanoparticles were synthesized and their catalytic activities were assessed. The Ln–TiO₂ nanoparticles and Ln–TiO₂/P₂W₁₈Sn₃ nanocomposites were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction, field emission scanning electron microscope, energy dispersive analysis of X-rays spectra and diffuse reflectance spectra. The photocatalytic efficiency of the Ln–TiO₂ and Ln–TiO₂/P₂W₁₈Sn₃ were examined in the photodegradation of methyl orange and methylene blue solutions. It was revealed through different characterization techniques that the P₂W₁₈Sn₃ was successfully loaded on the lanthanide-doped anatase phase TiO₂ nanoparticles and the particles diameter were relatively 20–30 nanometers. It was revealed that doping by the lanthanide ions followed by loading of polyoxometalates improves the photocatalytic performance of TiO₂ effectively. The effects of operational parameters and the kinetics of photocatalytic degradation under UV light were discussed. The prepared nanocomposites were stable and could be easily separated from the reaction system.     

Theoretical Prediction of Adsorption Properties of Carmustine Drug on Various Sites of the Outer Surface of the Single-Walled Boron Nitride Nanotube and Investigation of Urea Effect on Drug Delivery by DFT and MD

In this work, the adsorption behavior of Carmustine (BCNU) drug over the (6,0) zigzag single-wall boron nitride nanotube (SWBNNT) is studied by means of density functional theory calculations and molecular dynamics simulations (MD). The calculated adsorption energies proved that the adsorption of BCNU molecule on SWBNNT is a physisorption process. The natural bond orbital calculations demonstrated that existence of a charge transfer from the SWBNNT to the BCNU molecule. Moreover, quantum theory of atoms in molecules showed that the hydrogen bonds and electrostatic interactions are two major factors contributed to the overall stabilities of the complexes. Furthermore, interaction of BCNU with the surface of single wall BNNT at 310 K and 1 bar in the present of water and different concentration of Urea molecules has been studied by MD simulation. The MD results confirm that the highest number of hydrogen bond and the lowest value of Lennard-Jones (L-J) energy between nanotube and drug exist in the simulation system with concentration of 1 mol L^?1 Urea.     

Conclusive evidence for delayed autocatalytic behavior of Mn(II) ions at a critical concentration

The kinetics of the permanganic oxidation process of glycine, L-alanine and L-leucine in strong acid media were investigated using a spectrophotometric technique. Conclusive evidence has proven that the autocatalytic activity of Mn(II) in these reactions in strong acidic media is analogous to that of weak acid media, but in the former, Mn(II) ions should acquire a critical concentration for them to show autocatalytic characteristics. This critical concentration depends on the nature of the amino acid used. Considering the delayed autocatalytic behavior of Mn(II) ions, we herein present the rate equations and mechanisms satisfying observations for both catalytic and noncatalytic routes. The correspondence of the pseudo-order rate constants of the catalytic and noncatalytic pathways to Eyring law verify both the critical concentration as well as the delayed autocatalytic behavior concepts. In general, the onset of delayed behavior can be attributed to the concentration ratio of Mn(II) to amino acid which can be of a certain value for any particular amino acid.     

Mild and highly efficient method for the synthesis of 2-arylbenzimidazoles and 2-arylbenzothiazoles

A new, convenient method for the syntheses of 2-substituted benzimidazole and benzothizole is described. Short reaction times, large-scale synthesis, easy and quick isolation of the products, excellent chemoselectivity, and excellent yields are the main advantages of this procedure.     

High stable sandwich-type polyoxometallates based on . Synthesis, chemical properties and characterization of [(A-β-SiW9O34)2(MOH2)3CO3] (M = Y and Yb)

Highly hydrolytic and thermally stable sandwich-type polyoxometallates of [(A-β-SiW₉O₃₄)₂(MOH₂)₃CO₃]¹³⁻ (M = Y³⁺ and Yb³⁺) have been synthesized at room temperature by stoichiometric reactions of the trilacunary ligand with M³⁺ in 0.1 M carbonate solution. The new complexes were isolated as sodium and mixed sodium/potassium salts and were characterized by elemental analysis, IR, ¹³C and ²⁹Si NMR, UV–Vis spectroscopy, TGA, DSC and single crystal structure analysis. The crystal structure of the complexes consist of two lacunary Keggin moieties which are linked by a (H₂OMO)₃C belt into an assembly of virtual C₂ symmetry. Each M³⁺ ion adopts a mono-capped trigonal-prismatic coordination. The C₂ axis of the complexes and the local 3-fold axis of the MO₆ group lies in the (H₂OMO)₃C belt plane. The trigonal prismatic geometry is achieved by the two terminal oxygen atoms of an edge shared pair of WO₆ octahedra from each moiety and two oxygen from the belt, and the cap by one external water ligand. The hydrolytic and thermal stabilities of the complexes and the reasons that prove the retention of the isomeric form of the trilacunary ligand upon complexation are discussed.     

Electronic and optical properties of quaternary selenides for optoelectronic applications: Insights from DFT+U-computations

The optical properties, electronic charge density, electronic structure of the new layered selenides materials, BaGdCuSe₃, CsUCuSe₃, CsZrCuSe₃, and CsGdZnSe₃ compounds have been calculated by using the full potential and linear augmented plane wave (FP-LAPW) methods as applied in the WIEN2k package, which is based on the density functional theory. The ALnMSe3 compound's structure of these was (A = Cs, Ba; Ln = Zr, Gd, U; M = Cu, Zn) is composed of (n = 1, 2) layers, which might be separated by A atoms. It is to be observed that there is strong hybridization between the s, p, and d states of Zr, Gd, and Cu atoms. Around the gadolinium atom, the charge density contours are completely circular, but the Gadolinium “Gd” atom shows an ionic nature. To calculate the refractive index, we used Kramer's Kronig correlations with the imaginary part dielectric function. The decrease in the refractive index is due to the lack of probability for direct excitation of the electrons, resulting in a loss of energy. The value of the static refractive index for all reference compounds is about 1.75–2.25, which is indication that the material used in optoelectronic devices.     

