Zeta potential of pristine and PEI-functionalized carbon nanotubes. The zeta potential of 1 mg/ml pristine or PEI-grafted carbon nanotubes at 25°C and neutral pH was determined by dynamic light scattering. Error bars represent standard deviations (n ≥ 3). **p < 0.01 compared to PEI-NH-SWNTs.
Huang et al. Nanoscale Research Letters 2013 8:267 doi:10.1186/1556-276X-8-267