ISSN (print): 0036-0244, ISSN (online): 1531-863X Editor-in-Chief: Aslan Yu. Tsivadze Publisher: Pleiades Publishing Indexed in: RUS White List (level 3), Scopus, Web of Science (SCIE)
Solubility, Density, and Refractive Index of the Ternary System Na2B4O7 + Mg2B6O11 + H2O at 308.15 K
Experimental studies on the solubility, density and refractive index in the ternary system (Na2B4O7 + Mg2B6O11 + H2O) at 308.15 K were determined with the method of isothermal dissolution equilibrium. Based on the experimental results, the phase diagram and its corresponding physicochemical properties versus composition diagram in the system were plotted. In the phase diagram of the ternary system at 308.15 K, there are one eutectic point and two crystallization regions corresponding to the large area of inderite (Mg2B6O11 · 15H2O) and the relative small area of borax (Na2B4O7 · 10H2O), respectively. Neither double salt nor solid solution was found in this system. The physicochemical properties (density and refractive index) of the ternary system at 308.15 K changes regularly with the increasing of sodium borate concentration. The calculated values of density and refractive index using empirical equations of the ternary system are in good agreement with the experimental values.
Acoustic Data on Molecular Interactions in Mixtures of Nitromethane and Nitroethane in Acetone at 303–318 K
Densities and ultrasonic velocities of binary mixtures of (nitromethane + acetone) and (acetone + nitroethane) in the volumes fraction range 0.1–1 at 298–318 K were measured. The obtained data were used to compute adiabatic compressibility, intermolecular free length, acoustic impedance, molar volume, molar sound velocity, molar compressibility, relative association, excess volume, and excess adiabatic compressibility. The results were discussed in terms of the existence of dipole–dipole and dipole induced molecular interactions between the compounds in the liquid mixture under study. A comparative study has been established between two liquid mixtures under investigation.
Phase Diagram of the Nicotinic Acid + Ammonium Sulfate + Water System
The solid–liquid equilibria (SLE) in the ternary nicotinic acid + ammonium sulfate + water system were experimentally studied at T = 298.15, 323.15, and 348.15 K under atmospheric pressure by an isothermal equilibrium method. Three isothermal phase diagrams of the system were established based on the measured mutual solubility data. Meanwhile, the physicochemical properties (density and conductivity) of this system were measured. The phase diagram contained three crystallization regions, two crystallization curves, and one co-saturation point at each temperature. The crystallization field of both nicotinic acid and ammonium sulfate enlarged with increase of temperature. The crystallization region of ammonium sulfate was smaller than that of nicotinic acid at each temperature.
A Series of Novel Dendritic Salicylaldimine Iron Catalysts: Synthesis, Characterization, and Application in Ethylene Oligomerization
A series of novel dendritic salicylaldimine ligands and their corresponding iron complexes have been synthesized using 1.0 generation (1.0 G) dendritic macromolecules, salicylaldehyde and FeCl2 · 4H2O as raw materials. The structures of the ligands and iron complexes were characterized by FT-IR, 1H NMR, UV, ESI-MS, and elemental analysis. The dendritic salicylaldimine iron complexes presented moderate catalytic activity in ethylene oligomerization and selectivity for higher carbon number olefins products (≥C8) when they were activated with methylaluminoxane (MAO). The catalytic activity and product selectivity were related to the co-catalyst, solvent, bridged group length and reaction parameters such as reaction temperature, Al/Fe molar ratio and ethylene pressure. The complex C3 showed the highest catalytic activity (up to 13.75 × 104 g (mol Fe h)–1) and the selectivity of higher carbon number olefins (35.31%) at the optimized conditions. Moreover, the catalytic properties of dendritic salicylaldimine iron complex C3 was better than non-dendritic iron complex.
Theoretical Study of Solvent Effect on the Kinetics and Thermochemistry of the Reaction of a (NHC)Cu(boryl) Complex with Ethylene
In this investigation, we describe solvent effect on the ethylene insertion into Cu–B bond in a (NHC)Cu(boryl) complex using MPW1PW91 quantum chemical methods. Solvent effects were explored by using the self-consistent reaction field (SCRF) method based on polarizable continuum model (PCM) in cyclopentanol, acetone, methanol, nitromethane, and dimethylsulfoxide. The progress of the reaction was quantitatively studied using the bond orders of the C–C bond of ethylene, and the percentages of bond cleavage (BCCC) of C–C bond at the transition state were described. The linear correlations between barrier energy, bond distances variations and thermodynamic parameters with dielectric constants of solvents were investigated. Rate constant of the title reaction over the temperature range of 200–1200 K was calculated in gas phase.
