Lakshi Saikia

Efficient three-component coupling reactions catalyzed by Cu0-nanoparticles stabilized on modified montmorillonite

The in situ generation of Cu0-nanoparticles into the nanopores of modified montmorillonite and their catalytic performance in the three component (A3) coupling reactions of aldehyde, amine and alkyne to synthesize propargylamines have been described here. The modification of montmorillonite was carried out with HCl under controlled conditions for generating nanopores into the matrix and these pores act as a “host” for the in situ generation of Cu0-nanoparticles. The Cu0-nanoparticles were generated in the nanopores of the acid activated clay mineral matrix by the successful loading of a Cu(CH3COO)2 metal precursor using an incipient wetness impregnation technique followed by reduction with NaBH4. The TEM study reveals that Cu0-nanoparticles of below 10 nm in size are evenly distributed on the support. The synthesized Cu0-nanoparticles exhibit a face centered cubic (fcc) lattice. The Cu0-nanoparticles serve as an efficient green and heterogeneous catalyst for three-component coupling via C–H alkyne-activation to synthesize propargylamines with excellent yields (82–94%) and 100% selectivity under mild reaction conditions without requiring any additives or an inert atmosphere. The nanocatalysts can be recycled and reused several times without significant loss of their catalytic activity.

Facile synthesis of Fe3O4 nanoparticles on metal organic framework MIL-101(Cr): characterization and catalytic activity

Fe3O4 nanoparticles can be effectively incorporated into the matrix of MIL-101(Cr) to fabricate a Fe3O4@MIL-101 magnetite nanocomposite which behaves as a magnetic nanocatalyst for the solvent free oxidation of benzyl alcohol in the presence of TBHP. The composite material is magnetically separable and can be reused several times.

Magnetically recoverable chitosan-stabilised copper–iron oxide nanocomposite material as an efficient heterogeneous catalyst for azide–alkyne cycloaddition reactions

Chitosan-stabilised copper–iron oxide nanocomposite material is found to be a very efficient recyclable/reusable heterogeneous catalyst for azide–alkyne cycloaddition reaction under mild conditions. The as-synthesized nanocomposite material is magnetically recoverable and reusable for a minimum of four cycles without significant loss in its catalytic activity. The catalytic system is found to be highly useful for the regioselective synthesis of a wide range of 1,2,3-triazoles from various azides and alkynes.

Stabilized Fe3O4 magnetic nanoparticles into nanopores of modified montmorillonite clay: a highly efficient catalyst for the Baeyer–Villiger oxidation under solvent free conditions

In situ generation of Fe3O4 magnetic nanoparticles (Fe3O4@AT-mont.) into the nanopores of modified montmorillonite (AT-mont.) clay has been carried out. Modification of the montmorillonite was done by acid (4 M HCl) activation under controlled conditions for generating nanopores, which act as a “host” for the Fe3O4 nanoparticles. The synthesized Fe3O4@AT-mont. was characterized by PXRD, TEM, SEM-EDX, XPS, VSM and surface area analysis. The average particle size of Fe3O4 nanoparticles was found to be around 10 nm and exhibit a face centered cubic (fcc) lattice geometry. Fe3O4@AT-mont. showed efficient catalytic activity for the Baeyer–Villiger oxidation of various cyclic and aromatic ketones in the presence of hydrogen peroxide as an oxidant at room temperature under solvent free conditions and exhibited conversion of up to 98%. The catalyst was magnetically recovered and recycled up to the third run without any significant loss of efficiency.

Sulfonic acid-functionalized MIL-101(Cr) as a highly efficient heterogeneous catalyst for one-pot synthesis of 2-amino-4H-chromenes in aqueous medium

Sulfonic acid-functionalized MIL-101(Cr) was established to be an active heterogeneous catalyst for the one-pot synthesis of 2-amino-4H-chromenes via a three-component condensation reaction between resorcinol, malononitrile and a diverse range of aromatic aldehydes in aqueous medium. Here, sulfonation of the parent MIL-101(Cr) has been carried out through a post synthetic modification (PSM) technique. The resulting MIL-101(Cr)–SO3H has been characterized by employing powder X-ray diffraction, N2 sorption, FESEM, EDS, FT-IR and TGA studies. Furthermore, the catalyst can easily be recovered and recycled without much change in catalytic activity.

