Indian Association for the Cultivation of Science

About: Indian Association for the Cultivation of Science is a education organization based out in Kolkata, India. It is known for research contribution in the topics: Catalysis & Excited state. The organization has 3867 authors who have published 10457 publications receiving 220098 citations.

Fabrication of Ruthenium Nanoparticles in Porous Organic Polymers: Towards Advanced Heterogeneous Catalytic Nanoreactors.

Abstract: A novel strategy has been adopted for the construction of a copolymer of benzene-benzylamine-1 (BBA-1), which is a porous organic polymer (POP) with a high BET surface area, through Friedel-Crafts alkylation of benzylamine and benzene by using formaldehyde dimethyl acetal as a cross-linker and anhydrous FeCl3 as a promoter. Ruthenium nanoparticles (Ru NPs) were successfully distributed in the interior cavities of polymers through NaBH4, ethylene glycol, and hydrothermal reduction routes, which delivered Ru-A, Ru-B, and Ru-C materials, respectively, and avoided aggregation of metal NPs. Homogeneous dispersion, the nanoconfinement effect of the polymer, and the oxidation state of Ru NPs were verified by employing TEM, energy-dispersive X-ray spectroscopy mapping, cross polarization magic-angle spinning (13)C NMR spectroscopy, and X-ray photoelectron spectroscopy analytical tools. These three new Ru-based POP materials exhibited excellent catalytic performance in the hydrogenation of nitroarenes at RT (with a reaction time of only ≈ 30 min), with high conversion, selectivity, stability, and recyclability for several catalytic cycles, compared with other traditional materials, such as Ru@C, Ru@SiO2, and Ru@TiO2, but no clear agglomeration or loss of catalytic activity was observed. The high catalytic performance of the ruthenium-based POP materials is due to the synergetic effect of nanoconfinement and electron donation offered by the 3D POP network. DFT calculations showed that hydrogenation of nitrobenzene over the Ru (0001) catalyst surface through a direct reaction pathway is more favorable than that through an indirect reaction pathway.

Inhibition of electron flow through complex I of the mitochondrial respiratory chain of Ehrlich ascites carcinoma cells by methylglyoxal

Abstract: The effect of methylglyoxal on the oxygen consumption of Ehrlich-ascites-carcinoma (EAC)-cell mitochondria was tested by using different respiratory substrates, electron donors at different segments of the mitochondrial respiratory chain and site-specific inhibitors to identify the specific respiratory complex which might be involved in the inhibitory effect of methylglyoxal on the oxygen consumption by these cells. The results indicate that methylglyoxal strongly inhibits ADP-stimulated alpha-oxo-glutarate and malate plus pyruvate-dependent respiration, whereas, at a much higher concentration, methylglyoxal fails to inhibit succinate-dependent respiration. Methylglyoxal also fails to inhibit respiration which is initiated by duroquinol, an artificial electron donor. Moreover, methylglyoxal cannot inhibit oxygen consumption when the NNN'N'-tetramethyl-p-phenylenediamine by-pass is used. The inhibitory effect of methylglyoxal is identical on both ADP-stimulated and uncoupler-stimulated respiration. Lactaldehyde, a catabolite of methylglyoxal, can exert a protective effect on the inhibition of EAC-cell mitochondrial respiration by methylglyoxal. We suggest that methylglyoxal possibly inhibits the electron flow through complex I of the EAC-cell mitochondrial respiratory chain.

Fluorescence Anisotropy Decay in Polymer-Surfactant Aggregates

Abstract: The fluorescence anisotropy decay of two dyes merocyanine 540 and oxazine 1 has been studied in a polymer−surfactant aggregate containing poly(vinylpyrrolidone) (PVP) and sodium dodecyl sulfate (SDS). The results are analyzed in terms of the necklace model of the polymer−surfactant aggregate. The rotational motion of the probe is assumed to involve “wobbling-in-cone” along with translational motion along the micellar surface. It is observed that the presence of the polymer chains around the spherical SDS micelles causes significant retardation of both the wobbling motion as well as the translational motion of the two dyes. As a result, the wobbling and translational diffusion of the dyes in the PVP−SDS aggregate are slower than those in SDS micelle.

Silver nanoparticles embedded over mesoporous organic polymer as highly efficient and reusable nanocatalyst for the reduction of nitroarenes and aerobic oxidative esterification of alcohols

Abstract: Silver nanoparticles (Ag-NPs) have been finely dispersed at the mesoporous organic polymer via post-synthetic chemical grafting over mesoporous poly-triallylamine (MPTA-1). The resulting Ag-MPTA-1 nanomaterial has been characterized by elemental analysis, powder x-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), UV–vis diffuse reflectance spectroscopy (DRS), thermogravimetric analysis (TGA), EPR spectroscopy and AAS elemental analysis. The Ag-MPTA-1 acts as an efficient heterogeneous nanocatalyst in the reduction of substituted nitrobenzenes via transfer hydrogenation. The material also showed excellent catalytic activity in one-step catalytic oxidative esterification of primary alcohols using molecular oxygen as a green oxidant. The catalyst is air-stable, inexpensive, easy to prepare and reused several times without significant decrease in activity and selectivity.