Study on the Mechanism of Methylchlorosilanes Disproportionation Catalyzed by AlCl3/(AlCl2)\(_{Z}^{{Z + }}\)-γ-Al2O3
Dimethyldichlorosilane is the most versatile of organosilicon monomers and is produced in large quantites. In this paper, MP2/6-311++G (3df, 2pd) basis set has been used to calculate the reaction mechanism of disproportionation for producing dimethyldichlorosilane by catalyst AlCl3/(AlCl2)\(_{Z}^{{Z + }}\)-γ-Al2O3 (Z = 0–2). The activation energy (Z = 0–2) of the rate-determining step of main reaction is: 73.00, 60.26, and 66.39 kJ mol–1. By comparing the activation energy and reaction heat, it is found that the catalytic effect of AlCl3/(AlCl2)\(_{Z}^{{Z + }}\)-γ-Al2O3 (Z = 1) is the best.
Framework-Substituted Sn-MOR Zeolite Prepared by Multiple pH-Adjusting Сo-Hydrolysis As Efficient Catalyst for tert-Butylation of Toluene
A series of Sn-MOR samples with different tin species loadings were prepared via a mutiple pH‑adjusting co-hydrolysis method. Their properties were characterized by XRD, XRF, UV–Vis, FT-IR, Py-IR, N2 sorption and SEM techniques. The catalytic performance was evaluated in liquid-phase toluene alkylation with tert-butyl alcohol. The characterization results shows that compared to framework destruction of mordenite for the Sn/MOR sample with floccule prepared by ion exchange method, higher relative crystallinity and larger surface area and pore volume for Sn-MOR samples with walnut morphology can be obtained. The doping with tin species can increase the Lewis acidity and decrease the pore size resulting in both higher toluene conversion and p-tert-butyltoluene (PTBT) selectivity. The Sn-MOR(0.010) sample shows the highest catalytic performance with toluene conversion of 48.0% and PTBT selectivity of 85.6%. It shows high stability: toluene conversion of 45.3% and PTBT selectivity of 87.2% can be obtained even after 5 consecutive runs.
Spectrophotometric Oxidative Decolorization of Methyl Red with Chloramine-T and Bromamine-T: Comparative Kinetic Modeling and Mechanistic Study
Methyl Red (MR) is a synthetic mono-azo dye which is extensively used as a colorant in textile and paper printing industries. The widespread amount of MR dye in wastewater poses potential threat to ecosystem and human health. In this context, we have developed a simple and expeditious oxidative decolorization technique for the removal of MR dye by organic N-haloamines viz., chloramine-T (CAT) and bromamine-T (BAT) present in the wastewater. The reaction was focused to changes in: (i) concentration of p-toluenesulfonamide, (ii) ionic strength, (iii) dielectric permittivity, (iv) polymerization study, and (v) halide ions effects. The activation parameters were deduced. Oxidation products of MR dye were identified. The rate of oxidation of MR is about four times faster with BAT than with CAT. The chemical oxygen demand value of the dye was determined. Phytotoxicity and economic analysis were carried out for the proposed decolorization process. A plausible mechanism conforming the kinetic data, reaction stoichiometry and product analysis has been proposed. Further, the present redox system can be adopted for treating MR dye present in industrial effluents with suitable modifications to reduce the toxicity caused by MR dye in wastewater.
Acrylic Acid and Methacrylic Acid Based Microgel Catalysts for Reduction of 4-Nitrophenol
N-isopropylacrylamide (NIPAM) monomer is copolymerized with acrylic acid (AA) and methacrylic acid (MAA) to synthesize poly-N-isopropylacrylamide-acrylic acid) [P(NIPAM-AA)] and poly(N-isopropylacrylamide-methacrylic acid) [P(NIPAM-MAA)] microgels. Both of these microgels possess same mol percentage of monomer and co-monomer. In order to study the influence of nature of co-monomer on size of in-situ synthesized nanoparticles, silver ions are reduced within these microgels under same conditions. The prepared samples are analyzed by Fourier transform infrared microscopy (FTIR), scanning electron microscopy (SEM), dynamic light scattering (DLS) and UV‒Vis spectroscopy. Synthesized hybrid microgels are used as catalysts for reduction of 4-nitrophenol under same conditions to investigate the influence of nature of co-monomer on apparent rate constant (kapp) of catalysis. Effect of various catalyst dosages on value of kapp is also studied. It is observed that value of kapp does not linearly increase with increase in catalyst dosage but it follows a different pattern. The dependences of dosages of both hybrid microgels on kapp are also compared. The effect of dosages of both catalysts on reaction time and catalysis duration is also studied.
