Adsorption characteristics of poly(amidoamine) and poly(propylene imine) dendrimers on gold

The adsorption of poly(amidoamine) (PAMAM) and poly(propylene imine) (PPI) dendrimers having different generations from their aqueous solutions on gold electrode has been investigated using a 27 MHz quartz crystal microbalance. The adsorption of PAMAM dendrimers (generation G=3, 4, and 5) depends on the generation, whereas that of PPI dendrimers (G=2, 3, and 4) is almost independent on the generation. The occupied area by the dendrimers adsorbed suggests a formation of multilayer of the dendrimers where the number of the layer for PAMAM dendrimers is larger than that for PPI dendrimers. The mechanism for the formation of multilayer is also discussed.