Figure 8.

Schematic representation of the aggregation process for citrate-stabilised AgNPs. AgNPs are stabilised by an electrostatic repulsive force between particles. Aggregation occurs with the increasing of pH due to the protonation of citrate anions, which can be elucidated by Derjaguin-Landau-Verwey-Overbeek (DLVO) theory.^{67, 68}