High sensitive determination of trace amount of cobalt by catalytic adsorptive stripping voltammetry

A very sensitive and selective catalytic adsorptive cathodic stripping procedure for trace measurements of cobalt is presented. The method is based on adsorptive accumulation of cobalt-CCA (calcon carboxylic acid) complex onto a hanging mercury drop electrode followed by reduction of the adsorbed species by voltammetric scan using differential pulse modulation. The reduction current is enhanced catalytically by nitrite. The effect of various parameters such as pH, concentration of CCA, concentration of nitrite, accumulation potential and accumulation time on the selectivity and sensitivity were studied. The optimum condition for the analysis of cobalt, include pH 5.2 (Acetate buffer), 2.1 μM clacon carboxylic acid, 0.032 M sodium nitrite and an accumulation potential of 0.05 V (versus Ag/AgCl). Under these optimum conditions and for an accumulation time of 60 s, the measured peak current at −0.480 V is proportional to the concentration of cobalt over the entire concentration range tested 0.003–2.0 ng ml⁻¹ with a detection limit of 1 pg ml⁻¹ for an accumulation time of 60 s and 2.0–10.0 ng ml⁻¹ for an accumulation time of 40 s. The relative standard deviations for ten replicate measurement of 0.5 ng ml⁻¹ of cobalt were 3.1%. The main advantage of this new system is the microtrace Co(II) determination by ASV. The method was applied to determination of cobalt in a water sample and some analytical grade salts with satisfactory results. Published in Elektrokhimiya in Russian, 2009, Vol. 45, No. 2, pp. 221–228. The article is published in the original.     

Ultra-compact all-optical phase-controlled NAND,OR, XOR,XNOR, and NOT multi-function logic gate

Optical and Quantum Electronics - A theoretical analysis of the modulational instability (MI) in a nonlinear oppositely directional coupler with one channel fabricated from nonlinear medium having...     

Ferromagnetic insulating and reentrant spin glass behavior in Mg doped La0.75Sr0.25MnO3 manganites

In this study, the effect of Mg substitution on structural, magnetic and electrical properties of La_0.75Sr_0.25Mn_1?xMg_xO₃ and La_0.75Sr_0.25?xMg_xMnO₃ (nominal compositions) samples are investigated by XRD, Ac susceptibility and electrical resistivity measurements. It is found that Mg does not replace La in the perovskite lattice. Also the results show that by increasing Mg doping levels, the paramagnetic–ferromagnetic and metal–insulator transition temperatures decrease. The reason for decreasing transition temperatures with increasing Mg concentration is, that the long-range FM order has been destroyed by the Mg, which is randomly occupying Mn site. This leads to the suppression of double-exchange interaction in the Mn³⁺–O–Mn⁴⁺ networks. Also the reentrant spin glass (RSG) state accompanied by FM transition, exists in high doped samples. The RSG state could be understood on the basis of double exchange ferromagnetic interaction in Mn³⁺–O–Mn⁴⁺ and super-exchange antiferromagnetic interaction in the Mn⁴⁺–O–Mn⁴⁺ networks.     

Modulating opto-electronic and magnetic responses of Mo- and Zn-adsorbed LiNbO3 (1 1 1) surface for advanced energy harvesting applications: A comprehensive study

This study aimed to comprehensively investigate the optoelectronic and magnetic properties of Mo, Zn/LiNbO₃ (1 1 1) material. The primary objectives were to understand the potential for manipulating the material's magnetism and to elucidate the origin of spin-polarized states and magnetic moments, particularly with respect to the unpaired d orbitals of Nb, Mo, and Zn atoms. To achieve these objectives, we employed the Pardew–Burke–Ernzerhof (PBE) method within the Generalized Gradient Approximation (GGA + U) framework. This computational approach allowed us to examine the optoelectronic and magnetic characteristics of the material in detail. Our research yielded several key findings that enhance our understanding of Mo, Zn/LiNbO₃ (1 1 1) material. We observed a modest improvement in the material's absorption capacity within the visible spectrum, accompanied by a discernible red-shift. Notably, our study involved the calculation of the dielectric function and refractive constant of the material, revealing a strong correlation between absorption trends and the dielectric constant. Furthermore, our investigation uncovered that Mo, Zn/LiNbO₃ (1 1 1) exhibits distinct conduction and valence bands, with p and d orbitals predominantly contributing to each, respectively. The energy gap of the material falls within a range of 0.30–1.04 eV. A particularly significant finding was the narrower band gap of Mo, Zn/LiNbO₃ (1 1 1) material, which can be attributed to the superposition of Mo-d and Zn-p orbit energy levels with O-p orbit energy levels, ultimately forming a covalent bond. Importantly, our research demonstrated the material's heightened optical absorption within the visible spectrum, suggesting its suitability for various photonic and optoelectronic applications. Additionally, we calculated a wide range of optical characteristics, including the dielectric function, absorption coefficient, energy loss, reflectivity, refractive index, extinction coefficient, and optical conductivity, providing a comprehensive assessment of the material's optical properties.