Temperature and magnetic field induced structural transformation in Si-doped CeFe2: An in-field X-ray diffraction study

Using the X-ray powder diffraction technique at various temperatures and applied magnetic fields, we have studied the magnetostructural properties of Ce(Fe_0.95Si_0.05)₂. The X-ray diffraction data establish quantitative relationships between bulk magnetization and the evolution of structurally distinct phases with magnetic field and temperature, and confirm the distinct features of a first-order phase transition such as supercooling and superheating, metastability, and phase co-existence of different structural polymorphs. We observe the lattice volume mismatch across the structural phase transition, which appears to be the cause for the step behavior of the magnetization isotherms at low temperatures. The present study shows that the lattice distortion has to be treated explicitly, like spin, along with the effects of lattice–spin coupling to account for the magnetization behavior of this system. This structure template can resolve the issue of kinetics in this material as observed in different time scale measurements and with different experimental protocols.     

Dual solutions of Casson fluid flows over a power-law stretching sheet

A steady boundary layer flow of a non-Newtonian Casson fluid over a power-law stretching sheet is investigated. A self-similar form of the governing equation is obtained, and numerical solutions are found for various values of the governing parameters. The solutions depend on the fluid material parameter. Dual solutions are obtained for some particular range of these parameters. The fluid velocity is found to decrease as the power-law stretching parameter β in the rheological Casson equation increases. At large values of β, the skin friction coefficient and the velocity profile across the boundary layer for the Casson fluid tend to those for the Newtonian fluid.     

Effect of plasticizer on safranine-T-dye-based solid-state photo electrochemical cell

Effect of plasticizers on electrical and photovoltaic properties of safranine-T-dye-based solid-state photo electrochemical cell (PEC) is studied. Ethylene carbonate (EC) and propylene carbonate (PC) are used as plasticizers. Dark current–voltage characteristic and different photovoltaic parameters such as open-circuit voltage, short-circuit current, and power conversion efficiency are measured. To understand the effect of plasticizers on charge transport process, we analyze the dark current–voltage characteristics to estimate the trap energy. From detail analysis of dark I–V, it has been observed that there is a crossover voltage called transition voltage where the conduction mechanism changes. Above this voltage, the dark current is a space charge limited current (SCLC) in the presence of exponentially distributed traps. Below transition voltage, current is ohmic for the cell without plasticizers and dark current is an SCLC in presence of discrete traps for the cell with plasticizers. From our analysis, it is shown that the transition voltage reduces due to the presence of plasticizers but the characteristic trap energy (E_T) is not changed significantly. From photovoltaic measurements, it is observed that in presence of EC and PC power conversion efficiency of the device increase from 7.319 × 10⁻⁴% to 14.64 × 10⁻⁴% under illumination with polychromatic light of 100 mW/cm². It is expected that the power conversion efficiency depend on transition voltage. Due to the presence of plasticizers, the barrier potentials of the devices reduce which results lowering of transition voltage. Lowering of it assists the migration of charge carriers and as a result power conversion efficiency enhances.     

Effect of C<Subscript>60</Subscript> on methyl red and crystal violet dye-doped photovoltaic device

The potential of dye sensitization of organic photovoltaic devices has been investigated. The photoelectrical properties of such devices have been studied. With the help of spin-coating method, single layer and double layer structures are prepared with the help of both methyl red and crystal violet dye at a time. Methyl red and crystal violet dye are dispersed in polyvinyl alcohol used as an inert polymer binder and polyethylene oxide complexed with LiClO₄ ion salt as a solid electrolyte. Ethylene carbonate and propylene carbonate are used as plasticizers. A layer of this blend is sandwitched between two electrodes, one of which is indium tin oxide (ITO)-coated glass plate and another is Al electrodes. In this study, the use of a C₆₀ layer over the previously prepared blend is done. ITO-coated glass plate and Al electrodes are taken as counter electrodes. Use of C₆₀ molecule over the polymer blend in a heterojunction increased the efficiency of photovoltaic devices. In this type of device, the polymer blend acts as an electron donor to the second layers, whereas C₆₀ plays the role of an electron acceptor.     

