Sang Wook Han

Fabrication of superhydrophobic thin films on various substrates using SiO2 nanoparticles coated with polydimethylsiloxane: towards the development of shielding layers for gas sensors

Superhydrophobic membranes with high gas permeability were prepared and characterized. Materials such as a metal mesh, paper, fabric and polytetrafluoroethylene were dip-coated in a hexane-based solution of SiO2 nanoparticles coated with polydimethylsiloxane (PDMS). The dip-coating provided a superhydrophobic characteristic to the surfaces of our membranes with water contact angles exceeding 160°. On the other hand, a high membrane permeability of CO2 and dimethyl methylphosphonate vapor were obtained, indicating that our preparation method is useful for the fabrication of gas sensor shielding layers that allow selective permeation of gas vapors from gas/aqueous-liquids mixtures.

Use of NiO/SiO2 catalysts for toluene total oxidation: Catalytic reaction at lower temperatures and repeated regeneration

Abstract We deposited NiO via atomic layer deposition on mesoporous SiO2 particles with diameters of several hundred micrometers and a mean mesopore size of ∼14 nm. NiO was deposited within the shell region of mesoporous SiO2 particles with a shell thickness of ∼11 mm. We annealed the as-prepared NiO/SiO2 at 450 and 600 °C, respectively. These two samples were used as catalysts for the uptake of toluene molecules and their oxidative conversion to CO2. The sample annealed at 450 °C was generally more reactive in toluene uptake and its subsequent conversion to CO2. When the NiO/SiO2 annealed at 450 °C was exposed to toluene vapor at 160 °C and then heated to 450 °C, CO2 was emitted with almost no toluene desorption. We suggest that our catalysts can be used as building blocks for odor removal devices that operate below 200 °C. These catalysts can be regularly regenerated at ∼450 °C.