Molecular Interactions in Binary Mixtures of 2-Cholroaniline and Monosubstituted Benzene Derivatives at Various Temperatures
The densities (ρ), speed of sound (u) values, and viscosities (η) were reported for binary mixtures of 2-chloroaniline with benzene derivatives (chlorobenzene, bromobenzene and nitrobenzene) over the entire composition range at T = 303.15–318.15 K and at atmospheric pressure 0.1 MPa. The excess properties, such as excess molar volume, excess isentropic compressibility and deviation in viscosity were calculated from experimental data. The excess properties were correlated by the Redlich–Kister equation. The partial molar volumes, partial molar isentropic compressibilities, excess partial molar volumes and excess partial molar isentropic compressibilities were calculated for all the binary systems throughout the composition range and also at infinity dilutions. The VE results are analyzed in the light of Prigogine–Flory–Patterson theory. Analysis of each of the three contributions viz. interactional, free volume and P* effect to VE showed that interactional and P* contributions are positive for all systems, the free volume effect is negative for all the mixtures. The variations of these parameters with composition and temperature were discussed in terms of intermolecular interactions prevailing in these mixtures.
Ultrasonic Studies on Molecular Interactions of N-Phthaloylglycine in Protic and Aprotic Solvents at 303–318 K
Ultrasonic studies of (1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)acetic acid (N-phthaloylglycine) in polar and non polar solvent of various concentrations and temperatures 303–318 K are carried out. Ethyl alcohol and DMSO selected as polar and non-polar solvents respectively. Density and ultrasonic velocity measured. Different thermo-acoustical parameters viz. adiabatic compressibility, intermolecular free length, acoustic impedance, surface tension, Rao’s constant, molar volume, wada’s constant calculated with the help of these data using standard formulae. These data are used in understanding the molecular interactions in mixtures.
Molecular Interactions of Pyridoxine Hydrochloride in Aqueous Mixed Solutions of D-Glucose, D-Fructose, and D-Lactose at Different Temperatures
Density and ultrasonic velocity values for solutions of pyridoxine hydrochloride in aqueous mixed solutions containing D-glucose, D-fructose, and D-lactose have been obtained for various concentrations and at temperatures 298.15–313.15 K. Volumetric and acoustic parameters such as partial molar volumes, partial molar adiabatic compressibilities, partial molar expansibilities were determined using density and ultrasonic velocity data. The analysis of the obtained data has been done by using Masson’s equation and interpretation was done in terms of solute–solute and solute–solvent interactions. The pyridoxine hydrochloride acts as a structure breaker in water as well as in binary aqueous mixed solutions of D-glucose, D‑fructose, and D-lactose.
Concentration and Temperature Dependences of 2-Chloro-3-(trifluoromethyl)pyridine Solubilities in (DMF + Tetrahydrofuran) and (DMF + Isopropanol) Mixtures
The solubility of 2-chloro-3-(trifluoromethyl)pyridine (CTP) in (DMF + tetrahydrofuran) and (DMF + isopropanol) solvent mixtures were determined by isothermal static method within the temperature range from 273–303 K under 101.3 kPa pressure. The solubility of CTP increased with increasing temperature and the mass fraction of DMF in the binary solvent systems. On the premise of same temperature and mass fraction of DMF, the solubility of CTP in (DMF + tetrahydrofuran) was higher than that in (DMF + isopropanol). The Jouyban–Acree model, the Van’t-Hoff–Jouyban–Acree model, the modified Apelblat–Jouyban–Acree model and the Sun model were utilized to correlate the obtained experimental solubility data respectively, and the Sun model could well describe the dissolution behavior of CTP in the binary mixtures. On the basis of experimental solubility data, the dissolution enthalpy and the dissolution entropy of the dissolution process were calculated. The dissolution process of CTP in the two kind of mixed solvents was an endothermic process.
Molecular Interactions of Transition Metal Chlorides in Water and Water–Ethanol Mixtures at 298–318 K on Viscometric Data
Viscosities of solutions of manganese chloride, cobalt chloride, nickel chloride, copper chloride, cadmium chloride and magnesium chloride at different concentrations have been determined in water and in ethanol + water mixtures at 303.15 K. Effect of temperature was also studied in 5% of ethanol in water at 298–318 K. The measured viscosity data has been analyzed by using Jones–Dole equation. The obtained parameters have been interpreted in terms of ion–ion and ion–solvent interactions. Activation parameters have been determined which explain the mechanism of viscous flow. In the present study all the taken transition metal chlorides and magnesium chloride were found structure promoters in water and in water + ethanol mixtures.
