Double oxidation with oxygen and hydrogen peroxide for hole-forming in single wall carbon nanohorns

It has been reported that single wall carbon nanohorns (SWCNHs) with holes opened by slow air oxidation have few carbonaceous dusts inside nanohorns, which is advantageous for storing materials inside the inner nanospaces of SWCNHs. However, the number of carboxyl groups of air-oxidized SWCNHs is small, which is disadvantageous for chemical functionalization. We show in this report that the double oxidation, namely the slow air-oxidation followed by treatment with hydrogen peroxide at room temperature for 4 days successfully formed the holes in walls of SWCNHs without few carbonaceous dusts and with many carboxyl groups.