Synthesis of aza-, oxa-, and thiabicyclo[3.1.0]hexane heterocycles from a common synthetic intermediate

[reaction: see text] An efficient and stereospecific approach to the synthesis of structurally constrained aza-, oxa-, and thiabicyclo[3.1.0]hexane heterocycles has been achieved through application of the intramolecular cyclopropanation reaction of diazoacetates. The various constrained heterocycles (X = N, O, or S) are conveniently prepared from a common diol intermediate accessible from readily available cinnamyl alcohols. Application of the methodology to the synthesis of conformationally constrained oxazolidinone antibacterials is also discussed.     

A mild and efficient method for the oxidation of benzylic alcohols by two-phase electrolysis

Electrochemical oxidation of benzylic and substituted benzylic alcohols by two-phase electrolysis yields the corresponding aldehydes as products. The reaction was carried out in a single compartment cell with platinum electrodes at room temperature in chloroform using an aqueous sodium bromide solution (25%) containing a catalytic amount of HBr. The two-phase electrolysis resulted in high yields (74-96%) of benzaldehyde from primary alcohols and secondary alcohols were oxidized to the corresponding ketone but only in low yields under these conditions.     

In vitro dielectrophoresis of HEK cell migration for stimulating chronic wound epithelialization

This article describes a dielectrophoresis (DEP)-based simulation and experimental study of human epidermal keratinocyte (HEK) cells for wounded skin cell migration toward rapid epithelialization. MyDEP is a standalone software designed specifically to study dielectric particles and cell response to an alternating current (AC) electric field. This method demonstrated that negative dielectrophoresis (N_DEP) occurs in HEK cells at a wide frequency range in highly conductive medium. The finite element method was used to characterize particle trajectory based on DEP and drag force. The performance of the system was assessed using HEK cells in a highly conductive EpiLife suspending medium. The DEP experiment was performed by applying sinusoidal wave AC potential at the peak-to-peak voltage of 10 V in a tapered aluminum microelectrode array from 100 kHz to 1 MHz. We experimentally observed the occurrence of NDEP, which attracted HEK cells toward the local electric field minima in the region of interest. The DIPP-MotionV software was used to track cell migration in the prerecorded video via an automatic marker and estimate the average speed and acceleration of the cells. The results showed that HEK cell migration was accomplished approximately at 6.43 μm/s at 100 kHz with 10 V, and F_DEP caused the cells to migrate and align at the target position, which resulted in faster wound closures because of the application of an electric field frequency to HEK cells in random locations.     

Impact of the Chirality and Curvature of Carbon Nanostructures on Their Interaction with Aromatics and Amino Acids

Understanding noncovalent interactions on the surfaces of carbon nanostructures (CNSs) is of fundamental importance and also has implications in nano‐ and biotechnology. The interactions of aromatic compounds such as benzene, naphthalene, and aromatic amino acids with CNSs of varying diameter, chirality, and curvature were systematically explored by using density functional theory. Planar graphene exhibits stronger binding affinity than curved carbon nanotubes (CNTs), whereas zigzag CNTs appear to show stronger binding affinity than armchair CNTs. For hydrocarbons, there exist two competing modes, namely, π–π stacking interactions and CH ??? π interactions, which bring the aromatic motifs into parallel and perpendicular dispositions with respect to the CNSs, respectively. Our results reveal that π–π stacking interactions override CH ??? π interactions in such cases. However, in the case of aromatic amino acids, π–π interactions can exist simultaneously along with a range of other interactions, including CH ??? π. The polarizability and HOMO energy of the CNSs were found to be the key factors that determine the binding energies. The HOMO–LUMO energy gaps of the CNSs were found to be undisturbed by the noncovalent functionalization of the aromatic molecules.     

Effect of an applied electric current in epitaxial growth of GaAs layer on patterned GaAs substrate

Selective epitaxial growth of a GaAs layer on SiN_x masked Si-doped semi-insulating (1 0 0) GaAs substrate was performed by current-controlled liquid-phase epitaxy (CCLPE) in the conventional liquid-phase epitaxy. Experiments were carried out with and without the application of electric current. Surface morphology of (1 0 0) facet of the grown layer and the vertical and lateral growth rates were significantly improved under applied electric current. A thick layer of about 330 μm was achieved at relatively low growth time of 6 h with a current density of 20 Acm⁻². The epitaxial growth is realized by both electromigration of the solute and supercooling under a constant rate of furnace cooling. The dislocation density of the grown layer was significantly reduced, compared with that of the substrate (4×10⁴ cm²).     

