Point of zero charge is a useful measurement to assess the surface acidity of multi-walled carbon nanotubes and to characterize functional groups on the multi-walled carbon nanotube surface. Knowledge of point of zero charge also assists the choice of an appropriate metal precursor to be used for electrostatic adsorption to prepare metal particles supported on multi-walled carbon nanotubes. Multi-walled carbon nanotubes with points of zero charge that range from 2.2 to 11.8 have been prepared and characterized. An efficient reduction method, utilizing ethanol at 20 atm and 180 degrees C, is described and can be used to reduce nitric acid functionalized multi-walled carbon nanotubes to convert the functional groups to mostly hydroxyls. (C) 2010 Elsevier B.V. All rights reserved.