Exploring amino acid‐tethered polymethacrylates as CO2‐sensitive macromolecules: A concealed property

Carbon dioxide (CO₂)‐responsive polymers have been gaining considerable interest because of their reactions with CO₂, giving rise to gas‐switchable properties, which can easily be reversed by mild heating or purging with inert gases. Herein, the synthesis of a series of side‐chain amino acids (alanine, leucine, isoleucine, phenylalanine, tryptophan) appending poly(meth)acrylates carrying primary amine (? NH₂) groups via reversible addition‐fragmentation chain transfer (RAFT) polymerization method was reported. It was found that alanine, leucine, isoleucine containing polymers displayed solubility–insolubility transition behavior and their associated property changes (solution transmittance, electrical conductivity, pH, zeta potential, and hydrodynamic diameter) in water upon alternate bubbling of CO₂/N₂ at room temperature. Among the three CO₂‐sensitive polymers only leucine based macromolecule was further chain extended with a thermoresponsive motif, di(ethylene glycol) methyl ether methacrylate (DEGMMA), via RAFT polymerization. CO₂‐tunable lower critical solution temperature and self‐assembling behavior of the diblock copolymer was carefully examined by UV–vis, ¹H NMR spectroscopy, dynamic light scattering (DLS), and field emission‐scanning electron microscopy (FE‐SEM) to establish dual thermo and gas‐tunable flip–flop micellizaion from the as‐synthesized block copolymer. Formation of polyammonium methacrylate bearing bicarbonate as counter anion is responsible for pendant primary amine containing polymer induced CO₂‐responsiveness. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2794–2803     

Effect of coupling of spontaneous emission to the lasing mode in a two level model of quantum cascade lasers

In this paper, an improved two level model of quantum cascade lasers is extended to include the coupling of the spontaneous emission to the lasing mode. The variation of the electron numbers at the two levels, their difference and the variation of the light output with injected current are examined. The normalized modulation response for different ratios of the injected current to the threshold current is given.     

Guest-responsive polaritons in a porous framework: chromophoric sponges in optical QED cavities

Introducing porous material into optical cavities is a critical step toward the utilization of quantum-electrodynamical (QED) effects for advanced technologies, e.g. in the context of sensing. We demonstrate that crystalline, porous metal–organic frameworks (MOFs) are well suited for the fabrication of optical cavities. In going beyond functionalities offered by other materials, they allow for the reversible loading and release of guest species into and out of optical resonators. For an all-metal mirror-based Fabry–Perot cavity we yield strong coupling (∼21% Rabi splitting). This value is remarkably large, considering that the high porosity of the framework reduces the density of optically active moieties relative to the corresponding bulk structure by ∼60%. Such a strong response of a porous chromophoric scaffold could only be realized by employing silicon-phthalocyanine (SiPc) dyes designed to undergo strong J-aggregation when assembled into a MOF. Integration of the SiPc MOF as active component into the optical microcavity was realized by employing a layer-by-layer method. The new functionality opens up the possibility to reversibly and continuously tune QED devices and to use them as optical sensors.

A phthalocyanine-based porous material in optical cavity exhibited strong coupling and guest responsive polariton feature.     

Uncatalyzed condensation between aryl-1,2-diamines and diethyl bromomalonate: a one-pot access to substituted ethyl 3-hydroxyquinoxaline-2-carboxylates

A one-pot method for the synthesis of substituted ethyl 3-hydroxyquinoxaline-2-carboxylates under solvent and catalyst free conditions has been developed.     

Solvent extraction of Zn(II), Cu(II) and Sb(III) with N-m-tolyl-p-methoxybenzohydroxamic acid (TMBHA) into chloroform

Rapid methods have been described for the quantitative extraction of milligram amounts of Zn(II), Cu(II) and Sb(III) with TMBHA into chloroform. The separation factor for many elements was found to be at least greater than 10⁴. The metal: reagent stoichiometry determined by methods like slope ratio, mole ratio and substoichiometric extraction were found to be 12 for Zn(II) and Cu(II), and 23 for Sb(III).     

Protein surface-assisted enhancement in the binding affinity of an inhibitor for recombinant human carbonic anhydrase-II

We elaborate on a novel strategy for enhancing the binding affinity of an active-site directed inhibitor by attaching a tether group, designed to interact with the surface-exposed histidine residue(s) of enzymes. In this approach, we have utilized the recombinant form of human carbonic anhydrase-II (hCA-II) as the enzyme source and benzenesulfonamide and its derivatives as inhibitors. The steady-state kinetic and the ligand binding data revealed that the attachment of iminodiacetate (IDA)-Cu(2+) to benzenesulfonamide (via a triethylene glycol spacer) enhanced its binding affinity for hCA-II by about 40-fold. No energetic contribution of either IDA or triethylene glycol spacer was found (at least in the ground state of the enzyme-inhibitor complex) when Cu(2+) was stripped off from the tether group-conjugated sulfonamide derivative. Arguments are presented that the overall strategy of enhancing the binding affinities of known inhibitors by attaching the IDA-Cu(2+) groups to interact with the surface-exposed histidine residues will find a general application in designing the isozyme-specific inhibitors as potential drugs.