Correlation of Solubility and Solution Thermodynamics of DL-Malic Acid in Organic Solvents at Different Temperatures
The solubility of DL-malic acid in methanol, ethanol, propanol, butanol, ethyl acetate and acetonitrile in the temperature range 283–318 K was measured by acid–base titration method. The solubility of DL-malic acid increased with elevating temperature. The solubility data were correlated by the modified Apelblat, Buchowski–Książczak, Van’t Hoff, Wilson, and non-random two-liquid equations. The calculation results showed that these equations provide good prediction with the acceptable ARD values and RMSD values among all the satisfactory fitting results given by each equation. The mixing Gibbs energy, enthalpy and entropy of real solution were derived based on the Wilson equation and the measured solubility data.
Binding Affinities and Spectroscopy of Complexes Formed by Polysiloxanes with Aniline and Chlorophenol Acetates
The theoretical binding energies of the complexes formed by polysiloxanes with aniline and chlorophenol acetates were calculated at B3LYP/6-31G(d, p) level after the basis set superposition error (BSSE) based on B3LYP/6-31G(d) optimized geometries. The high binding energies of the complexes lead to the long experimental retention times in gas chromatography (GC). The energy gaps of the complexes are reduced owing to the formation of the hydrogen bonds. The chemical shifts of the α-C atoms connected to the amino groups in the NMR spectra of the complexes computed with B3LYP/6-31G(d) method are gradually changed downfield as the Si–O chain increases. The aromaticities of the benzene rings in the complexes are decreased due to the transfer of electron clouds from the benzene rings to the Si–O chains based on the nuclear independent chemical shifts (NICS) calculated at B3LYP/6-31G(d) level.
Evaluating Electron Diffusivity and Conductivity in Crystalline Cadmium Oxide
We investigate diffusivity and conductivity in the context of electronic transport in crystalline cadmium oxide by knowing the electron concentration in CdO as a function of the partial pressure of oxygen in the deposition process of the material in question. From the chemical kinetics of the reaction by which CdO is formed, first we consider an approximate relationship for the electron concentration in terms of the above pressure. In fact, by taking into account this relationship and other issues, we determine the product diffusivity\( \times \)conductivity in crystalline CdO. This product can be considered as a significant figure of merit.
Semiconducting Properties of Ag3PO4 and Its Application to Rhodamine Degradation under Solar Light
To assess its photocatalytic activity under visible light, Ag3PO4 nanopowder was prepared by precipitation of Ag3PO4 with Na2HPO4. The powder was identified by X-ray diffraction and characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, thermal analysis and diffuse reflectance spectroscopy. Ag3PO4 grains with sizes in the range (0.8–10 µm) were obtained. The optical gap, determined from the Kubelka–Munk function, is found to be 2.49 eV and the electrical conductivity is characteristic of a classical semiconductor with activation energy of 0.18 eV. The capacitance measurement indicates n type conductivity with a valence band (2.05), deriving from Ag+: 5s orbital, more anodic than the level O2/\({\text{O}}_{2}^{ \bullet }\). So, the compound was tested with success for the oxidation by \({\text{O}}_{2}^{ \bullet }\) radicals of the rhodamine B under solar light. The degradation obeys to a first order kinetic with a rate constant of 0.28 min−1. Some peaks of Ag metal (~6%) appeared after the photocatalytic process and the optical gap shows red shift by 0.04 eV; such results are in contradiction with those reported by others.
Studies on EPR Parameters and Local Structures for the Rhombic Cu2+ Center in the ZnGeO4 · 6H2O Crystal
The electron paramagnetic resonance (EPR) parameters (g factors and hyperfine structure constants) and local structures for the impurity Cu2+ center in ZnGeO4 · 6H2O crystal are theoretically studied using the perturbation formulas of these parameters for a 3d9 ion in rhombically elongated octahedra. These formulas are based on a two-spin-orbit-parameter model in which the contributions to the EPR parameters due to both the spin-orbit parameter of the central 3dn ion and that of ligand ion are included. Based on the calculation, the relative axial elongation ratio ρ (≈7.3%) along z-axis and the relative planar bond length variation τ (≈4.3%) along x- and y-axes are found for [Cu(H2O)6]2+ cluster in ZnGeO4 · 6H2O crystal. The above local rhombic distortions of the Jahn–Teller nature around Cu2+ can suitably account for the axial and perpendicular anisotropies of the observed EPR parameters.
