I tried to treat my CNT samples with H2SO4/HNO3 mixture (3:1).My CNTs are grown using camphor oil as a carbon source and ferrocene as a catalyst and my substrate is SI.
Unfortunately,during sonication all the carbon nano tubes started to leaching from silicon substrate and suspended in the solution and at end of sonication there was no CNTs on the surface of Si.
what can I do for that? what is the reason because I followed the literature but I didn't have result.
I would be grateful if you kindly inform me about the reason and how can I modify the steps to get results.
Long time Sonication process always damage the CNTs. u can change the frequency as well as reduce the time of sonication...
Dear Amin,
I have never done experiments like those you are trying to perform, nevertheless, i have 2 suggestions if i understood correctly what you want to do.
1. Try dip the substrate with the cnts in hot acid but don't do sonic. If its possible set a small movement of the acid.
2. In order to functionalize the aligned cnts with carboxylic acid groups i would think that a possible and fast route would be to first burn a small metal plate (and while it is still red) simply attach it over the CNTs. The cnts will be burned and after the removal of the soot i pretty sure that you will see some -COOH!!!
Thank you for reading my answer and i hope it will do the trick either way.
Andreas A. Stefopoulos
CNT forests are weakly bound to your growth substrate. I've noticed, when working with forests that are grown on planar substrates, that the CNT forests are not mechanically stable enough to be exposed to liquid solutions.
Are you trying to remove metal contaminates from the CNTs?
is it SWCNT or MWCNT??
If its SWCNT, 4 hours is too long.. CNT structure will collapse and you may end up with graphene nano-ribbons with high amorphous carbon content.
Thank you all,
My samples are MWCNTs and due to the molecular wight of camohor oil the CNTs shouldn't be stable enough to the substrate. That's why I can not treat it with this mixture.If I reduce the time or speed of the sonication at low temperature I will have treated CNT's or not?
I think all your kind answers are clarify the reasons but could you please let me know about an approach to treat the CNT using H2SO4/HNO3 mixture (3:1)?
Thanks you all,
Hi! Treating CNTs with H2SO4/HNO3 is the main method to oxidize them. So they become hydrophilic while Si wafer is hydrophobic. Therefore, it is obvious that you cannot place them on Si surface. I suggest to make your Si substrate hydrophilic by using oxygen plasma and then try to coat the CNTs on it.
You can find some info about the oxidation of CNTs below.
http://www.sciencedirect.com/science/article/pii/S0927024809003390
As stated before, CNTs are weakly bound to the growth substrate. The capillary action that occurs upon wetting the substrate with a liquid will lift the CNTs off the substrate, as you have noticed. I have had similar difficulties in working with CNTs and trying to oxidize them. I needed the surface of CNTs to be rich in oxygen moieties for ALD reactions. As a result I ended up doing a gas phase oxidation of CNTs using ozone which rendered the CNTs hydrophilic and attached to the growth substrate. You can find my method here http://scitation.aip.org/content/avs/journal/jvstb/31/3/10.1116/1.4801834
Let me know if you want a copy of it.
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