Chitosan as capping agent in a robust one-pot procedure for a magnetic catalyst synthesis.

Here, we report a one-pot solvothermal method for the development of magnetically recoverable catalysts with Ru or Ag nanoparticles (NPs) capped by chitosan (CS), a derivative of natural chitin. The formation of iron oxide NPs was carried out in situ in the presence of CS and iron acetylacetonate in boiling triethyleneglycol (TEG) due to CS solubilization in warm TEG. Coordination with Ru or Ag species and the NP formation take place in the same reaction solution, eliminating intermediate steps. In optimal conditions the method developed allows stabilization of 2.2 nm monodisperse Ru NPs (containing both Ru0 and Ru4+ species) that are evenly distributed through the catalyst, while for Ag NPs, this stabilizing medium is inferior, leading to exceptionally large Ag nanocrystals. Catalytic testing of CS-Ru magnetically recoverable catalysts in the reduction of 4-nitrophenol to 4-aminophenol with excess NaBH4 revealed that the catalyst with 2.2 nm Ru NPs exhibits the highest catalytic activity compared to samples with larger Ru NPs (2.9-3.2 nm). Moreover, this catalyst displayed extraordinary shelf-life in the aqueous solution (up to ten months) and excellent reusability in ten consecutive reactions with easy magnetic separation at each step which were assigned to its conformational rigidity at a constant pH. These characteristics as well as favorable environmental factors of the catalyst fabrication, make it promising for nitroarene reduction.

Polylactide-Based Chiral Porous Monolithic Materials Prepared Using the High Internal Phase Emulsion Template Method for Enantioselective Release.

Polylactide [PLA, two enantiomers: poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA)] has been widely applied as biomaterials because of its biocompatibility, biodegradability, and good mechanical capacity. However, the chirality of PLA materials has not been intensively explored yet. In the present study, chiral porous poly(high internal-phase emulsion)s (polyHIPEs) derived from enantiopure PLAs were successfully prepared via a HIPE template method. The resulting polyHIPEs show optical activity. More interestingly, the polyHIPEs demonstrate enantioselective release capacity, using cinchona alkaloid and naproxen as the model chiral drugs. Notably, PLLA-based polyHIPE shows enantioselectivity in both the drug-loading step and drug-releasing step, while PDLA-based polyHIPE fails. The interesting finding is essentially different from other chiral polymer materials reported earlier. The cytotoxicity test demonstrates that all the three types of polyHIPEs, PLLA-, PDLA-, and PDLLA-based polyHIPE show biocompatibility; however, their different chirality exerts varying effects on cell growth. Accordingly, special attention should be devoted to the chirality of PLA when used as biomaterials.