Physical and electronic properties in multiwalled carbon nanotube–poly(3‐dodecylthiophene) nanocomposites

The properties of nanocomposites of dodecyl ester functionalized multiwalled carbon nanotube (FMWNT) and four poly(3‐dodecyl thiophene) (P3DDT) samples with different molecular weight and chain regioregularity are reported here. Uniform dispersion of FMWNT in the composites is evident from TEM study. π–π and CH–π interactions are evident from FTIR spectra in the low molecular weight (M_w = 8 × 10⁴) and high regiorandom (head‐tail = 69 mol %) P3DDT (ILM) composites; however, such interactions are not so prominent for other P3DDTs. Wide‐angle X‐ray scattering patterns indicate intact interchain lamellar structure of P3DDT in the composites. DSC study shows decrease of main chain melting peak of P3DDT (ILM) with increasing F‐MWNT content but the decrease is lower with higher molecular weight and higher regioregular samples. Dynamic mechanical analyzer study indicates that there is no significant change in the T_g, T_β, and T_γ transition temperature with FMWNT concentration indicating almost ideal mixing of the components. The percent increase of G′ increases with increasing FMWNT loading and also with temperature showing an 84% increase in storage modulus at –20 °C for ILM12 samples. The UV–vis spectrum indicates a decrease in band gap with FMWNT concentration for ILM composites, however, it is negligible with other P3DDTs. Photoluminescence quenching and multiple emission peaks occur in the composites. dc‐Conductivity of the composites increases by two orders and current‐voltage (I–V) curves show memory effect only in ILM‐MWNT composites. The I–V curves of other P3DDT nanocomposites exhibit rectification property. Quantitative explanation of electronic properties has been afforded from the band energy and work function values. So, the electronic properties of the nanocomposite can be tuned by changing the molecular weight, regioregularity, and concentration of FMWNT. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1412–1425, 2009     

Controlled Orientation in a Bio‐Inspired Assembly of Ag/AgCl/ZnO Nanostructures Enables Enhancement in Visible‐Light‐Induced Photocatalytic Performance

In a bio‐inspired approach, polyamine‐mediated mineralization of ZnO was explored to develop an environmentally benign methodology for synthesizing Ag/AgCl/ZnO nanostructures. The assembling properties displayed by the polyamines to create composite structures was utilized to have the nanocomponents effectively interact with each other in a way that is desirable for the application envisaged. The polyamines, which act as a mineralizing agent for ZnO nanoparticles, also facilitate the formation of Ag/AgCl within ZnO under ambient conditions. Thus synthesized Ag/AgCl/ZnO nanostructures represent a multi‐heterojunction system in which the nanocomponents lead in a synergistic way to enhancement in the photocatalytic activity under visible‐light irradiation.     

Arithmetic behaviour of Hecke eigenvalues of Siegel cusp forms of degree two

The Ramanujan Journal - Let F and G be Siegel cusp forms for $${\mathrm{Sp}}_4({{\mathbb {Z}}})$$ and weights $$k_1, k_2$$ , respectively. Also let F and G be Hecke eigenforms lying in distinct...     

The Emergence of Palladium-Catalyzed C(sp3)−H Functionalization of Free Carboxylic Acids

Palladium-catalyzed directing group assisted C−H bond activation has emerged as a powerful tool in synthetic organic chemistry. However, only recently, among various directing groups, widely available carboxylate moiety is recognized as a versatile candidate for the regioselective transformations. Notably, palladium-catalyzed carboxylate directed C(sp³)−H bond activation and diverse functionalization is highly challenging and has gained huge attention for its versatile applications. Mono- and bidentate ligands have proven to be useful for accelerating the C(sp³)−H bond activation step, which helps to control reactivity and selectivity (including enantioselectivity). In this Minireview, we discuss the recent progress made in palladium-catalyzed C(sp³)−H bond functionalization reactions for the construction of C−C and C−Heteroatom bonds with the direction of free carboxylic acid.     