Positron Annihilation Doppler Broadening Studies on Ruthenium(III) Antibiotic Sulfa-Drug Complexes
The structural difference between five sulfa drug compounds and their Ru(III) complexes with 1 : 2 molar ratio were examined using the positron annihilation Doppler broadening (PADB) spectroscopy. The PADB measurements were performed with a HPGe γ-ray spectrometer. The change of defect structure due to the Ru(III) complexation process was confirmed. The correlation between the DP line-shape parameters (S and W) and the previous reported results of the microanalytical, physicochemical, biological and positron annihilation lifetime (PAL) measurements of sulfa drug Ru(III) complexes were examined.
Investigations of g Factors and Local Structures for Cu(en)\(_{3}^{{2 + }}\)Groups in Cu(en)3SO4 and Cu(en)3Cu(CN)3 Polycrystalline Powders
From the perturbation formulas for g factors for an orthorhombically compressed octahedral 3d9 group, g factors, and local structures for the [Cu(en)3]2+ groups in Cu(en)3SO4 and Cu(en)3Cu(CN)3 powders are theoretically investigated. The local structure of Cu2+ in Cu(en)3Cu(CN)3 is evaluated by analyzing the experimental g factors and found to exhibit moderate axial compression ΔZ (≈0.018 Å) and planar bond length variation ΔR (≈0.015 Å) related to an ideal octahedron due to the Jahn–Teller effect. The larger experimental axial anisotropy Δg (= (gx + gy)/2 − gz) of Cu(en)3SO4 than Cu(en)3Cu(CN)3 is mainly ascribed to the larger ΔZ (≈0.053 Å) in the former. The calculated g factors for both systems show reasonable agreement with experiment by including the charge transfer (CT) contributions to gz, which have the same sign and much larger magnitude compared to the conventional crystal-field ones and should be included.
Eco-Friendly In Situ Fabrication of Reduced Graphene Oxide Gold Nanocomposites for Catalysis and Dye Degradation
The invention represents a development of robust eco-friendly method use for water waste management and polluted water. The inadvertent role of peanut peels extract helps to simultaneously convert and form reduced graphene oxide gold nanocomposite (rGO@AuNCs) in single step. Fabricated nanocomposite was evaluated for its catalytic performance using reduction of 4-nitrophenol to 4-aminophenol as well as elimination of methylene blue (MB) and malachite green (MG) dyes from water. Graphene oxide (GO) and rGO@AuNCs, were synthesized using simplified approaches and preliminary characterization was done using UV–Vis spectrophotometer and Fourier transform infrared spectroscopy. Least concentration of rGO@AuNCs is required to eliminate MB and MG around 77 and 93%, respectively. Furthermore, surface morphology and elemental analysis of rGO@AuNCs confirm successful fabrication methods as well as X‑ray diffraction pattern confirms the crystalline behavior of nanocomposite. The study illustrates an environment-friendly and cost effective in situ fabrication rGO@AuNCs from industrial agro waste for an environmental remediation.
A Theoretical Examination of the Antioxidant Activity of NH2, OMe, and tert-Butyl Sesamol Derivatives and Their Drug Delivery with C60 Nanocage
The antioxidant activity of NH2, OMe, and tert-butyl derivatives of sesamol and their drug delivery with C60 were investigated in gas phase and water. Results show that, C60 can interact with NH2, OMe, and tert-butyl sesamol derivatives and their adsorptions are exothermic and possible from the energetic viewpoint. Results show that, replacing NH2 sesamol derivative has high antioxidant activity and high interactions with C60. Results show that, NH2 and OMe substitutions can increase the antioxidant activity of sesamol. Results show that BDE an IP values of sesamol derivatives and their Ead values have linear dependencies. Calculated results can be used to propose the novel sesamol derivatives with high antioxidant activity.
Rapid Preparation and Luminescence Properties of YbAG:Tm3+ Nanoparticles
(TmxYb1 –x)3Al5O12 (YbAG:Tm3+) nanoparticles (NPs) with mean diameter of 56 nm were prepared by a rapid carbonate coprecipitation method with a short calcination time of only 1 min. Our results confirmed the structure and purity of the prepared material and proved that Tm3+ was successfully incorporated into YbAG. The results on the upconversion luminescence show that the emission peaks were located at 486 and 684 nm, corresponding to the 1G4 → 3H6 and 3F2 → 3H6 transitions of Tm3+. The transition mechanism of the blue and red emission was discussed.This rapid method could improve the production efficiency of YbAG:Tm3+ nanoparticles, and may have certain implications for the preparation of other upconversion nanomaterials.
