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.     

Regioselective deiodination of thyroxine by iodothyronine deiodinase mimics: an unusual mechanistic pathway involving cooperative chalcogen and halogen bonding

Iodothyronine deiodinases (IDs) are mammalian selenoenzymes that catalyze the conversion of thyroxine (T4) to 3,5,3'-triiodothyronine (T3) and 3,3',5'-triiodothyronine (rT3) by the outer- and inner-ring deiodination pathways, respectively. These enzymes also catalyze further deiodination of T3 and rT3 to produce a variety of di- and monoiodo derivatives. In this paper, the deiodinase activity of a series of peri-substituted naphthalenes having different amino groups is described. These compounds remove iodine selectively from the inner-ring of T4 and T3 to produce rT3 and 3,3'-diiodothyronine (3,3'-T2), respectively. The naphthyl-based compounds having two selenols in the peri-positions exhibit much higher deiodinase activity than those having two thiols or a thiol-selenol pair. Mechanistic investigations reveal that the formation of a halogen bond between the iodine and chalcogen (S or Se) and the peri-interaction between two chalcogen atoms (chalcogen bond) are important for the deiodination reactions. Although the formation of a halogen bond leads to elongation of the C-I bond, the chalcogen bond facilitates the transfer of more electron density to the C-I σ* orbitals, leading to a complete cleavage of the C-I bond. The higher activity of amino-substituted selenium compounds can be ascribed to the deprotonation of thiol/selenol moiety by the amino group, which not only increases the strength of halogen bond but also facilitates the chalcogen-chalcogen interactions.     

Synthesis, properties and perspectives of hybrid nanocrystal structures

Current efforts and success of nanoscale science and technology are related to the fabrication of functional materials and devices in which the individual units and their spatial arrangement are engineered down to the nanometer level. One promising way of achieving this goal is by assembling colloidal inorganic nanocrystals as the novel building blocks of matter. This trend has been stimulated by significant advances in the wet-chemical syntheses of robust and easily processable nanocrystals in a wide range of sizes and shapes. The increase in the degree of structural complexity of solution-grown nanostructures appears to be one of the natural directions towards which nanoscience will increasingly orient. Recently, several groups have indeed devised innovative syntheses of nanocrystals through which they have been able to group inorganic materials with different properties in the same particle. These approaches are paving the way to the development of nanosized objects able to perform multiple technological tasks. In this critical review (165 references), we will summarize the recent advances in the synthesis of colloidal nanocrystals, with emphasis on the strategies followed for the fabrication of nano-heterostructures, as well as on their properties and the perspectives in this field.     

Large deviations for the stochastic shell model of turbulence

In this work, we first prove the existence and uniqueness of a strong solution to stochastic GOY model of turbulence with a small multiplicative noise. Then using the weak convergence approach, Laplace principle for solutions of the stochastic GOY model is established in certain Polish space. Thus a Wentzell–Freidlin type large deviation principle is established utilizing certain results by Varadhan and Bryc.      

Self‐Assembly of Amphiphilic Nanocrystals

Amphiphilic hybrid materials are formed from polymer‐coated semiconductor nanoparticles that simulate a surfactant‐like response (see picture). The strength and density of the surface coating are the key assembling forces driving a transition from single particles to cylindrical or vesicular superstructures.

     

Magnetic–Fluorescent Colloidal Nanobeads: Preparation and Exploitation in Cell Separation Experiments

Nanostructures displaying fluorescence and magnetic properties at the same time are potentially useful for achieving simultaneous bio‐separation and bio‐sensing (e.g., magnetic separation coupled with multiplexing optical detection of different tumour cell populations). Spherical nanobeads that display both fluorescent and magnetic features are reported; they are fabricated by grafting fluorescent oligothiophene molecules to an amphiphilic polymer that is then used to enwrap iron oxide nanoparticles, which acts as the magnetic domain. By tuning experimental conditions, control over the number of magnetic nanoparticles per bead and over the bead diameter (30–400 nm) was achieved. A cell separation efficiency of the level required for cell sorting applications is also reported.

     

Evidence of a core–shell structure in the antiferromagnetic La0.2Ce0.8CrO3 nanoparticles by neutron scattering

We report the evidence of a core?Cshell structure in the antiferromagnetic La_0.2Ce_0.8CrO₃ nanoparticles by using a combination of neutron diffraction, polarized neutron small angle scattering (SANSPOL), and dc magnetization techniques. The neutron diffraction study establishes that the present nanoparticles are antiferromagnetic in nature. The magnetic scattering in the SANSPOL study arises from the shell part of the nanoparticles due to the disordered surface spins. The analysis of the SANSPOL data shows that these nanoparticles have a mean core diameter of 12.3±1.1?nm, and a shell thickness of 2.8±0.4?nm, giving a core?Cshell structure with an antiferromagnetic core, and a shell with a net magnetic moment under an applied magnetic field.     

Characterization and growth of CdS nanoparticles by a cost effective chemical reduction method

A simple chemical reduction method is followed to grow CdS nanoparticles at room temperature with different duration of time. The grown samples are ultrasonicated in ethanol. The dispersed samples are characterized using electron diffraction techniques. Simultaneously optical absorption, photoluminescence and longtime photorelaxation of these samples are studied at room temperature. An increase in band gap is observed in each case as compared to bulk CdS. Also particle size increases with increase of growth time and hence there is decrease of band gap with increase of growth duration. Simultaneously long time relaxation increases with increase of growth time. An attempt is made to correlate the structural, optical, electrical and opto‐electrical properties. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Pd-Catalyzed Regioselective Domino C−C Bond Formation to Access N-Fused Benzimidazo-Indolo-Isoquinoline Heterocycles

Regioselective synthesis of N-fused benzimidazo-indolo-isoquinoline heterocycles via Pd-catalyzed domino coupling reaction of 1-(1-methyl-1H-indol-2-yl)-1H-benzimidazoles and aryl halides was developed. This one pot methodology proceeded via a five-member carbopalladacycle intermediate and provided direct and facile route to access structurally complex polyheterocycles in moderate to good yields. These unique hybrid molecules resembled structural similarity with naturally isolated alkaloids. Notably, the present domino process occurred through activation of three C−H bonds and the simultaneous formation of two new C−C bonds in one-shot. These molecules exhibited strong solid and solution phase fluorescence and their emission spectra in both the medium are reported here.