Introdution: Cerium oxide nanoparticles (CONPs or nanoceria) are used as radiation protection agent, a catalyst and an insulating layer on silicon substrates. The aim of this study was optimization of condition for cerium oxide nanoparticles dispersion with anionic surfactant sodium dodecyl sulfate (SDS) in deionized water.
Methods: This study was a cross-sectional descriptive. The dimensions, image and chemical composition of nanoceria were obtained using scanning electron microscopy (SEM). UV/VIS absorption spectrum of nanoceria suspension in the presence of SDS and Tween 20 surfactants were recorded and maximum absorption wavelength was determined. 
Results: According to the SEM images taken in this study, the shape of a nanoceria was spherical, consisting of cerium with 97.9 wt% and oxide with 2.1 wt%. The dimensions of nanoparticles were determined 29.3 nm. UV/VIS maximum absorption was recorded at 318 nm. The mean sustained concentration of nanoceria suspension with 0.45 wt% of SDS had a significant increase than the presence of 0.05 wt%, 0.15 wt%, and 0.25 wt% of SDS (P-value = 0.001). An increase of 5 hours of sonication time resulted in a significant increase in the mean sustained concentration of nanoceria suspension (P-value = 0/000).
Conclusion: An anionic surfactant SDS with an optimum weight percentage of 0.45 can be used to increase the stability of the nanoceria distribution. Furthermore, increasing the sonication time for 5 hours can be a better alternative than increasing the weight percentage of anionic surfactant SDS to achieve a stable distribution.