Characterization and Optical Properties of Three Dimensional (3D) CeO2 Microstructures Synthesized by a Template-Free Method
Three dimensional (3D) of CeO2 nanostructures such as convex lens-like, hollow triangular prism, broccolilike, grapelike CeO2 have been successfully synthesized by cerium carbonate hydroxide (CeOHCO3) precursors, which were prepared by a hydrolysis process followed by a facile hydrothermal method without using any template or surfactant. The influence of urea amount on CeO2 nanostructures was discussed. The synthesizing mechanism and the morphological evolution of CeOHCO3 and CeO2 were proposed. The CeO2 samples were examined by XRD, SEM, TEM, UV–Vis, PL, and Raman scattering. The UV–Vis absorption spectrum of the CeO2 samples showed that the band gap energy (Eg) in rang of 2.6–2.9 eV, which is lower than that of bulk ceria.
Sonochemical Synthesis of Br-Doped Bismuth Oxyiodide Nanobelts Used for N-Deethylation of Rhodamine B
Tetragonal Br-doped bismuth oxyiodide (BiOI) as visible-light-driven photocatalysts were synthesized by sonochemical method. The as-synthesized products were characterized by X-ray diffractometry (XRD), transmission electron microscopy (TEM) and an X-ray photoelectron spectrometry (XPS). Among the different studied photocatalysts, 10 wt % Br-doped BiOI showed the highest activity of 98.88% in photodegradation of rhodamine B (RhB) under visible light irradiation within 180 min.
Adsorption of Azo Dye Direct Blue 71 from Aqueous Solution Using NiFe2O4/CP Nanoparticles: Kinetic and Isotherm Model
Removal of azo dye Direct Blue 71 (DB71), from aqueous solution using synthesized nickel ferrite nanoparticles (NFN) (NiFe2O4) supported on Clinoptilolite zeolite (CP) was studied. The prepared NFN-CP were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray (EDX), and Brunauer–Emmett–Teller (BET) surface area analysis. The kinetic and isotherm of dye adsorption was studied. The effects of operational parameter such as: pH, adsorbent dosage and contact time on the process were studied and optimized. The results showed that pH 6, adsorbent dosage 0.12 g, contact time 45 min was optimum conditions for adsorption process. The results showed that the dye adsorption onto CP and NFN-CP followed Langmuir isotherm. Adsorption kinetics of DB71 onto the NFN-CP followed the pseudo-second-order kinetic model.
Carbon Coated SnO2 Hollow Nanocubes with Superior Sodium Storage Performance
Carbon coated SnO2 hollow nanocubes were synthesized by a facile hydrothermal route. The sample with large surface area exhibits a hollow cube particle shape with an average length of ~400–500 nm. It is found that the SnO2@C−HNC shows a high discharge capacity of 799.1 mA h g−1 with the first cycle coulombic efficiency of 53.4% at the current density of 100 mA h g–1. At the high current density of 2 A g–1, it can still deliver a discharge capacity of 203.1 mA h g–1. The SnO2@C−HNC composite exhibits a good rate capability and stable cycling performance, indicating potential available as large-scale storage device.
Chemometrically-Assisted Fabrication of a Potentiometric Sensor for Potassium Ion Based on Kryptofix 22 Ionophore
A novel ion-selective membrane electrochemical sensor based on Kryptofix 22 as an ionophore was constructed for determination of potassium ion in real samples. The D-optimal mixture design (D‑OMD) was used as an experimental design strategy for optimal formulation of the membrane ingredients. The fabricated electrode exhibits a Nernstian slope of 59.80 ± 0.65 mV per decade and a linear range of 1.0 × 10–4 to 1.0 × 10–1 mol/L with respect to potassium ion at the pH range of 3.0 to 7.0 and its detection limit was found to be 6.2 × 10–5 mol/L. The response of the electrode is very stable and it exhibits a good reproducibility with a fast response time (~10 s). The experimental results, showed a good selectivity towards the K+ ion at present of interfering ions. The obtained results by using D-OMD showed a non-linear relation between the slope of the electrode and its ingredients. The proposed electrode was successfully applied for determination of potassium ion in vegetables and urine samples.
