Effect of alkylpyridinium chlorides on aggregation stability of aqueous dispersions of detonation nanodiamonds

Adsorption of decyl-, dodecyl-, and hexadecylpyridinium chlorides (DePC, DoPC, and CPC, respectively) from aqueous solutions on the surface of detonation nanodiamonds (NDs) and its effect on the aggregation stability of ND hydrosols are studied. Hydrophobic interactions, which are enhanced with the length of hydrocarbon chains in surfactant molecules, are found to play the main role in surfactant adsorption on the ND surface. DePC is almost not adsorbed on NDs, and its addition has no effect on both the size and ζ potential of nanoparticles. Adsorption of DoPC decreases the ζ potential of ND particles, thus causing their coagulation. Superequivalent adsorption of CPC results in sign reversal of the ζ potential of ND particles, thereby leading to alternation of the zones of aggregation stability and coagulation of the hydrosols with a rise in the concentration of this surfactant.