A safer and flexible method for the oxygen functionalization of carbon nanotubes by nitric acid vapors.

Highlights: [•] The so-called “salt effect” is exploited to improve the vapor phase oxidation method. [•] Nitric acid vapors are generated adding 20wt% of Mg(NO3)2 to HNO3 +H2O solution. [•] This allows handling more diluted solutions and varying the HNO3 vapor concentration. [•] The CNT functionalization degree increases linearly with the HNO3 vapor concentration. [•] Selecting the proper acid vapor concentration allows obtaining the desired oxidation degree. [ABSTRACT FROM AUTHOR]