Synthesis and physicochemical studies of ferrocene‐containing materials

Low‐temperature solution‐phase polycondensation of 1,1′‐ferrocenedicarboxylic acid chloride with newly synthesized aromatic diamines was carried out in tetrahydrofuran in the presence of triethylamine to form several new organometallic aromatic polyamides containing ferrocene units. The organometallic aromatic polyamides derived were in good yields ranging from 75 to 80%, amorphous with melting temperatures of > 350 °C. The monomers and the resulting polymers were characterized by their physical properties, elemental analysis, 1 H NMR and FTIR spectroscopy. The differential scanning calorimetry and thermogravimetric studies of the resulting aramids were also carried out. All the polymers were insoluble in common organic solvents. However, all dissolved in concentrated H₂SO₄ forming reddish brown solutions. Their glass transition temperatures were quite high, which is characteristic of aramids. They were also stable up to 450 °C with 10% mass losses (14–23%) recorded in the range 400–470 °C. The activation energies for decomposition of each aramid were also calculated using the Horowitz and Metzger method. All polymers showed reduced solution viscosities in concentrated sulphuric acid, which may be attributed to non‐Newtonian behavior. Copyright © 2007 John Wiley & Sons, Ltd.     

Assessment of three digestion procedures for Zn contents in Pakistani soil by flame atomic absorption spectrometry

Evaluation of three different digestion procedures for accurate determination of elemental concentration in soils was undertaken. The digestion procedures, two leaching and a total dissolution processes were compared for twenty-one soil samples. The soil standard reference materials (SRMs), IAEA Soil-5 and IAEA Soil-7 were analysed for quality control purposes. Zinc (Zn) was analysed using flame atomic absorption spectrometry (FAAS). Precise analysis was accomplished in the SRM and soil samples, which was better than 4.7% for leaching and total dissolution procedure. Compared with the elemental concentration in soil samples, HF–HClO₄ procedure achieved greater accuracy, where as HNO₃–H₂O₂ and HNO₃–H₂SO₄–HCl procedures were comparable with slight variation in a few samples.     

Liquid‐Crystal‐Mediated Self‐Assembly of Porous α‐Fe2O3 Nanorods on PEDOT:PSS‐Functionalized Graphene as a Flexible Ternary Architecture for Capacitive Energy Storage

A novel aqueous‐based self‐assembly approach to a composite of iron oxide nanorods on conductive‐polymer (CP)‐functionalized, ultralarge graphene oxide (GO) liquid crystals (LCs) is demonstrated here for the fabrication of a flexible hybrid material for charge capacitive application. Uniform decoration of α‐Fe₂O₃ nanorods on a poly(3,4‐ethylene‐dioxythiophene): poly(styrenesulfonate) (PEDOT:PSS)‐functionalized, ultralarge GO scaffold results in a 3D interconnected layer‐by‐layer (LBL) architecture. This advanced interpenetrating network of ternary components is lightweight, foldable, and possesses highly conductive pathways for facile ion transportation and charge storage, making it promising for high‐performance energy‐storage applications. Having such structural merits and good synergistic effects, the flexible architecture exhibits a high specific discharge capacitance of 875 F g^?1 and excellent volumetric specific capacitance of 868 F cm^?3 at 5 mV s^?1, as well as a promising energy density of 118 W h kg^?1 (at 0.5 A g^?1) and promising cyclability, with capacity retention of 100% after 5000 charge–discharge (CD) cycles. This synthesis method provides a simple, yet efficient approach for the solution‐processed LBL insertion of the hematite nanorods (HNR) into CP‐functionalized novel composite structure. It provides great promise for the fabrication of a variety of metal‐oxide (MO)‐nanomaterial‐based binder and current collector‐free flexible composite electrodes for high‐performance energy‐storage applications.     

