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

Abstract

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 SiO 2 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 CO 2 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. Fig. 1 Schematic diagram of the experimental set-up for (a) the preparation of hydrophobic coating on silica nanoparticles, and (b) the preparation of dip-coating solution and superhydrophobic films. 40596 | RSC Adv., 2015, 5, 40595-40602 This journal is

Oil–Water Separation Using Superhydrophobic PET Membranes Fabricated Via Simple Dip‐Coating Of PDMS–SiO2 Nanoparticles

“…A dip‐coating solution was prepared by mixing the P‐SiO 2 solution with an adhesive solution at a volume ratio of 29:1 (we used 2000 mL of P‐SiO 2 solution and 69.0 mL of adhesive solution). The P‐SiO 2 solution was prepared by dispersing 13.8 g of P‐SiO 2 nanoparticles in 2000 mL of hexane; adhesive solution was obtained by mixing hexane, PDMS and a curing agent at a volume ratio of 80:10:1 (we used 80 mL of hexane, 10 mL of PDMS, and 1 mL of curing agent) …”

“…In addition to mass production, there are many other properties to be considered for the application of SOMs to oil–water separation filters. The SOMs should be chemically stable under acidic or basic solutions to some extent . The oil‐separation rate of the SOM must also be considered; this can change as a function of the membrane porosity and thickness and the properties of the oil (viscosity).…”

“…The oil‐separation rate of the SOM must also be considered; this can change as a function of the membrane porosity and thickness and the properties of the oil (viscosity). The SOM also must withstand the water pressure in the operating environment . Again, the waterproof ability of the membrane is closely related to the membrane thickness and porosity .…”

“…The SOM also must withstand the water pressure in the operating environment . Again, the waterproof ability of the membrane is closely related to the membrane thickness and porosity . Intuitively, a SOM with higher thickness and lower porosity should exhibit lower oil–water separation efficiency and higher waterproof ability.…”

“…In our previous work, we developed a fabrication method for SOMs that is simple and applicable to various substrates, and is based on the hydrophobization of SiO 2 nanoparticles via the thermal deposition of a polydimethylsiloxane (PDMS) layer and a wet‐chemical hydrophobized SiO 2 coating applied using a PDMS binder . We had also showed that our dip‐coating of PDMS‐coated silica results in better performances compared to other methods using PDMS (dry‐coating of PDMS and wet‐coating of PDMS on fibers) in terms of hydrophobicity and oil–water selectivity .…”