Synthesis of oxidized multiwalled carbon nanotubes (oxMWCNTs) and preparation of them suspension
2 g of multiwalled carbon nanotubes MWCNTs were suspended in 100 mL of concentrated HNO3 and refluxed for 6 h at 100 C.
Finally, the mixture was filtered and washed with deionized water until pH of filtrate was 7. The filtered solid was dried in an oven at 60 C. The suspension of ox-MWCNTs (5 mg·mL-1) was prepared using high purity water. Before the use, the ox-MWCNTs suspension was sonicated for 30 min to obtain a homogeneous dispersion.