Abstract. A clean and simple wet chemical process using dilute aqueous ozone (O3) solution with or without ultrasound (US) was used to functionalize single-walled carbon nanotubes (SWCNTs). Both O3 and O3/US treatments greatly increased the stability of SWCNTs in water. Results of X-ray photoelectron spectroscopy (XPS) showed that the surface oxygen to carbon atomic ratio increased by more tha…