Tuning the Efficiency of Dendritic Nanocarriers using Conformational Constraints

A series of deoxycholic and cholic acid‐derived oligomers were synthesized and their ability to extract hydrophilic dye molecules of different structure, size, and functional groups into nonpolar media was studied. The structure of the dye and “dendritic effect” in the extraction process was examined using absorption spectroscopy and dynamic light scattering (DLS). The efficiency of structurally preorganized oligomers in the aggregation process was evaluated by 1‐anilinonaphthalene‐8‐sulfonic acid (ANS) fluorescence studies. The possible formation of globular structures for higher‐generation molecules was investigated by molecular modeling studies and the results were correlated with the anomaly observed in the extraction process with this molecule. The ability of these molecules for selective extraction of specific dyes from blended colors is also reported.     

Higher order stable generalized finite element method

The generalized finite element method (GFEM) is a Galerkin method, where the trial space is obtained by augmenting the trial space of the standard finite element method (FEM) by non-polynomial functions, called enrichments, that mimic the local behavior of the unknown solution of the underlying variational problem. The GFEM has excellent approximation properties, but its conditioning could be much worse than that of the FEM. However, if the enrichments satisfy certain properties, then the conditioning of the GFEM is not worse than that of the standard FEM, and the GFEM is referred to as the stable GFEM (SGFEM). In this paper, we address the higher order SGFEM that yields higher order convergence and suggest a specific modification of the enrichment function that guarantees the required conditioning, yielding a robust implementation of the higher order SGFEM.     

Mechanistic approach for expeditious and solvent-free synthesis of α-hydroxy phosphonates using potassium phosphate as catalyst

An extremely simple, high yielding, highly rapid and solvent-free protocol has been described for hydrophosphylation of aldehydes using potassium phosphate as catalyst. Easy commercial availability of the reusable catalyst, operational simplicity at ambient temperature and avoidance of conventional work-up as well as purification procedure makes this solvent-free protocol a near-ideal synthesis.     

Direct C–H amination of benzothiazoles by magnetically recyclable CuFe2O4 nanoparticles under ligand-free conditions

A simple and highly practical method for the synthesis of 2-N-substituted benzothiazoles has been developed by using nano copper ferrite as a magnetically separable, recyclable catalyst. The present tandem process allows to get access to a wide range of 2-N-substituted benzothiazoles in good to excellent yields by the reaction of benzothiazole with nitrogen nucleophiles in the presence of Cs₂CO₃ as a base. The nano CuFe₂O₄ could be recovered and reused with no significant loss of catalytic activity.     

Catalytic reduction of organic dyes at gold nanoparticles impregnated silica materials: influence of functional groups and surfactants

Gold nanoparticles (Au NPs) in three different silica based sol–gel matrixes with and without surfactants are prepared. They are characterized by UV–vis absorbance and transmission electron microscopic (TEM) studies. The size and shape of Au NPs varied with the organo-functional group present in the sol–gel matrix. In the presence of mercaptopropyl functionalized organo-silica, large sized (200–280 nm) spherical Au NPs are formed whereas in the presence of aminopropyl functionalized organo-silica small sized (5–15 nm) Au NPs are formed inside the tube like organo-silica. Further, it is found that Au NPs act as efficient catalyst for the reduction of organic dyes. The catalytic rate constant is evaluated from the decrease in absorbance of the dye molecules. Presence of cationic or anionic surfactants greatly influences the catalytic reaction. The other factors like hydrophobicity of the organic dyes, complex formation of the dyes with anionic surfactants, repulsion between dyes and cationic surfactant, adsorption of dyes on the Au NPs also play important role on the reaction rate.     

Investigations on co-evaporated Cu2SnSe3 and Cu2SnSe3-ZnSe thin films

Cu₂SnSe₃ is an important precursor material for the growth of Cu₂ZnSnSe₄, an emerging solar cell absorber layer via solid state reaction of Cu₂SnSe₃ and ZnSe. In this study, we have grown Cu₂SnSe₃ (CTSe) and Cu₂SnSe₃-ZnSe (20%) films onto soda-lime glass substrates held at 573 K by co-evaporation technique. The effect of annealing of these films at 723 K for an hour in selenium atmosphere is also investigated. XRD studies of as-deposited Cu₂SnSe₃ and Cu₂SnSe₃-ZnSe films indicated SnSe as secondary phase which disappeared on annealing. The direct optical band gap of annealed Cu₂SnSe₃ and Cu₂SnSe₃-ZnSe films were found to be 0.90 eV and 0.94 eV respectively. Raman spectroscopy studies were used to understand the effect of ZnSe on the properties of Cu₂SnSe₃.     

Gravity effects on partially premixed flames: an experimental-numerical investigation

While premixed and nonpremixed microgravity flames have been extensively investigated, the corresponding literature regarding partially premixed flames (PPFs) is sparse. We report the first experimental investigation of burner-stabilized microgravity PPFs. Partially premixed flames with multiple reaction zones are established in microgravity on a Wolfhard–Parker slot burner in the 2.2 s drop tower at the NASA Glenn Research Center. Microgravity measurements include flame imaging, and thermocouple and radiometer data. Detailed simulations are also used to provide further insight into the steady and transient response of these flames to variations in g. The flame topology and interactions between the various reaction zones are strongly influenced by gravity. The flames widen substantially in microgravity. During the transition from normal to microgravity, the flame structure experiences a fast change and another relatively slower transient change. The fast response is due to the altered advection as the value of g is reduced, while the slow response is due to the changes in the diffusive fluxes. The radiative heat loss from the flames increases in microgravity. A scaling analysis based on a radiation Damköhler number is able to characterize the radiation heat loss.     

Thermoanalytical and gas chromatographic properties of the copper(II) complexes of alkyl-substituted Schiff's bases

Summary A study is presented of the thermoanalytical and gas chromatographic (GC) properties of the copper(II) complexes of twenty four tetradenate Schiff's bases. Variations in thermal stability, volatility and GC retention of the complexes are discussed in terms of stereo-electronic effects of the substituents. Although some complexes decomposed extensively during vaporization above 250°C all, apparently, survive chromatography intact at 200°C. Certain complexes were separated as distinct regio-isomers by GC. Fluorinated ligands still appear to be the most suitable derivatizing reagents for Cu(II).