Monoclinic CuO nanoflowers on resin support: recyclable catalyst to obtain perylene compound

Monoclinic CuO crystallite in grams has been obtained from resin bound Cu(II)-1,10-phenanthroline complex, R(-)[Cu(1,10-phen)(2)](2+) that becomes a recyclable catalyst for oxidative phenol coupling (OPC) reaction. Thus an exclusively intuitive blue fluorescing perylene derivative is derived from colorless 2,7-dihydroxynaphthalene (2,7-DHN) in high yield.     

Fabrication of Large‐Scale Hierarchical ZnO Hollow Spheroids for Hydrophobicity and Photocatalysis

We report here the preparation of a crystalline, pure hexagonal phase of ZnO as hollow 500–800 nm spheroids in the presence of organic bases, such as pyridine, using zinc acetate as the precursor salt. The spheroids exhibit unique 3D hierarchical architectures, like cocoons, and demonstrate improved superhydrophobic (water contact angle, 150°) character due to the inherited air‐trapped capillarity within the cocoon structure. The simple synthetic strategy used in this process is modified hydrothermolysis (MHT), which represents a general approach and may contribute to the formation mechanism of the hollow nanostructures with highly improved porosity. Depending on the concentration of the precursor salt, it has been possible to cover glass plates or the inner wall of a reaction vessel with ZnO nanocrystals. A low salt concentration (<0.01 M ) allows the easy preparation of a superhydrophobic glass surface, whereas a high salt concentration (>0.01 M ) results in the precipitation of cocoons at the bottom of the reaction vessel as a solid mass together with a deposited thin film of ZnO nanocrystals covering the inner wall of the glass vessel. The thickness of the film successively grows through repetitive hydrothermolysis processes for which a low salt concentration (<0.01 M ) was employed. Because of the hollow cocoonlike morphology, the surface area of the film is greatly increased, which makes it accessible for functionalization by incoming substrates from both sides (internally and externally) and helps to drive a competent photocatalytic dye degradation pathway. The heterocyclic base pyridine exclusively develops cocoons. Thus, the mechanism of self‐aggregation of ZnO nanocrystals under MHT reaction conditions has been studied and the characterization of the compounds has been supported with physical measurements.     

Effect of nanoparticle dispersion on glass transition in thin films of polymer nanocomposites

We present spectroscopic ellipsometry measurements on thin films of polymer nanocomposites consisting of gold nanoparticles embedded in poly(styrene). The temperature dependence of thickness variation is used to estimate the glass transition temperature, T _g . In these thin films we find a significant dependence of T _g on the nature of dispersion of the embedded nanoparticles. Our work thus highlights the crucial role played by the particle polymer interface morphology in determining the glass transition in particular and thermo-mechanical properties of such nanocomposite films.     

Synthesis and photo physical properties of Au @ Ag (core @ shell) nanoparticles disperse in poly vinyl alcohol matrix

Synthesis of core @ shell (Au @ Ag) nanoparticle with varying silver composition has been carried out in aqueous poly vinyl alcohol (PVA) matrix. Core gold nanoparticle (~15 nm) has been synthesized through seed-mediated growth process. Synthesis of silver shell with increasing thickness (~1–5 nm) has been done by reducing Ag⁺ over the gold sol in the presence of mild reducing ascorbic acid. Characterization of Au @ Ag nanoparticles has been done by UV–Vis, High resolution transmission electron microscope (HRTEM) and energy dispersive X-ray (EDX) spectroscopic study. The blue shift of surface plasmon resonance (SPR) band with increasing mole fraction of silver has been interpreted due to dampening of core, i.e. Au SPR by Ag. The dependence of nonlinear optical response of spherical core @ shell nanoparticles has been investigated as a function of relative composition of each metal. Simulation of SPR extinction spectra based on quasi-static theory is done. A comparison of our experimental and the simulated extinction spectra using quasi-static theory of nanoshell suggests that our synthesized bimetallic particles have core @ shell structure rather than bimetallic alloy particles.     

