Hydrophobic surface treatment of carbon black nanoparticles in isopropyl alcohol solution using He/SF₆ atmospheric plasma jet

Nanoparticles in a solution can be modified by various methods including wet treatment, UV light treatment, and plasma treatment for the functionalization of the nanoparticles. Especially, for the plasma treatment of nanoparticles in a solution, hydrophilic treatment is generally carried out by forming -OH in the solution while the plasma treatment system is located at the outside of the nanoparticle solution. In this study, using a He/SF₆ atmospheric plasma jet (APPJ) sources located outside and inserted in the IPA solution with carbon black nanoparticles, carbon black nanoparticles were modified to improve hydrophobic properties. By inserting the plasma jet tip in the solution, the carbon black nanoparticles were more easily modified compared the plasma jet located outside of the solution. After the He/SF₆ plasma treatment of carbon black nanoparticles with the APPJ in the solution, the contact angle of the sprayed-coated carbon black was increased from ˜30 to ˜140° while no significant change of contact angle was observed for the carbon black nanoparticles treated by the APPJ located outside of the solution. After the He/SF6 plasma treatment, fluorine percentage of ˜7.97% in the carbon black was observed without noticeable thickness change of carbon black nanoparticles. It is believed that, the fluorine radicals dissolved in the solution form C–F_x bonding on the carbon black surface and increase the hydrophobicity significantly. This technique can be applied in modifying the surface properties of various other particles in solution.