New heterometallic coordination polymers derived form chalcogenocyanates: synthesis,characterization and electrical properties

A series of conducting mixed-metallic coordination polymers: Cu₂Pb(SCN)₄, CuPb(SeCN)₄, Cu^II _0.50Cu^IPb (SCN·SeCN)₂, CuAg(SCN)₂, CuAg(SeCN)₂ and CuAg(SCN·SeCN) have been synthesized by the reaction of Cu and Pb^II or Ag^Initrates with KSCN or KSeCN, or both KSCN and KSeCN in H₂O. Of significance are the aerobic reactions which yield heterometallic complexes viaoxidation of SCN^– and SeCN^– into (SCN)₂ and (SeCN)₂ followed by quantitative reduction of Cu^II into Cu^I; in the case of CuPb(SeCN)₄ reduction of Cu^II into Cu^I is not observed, while in Cu^{II 0.50}Cu^IPb(SCN·SeCN)₂, Cu^II is partially reduced to Cu^I. These compounds have been characterized by elemental (C, N, S and Se) analyses, magnetic moment measurements, relevant spectroscopies (i.r., far i.r., Raman, u.v.–vis. and e.p.r.), powder X-ray diffraction pattern and conductivity technique. The v(CN) vibrations in 2162–2087cm^–1 and far i.r. bands (500–100cm^–1) corroborated by Raman bands are conclusive of the bridging (N, S/Se) mode and metal-NCS and metal-SCN/SeCN^– bonding respectively in the complexes. Room temperature magnetic moment, electronic absorption spectra and e.p.r. active/silent nature confirm the oxidation state of copper in these solids. Room temperature compressed pellet conductivities _rt, 10^–9to 10^–7Scm^–1 with activation energies, E _a=0.19–0.25eV and increase in the conductivity with increase in temperature in the 305–423K, range and decrease in conductivity with decrease in temperature in the 295–200K range, show their semiconductor properties.     

Reactivity of a N-heterocyclic carbene, 1,3-di-(1-adamantyl) imidazol-2-ylidene, with a pseudo-acid: structural characterization of Claisen condensation adduct

The reactivity of a N-heterocyclic carbene (NHC) with a pseudo-acid (ester in this case) is described. The product results from an unusual C-H bond activation. The structure of the product has been established by a single crystal diffraction study.     

Characterization of aliphatic and aromatic polyester hyperbranched dendrimers by AFM imaging

The aggregates of aliphatic (AL-PE) and aromatic polyester (AR-PE) hyperbranched dendrimers were imaged by tapping mode atomic force microscopy (AFM). The second and third generations of AL-PE dendrimers were adsorbed on mica in large aggregates of 150- and 166-nm diameters with little heights (ca. 1–2 nm). The origin of such flattened aggregates is attributed to their favorable adsorption on mica in view of the presence of –OH surface groups. AR-PE did not show such flattened aggregates instead small aggregates of 63 nm were observed in an organized manner beaving a cavity in the center of each aggregate. The organized aggregates of AR-PE with smaller dimension than AL-PE are ascribed to less favorable adsorption of the latter on mica in view of its stronger hydrophobicity.     

Polymeric Nanoparticles Amenable to Simultaneous Installation of Exterior Targeting and Interior Therapeutic Proteins

Effective delivery of therapeutic proteins is a formidable challenge. Herein, using a unique polymer family with a wide‐ranging set of cationic and hydrophobic features, we developed a novel nanoparticle (NP) platform capable of installing protein ligands on the particle surface and simultaneously carrying therapeutic proteins inside by a self‐assembly procedure. The loaded therapeutic proteins (e.g., insulin) within the NPs exhibited sustained and tunable release, while the surface‐coated protein ligands (e.g., transferrin) were demonstrated to alter the NP cellular behaviors. In vivo results revealed that the transferrin‐coated NPs can effectively be transported across the intestinal epithelium for oral insulin delivery, leading to a notable hypoglycemic response.     

Morphology-controlled assembly of ZnO nanostructures: a bioinspired method and visible luminescence

In a bioinspired methodology, positively charged polypeptides and polyamines directly catalyse ZnO mineralization under "green" conditions of room temperature and neutral pH. The polyamines not only act as mineralizing agents for the formation of ZnO nanoparticles, but also self-assemble the nanoparticles to form spindle-like morphologies at these very ambient conditions. Both the directional growth of ZnO and its luminescent property have a pH dependency. At higher pH, the ZnO shape changes to a rodlike morphology that exhibits green photoluminescence with different intensity than that for ZnO spindles.     

