A control over accessibility of immobilized enzymes through porous coating layer

We report immobilization of an enzyme by layer-by-layer (LbL) film deposition technique. All the enzyme layers, including the inner ones, contributed to the activity. We put-forwarded additional coating layers to protect the enzymes. To control the accessibility of the enzymes beneath the coating layer, pores have been introduced. Our results show controlled accessibility of immobilized enzymes in solid-state matrices.     

Low temperature magnetization behavior in Co36Fe36Si3Al1Nb4B20 (at%) nanostructured alloy

The investigation addresses low temperature magnetization behavior in Co₃₆Fe₃₆Si₃Al₁Nb₄B₂₀ alloy ribbons in their as-spun as well as annealed state. Optimum heat treatment at 875 K led to nanocrystallization whereby bcc-(FeCo)SiAl nanoparticles were dispersed in an amorphous matrix as evidenced from transmission electron microscopy. Low temperature magnetization studies were carried out in the range 77-300 K. Using the method of mathematical fittings, magnetization extrapolated to 0 K was obtained. The dependence of the magnetization with respect to temperature of BT^3/2 was used to determine the Bloch coefficient “B” and spin wave stiffness constant “D”. Magnetic softening revealed by lowering in the coercivity in the optimum nanostructured state was also the cause of a drop in the stiffness constant. The range of exchange interaction given by D/T_C was higher in the nanostructured state compared to the as-spun amorphous state. The effect of nanocrystallization and the resulting ferromagnetic coupling was further evidenced by low temperature magnetization studies.     

Enhancement in soft magnetic and ferromagnetic ordering behaviour through nanocrystallisation in Al substituted CoFeSiBNb alloys

The effect of substituting Al for Si in Co₃₆Fe₃₆Si_4−xAl_xB₂₀Nb₄, (X=0, 0.5, 1.0, 1.5, 2.0 at%) alloys prepared in the form of melt-spun ribbons have been investigated. All the alloys were amorphous in their as-cast state. The onset of crystallization as observed using differential scanning calorimetry (DSC) was found to rise at low Al content up to X=1 at% beyond which there was a decreasing trend. The alloys also exhibited glass transition at ‘T_g’. Microstructural studies of optimally annealed samples indicated finer dispersions of nanoparticles in amorphous matrix which were identified as bcc-(FeCo)Si and bcc-(FeCo)SiAl nanophases by X-ray diffraction technique. Alloy with optimum content of Al around X=1 at% exhibited stability in coercivity at elevated temperatures. Though Al addition is known to lower magnetostriction, such consistency in coercivity may also be attributed towards lowering in the nanoparticle size compared to X=0 alloy. In the nanostructured state, the alloy containing optimum Al content (X=1) exhibited further enhancement in ferromagnetic ordering or the Curie temperature by 100 K compared to alloy without Al. Such addition also attributed to better frequency response of coercivity and low core losses.     

Fluctuation induced magneto-conductivity studies in YBa2Cu3O7−δ + xBaZrO3 composite high-Tc superconductors

Fluctuations on the electrical conductivity of polycrystalline YBa₂Cu₃O_7?δ + xBaZrO₃ (x = 1.0, 2.5, 5.0 and 10.0 wt.%) superconductors were investigated from the resistivity vs. temperature data for zero field and 8 T (Tesla) external magnetic fields. Attempts have been made to identify the optimum inclusion of BaZrO₃ (BZO) in YBa₂Cu₃O_7?δ (YBCO) superconductors. The phase formation, texture and grain alignments were analyzed by XRD and SEM techniques. Then the effects of superconducting fluctuations on the electrical conductivity of granular composite superconductors were studied for zero field and 8 T external magnetic fields. Though inclusions of BZO sub-micron particles are not expected to influence superconducting order-parameter fluctuation (SCOPF) much, the transition from 2D to 3D of the order parameter in the mean-field region depends on the BZO content in the composites. It has been observed that BZO residing at the grain boundary of YBCO matrix influences the tailing region without having significant change in the mean-field critical temperature. In the present work, attention has been focused mostly in the experimental domain relatively above the T_c. It reveals that, 1 wt.% composite exhibits a better superconducting property in comparison with pure YBCO.     