Trimeric Surfactant Modified Montmorillonite Immobilized in Alginate Beads: An Efficient Adsorbent for Removal of Cu2+ and Methyl Orange from Aqueous Solution
Trimeric surfactant modified montmorillonite immobilized in alginate beads (CA/3RenQ-Mt) sorbent was synthesized to simultaneously remove Cu2+ and methyl orange (MO) from aqueous solution. The CA/3RenQ-Mt was characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TG), zeta potential analysis and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) analysis. The adsorption of Cu2+ and MO by CA/3RenQ-Mt was studied by the operational variables including contact time, pH and temperature. The results showed CA/3RenQ-Mt exhibited higher affinity to both Cu2+ and MO compared to sodium montmorillonite (Mt-Na), trimeric surfactant modified montmorillonite (3RenQ-Mt) or calcium alginate (CA). The pseudo-first-order kinetic model and Langmuir isotherm model were found to describe the MO adsorption well; the pseudo-second-order kinetic model and Freundlich isotherm model fitted well with the Cu2+ adsorption. The adsorption of MO onto CA/3RenQ-Mt is an endothermic spontaneous process, and ion-exchange was the dominant adsorption mechanism. Accordingly, the adsorption of Cu2+ on CA/3RenQ-Mt involved endothermic spontaneous chemical adsorption by means of coordination/chelation between Cu2+ and the oxygen atoms of carboxyl and hydroxyl groups of alginate. In general, CA/3RenQ-Mt can be applied as multifunctional adsorbent to remove heavy ions and anion dyes from aqueous solution.
Structural, Thermal, and Electrical Behavior of Cu-Substituted KPbI3 Ternary Compound
Series of ion conducting system (KI)4 – x‒(CuI)x‒PbI2, x = 0.0‒0.4, have been prepared by solid state reaction method and studied by powder X-ray diffraction, DTA techniques and conductivity measurements. Room temperature XRD reveals the presence of the orthorhombic KPbI3 as the major component in the sample. The X-ray diffraction analysis also confirms the presence of both KI and CuPbI3 in the samples. DTA of x = 0.0 composition shows an endothermic peak at 349°C attributed to the melting of the compound. AC impedance spectroscopy revealed that the contribution of grain is strong over the grain boundary. The addition of CuI content results in the increase of electrical conductivity of the samples. The maximum ionic conductivity σ = 6.33 × 10–1 S cm–1 was shown by x = 0.3 composition at 633 K with lowest activation energy of ~0.11eV in the temperature range of 298‒633 K.
Interactions of Pluronic F127 in Rhodamine B Dye and Effects of Inorganic Cations through Fluorescence Data
Non-ionic surfactant block copolymer of polypropylene glycol flanked by two blocks of polyethylene glycol known as pluronic. Pluronic F127 or poloxamer 407 is used to improve the solubility and enhance the bioavilability of many drugs. The interactions of pluronic F127 was studied in Rhodamine B dye and effects of inorganic cations through fluorescence data were observed. Fluorescence quenching were studied by series cations of salts viz CdSO4, MnSO4, ZnSO4, FeSO4, CuSO4 in the above system. Cu2+ was found to be extremely efficient quencher, Cd2+ and Fe2+ were moderate quenchers. Apart from fluorescence, lifetime, DLS, and SEM were used as characterization for the above study.
Reconstruction of STO-3G Family Basis Set for the Accurate Calculation of Magnetic Properties
The new approach for the determination of orbital exponents and contracted coefficients for STO-3G family basis sets has been proposed. Calculations of the necessary coefficients have been performed using Mathcad program package with Minerr solving block. This approach has been used to perform the approximation of the Slater-type orbital (STO) by three Gaussian-type orbitals (GTO). The performance of such modified basis sets has been tested for the calculations of atomic energies using STO(0)-3G basis set and for nuclear magnetic shielding tensors using STO(1M)-3G basis set. The obtained atomic energies are characterized by lower values than those calculated using old parameters. The results for 1H and 13C chemical shifts calculations demonstrate better agreement with the experimental data compared to the data obtained using standard basis sets, such as 6-311G (2d, p), cc-pVDZ and pcS-1. Required time of calculations using the basic set suggested by us is less than the time spent on the calculation using standard basic sets with a similar number of basis functions. Physically adapted and at the same time small by size basic set STO(1M)-3G is perspective for the calculation of magnetic properties of big molecular systems. Proton and 13C chemical shifts have been calculated for molecules of adenosine monophosphate (AMP) and flavinadenine dinucleotide (FAD), that play an important role in various biological processes. For both molecules the results of the calculation have shown values close to the experimental data.
