Suspension of PEI-NH-SWNTs and PEI-NH-MWNTs in water. PEI-NH-SWNTs (A) and PEI-NH-MWNTs (B) were solubilized in ddH2O at a concentration of 1 mg/ml and sonicated for 15 min (left images). Large aggregates were removed by centrifugation at 3,000 rpm for 30 min to obtain a more homogeneous suspension (right images).
Huang et al. Nanoscale Research Letters 2013 8:267 doi:10.1186/1556-276X-8-267