Size quantification of sub-micron ZnSe semiconductor particles by laboratory scattering methods

A novel route has been developed to synthesize sub-micron Zinc Selenide semiconductor particles through elemental solvothermal process. Transparent polyvinyl alcohol matrix was chosen as host material for embedding these ZnSe particles in order to stop agglomeration of the particles as well as to facilitate optical characterization. Structural and morphological characterizations were carried out through high resolution electron microscopy and UV-vis spectroscopy. In order to understand light scattering phenomena of these particles, they were investigated by a custom made set up which uses a He-Ne laser of wavelength 632.8nm and an array of Silicon photodetectors. An attempt was made to experimentally determine the most significant element of the Mueller scattering matrix. Novel computational technique, involving single scattering for spherical particles using T-matrix theory was applied. The analysis of the experimental data was done by the method of comparison with theoretically generated data. The theoretical prediction was found to agree well qualitatively with the experimental data. Our results validitate that within an acceptable margin of error of the experimental results, the combination of experimental setup and associated computational method is an efficient and reliable in-situ system for size quantification of sub- micron semiconductor particles in the laboratory.     

Structural and optical properties of Mn doped ZnS semiconductor nanostructures

Manganese doped zinc sulphide nanoparticles were fabricated by adopting an inexpensive solution growth route. Different samples were fabricated by varying Mn concentrations. UV-VIS study reveals blue-shift on the onset of absorption and hence enhancement in the optical band gap upto 0.75 eV, indicating strong quantum confinement. Photoluminescene study for all the samples display characteristic band edge peak at ∼410 nm. The broad peak ∼560–580 nm is ascribed to Mn incorporation. Further, structural investigations were carried out by using X-Ray diffraction and transmission electron microscopy (TEM).     

Adsorption of Cr(VI) and Se(IV) from their aqueous solutions onto Zr4+-substituted ZnAl/MgAl-layered double hydroxides: effect of Zr4+ substitution in the layer

Hydrotalcite-like compounds (layered double hydroxides, LDHs) containing varying amounts of Al(3+), Zr(4+), and Zn(2+) or Mg(2+) in the metal hydroxide layer have been synthesized and characterized by various physicochemical methods. The adsorption behavior of uncalcined (as-synthesized) and calcined LDHs have been investigated for Cr(2)O(7)(2-) and SeO(3)(2-). The mixed oxides, obtained on calcination at 450 degrees C, exhibit high adsorption capacities for Cr(2)O(7)(2-) (1.6-2.7 meq/g) and SeO(3)(2-) (1.1-1.5 meq/g), where adsorption occurs through rehydration. Substitution of Zr(4+) in the LDHs, for either M(2+) or Al(3+) ions, increases the adsorption capacity up to 20%, thus providing an alternative way to enhance the adsorption capacity of this type of material. The high adsorption capacity of these materials could be successfully used for removal of undesirable anions from water and also for synthesis of intercalated materials with tailored acidobasicity.     

Syntheses, structures, absorption and emission properties of a tetraiminodiphenol macrocyclic ligand and its dinuclear Zn(II) and Pb(II) complexes

Synthesis of a Robson type macrocyclic ligand [H₄L](ClO₄)₂ (1) obtained on condensation of 2,6-diformyl-4-methylphenol and 2,2′-dimethyl-1,3-diaminopropane, template synthesis of a dinuclear lead(II) complex [Pb^II₂L(NO₃)₂] (2), synthesis of a dinuclear zinc(II) complex [Zn^II₂L(NO₃)(H₂O)](ClO₄) (3) through metal substitution reaction and synthesis of another dinuclear zinc(II) complex [Zn^II₂L(H₂O)₂](ClO₄)₂·(H₂O)₂ (4) obtained directly from 1 are described in the present study. Crystal structure determinations of 1 and 3 have been carried out. Both the compounds 1 and 3 crystallize in the orthorhombic system with the space groups Fdd2 and P2₁2₁2, respectively. Spectrophotometric and spectrofluorometric titrations of 1 with triethylamine as well as with zinc(II) acetate are also reported.     

Ratios ofB andD meson decay constants with heavy quark symmetry

SU(3) flavor symmetry allows the decay constantsf _{D 1} andf _{D 2} as well asf _{B 1} andf _{B 1} to be equal. But due toSU(3) flavor symmetry breaking the ratiosf _{B 1}/f _{B 2} andf _{D 1}/f _{D 2} are deviated from unity. We have estimated these ratios in the heavy quark effective theory and obtainedf _{B 1}/f _{B 2}=0.93,f _{D 1}/f _{D 2}=0.94 and the double ratio (f _{B 1}/f _{B 2})/(f _{D 1}/f _{D 2})=0.99.