Synthesis and characterization of a new phase of zirconium phosphate for the separation of metal ions

The tetravalent metal acid (TMA) salt amorphous zirconium phosphate (ZP), an inorganic ion exchanger, has been synthesized by sol-gel method. The material has been characterized by elemental analysis (ICP-AES), thermal analysis (TGA, DSC), FT-IR and X-ray diffraction studies. Chemical resistivity of the material in various media-acids, bases and organic solvents has been assessed. The Na⁺ ion exchange capacity (IEC) and the effect of heating on the IEC have been determined, and showed the distribution and elution behavior of ZP towards several metal ions in different electrolyte media/concentrations. Based on the distribution studies, a few binary metal ion separations have been achieved.     

Antifungal activity of multifunctional Fe3O4-Ag nanocolloids

In recent years, rapid increase has been observed in the population of microbes that are resistant to conventionally used antibiotics. Antifungal drug therapy is no exception and now resistance to many of the antifungal agents in use has emerged. Therefore, there is an inevitable and urgent medical need for antibiotics with novel antimicrobial mechanisms. Aspergillus glaucus is the potential cause of fatal brain infections and hypersensitivity pneumonitis in immunocompromised patients and leads to death despite aggressive multidrug antifungal therapy. In the present article, we describe the antifungal activity of multifunctional core-shell Fe₃O₄-Ag nanocolloids against A. glaucus isolates. Controlled experiments are also carried out with Ag nanocolloids in order to understand the role of core (Fe₃O₄) in the antifungal action. The minimum inhibitory concentration (MIC) of nanocolloids is determined by the micro-dilution method. MIC of A. glaucus is 2000 μg/mL. The result is quite promising and requires further investigations in order to develop a treatment methodology against this death causing fungus in immunocompromised patients.     

Cyclodehydration of 1,4-butanediol catalyzed by metal(IV) phosphates

Metal(IV) phosphates of tin, zirconium and titanium in different morphological forms, viz. amorphous, calcined and crystalline, have been used as catalysts for selective cyclodehydration of 1,4-butanediol to tetrahydrofuran. A comparative study of the three catalysts for the above reaction has been carried out to understand the effect of their composition and morphology on the catalytic activity.     

Nanoengineering of methylene blue loaded silica encapsulated magnetite nanospheres and nanocapsules for photodynamic therapy

Core–shell nanostructures have emerged as an important class of functional materials with potential applications in diverse fields, especially in health sciences. In this article, nanoengineering of novel magnetic colloidal dispersion containing surface modifiable silica with a core of single domain magnetite nanoparticles loaded with photosensitizer (PS) drug “Methylene blue” (MB) has been described. Magnetite core is produced by the well-established chemical coprecipitation technique and silica shell is formed over it by the modified hydrolysis and condensation of TEOS (tetraethyl orthosilicate). Conditions for reaction kinetics have been established to tailor the core–shell structures in the form of nanospheres and nanocapsules. MB is loaded into the nanostructures by demethylation reaction. The major conclusion drawn from this study is that the synthesis route yields stable, non-aggregated MB loaded superparamagnetic magnetite-silica nanostructures with tailored morphology, tunable loading, and excellent magnetic properties.     

Synthesis, characterization and proton transport properties of mixed metal phosphonate-zirconium titanium hydroxy ethylidene diphosphonate

Novel hybrid material, zirconium titanium hydroxy ethylidene diphosphonate (ZTHEDP) of the class of tetravalent bimetallic acid (TBMA) salt was synthesized using sol-gel route. ZTHEDP was characterized for elemental analysis (zirconium, titanium and phosphorus by ICP-AES and carbon and hydrogen by CHN analyzer), spectral analysis (FTIR), thermal analysis (TGA), X-ray diffraction studies and SEM. Chemical resistivity of this material was assessed in various media-acids, bases and organic solvents. The protons present in the structural hydroxyl groups in ZTHEDP indicate good potential to exhibit solid state proton conduction. The proton transport property of ZTHEDP was explored by measuring specific conductance at different temperatures in the range of 303–423 K at 10 K intervals, using Solartron Impedance Analyzer (SI 1260) over a frequency range 1 Hz-32 MHz at a signal level below 1 V. Zirconium hydroxy ethylidene diphosphonate (ZrHEDP) and titanium hydroxy ethylidene diphosphonate (TiHEDP) were also synthesized under identical conditions, characterized and their proton transport properties investigated for comparative studies. It is observed that, in all cases, conductivity decreases with increasing temperature. Conductivity performance of ZTHEDP, ZrHEDP and TiHEDP is discussed based on conductivity data and activation energy. It is observed that, ZTHEDP exhibits enhanced conductance and the mechanism of transportation is proposed to be Grotthuss type.     