Optimization of Operating Parameters in Photocatalytic Activity of Visible Light Active Ag/TiO2 Nanoparticles
Reactive Blue 255 (RB 255) is a textile dye with global usage and is found in the wastewater of textile industries in large quantities. In the present study, silver-doped TiO2 (Ag/TiO2) nanoparticles with various Ag doping (wt %) were prepared by a combination of sol-gel and ultrasonication techniques. Ag/TiO2 nanoparticles were characterized by EDXA, SEM, TEM, and XRD methods. Based on the Taguchi method, photocatalytic degradation of RB 255 azo dye was investigated with Ag/TiO2 nanoparticles under visible light irradiation. By using this method, operation factors such as Ag doping (wt %), pH, catalyst load, and RB 255 concentration were optimized successfully. The results showed that pH, when compared to the other factors, plays an important role in the photocatalytic degradation of RB 255 azo dye. The isotherm study shows that Weber–Van Vliet and Fritz–Schlunder (IV) models are the best descriptors of equilibrium behavior. The experimental kinetic study results may be well described by a pseudo first-order model.
Synthesis and Photoluminescence Properties of Novel Sr2La8(SiO4)6O2:Eu3+ Oxyapatite Phosphors
A novel red-emitting phosphor Sr2La8(SiO4)6O2:Eu3+ was synthesized by high-temperature solid-state reaction method. X-ray powder diffraction (XRD) analysis confirmed the formation of Sr2La8(SiO4)6O2:Eu3+ phase. The photoluminescence excitation (PLE) and emission (PL) spectra show that the phosphor can be efficiently excited by near ultraviolet (NUV) and blue light, and emits red light. The phosphor demonstrates much higher quantum efficiency, and its color coordinates lie in the red region. All results in the present work suggest that the prepared phosphors have potential application as red emitting phosphors for near ultraviolet white light emitting diodes (NUV WLEDs).
Visible-Light Induced Photodegradation of Organic Contaminants in Water Using Fe3O4 Nanoparticles Modified Polypyrrole/Fly Ash Cenosphere Composite
Ternary nano-composites of polypyrrole/iron oxide/fly ash cenosphere (PPY/Fe3O4/FAC) were synthesized and used as magnetic photocatalyst. The synergistic effect of FAC, a buoyant carrier and polypyrrole, a conducting polymer enhanced the photocatalytic activity. Different composites were synthesized by varying the concentration of Fe3O4 and FAC to evaluate its effect on the photocatalytic properties of composites. The presence of Fe in Fe2+ and Fe3+ oxidation states at binding energies of 709.3 and 711.4 eV respectively was depicted by XPS curve. PPY/Fe3O4/FAC (1 : 3) composite showed the highest photocatalytic activity with rate constant (k) 0.0058 min–1. The removal efficiency of BPA was found to be around 75% and ~62% total organic content (TOC) was eliminated at optimized conditions from the solution. Transmission electron microscopy (TEM) showed the cluster morphology of the PPY/Fe3O4/FAC nano-composites with ~6–10 nm size of Fe3O4. X-ray diffraction studies elucidated the characteristic peaks of both PPY and Fe3O4 at 2θ ~ 20°–30°, and 26.04°, respectively in the composites which also confirmed the interaction of PPY with Fe3O4.
Ag3PO4 Nanoparticles Decorated Hexagonal α-Fe2O3 Nanoplates with Enhanced Photocatalytic Performance under Visible Light Irradiation
In this work, a series of Ag3PO4 nanoparticles decorated hexagonal α-Fe2O3 nanoplates with different Ag3PO4 contents were synthesized by combining solvothermal method and ultrasonic-assisted chemical precipitation method for the first time. Structure, morphology, and chemical composition of as-synthesized products were analyzed with the aid of X-ray diffraction (XRD), Fourier transform-infrared spectro-scopy (FT-IR), field-emission scanning electron microscopy (FE-SEM) and X-ray energy dispersive analysis (EDS). Additionally, the photocatalytic performance of the samples was evaluated by investigating the degradation process of Orange II (OII) under visible-light irradiation. Compared with pure α-Fe2O3, all α‑Fe2O3/Ag3PO4 samples exhibit enhanced activity. The decoration of Ag3PO4 could enhance the photocatalytic activity of α-Fe2O3 effectively, and increasing the loading amount of Ag3PO4 could further improve the photocatalytic activity of α-Fe2O3/Ag3PO4 samples. The results of this study should be useful for the further application of α-Fe2O3/Ag3PO4 composite photocatalysts with different microstructures.
Effect of Addition of Salts on Excess Enthalpy in Methanol–Carbon Tetrachloride Mixture
The effect of dissolved sodium acetate (5 and 10%), potassium acetate (5 and 10%) and zinc acetate (5 and 10%) on the endothermic enthalpy of mixing in the binary system methanol–carbon tetrachloride has been investigated at 303.15 K in a displacement calorimeter with vapor space. Experimental values were fitted into a Redlich–Kister equation. Experimental values and predicted values were plotted against mole fraction of methanol and deviations were reported. The data obtained may be of interest to specialists in the field of thermodynamic of solutions.