The effects of formation and functionalization of graphene-based membranes on their gas and water vapor permeation properties.

The gas and water vapor permeabilities of graphene-based membranes can be affected by the presence of different functional groups directly bound to the graphene network. In this work, one type of carboxylated graphene oxide (GO-COOH) and two types of graphene oxide synthesized i) under strong oxidative conditions directly from graphite (GO-1) and ii) under mild oxidative conditions from exfoliated graphene (GO-2) were used as precursors of self-standing membranes prepared with thicknesses in the range of 12-55 µm via slow-vacuum filtration preparation method. It was observed that the permeabilities for all tested gases decreased in order GO-2 > GO-1 > GO-COOH and depended on both the arrangement of graphene sheets and their functionalization. The GO-1 membrane with a high content of oxygen-containing groups showed the best performance for water vapor permeability. The GO-2 membrane with a thickness of 43 µm exhibited a disordered GO sheet morphology and, therefore, unique gas-separation performance towards H2/CO2 gas pair, showing high hydrogen permeability while keeping extremely high H2/CO2 ideal selectivity that exceeds the Robeson 2008 upper bound of polymer membranes.

Push-pull amino-nitro helicenes: synthesis, (chir)optical properties and self-assembly into thin films.

A series of regioisomeric push-pull amino-nitro [6]helicenes and a related [7]helicene derivative were prepared and their racemates resolved into enantiomers. Compared to the parent helicenes, they exhibit red-shifted UV-Vis spectra, pronounced dipole moments, altered chiroptical properties such as remarkable optical rotatory power, and can form nanocrystalline Langmuir-Blodgett films.

Room-temperature synthesis of nanoceria for degradation of organophosphate pesticides and its regeneration and reuse.

A simple low-temperature water-based and one-pot synthesis was developed for the preparation of nanocrystalline CeO2 that was used for degradation of the toxic organophosphate pesticide parathion methyl. By changing the reaction temperature in the range from 5 °C to 95 °C, several properties (i.e., crystallinity, grain size and surface area) of nanoceria can be easily controlled. The catalytic decomposition of parathion methyl to its degradation product 4-nitrophenol was highly dependent on the CeO2 preparation temperature. It was demonstrated that at low temperature (i.e. 5 °C), CeO2 with very small crystallites (<2 nm) and high surface area can be obtained. For practical use, it was demonstrated that highly crystalline CeO2 can be prepared at room-temperature (30 °C) in at least 100 g batches. It was shown that precipitated nanoceria had high thermal stability and its post-synthesis annealing up to 400 °C did not significantly alter the material properties and hence the catalytic activity. Furthermore, as shown by the reusability tests, the sorbent can be reactivated by simply washing with water which demonstrated its durability.