Palladium nanoparticles immobilized on an amine-functionalized MIL-101(Cr) as a highly active catalyst for oxidative amination of aldehydes

The present work reports the synthesis of well dispersed palladium nanoparticles immobilized on an amino functionalized nanoscale metal–organic framework MIL-101(Cr), by using a facile polyol method. The resulting Pd/NH2-MIL-101(Cr) nanocomposite is established to be an active heterogeneous catalyst for oxidative amination of aldehydes under solvent free conditions using hydrogen peroxide as an oxidant. The synthesized Pd/NH2-MIL-101(Cr) is characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, field emission scanning electron microscopy, Brunauer–Emmett–Teller (BET) surface area analysis, Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and atomic absorption spectroscopy (AAS). The catalyst could easily be recovered and recycled without any significant loss of its catalytic activity.

Flower shaped homocentric pencil like ZnO nanorod bundles: synthesis, characterisation and study of their photocatalytic activity

Flower shaped homocentric pencil like ZnO nanorod bundles are synthesized by a hydrothermal method. The PXRD pattern corresponds to the typical wurtzite structures of ZnO, which exhibits excellent activity as a photocatalyst for the degradation of malachite green under solar light irradiation.

Template-free synthesis of Fe3O4 nanorod bundles and their highly efficient peroxidase mimetic activity for the degradation of organic dye pollutants with H2O2

Highly crystalline Fe3O4 nanorod bundles were synthesized via a facile template-free method. The high surface to volume ratio of Fe3O4 nanorods facilitates the excellent activation of H2O2via their peroxidase mimetic activity for the degradation of crystal violet (CV) as a model organic dye pollutant. The self sensitization of CV dye by solar irradiation also indirectly helps in the photo-Fenton-like degradation process.

Gold nanoparticles supported on nanoscale amine-functionalized MIL-101(Cr) as a highly active catalyst for epoxidation of styrene

In this study, well dispersed gold nanoparticles (Au Nps) were embedded on an amine-functionalized nanoscale metal–organic framework MIL-101(Cr) via a simple solution approach. The resulting Au/NH2-MIL-101(Cr) exhibited a high isoelectric point (IEP) value with Bronsted basic sites that played an important role in determining the size and dispersion of Au Nps onto its matrix. In addition, the uniform nanomorphology of the catalyst provides the advantage of its good dispersion in aqueous media. The synthesized Au/NH2-MIL-101(Cr) catalyst was successfully characterized by different analytical techniques like powder X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller (BET) surface area analysis, Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), zeta potential analysis and atomic absorption spectroscopy (AAS). The catalytic activity of the synthesized material was explored for the epoxidation of styrene using tert-butyl hydroperoxide as oxidant. The catalyst could easily be recovered and recycled up to the fourth catalytic cycle without any significant change in its catalytic activity.

Facile synthesis of gold nanoparticles on propylamine functionalized SBA-15 and effect of surface functionality of its enhanced bactericidal activity against gram positive bacteria

The facile synthesis of an SBA-15-pr-+NH3.Au0 nano-hybrid material by spontaneous autoreduction of aqueous chloroaurate anions on propylamine functionalized SBA-15 was successfully demonstrated. The as-synthesized SBA-15-pr-+NH3.Au0 nano-hybrid material was well characterized using low and wide angle x-ray diffraction (XRD), N2 adsorption–desorption isotherms, Fourier transform infrared (FTIR), transmission electron microscopy (TEM), scanning electron microscopy-energy dispersive x-ray spectroscopy (SEM-EDX), x-ray photoelectron spectroscopy (XPS), UV-Visible spectroscopy and atomic absorption spectroscopy (AAS). The activity of the nano-hybrid material as a potent bactericidal agent was successfully tested against Gram positive/negative bacteria viz. Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. The colony killing percentage of Gram positive bacteria was found to be higher than Gram negative bacteria due to the stronger electrostatic interaction between the positively-charged amine functionality of SBA-15 and the negatively charged functionality of the bacterial cell wall.