A rapid synthesis of nanofibrillar cellulose/polystyrene composite via ultrasonic treatment.

A new method of the synthesis of nanofibrillar cellulose/polystyrene composite based on ultrasonic treatment of styrene emulsion in cellulose-water solution was elaborated. A new approach does not require additional heating and proposes a significantly faster synthesis (15 min, 45 °C) of the target composite compared to the methods described previously. A comprehensive analysis did not reveal any significant differences between mechanical, physical and biodegradable properties of the composite obtained by ultrasonic method and that one obtained by conventional thermal method, which requires much higher temperature (above 75 °C) and reaction duration (from 3 h).

Nanoparticle catalysed oxidation of sulfides to sulfones by in situ generated H2O2 in supercritical carbon dioxide/water biphasic medium.

In a one-pot reaction, hydrogen peroxide generated from H(2) and O(2) on a Pd catalyst was utilised as oxidant for the TiO(2) catalyzed conversion of a sulfide to a sulfone. This transformation, where two different nanoparticle catalysts were employed in a supercritical carbon dioxide/water biphasic system, demonstrates the potential of compartmentalising catalytic processes in consecutive reactions.

Synphos modified Pt nanoclusters, their heterogenization by silica sol-gel entrapment, and catalytic activity in hydrogenolysis of bicyclo[2.2.2]oct-7-enes and hydrogenation of ethyl pyruvate.

Platinum (Pt) colloids modified by the chiral ligand synphos were prepared with the goal of obtaining a catalytic nanomaterial and were subsequently embedded in silica to form a heterogeneous catalyst. The systems were characterized by (31)P-NMR, x-ray diffraction, molecular modeling and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTs) measurements. These colloids, both as 'quasi-homogeneous catalysts' (or soluble heterogeneous catalysts) and embedded in silica (heterogeneous catalysts) were employed in the selective hydrogenolysis of highly sterically constrained bicyclo[2.

Enantioselective hydrogenation of ethyl pyruvate over diop modified Pt nanoclusters. Determination of geometry of the ligand adsorption mode via DRIFTS.

Immobilization of chiral ligands on the surface of metal nanoparticles is one concept for heterogenation of enantioselective catalysts. Diop modified Pt nanoclusters were found to be able to induce enantioselectivity and enhancement of the reaction rate in hydrogenation of ethyl pyruvate. The model of geometry of the diop adsorption has been proposed based on DRIFTS and molecular modelling investigations.

Determination of geometric orientation of adsorbed cinchonidine on Pt and Fe and quiphos on Pt nanoclusters via DRIFTS.

Platinum nanoclusters modified with cinchonidine have been employed as 'quasi-homogeneous' catalysts for the hydrogenation of ethyl pyruvate and have demonstrated exceptional activities while the ee's of these systems are currently inferior to the traditional Pt/Al2O3 heterogeneous system. For the bulk systems it has been shown that the orientation of the modifier on the metal surface is a critical parameter influencing catalytically induced enantioselectivity. It has been speculated that the lower observed ee's for the nanocluster systems are a result of the modifier assuming an orientation unfavorable for inducing enantioselectivity due to the lack of large numbers of planar metal atoms.