Solubility increase of multi-walled carbon nanotubes in water

Water-soluble hydroxylated multi-wall carbon nanotubes (MWCNTols) were synthesized by the NaOH/H2O2 oxidation method. A L9(34) orthogonal experimental design was used to optimize the preparation conditions, and TEM, SEM and Raman spectroscopy were used to characterize the products. The solubility of as-prepared MWCNTols in water was 0.72 mg/mL. Furthermore, MWCNTols were wrapped by polyvinylpyrrolidone (PVP) by solution blending. Good water-solubility of PVP further increases the stability and dispersibility of MWCNTols in water. The content of MWCNTols in PVP-MWCNTols is calculated to be as high as 41 wt%. The solubility of PVP-MWCNTols in water was up to 2.34 mg/mL. No aggregation or sedimentation was observed for a saturated solution during more than 2 month storage at room temperature. [New Carbon Materials 2013, 28(2): 94–100]