VEGFR-2 targeted cellular delivery of doxorubicin by gold nanoparticles for potential antiangiogenic therapy

We report a novel gold nanobioconjugate system that achieves targeted delivery of the small molecule drug doxorubicin to endothelial cells using anti-VEGFR-2 antibody conjugated gold nanoparticles (GNPs). The reported nanobioconjugate system combines the inherent ability of GNPs to undergo high levels of derivatization with the precision of antibody recognition of a cell surface antigen. Transmission electron microscopy (TEM) and surface-enhanced Raman spectroscopy (SERS) confirmed intracellular presence of the GNPs. Using a VEGFR-2 expressing cell line and a cell line that is negative for the receptor, in combination with competition assay we established the cell specific targeted delivery of the nanobioconjugate. The nanobioconjugate system described here may have potential drug delivery applications for antiangiogenic cancer therapy.     

Proton radioactivity with a Yukawa effective interaction

The half-lives of proton radioactivity of proton emitters are investigated theoretically. Proton-nucleus interaction potentials are obtained by folding the densities of the daughter nuclei with a finite-range effective nucleon-nucleon interaction having Yukawa form. The Wood-Saxon density distributions for the nuclei used in calculating the nuclear as well as the Coulomb interaction potentials are predictions of the interaction. The quantum mechanical tunneling probability is calculated within the WKB framework. These calculations provide reasonable estimates for the observed proton radioactivity lifetimes. The effects of neutron-proton effective mass splitting in neutron-rich asymmetric matter as well as the nuclear matter incompressibility on the decay probability are investigated.     

Domain wall dynamics of the spin-$\frac{1}{2}$ Ising-like antiferromagnetic chain in presence of Dzyaloshinskii-Moriya interactions

We consider a one-dimensional Ising-like S = \frac12\frac{1}{2} Heisenberg antiferromagnetic Hamiltonian and study the dynamics of domain wall excitations in presence of both uniform and staggered Dzyaloshinskii-Moriya interactions. We obtain dispersion relations and dynamical spin correlation functions, S ^{x x} (q, ω) using the basis of domain wall pair states. It is shown that the line shapes of S ^{x x} (q, ω) are highly asymmetric over the whole Brillouin zone such that the spectral weights mainly concentrate in the low energy side. It is observed that presence of staggered Dzyaloshinskii-Moriya interaction explains the experimental results on the Ising-like antiferromagnetic compounds CsCoCl₃ and CsCoBr₃ very well.     

Lowest lying <Superscript>1</Superscript>D<Superscript>e</Superscript> resonance of H<Superscript>-</Superscript> in Debye plasma

Electron-hydrogen scattering has been investigated in Debye plasma environment employing the close-coupling approximation. Two models, viz., 6-state CCA and 9-state CCA have been used. Plasma screening has been taken into account via Debye-Hückel model potential. The lowest lying ¹D^e^1{\rm D}^{{\rm e}} auto-detaching resonance of the hydrogen negative ion has been successfully predicted for various plasma conditions. The resonant state changes to shape resonance for Debye scattering lengths less than a critical value.     

Effect of harmonic confinement on correlation studies of a spin-polarized s-wave superconductor

We study different correlation functions for a spin imbalanced and harmonically trapped Fermi gas in two dimensions described by an attractive Hubbard model. Eigensolutions obtained via numerically solving Bogoliubov de Gennes equations are used to compute the local pairing amplitudes which show significantly different behaviour for the trapped case where the profile is radially modulated in contrast with a spatial modulation extending throughout the lattice geometry when trap effects are switched off. Further, different experimentally accessible quantities, such as pair–pair, density–density correlations and local density fluctuations show characteristic fluctuations for the spin polarized phase, which however wash away as the trapping effects are turned on. A contrasting scenario is presented corresponding to the case when the spin polarization effects are turned off.     

ProSTRIP: A method to find similar structural repeats in three-dimensional protein structures

The occurrence of similar structural repeats in a protein structure has evolved through gene duplication. These repeats act as a structural building block and form more than one compact structural and functional unit called a repeat domain. The protein families comprising similar structural repeats are mainly involved in protein–protein interactions as well as binding to other ligand molecules. The identification of internal sequence repeats in the primary structure is not sufficient for the analysis of structural repeats. Thus, a new method called ProSTRIP has been developed using dynamic programming to find the similar structural repeats in a three-dimensional protein structure. The detection of these repeats is made by calculating the protein backbone Cα angles. An internet computing server is also created by implementing this method and enables graphical visualization of the results. It can be freely accessed at http://cluster.physics.iisc.ernet.in/prostrip/.