Characterization and applications of as-grown β-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> nanoparticles prepared by hydrothermal method

The production of low-dimensional nanoparticles (NPs) with appropriate surface modification has attracted increasing attention in biological, biochemical, and environmental applications including chemical sensing, photocatalytic degradation, separation, and purification of toxic molecules from the matrices. In this study, iron oxide NPs have been prepared by hydrothermal method using ferric chloride and urea in aqueous medium under alkaline condition (pH 9 ~ 10). As-grown low-dimensional NPs have been characterized by UV–vis spectroscopy, FT-IR, X-ray diffraction, Field emission scanning electron microscopy, Raman spectroscopy, High-resolution Transmission electron microscopy, and Electron Diffraction System. The uniformity of the NPs size was measured by the scanning electron microscopy, while the single phase of the nanocrystalline β-Fe₂O₃ was characterized using powder X-ray diffraction technique. As-grown NPs were extensively applied for the photocatalytic degradation of acridine orange (AO) and electrochemical sensing of ammonia in liquid phase. Almost 50% photo-catalytic degradation with AO was observed in the presence of UV sources (250 W) with NPs. β-Fe₂O₃ NP-coated gold electrodes (GE, surface area 0.0216 cm²) have enhanced ammonia-sensing performances in their electrical response (I–V characterization) for detecting ammonia in liquid phase. The performances of chemical sensor were investigated, and the results exhibited that the sensitivity, stability, and reproducibility of the sensor improved significantly using β-Fe₂O₃ NPs on GE surface. The sensitivity was approximately 0.5305 ± 0.02 μAcm⁻²mM⁻¹, with a detection limit of 21.8 ± 0.1 μM, based on a signal/noise ratio of 3 with short response time.     

Insulator-to-metal transition in sulfur-doped silicon

We observe an insulator-to-metal transition in crystalline silicon doped with sulfur to nonequilibrium concentrations using ion implantation followed by pulsed-laser melting and rapid resolidification. This insulator-to-metal transition is due to a dopant known to produce only deep levels at equilibrium concentrations. Temperature-dependent conductivity and Hall effect measurements for temperatures T>1.7 K both indicate that a transition from insulating to metallic conduction occurs at a sulfur concentration between 1.8 and 4.3×10(20) cm(-3). Conduction in insulating samples is consistent with variable-range hopping with a Coulomb gap. The capacity for deep states to effect metallic conduction by delocalization is the only known route to bulk intermediate band photovoltaics in silicon.     

Redox Mechanism and Evaluation of Kinetic and Thermodynamic Parameters of 1,3‐Dioxolo[4,5‐g]pyrido[2,3‐b]quinoxaline Using Electrochemical Techniques

The electrochemical behavior of a biologically important heterocyclic compound, 1,3‐dioxolo[4,5‐g]pyrido[2,3‐b]quinoxaline was investigated by cyclic, square wave and differential pulse voltammetry in solutions of different pH. Kinetic and thermodynamic parameters like standard rate constant, diffusion coefficient, apparent energy of activation_, standard Gibbs free energy and enthalpy and entropy changes were evaluated. Limits of detection and quantification were determined by square wave voltammetry. The redox mechanism of the compound was proposed on the basis of experimental results. Computational chemistry was used as a tool for the verification of experimental outcomes and assessment of different theoretical parameters     

Highly Magnetic Nanoporous Carbon/Iron‐Oxide Hybrid Materials

The preparation of size‐controllable Fe₂O₃ nanoparticles grown in nanoporous carbon with tuneable pore diameters is reported. These hybrid materials exhibit strong non‐linear magnetic properties and a magnetic moment of approximately 229 emu g^?1, which is the highest value ever reported for nanoporous hybrids, and can be attributed to the nanosieve effect and the strong interaction between the nanoparticles and the carbon walls.     

Study of the base-catalysed oxidation of the anti-bacterial and anti-protozoal agent metronidazole by permanganate ion in alkaline medium

The mechanism of dismutation of MnO₄ ^2? via the complex [MTZ–MnO₄·OH]^2?, formed during the oxidation of metronidazole (MTZ), has been investigated spectrophotometrically at different temperatures. The stoichiometry of the reaction is 1:1, i.e. 1 mol MTZ reacts with 1 mol Mn(VII).The reaction is first order in permanganate, less than first order in [MTZ] and [alkali]. The effects of added products and the dielectric constant and ionic strength of the reaction medium were investigated. The main products were identified by spot test and FT-IR. A mechanism involving a free radical has been proposed. In the equilibrium step MTZ binds to the MnO₄ ^? species to form a complex (C). Investigation of the reaction at different temperatures enabled determination of the activation data for the slow step of proposed mechanism. The proposed mechanism and the derived rate laws are consistent with the observed kinetics.     

Study of projectile fragmentation in the reaction (158 A GeV) Pb + Pb using CR-39

The fragmentation of Pb ions at 158 A GeV energy produced in the interaction with Pb target has been studied using a CR-39 track detector. A stack comprising of 64 detectors was prepared such that a target of 1 cm thickness was sandwiched between the sheets of CR-39. The purpose of this exposure geometry was to calibrate CR-39 with respect to relativistic heavy ions as well as to study the fragmentation of Pb ions at 158 A GeV energy. The exposure was carried out at the SPS beam facility of CERN at normal incidence with a fluence of . Two detectors from the exposed stack have been selected for this study: one before and the other after the target material. After etching, the detectors were scanned using an optical microscope and the etched track lengths and the diameters of the track openings were measured manually. Considering that the lengths of tracks provide the best charge resolution for Z>65, we have measured track lengths for a sufficiently large number of fragments to identify individual charge states for 65<Z<83. The total charge-changing cross section has also been determined.     

Finite temperature radiative corrections to neutron decay and related processes

We present a detailed calculation of the radiative corrections at finite temperature to the processes nν ? pe, ne ? pν. and n ? peν. The temperature range considered is approximately 100 keV to 3 MeV, which is the range relevant for nucleosynthesis calculations. Photon absorption and emission, photonic corrections to the vertex and fermion wave-function renormalizations, as well as the correction to the electron “mass” are calculated explicitly. It is shown that infrared divergences are only cancelled when absorption and induced photon emission are included. We analyze the effect of these processes on the various reaction rates, and discuss the effects of these corrections on the calculated helium abundance in the universe.     

Nanostructured microspheres of MnO2 formed by room temperature solution processing

Nanostructured microspheres of manganese oxide have been prepared by the solution processing ofmanganese(II) salts using 1,4,7,10-tetraazacyclododecane and utilizing a crystalline intermediate stage.