Composite materials for medical purposes based on polyvinylpyrrolidone modified with ketoprofen and silver nanoparticles

A method for obtaining composite medical materials based on polyvinylpyrrolidone (PVP K15) modified with ketoprofen in a medium of supercritical carbon dioxide and with Ag nanoparticles prepared by metal vapor synthesis is developed. A system in which ketoprofen and Ag nanoparticles with an average size of ∼16 nm are uniformly distributed over the bulk of PVP is obtained. It is found that the yield of ketoprofen from the composite in the physiological solution is higher than that for an analogous system obtained by mechanical mixing of the components.     

A homochiral luminescent 2D porous coordination polymer with collagen-type triple helices showing selective guest inclusion

A homochiral luminescent porous coordination polymer, [Cd(L)(H(2)O)]·3H(2)O, with interconnected collagen like triple-helical chains has been synthesized solvothermally by using cadmium(II) salt and a newly designed d-isosorbide-based, enantiomerically pure chiral ligand. The framework is a 2D porous material and forms a 1D channel along the a axis, with the channel dimensions ~6.2 × 4.4 ?(2). The compound has high selectivity in the uptake of water and methanol over other solvents (e.g., tetrahydrofuran, ethanol, benzene, and cyclohexane) inside the channels.     

Palladium(II) complex with a potential N4-type Schiff-base ligand as highly efficient catalyst for Suzuki-Miyaura reactions in aqueous media

Two new air-stable palladium(II) complexes containing a N₄-Schiff-base ligand have been synthesized and investigated as catalysts for the Suzuki-Miyaura reactions. The binuclear complex 2 has proven to be an excellent catalyst for additive-free Suzuki-Miyaura reactions of aryl bromides in neat water at room temperature and aryl chlorides in aqueous-glycerol at 80 °C. Satisfactory to excellent yields of biaryls are obtained with a wide range of substrates with relatively low loading of catalyst.     

Oriented morphogenesis of ZnO nanostructures from water-soluble zinc salts under environmentally mild conditions and their optical properties

Herein, we report a bottom-up, mineralization strategy, which borrows key principles from biomineralization processes, to synthesize nanostructured materials. A long-chain polyamine simultaneously mineralizes and assembles ZnO nanoparticles directly from water-soluble zinc salts under sustainable synthesis conditions. These thus-generated oriented structures undergo interesting morphogenesis that is controlled by changing the ratio of polyamine/Zn(2+) ions. As the ratio increases, the morphology changes from a spherical shape to oval-, dumbbell-, and finally hexagonal-rod-shaped structures that contain unique hollow rod structures. Using XPS, XRD, FT-IR, Raman spectroscopy, DLS, and confocal fluorescence microscopic analysis, we elucidate the mechanism of structural evolution; this mechanism involves the initial formation of a zinc/amine complex that is furnished with polyamine chains. These chains facilitate the condensation process to form ZnO nanoparticles and their assembly in aqueous medium at neutral pH. Further, the presence of defects in the thus-morphogenized ZnO structures leads to blue luminescence and efficient photoinduced activity, assisted by the surface-hole-trapping effect of polyamines.     

A rigorous approach to the formulation of extended Born‐Oppenheimer equation for a three‐state system

If a coupled three‐state electronic manifold forms a sub‐Hilbert space, it is possible to express the non‐adiabatic coupling (NAC) elements in terms of adiabatic–diabatic transformation (ADT) angles. Consequently, we demonstrate: (a) Those explicit forms of the NAC terms satisfy the Curl conditions with non‐zero Divergences; (b) The formulation of extended Born‐Oppenheimer (EBO) equation for any three‐state BO system is possible only when there exists coordinate independent ratio of the gradients for each pair of ADT angles leading to zero Curls at and around the conical intersection(s). With these analytic advancements, we formulate a rigorous EBO equation and explore its validity as well as necessity with respect to the approximate one (Sarkar and Adhikari, J Chem Phys 2006, 124, 074101) by performing numerical calculations on two different models constructed with different chosen forms of the NAC elements. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009