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Table 4 Quantification of carboxyl and sulfonate density using dye assay

From: Single-step electrochemical functionalization of double-walled carbon nanotube (DWCNT) membranes and the demonstration of ionic rectification

  Modification on glassy carbon Charge density Carboxyl density Sulfonate density
   (molecules/cm2) (molecules/cm2) (molecules/cm2)
Step 1 in two-step functionalization Electrochemical grafting of 4-carboxyl phenyl diazonium for 8 min 1.3 × 1015 1.3 × 1015 -
Step 2 in two-step functionalization Carbodiimide coupling of dye 2.0 × 1015 1.07 × 1015 0.93 × 1015
One-step functionalization Electrochemical grafting of dye by amine oxidation for 8 min 0.9 × 1015 - 0.9 × 1015