Dae Han Kim

Hydrophobic Polydimethylsiloxane (PDMS) Coating of Mesoporous Silica and Its Use as a Preconcentrating Agent of Gas Analytes

Mesoporous silica with mean pore size of ∼14 nm was coated by polydimethylsiloxane (PDMS) using a thermal deposition method. We showed that the inner walls of pores larger than ∼8 nm can be coated by thin layers of PDMS, and the surfaces consisting of PDMS-coated silica were superhydrophobic, with water contact angles close to 170°. We used the PDMS-coated silica as adsorbents of various gas-phase chemical warfare agent (CWA) simulants. PDMS-coated silica allowed molecular desorption of various CWA simulants even after exposure under highly humid conditions and, therefore, is applicable as an agent for the preconcentration of gas-phase analytes to enhance the sensitivities of various sensors.

Fabrication of conductive, transparent and superhydrophobic thin films consisting of multi-walled carbon nanotubes

Polydimethylsiloxane (PDMS) was coated on multi-walled carbon nanotubes (MWCNTs) using a chemical vapour deposition method, and the PDMS-coated MWCNTs were well dispersed in various solvents without additional dispersants. Spin casting of the MWCNT-containing solution on a substrate pre-treated with PDMS-SiO2 nanoparticles resulted in the formation of a uniform thin film. The resulting thin film containing MWCNTs showed high optical transparency, conductivity and superhydrophobicity. We demonstrated that such multifunctional thin films can also be prepared on flexible substrates.

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.

Superhydrophobic, flexible and gas-permeable membrane prepared by a simple one-step vapor deposition

We demonstrate the fabrication of superhydrophobic, flexible and gas-permeable membranes by a simple one-step process consisting only of thermal evaporation of a fluid polydimethylsiloxane (PDMS) polymer, without the use of any other chemicals such as curing agents or solvents of PDMS. As a substrate for the PDMS coating, a stainless steel mesh approx. 100 μm thick was used, which is flexible and becomes superhydrophobic after PDMS coating, attaining a water contact angle above 160°. The flexible mesh remained gas-permeable upon superhydrophobic coating, since PDMS evenly coated each strand of the metal mesh, and the vacancies between wires remained unclogged upon coating. The mechanical and chemical stability of the superhydrophobic, flexible and gas-permeable membrane is demonstrated herein.

Peptide-based bimetallic nanostructures with tailored surface compositions and their oxygen electroreduction activities

We report the synthesis of surface-composition-controlled gold–platinum (AuPt) bimetallic nanostructures on carbon nanotubes by peptide-based self-assembly and their catalytic responses to oxygen reduction. Our results can provide a great opportunity to construct various nanostructures with tailored properties.