as you know amorphous carbon can be removed by heating and also by acid treatment such as mineral acid and this treatment also will be remove the nano particles of catalysts, so i think presence of this catalysts will be make change in the intensity and position of the three main bands of CNTs which is R.S.D, G and D.

good luck

I just know a little about the acid treatment. As far as I know, this treatment could oxidate the surface of CNTs. I wonder how serious the oxidation could be by acid treatment? Because I just want to purify my CNTs, don't want to oxidate them.

We have been working in several methods to purify CNTs. Best results are found when thermal oxidation is carried out first (400-460 °C) and then acid treatment (Reflux: HCl 10% v/v). Also sonication in acidic conditions before refluxing could improve the purification process. (Thermal oxidation+HCl (10%) sonication + HCl (10%) reflux. Purity measured by TGA is > 96%. No damages in CNTs were observed by SEM, TEM and Raman. Please check one of our publications.

Your publication seems not to be written in English. I noticed that you suggested to use HCl instead of HNO3. Is there any reason for that?

Yes, the main reason is that HNO3 is a strong acid and oxidizes CNTs. Actually when you use HNO3 you can introduce functional groups (carboxylic, mainly). If you check the literature, researchers use HNO3 or a mixture of HNO3/H2SO4 for that. HNO3 treatment is also known to produce shortened and open-ended nanotubes. That is why we decided to use HCl. We tested several concentrations as mentioned before. IMO and based in the characterization results, HCl is suitable to obtain CNTs without structural damages and purity > 96% under the experimental conditions we tested.

Here is a partial translation of our publication.

By EDX analysis it was possible to determine the percentage of metallic impurities in the NTsC after purification. A consequent decrease of impurities after acid (HCl) treatment at several concentrations was observed and compared to the residual percentage obtained by TGA, which are shown in Figure 1.

A solution of HCl 5% v / v was insufficient to completely remove the impurities while maintaining high rates of metallic residue ( Fe , Co , Ca ) , however , when a HCl solution is used at a concentration of 10% v / v , both EDX analysis TGA showed lower quantity of impurities (10%). At higher concentrations of HCl (20 % v / v 32.8% v / v ) tt was observed an unexpected increase in the metal content of CNTs, this behavior could be attributed to the creation of imperfections in the structure; such imperfections are not present in the nanotubes without acid treatment (Figure 2 ) (based on the L/D ratio) , and also because CNT openings might cause encapsulation of the metal particles . This can be seen through the MIX mode SEM images (using xT Microscope FEI program). In this way , overlapped images from secondary signals with backscattered electrons, allow through two contrasting colors as the atomic number (blue and red , respectively ) , to observe the morphological differences (Figure 3 ) . In Figure 3d we can observe the presence of red spots inside the

CNTs attributable to the encapsulation of the catalytic material .

The acid treated CNTs micrographs of at various concentrations, showed the appearance of unconventional shapes other than CNTs, when HCl concentration of 20 % v / v 32.8% v / v , (Figure 4 ) was used . TGA of acid treated NTsC at different concentrations, showed structural changes in the material. In CNTs treated with acid at 5% , 10%, 20 % and 32.8% v/v, two oxidation points in all cases were observed, one around 450 ° C typical of amorphous material [ 12,13 ] of CNTs and another between 600-700 °C according to DTGA analysis (figure 5). this weight loss is correlated with the combustion of CNTs in air (inflection point in TGA curve). DTGA curve when HCl at 10% v / v was used , showed a single oxidation point , which indicates a lower presence of amorphous material. The samples showed mass losses of 89 % (HCl 5 % v / v); 96 % (HCl 10% v / v ); 93 % (HCl 20 % v / v) and 85 % (HCl 32.8 % v / v). Treatment with HCl at 10 and 20 % v / v showed a smaller amount of residual material after the TGA, this demostrated that this concentrations were more effective in the removal of the catalytic material.

Best regards and sorry if you find a misspelling in the translation.

Hi, Jose! Thanks very much for your kind translation! I tried to download the full text of your article. But our univeristy doesn't have the full-text acess to that database. Your translation is perfect! If you don't mind, may I have your the full-text of your article?

Thanks a lot in advance!

Best Regards,

Yin LI