No matter what kind of carbon structures, I want to achieve to a carbon structure which can show hydrophilic behavior.
Carbon is hydrophobic only if pure aromatic carbon layers are considered, such as graphite is made of. But the edges of carbon layers need to satisfy their valence, therefore many moieties can be found there. As far as these moieties are oxygenated, the carbon support becomes hydrophilic. And the effect increases with the number of edges bearing moieties, in other words, increases with the surface area. This is the reason why all activated carbons are hydrophilic and spontaneoulsy adsorb moisture at a leval equal to 5 - 15 % of their weight. So any carbon structure can be made more hydrophylic (or less hydrophobic) by oxidation. Treatment of carbon in hot concentrated nitric acid is very efficient, but also in concentrated hydrogen peroxide, in permanganate, or even in sodium hypochlorite. You can observe the efficiency of the oxidation by weighing the material before and after treatment. Oxidation leads to a significant weight increase.
Alain
Although most carbon structures are quite hydrophobic, you can do some treatments which increase oxygenated surface groups, which helps make them more hydrophylic. A while ago I ran into this paper (Xu et al., Materials Research Bulletin, 39 (2004) 1499), for example, which pre-treats CNTs in acid, in order to then plate copper onto them. We've used this or similar pre-treatment methods on other types of carbon, such as Vulcan and nanodiamonds (Chemical Communications 2011; 47(27):7656-8. DOI:10.1039/c1cc12387d) and it does seem to help with hydrophylicity...
Carbon is hydrophobic only if pure aromatic carbon layers are considered, such as graphite is made of. But the edges of carbon layers need to satisfy their valence, therefore many moieties can be found there. As far as these moieties are oxygenated, the carbon support becomes hydrophilic. And the effect increases with the number of edges bearing moieties, in other words, increases with the surface area. This is the reason why all activated carbons are hydrophilic and spontaneoulsy adsorb moisture at a leval equal to 5 - 15 % of their weight. So any carbon structure can be made more hydrophylic (or less hydrophobic) by oxidation. Treatment of carbon in hot concentrated nitric acid is very efficient, but also in concentrated hydrogen peroxide, in permanganate, or even in sodium hypochlorite. You can observe the efficiency of the oxidation by weighing the material before and after treatment. Oxidation leads to a significant weight increase.
Alain
Dear Saman,
You can increase carbon oxydation by several chemicals in aqueous solution: nitric acid, hydrogen peroxide, and ammonium persulphate. Please look at the manuscript:
'Synthesis, characterization and performance in arsenic removal of iron-doped activated carbons prepared by impregnation with Fe(III) and Fe(II)' in my RG profile
Hello Saman,
As far as this question is for long time ago, did it work for you? I have the same issue as I need carbon paper with ones side of PTFE which is hydrophobic And the other side which is carbon to be hydrophilic! However, it is not. I was wondering if this acid or peroxide treatment can help?
Paniz
The transition from hydrophobic to hydrophilic behavior can be done by oxidation.
Thanks Jan for the response,
I'm working with carbon paper which has one hydrophobic surface (30% PTFE) which I need to keep it and the other side of carbon which is hydrophobic and I need this surface to be hydrophilic. I tried CV in a high range of oxidation but wasn't successful!
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