Average particle size of PEI-NH-SWNTs and PEI-NH-MWNTs before and after centrifugation. The average particle diameters of 5, 50, and 100 μg/ml of PEI-NH-SWNTs (A) or PEI-NH-MWNTs (B) before and after removal of large aggregates through centrifugation was analyzed by dynamic light scattering. Before centrifugation, PEI-NH-SWNTs or PEI-NH-MWNTs were solubilized in ddH2O at a concentration of 1 mg/ml and sonicated for 15 min; after centrifugation, PEI-NH-SWNTs or PEI-NH-MWNTs were centrifuged at 3,000 rpm for 30 min to remove large aggregates. Error bars represent standard deviations (n ≥ 3). *p < 0.05 and **p < 0.01 compared to PEI-NH-SWNTs or PEI-NH-MWNTs of the same concentration before centrifugation.
Huang et al. Nanoscale Research Letters 2013 8:267 doi:10.1186/1556-276X-8-267