What will be the sign of zeta potential for amine functionalized nanoparticles? The amines are neutral (not protonated). Due to the electron rich character of amine functional group shall I expect net negative charge?
Depends on the pH and the presence of other ions e.g. phosphate in the surrounding medium. Zeta potential is a holistic not particle-only dependent property.
Zeta potential for amine functionalized nanoparticles can be negative. This depends on the effect of other side group positioned with amines. As zeta potential also depicts adsorption mechanism of ligands around nanoparticles.