ESR and NMR studies of poly (amidoamine) dendrimers with ionic surfactants in different media

The electron paramagnetic resonance (EPR) study has been carried out for the micellar solutions of various ionic surfactant solutions as well as various generations of aqueous dendrimer both in their respective presence as well as their absence at 25°C and in different media. From these measurements, the rotation correlation time (τ_B) have been calculated for all the ionic surfactant + PAMAM + water system. A variation in the τ_Bvalue remains mostly constant for the dodecyltrimethyammonium bromide (DTAB) and tetradecyltrimethylammonium bromide (TTAB) + PAMAM + water ternary mixtures. The τ_Bvalue shows an increase with the increase in the amount of PAMAM for SDS in basic medium and for 12-2-12 in acidic medium. It has been concluded from these results that SDS undergo complexation with all generations of PAMAM in basic medium and 12-2-12 in acidic medium and produce stronger hydrophobic environment. The nuclear magnetic resonance study (NMR) allowed us to evaluate the spin–spin relaxation (T₁) times of SDS in the presence of all generations of PAMAM. The T₁ values for all the tail protons of SDS showed a slight decrease with the increase in the constant amount of PAMAM suggesting the adsorption of PAMAM molecules on the micelle surface.     

Synthesis of phosphorus esters by transesterification mediated by N-heterocyclic carbenes (NHCs)

The versatile nucleophilic organic catalysts N-heterocyclic carbenes (NHCs) have been shown to effectively mediate the transesterification of phosphorus esters under mild conditions; user-friendly imidazolium salts can also be employed as pre-catalysts.     

Design of a silicon-based field-effect electro-optic modulator with enhanced light-charge interaction

A new design for an all-silicon field-effect optical modulator in a ring resonator geometry is proposed and modeled by means of finite-element method simulations. It is shown that the optimal relative placement of the ultrathin field-effect-generated charge layers and the optical mode in the strong-confinement waveguides leads to more than an order-of-magnitude enhancement in the light-charge interaction compared with the recent predictions in the literature. We show that such an enhancement could provide optical modulation with a >7 dB extinction-ratio using a voltage swing of only 2 V, thus making our design compatible with complementary metal-oxide semiconductor technology.     

Analysis of electro-optical and dielectric parameters of TiO2 nanoparticles dispersed nematic liquid crystal

The present investigation is focused on to find out the role of TiO₂ nanoparticles (NPs) on altering the dielectric and electro-optical parameters of nematic liquid crystal (NLC). In addition to this, we also optimized the concentration of dopant (0.25 wt%) for a saturation value of permittivity and dielectric anisotropy in the doped system. Dielectric spectroscopy has been performed with the variation of frequency and temperature to investigate the various dielectric parameters, which demonstrate that the investigated NLC is of positive dielectric anisotropy; the observed result shows a decrement in the value of relative permittivity and dielectric anisotropy; however, the permittivity value increases for higher concentration of dopant but remains less than that of pure NLC. Electro-optical measurements have also been performed to compute the optical response of pure and dispersed NLC. It is found that optical response decreases for the NP-doped systems. This optimized concentration of NPs in NLC matrix can have various credential applications in the field of active matrix display and holography.     

Preparation and preliminary evaluation of a tris-metronidazole-<Superscript>99m</Superscript>Tc(CO)<Subscript>3</Subscript> complex for targeting tumor hypoxia

Conventional ^99mTc-radiopharmaceuticals for the detection of tumor hypoxia generally possess a single nitroimidazole moiety. Herein, we report the synthesis and evaluation of a ^99mTc-complex with three-nitroimidazole moieties in an attempt to improve hypoxic cell detection. Isocyanide derivative of metronidazole (MetroNC) was synthesized and subsequently radiolabeled with [^99mTc(CO)₃(H₂O)₃]⁺ precursor complex, wherein the three labile water molecules were replaced with MetroNC ligand to form a pseudo-octahedral [^99mTc(CO)₃(MetroNC)₃]⁺ complex. Analysis of corresponding Re(CO)₃-analog prepared in macroscopic scale confirmed the formation of expected complex. Cyclic voltammetric studies of [Re(CO)₃(MetroNC)₃]⁺ complex showed no significant change in single-electron reduction potential (SERP) of MetroNC ligand (??0.96 V) upon forming the [Re(CO)₃(MetroNC)₃]⁺ complex (??0.90 V). In vitro studies in Chinese hamster ovary (CHO) cells showed three-fold preferential accumulation of [^99mTc(CO)₃(MetroNC)₃]⁺ complex in hypoxic cells over normoxic cells. Biodistribution studies of [^99mTc(CO)₃(MetroNC)₃]⁺ complex in Swiss mice bearing fibrosarcoma tumor showed tumor uptake and steady retention till 60 min post injection. Present study constitutes a novel design approach towards development of a ^99mTc-radiopharmaceutical for hypoxia imaging application, which could be extended to other potential nitroimidazole ligands.