Gold nanoparticles functionalized with deep-cavity cavitands: synthesis, characterization, and photophysical studies

In this report, we present methods of functionalization of AuNP's with deep-cavity cavitands that can include organic molecules. Two types of deep-cavity cavitand-functionalized AuNP's have been synthesized and characterized, one soluble in organic solvents and the other in water. Functionalized AuNP soluble in organic solvents forms a 1:1 host-guest complex where the guest is exposed to the exterior solvents. The one soluble in water forms a 2:1 host-guest complex where the guest is protected from solvent water. Phosphorescence from thiones and benzil included within heterocapsules attached to AuNP was quenched by gold atoms present closer to the guests included within deep-cavity cavitands. During this investigation, we have synthesized four new deep-cavity cavitands. Of these, two thiol-functionalized hosts allowed us to make stable AuNP's. However, AuNP's protected with two amine-functionalized cavitands tended to aggregate within a day.     

Catalytic oxidation and C–C coupling reactions of new ruthenium(III) Schiff base complexes containing PPh<Subscript>3</Subscript> or AsPh<Subscript>3</Subscript> co-ligands

New mononuclear ruthenium(III) Schiff base complexes of the type [RuX₂(EPh₃)(L)] (X = Cl or Br; E = P or As; L = monobasic tridentate Schiff base derived from o-aminophenol or o-aminothiophenol with ethylacetoacetate or ethylbenzoylacetate) have been synthesized. The Schiff base ligands chelate to ruthenium through O, N, and O/S by dissociation of the phenolic proton/thiophenolic proton forming chelate rings. These complexes have been characterized by physico-chemical and spectroscopic methods. Cyclic voltammetric data of all the complexes showed Ru(III)/Ru(IV) oxidation and Ru(III)/Ru(II) reduction within the range of 0–1.5 V and 0 to −1.5 V with respect to Ag/AgCl, respectively. The complexes were tested as catalysts in the oxidation of alcohols using molecular oxygen at ambient temperature, and also in C–C coupling reactions. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Effective atomic numbers in some food materials and medicines for $$\gamma $$-ray attenuation using $$^{137}$$137Cs $$\gamma $$-ray

A light-weight multichannel analyser (MCA)-based \(\gamma \)-ray spectrometer, developed earlier at the Inter University Accelerator Centre, New Delhi, has been used as part of the PG curriculum, to determine the effective atomic numbers for \(\gamma \) attenuation of \(^{137}\)Cs \(\gamma \)-ray in different types of samples. The samples used are mixtures of graphite, aluminum and selenium powders in different proportions, commercial and home-made edible powders, fruit and vegetable juices as well as certain allopathic and ayurvedic medications. A narrow beam good geometry set-up has been used in the experiments. The measured attenuation coefficients have been used to extract effective atomic numbers in the samples. The results are consistent with XCOM values wherever available. The present results suggest that the \(\gamma \) attenuation technique can be used as an effective non-destructive method for finding adulteration of food materials.     

Synthesis, Characterization, and Thermal Decomposition of Double Rare Earth Monomethylammonium Selenates

Summary.  Double rare earth monomethylammonium selenates of the general formula CH₃NH₃ Ln (SeO₄)₂·5H₂O (Ln = Sm, Eu, Gd, Tb, Ho, Y) were synthesized and characterized using X-ray powder diffraction and infrared spectroscopy. The thermal decomposition of the compounds were investigated using TG, DTG, and DTA techniques. Corresponding author. E-mail: vrajgaonkar@yahoo.com, vrajgaonkar@mail.mu.ac.in Received November 5, 2001. Accepted (revised) March 6, 2002     

Plasmon induced photoluminescent emission from PED Ag–In alloy

Research on Chemical Intermediates - Blending of two metals possessing localized surface plasmon resonance (LSPR) alters the optical behavior and aids in tuning the resonance frequency of...