Optical Transmittance and Band Gap of Ferroelectric BaTi2O5 Bulk Glass

Optical transmittance and reflectance on ferroelectric BaTi₂O₅ glasses prepared recently by a containerless synthesis technique are measured at room temperature in the wavelength range 190-800nm. The fundamental absorption edge located around 340nm demonstrates the colourless and transparent character of the glass. The optical band gap of 3.32eV has been estimated. The tail of the optical absorption near the fundamental absorption edge is found to follow the Urbach rule. Our analysis of the experimental spectra supports an indirect allowed interband transition between the valence band formed by O-2p orbitals and the conduction band formed by Ti-3d orbitals.     

Synthesis of cellulose–metal nanoparticle composites: development and comparison of different protocols

Deposition of nanoparticles on the surface of a variety of materials is a subject of great interest due to their potential applications in electronic devices, sensing, catalysis and bio-medical sciences. In this context, we have explored and compared various methodologies to generate gold and silver nanoparticles on the surface of cellulose fibers. It was found that boiling of the cellulose fibers in alkaline solution of gold and silver salts led to the formation and immobilization of gold and silver nanoparticles. However, in case of lecithin treated and thiol-modified cellulose fibers, high temperature was not essentially required for the formation and deposition of nanoparticles on cellulose substrate. In both these cases, fairly uniform metal nanoparticles were obtained in good yields (~43 wt% gold loading in case of thiol modified cellulose fibers) at room temperature. Borohydride-reduction method resulted in relatively lower loading (~22 wt%) with a wide size distribution of gold and silver nanoparticles on cellulose fibers. All these nanoparticle–cellulose composites were thoroughly characterized using scanning electron microscopy, energy dispersive X-ray, Fourier transform infrared spectroscopy, UV–visible spectroscopy, and elemental analyzer. Thiol modified cellulose–gold nanoparticle composites served as active catalysts in the reduction of 4-nitrophenol into 4-aminophenol.     

Semiconductor nanoparticles for photoinitiation of free radical polymerization in aqueous and organic media

Photoinduced free radical polymerization of vinyl monomers by using semiconductor inorganic nanoparticles (NPs) is investigated. Zinc oxide and iron‐doped zinc oxide were used as photosensitive compounds to initiate the polymerization of acrylamide as a water‐soluble monomer in aqueous environment and methyl methacrylate as an oil‐soluble monomer in organic media under UV‐light irradiation. The method uses photochemically generated electrons and holes from the NPs to form initiating hydroxyl radicals in aqueous media, while tertiary amines and iodonium salt served as coinitiator in organic media. The initiation mechanism in organic media involves hydrogen abstraction or reduction processes via charge carriers, respectively. The kinetic of the polymerization in both environments was studied by means of a photo‐differential scanning calorimetry. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1500–1507     

Effects of additional Higgs doublets on the Coleman-Weinberg SU(2) × U(1) → U(1)em phase transition

In the standard electroweak theory with a Coleman-Weinberg Higgs doublet, it has been shown that the SU(2) × U(1) → U(1)_em phase transition is driven by chiral symmetry breaking and that a phenomenologically dangerous amount of entropy is produced. We show that the addition of a second, sufficiently heavy Coleman-Weinberg doublet will make the transition go via tunneling and will suppress excessive entropy generation.     

Excitation of nonlinear surface modes by wave beams

We consider the interaction of 2-D and 3-D wave beams with an interface between linear and nonlinear media. The range of parameters of Gaussian beams exciting nonlinear surface waves (NSW) with high efficiency is analytically determined. Different regimes of NSW excitation are numerically studied. Analytical data are in good agreement with numerical results.Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, Nos. 3–4, pp. 246–255, March–April, 1995.     

Sorption Studies of Nickel ions Onto Sawdust of Dalbergia Sissoo

Sawdust of Dalbergia sissoo, a byproduct of sawmills, was found to be a promising adsorbent for the removal of nickel ions from aqueous solution. Sorption of nickel ions onto sawdust of Dalbergia sissoo was studied using the batch technique. Kinetics studies show that nickel ions sorption process obeys a first order rate law. The applicability of the Langmuir and Freundlich models for the data was tested. Both the models adequately describe the experimental data of the biosorption of nickel ions. The sorption capacities and energies were calculated. Langmuir parameters X_m and K₁ were found to increase with rise in temperature; Freundlich constants 1/n and K_f have been evaluated for 293K, 303K, 313K and 323K. Thermodynamic parameter ΔH° = 4.80 kJ mol^?;1 shows that sorption of nickel ions onto sawdust is an endothermic process.