Influence of Dodecylsulfate Adsorption on the Stability of Cerium Oxide Nanoparticle-Based Colloidal Aqueous...

In this contribution, the influence of the adsorption of dodecylsulfate, an anionic surfactant, on the stability of colloidal aqueous dispersions containing ceria (CeO₂) nanoparticles (NPs) was investigated using zetametry, UV-visible spectrophotometry, and potentiometry involving an ionic surfactant-selective electrode (ISSE). In particular, thanks to absorbance follow-ups carried out as a function of time, aqueous dispersions containing a given loading of CeO₂ NPs were found simultaneously to stabilize more quickly with time and to adopt a higher opacity and a more pronounced light-yellow color as the sodium dodecylsulfate (SDS) concentration increased. Knowing that this absorbance was attributed undoubtedly to CeO₂ NPs, the fact that the measured absorbance is lower for a higher amount of CeO₂ NPs in suspension, as revealed by a higher opacity of the studied dispersions, is somewhat counterintuitive. Besides the higher opacity of the dispersions, a shield effect of the adsorbed SDS layer toward UV-visible light may also explain this observation. The adsorption of dodecylsulfate on CeO₂ NPs was indeed demonstrated using zetametry measurements in the presence of SDS and the potentiometric method combined with an ISSE. This latter method did not only allow the accurate determination of impoverishment in freely diffusing dodecylsulfate (DS) anions resulting from DS adsorption on CeO₂ NPs but it also showed that this latter obeys a Freundlich isotherm.