Highly bacterial resistant silver nanoparticles: synthesis and antibacterial activities

In this article, we describe a simple one-pot rapid synthesis route to produce uniform silver nanoparticles by thermal reduction of AgNO₃ using oleylamine as reducing and capping agent. To enhance the dispersal ability of as-synthesized hydrophobic silver nanoparticles in water, while maintaining their unique properties, a facile phase transfer mechanism has been developed using biocompatible block co-polymer pluronic F-127. Formation of silver nanoparticles is confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV–vis spectroscopy. Hydrodynamic size and its distribution are obtained from dynamic light scattering (DLS). Hydrodynamic size and size distribution of as-synthesized and phase transferred silver nanoparticles are 8.2 ± 1.5 nm (σ = 18.3%) and 31.1 ± 4.5 nm (σ = 14.5%), respectively. Antimicrobial activities of hydrophilic silver nanoparticles is tested against two Gram positive (Bacillus megaterium and Staphylococcus aureus), and three Gram negative (Escherichia coli, Proteus vulgaris and Shigella sonnei) bacteria. Minimum inhibitory concentration (MIC) values obtained in the present study for the tested microorganisms are found much better than those reported for commercially available antibacterial agents.     

Determination of structural modification in acid activated montmorillonite clay by FT-IR spectroscopy

The structural modifications and the Bronsted acid sites generated during the acid treatment of montmorillonite clay with varied concentration of sulphuric acid was determined using FT-IR spectroscopy. Octahedral sheet is affected at low acid concentration resulting into the dissolution of cations; among them Mg2+ cations are prone to dissolve than Fe2+/3+ and Al3+. Tetrahedral sheet is affected at higher acid concentration. The partial substitution of octahedral Al3+ by Mg2+ or Fe2+/3+ cations and the presence of other non-smectite minerals such as kaolinites was also been clearly identified, thus making FT-IR spectroscopy as a rapid technique for monitoring the structural features of montmorillonite clay.     

Synthesis and characterization of cadmium tartrate single crystals

Efforts have been successful to crystallize the electroceramic compound of cadmium tartrate through silica hydrogel. Analysis of thermograms reveals decomposition of the crystals to take place within the temperature range 65 to 442°C in air atmosphere. Some important characteristic data, i.e., valance electron plasma energy, Penn gap, Fermi energy, interionic distance, electronic polarizability have been obtained. The DC conductivity of the crystal typically lies between the conductivities of metal and insulator and we derived several pertinent parameters such as hopping energy, hopping distance, coulomb gap, etc. The micromechanical indentation of the crystal shows nonlinear variation of the impact microhardness as a function of the applied load. The estimation of fracture toughness, fragility coefficient and yield strength has too been made for the synthesized crystal. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

One-pot thiol–amine bioconjugation to maleimides: simultaneous stabilisation and dual functionalisation

Maleimide chemistry is widely used in the site-selective modification of proteins. However, hydrolysis of the resultant thiosuccinimides is required to provide robust stability to the bioconjugates. Herein, we present an alternative approach that affords simultaneous stabilisation and dual functionalisation in a one pot fashion. By consecutive conjugation of a thiol and an amine to dibromomaleimides, we show that aminothiomaleimides can be generated extremely efficiently. Furthermore, the amine serves to deactivate the electrophilicity of the maleimide, precluding further reactivity and hence generating stable conjugates. We have applied this conjugation strategy to peptides and proteins to generate stabilised trifunctional conjugates. We propose that this stabilisation-dual modification strategy could have widespread use in the generation of diverse conjugates.

An alternative approach to maleimide conjugate stabilisation is presented, by the consecutive addition of a thiol and an amine to dibromomaleimides. The amine serves to simultaneously deactivate the maleimide and enable dual functionalisation.