Hi Muhammad Kashif . Formaldehyde probably won't to anything to the MWCNT or the MWCNT-COO. It will form a Schiff base with the MWCNT-NH2 that could crosslink with other MWCNT-NH2. If the crosslinking happens, you will have a huge insoluble complex.

please refer to the following:

Poster Investigation of formaldehyde interaction with carbon nanotu...

Thanks for your suggestion. but my question is that I am doing electrochemical measurements and in that case, if I have one electrode with MWCNT and one pt electrode and formaldehyde is dissolved in PBS so what will be the impact of that on CNT resistance.

Dear Muhammad, formaldehyde is a rather polar molecule. Thus it is not surprising that it has been found to show adsorptive interactions with MWCNTs:

Poster Investigation of formaldehyde interaction with carbon nanotu...

This paper has not yet been posted as public full text on RG, but I think that the essential information can be found in the Abstract. As for your electrochemical measurements I'm not an expert enough to judge if formaldehyde will interfere. As a neutral molecule it will perhaps not have much effect.

Good luck with your experiments and best wishes!