Materials Literature
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Abstract Chitin was extracted from shrimp shells and then deacetylated to obtain chitosan. The degree of deacetylation of the chitosan was determined to be 0.76 using pH‐metric titration. A large number of cyanide functional groups were introduced onto chitosan by grafting with polyacrylonitrile as an efficient way of…
Photoluminescence lifetimes and optical absorption cross sections of Si nanocrystals embedded in SiO2 have been studied as a function of their average size and emission energy. The lifetimes span from 20 μs for the smallest sizes (2.5 nm) to more than 200 μs for the largest ones (7 nm). The passivation of nonradiative…
Previous studies of 5,10,15,20-tetraarylporphyrins have shown that the barrier for meso aryl-porphyrin rotation (DeltaG++(ROT)) varies as a function of the core substituent M and is lower for a small metal (M = Ni) compared to a large metal (M = Zn) and for a dication (M = 4H(2+)) versus a free base porphyrin (M = 2H)…
An empirical method based on chemical bond theory for the estimation of the lattice energy for ionic crystals has been proposed. The lattice energy contributions have been partitioned into bond dependent terms. For an individual bond, the lattice energy contribution made by it has been separated into ionic and covalen…
A systematic method to fabricate porous-silicon one-dimensional photonic crystals has been engineered to have a photonic bandwidth up to 2000 nm. The observation of the tailorability of the photonic band gap (PBG) underscores the requirement of the large refractive index contrast for making broad PBG structures. In th…
The structural, electronic, and magnetic properties of ultrathin Cu-coated Co nanowires have been studied by using empirical genetic algorithm simulations and a tight-binding $spd$ model Hamiltonian in the unrestricted Hartree-Hock approximation. For some specific stoichiometric compositions, Cu atoms occupy the surfa…
The experimental study of magnetic flux penetration under crossed magnetic fields in Bi2212:Pb single crystal performed by magnetooptic technique (MO) reveals remarkable field penetration pattern alteration (flux configuration change) and superconducting current anisotropy enhancement by the in-plane field. The anisot…
Short dangling bond wires (DB wires), fabricated on H-terminated Si(001) surfaces, show patterns of displacement that depend on their length. We have performed density function calculations, with and without spin-polarisation, designed to investigate the atomic and electronic structure of these wires. As expected, we…
Synchrotron x-ray scattering studies of anti-ferroelectric nanoregions (AFR) as fluctuations, which give rise to 1/2(hk0) superlattice reflections (alpha spots), were systematically performed in Pb(Mg1/3Nb2/3)O3 (PMN) ferroelectric relaxor. Separation of the alpha spots from underlying diffuse scattering background al…
Transient electric birefringence measurements were performed on dilute solutions of CdSe nanorods. The results confirm the existence of a permanent dipole along the c-crystallographic axis. Measurements on nanorods with different widths and lengths show that the longitudinal permanent dipole moment scales linearly wit…
We have studied the effect of particle wettability on the structure of planar monolayers of micron size monodisperse silica particles at the octane−water interface. The particles' wettability was adjusted by silanization of their surfaces with dichlorodimethylsilane; thus their contact angle at the octane−water interf…
In a previous work (part 1), nanocomposite materials were obtained using a latex of either unvulcanized or prevulcanized natural rubber as the matrix and a colloidal suspension of crab chitin whiskers as the reinforcing phase. The mechanical behavior of the resulting nanocomposite films was analyzed in both the linear…
Temperature dependent (4.2–300 K) photoluminescence (PL) of bulk (0001)-oriented ZnO in the range of free- and bound-exciton emission is presented. Emission from several bound excitons and the free A exciton were observed from the low temperature (20 K) PL spectrum. The temperature dependence of the free-exciton peak…
ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTCapping of Gold Nanoparticles by the Amino Acid Lysine Renders Them Water-DispersiblePR. Selvakannan, Saikat Mandal, Sumant Phadtare, Renu Pasricha, and Murali SastryView Author Information Materials Chemistry Division, National Chemical Laboratory, Pune 411 008, India Cite thi…
The spontaneous polarization of epitaxial BaTiO3/SrTiO3 superlattices is studied as a function of composition using first-principles density-functional theory within the local density approximation. With the in-plane lattice parameter fixed to that of bulk SrTiO3, the computed superlattice polarization is enhanced abo…
A planar slab of material, for which both the permittivity and permeability have the values of −1, can bring not only the propagating fields associated with a source to a focus, but can also refocus the nonpropagating near fields, thereby achieving resolution beyond the diffraction limit. We study the sensitivity of t…
Nanocomposite materials were obtained from a colloidal suspension of chitin whiskers as the reinforcing phase and latex of both unvulcanized and prevulcanized natural rubber as the matrix. The chitin whiskers, prepared by acid hydrolysis of chitin from crab shell, consisted of slender parallelepiped rods with an aspec…
High-resolution electron microscope observations of shock-loaded boron carbide have revealed the formation of nanoscale intragranular amorphous bands that occur parallel to specific crystallographic planes and contiguously with apparent cleaved fracture surfaces. This damage mechanism explains the measured, but not pr…
Understanding the structure−property relationship in polymer/layered silicate nanocomposites is of fundamental importance in designing materials with desired properties. To understand these relations in the case of poly(butylene succinate) (PBS)/organically modified layered silicate (OMLS) nanocomposites, we studied t…
The synthesis, spectroscopic characterization, and fluorescence quenching efficiency of polymers and copolymers containing tetraphenylsilole or tetraphenylgermole with Si-Si, Ge-Ge, and Si-Ge backbones are reported. Poly(tetraphenyl)germole, 2, was synthesized from the reduction of dichloro(tetraphenyl)germole with 2…