Determination of <Superscript>90</Superscript>Sr in environment of district Swat,Pakistan

Assessment of ⁹⁰Sr is of great interest owing to the fact that this artificially produced radionuclide has high radiological importance because of its high fission yield, chemical similarity to calcium and its relatively long biological and physical half-life. To assess the likely hazard to population, low level ⁹⁰Sr in environmental samples is determined using pre-equilibrated tri-butyl phosphate (TBP) solvent and extraction-liquid scintillation procedure. ⁹⁰Y is selectively extracted from nitric acid solution into TBP solvent and stripped into aqueous phase as oxalate. The activity is finally measured by low level liquid scintillation counter using Cerenkov radiation. The specific activity is found only in three vegetation samples with average value of 2.86±1.7 Bq·kg⁻¹ of dry weight. In all other samples analyzed, the activity is below the detectable limit, i.e., 0.03 Bq. Results obtained are comparable with other areas of Pakistan. The chemical recovery of ⁹⁰Y varies from 75 to 90% for soil, vegetation and water. The present study provides a general background of the detectable radionuclide for the surveyed area that will be helpful in any radiological emergency.     

Design, synthesis, and characterization of a single-chain peptide antagonist for the relaxin-3 receptor RXFP3

Relaxin-3 is a two-chain disulfide-rich peptide that is the ancestral member of the relaxin peptide family and, together with its G protein-coupled receptor RXFP3, is highly expressed in the brain. Strong evolutionary conservation of relaxin-3 suggests a critical biological function and recent studies have demonstrated modulation of sensory, neuroendocrine, metabolic, and cognitive systems. However, detailed studies of central relaxin-3-RXFP3 signaling have until now been severely hampered by the lack of a readily available high-affinity antagonist for RXFP3. Previous studies have utilized a complex two-chain chimeric relaxin peptide, R3(BΔ23-27)R/I5, in which a truncated relaxin-3 B-chain carrying an additional C-terminal Arg residue was combined with the insulin-like peptide 5 (INSL5) A-chain. In this study we demonstrate that, by replacing the native Cys in this truncated relaxin-3 B-chain with Ser, a single-chain linear peptide of 23 amino acids that retains high-affinity antagonism for RXFP3 can be achieved. In vivo studies demonstrate that this peptide, R3 B1-22R, antagonized relaxin-3/RXFP3 induced increases in feeding in rats after intracerebroventricular injection. Thus, R3 B1-22R represents an excellent tool for biological studies probing relaxin pharmacology and a lead molecule for the development of synthetically tractable, single-chain RXFP3 modulators for clinical use.     

Mechanistic study of hydrolytic erosion and drug release behaviour of PLGA nanoparticles: Influence of chitosan

The hydrolytic erosion of poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles (PLGA-NPs) was investigated in vitro. The changes in physical properties of the nanoparticles with time were evaluated by ultra high-pressure liquid chromatographic (UHPLC) analysis, particle size analysis and scanning electron microscopy (SEM). Mass reduction data demonstrated a triphasic erosion pattern for PLGA-NPs with nearly no mass loss (3.0%) up to a week, followed by a rapid mass loss (weeks 1-3, 61.4%), and further followed by slow mass loss (weeks 3-5, 19.8%). SEM revealed microcavitation on the surface of nanoparticles, which tended to increase with the erosion time and eventually particle fragmentation was evident at 5 weeks. A significant increase in particle size was observed at 4 weeks which can be attributed to particle aggregation, however, at about 5 weeks, the particle size decreased significantly owing to particle fragmentation. The hydrolytic erosion of PLGA-NPs was found to be specifically proton catalyzed. The release profile of the model drug, moxifloxacin, from PLGA-NPs was closely related to nanoparticle erosion except for the initial burst release which was based on diffusion. The presence of chitosan in the PLGA-NPs accelerated the rate of erosion of the nanoparticles and reduced the burst release of the drug. An understanding of the erosion mechanism and alteration in erosion by chitosan could give desirable and more uniform drug release kinetics from PLGA-NPs.