One-pot synthesis of pyranocoumarins via microwave-assisted pseudo multicomponent reactions and their molecular switching properties.

Two new pyranocoumarins were synthesized via one-pot, microwave-assisted pseudo multicomponent condensations of coumarin and 4-methylquinoline to investigate their molecular switching properties. Both are light-sensitive and have a distinct change of color upon UV irradiation. The reaction can be reverted by treating the photogenerated products with imidazoline-functionalized magnetic nanoparticles, which can be swiftly recycled with an external permanent magnet.

Removal of organic compounds by alginate gel beads with entrapped activated carbon.

The adsorption of alginate gel (AG) beads and AG with activated carbon entrapped (AG-AC) beads prepared using different types of metal ions were investigated by measuring the removal of several organic compounds with different charges and size. AG-AC beads prepared in a CaCl2 solution adsorbed strongly positively charged compounds as well as electrically neutral and low molecular weight compounds such as p-chlorophenol. However, a high molecular weight humic acid was not adsorbed by AG-AC. The AG-AC selectively adsorbed p-chlorophenol from a humic acid solution. The adsorption capacity obtained from the adsorption isotherm of AC entrapped in AG was compared with that of AC. The AG-AC beads prepared in a solution of FeCl3 were able to specifically adsorb negatively charged gallic acid. Thus, entrapping AC into AG resulted in the selective adsorption.

Caged multiwalled carbon nanotubes as the adsorbents for affinity-based elimination of ionic dyes.

Multiwalled carbon nanotubes (MWCNTs) were used as the active elements for the first time for affinity-based elimination of ionic dyes. MWCNTs were encapsulated in cross-linked alginate (ALG) microvesicles using Ba2+ as the bridging ion. The Ba2+-alginate matrix constitutes a cage which holds the physically trapped MWCNTs. The cage carries negative charges on its surface. The cage restricts the access of anions of large molecular weight, such as humic acids, because of electrostatic repulsion. The cage also restricts the access of colloids of large size, because of size exclusion. Ionic dyes partition into the cage and then are captured by MWCNTs probably on the basis of van der Waals interactions occurring between the hexagonally arrayed carbon atoms in the graphite sheet of MWCNTs and the aromatic backbones of the dyes. As a result of these interactions the target species, namely, the ionic dyes, are eliminated efficiently by the MWCNTs of Ba2+-ALG/MWCNT composite adsorbents. The adsorptive capacities for elimination of acridine orange, ethidium bromide, eosin bluish, and orange G (the model species used for this study) were found as high as 0.44, 0.43, 0.33, and 0.31 micromol, respectively, for 1.0 mg of the caged MWCNTs. Adsorptive experiments with carbon nanofibers and activated carbons as the adsorbents were also performed. The MWCNT-based adsorbents provided the best capability for the affinity-based elimination of these targeted species. Biocompatibility experiments performed in vitro and in vivo provided promising results, suggesting potential applications of the caged MWCNTs in in situ environmental remediation.