Introduction: Cerium oxide nanoparticles (CONPs) are used as radiation protection agent in the in-vivo and in-vitro studies. The distribution stability of nano-suspension is one of the important factors during the studies. The aim of this study is optimization of condition for CONPs dispersion with sodium dodecyl sulfate (SDS-anionic surfactant) and tween 20 (nonionic surfactant) in deionized water.
 
Materials and Methods: CONPs were obseved under scanning electron microscopy (SEM), then the dimensions and structure were obtained. The chemical composition of nanoceria was determined using Energy Dispersive X-Ray spectroscopy (EDS) analysis. The UV-VIS absorption spectrum of nanoceria suspension in the presence of SDS and Tween 20 surfactants were recorded and maximum absorption wavelength was determined. The mean sustained concentration of nanoceria suspension with different weight percentages of SDS (0.05, 0.15, 0.25, 0.45 and 0.65 wt%) was determined using standard curve. To increase the stability of the suspension distribution, the sonication time with a constant weight percentage of SDS was increased and the mean concentration was determined and then it was compared with suspensions containing various weight percentages of SDS.
 
Results: According to the SEM images taken in this study, the shape of nanoceria was spherical approximately. EDS analysis determined that the CONPs consisting of cerium with
97.9 wt% and oxide with 2.1 wt% with a high percentage of confidence. The dimensions of nanoparticles were determined 29.3 nm. The UV-VIS maximum absorption of nanoceria suspension was recorded at 318 nm. The wavelength of maximum absorption was changed at the presence of tween 20. So it was removed from the study. The mean sustained concentration of nanoceria suspension with 0.45 wt% of SDS had a significant increase than the presence of 0.05, 0.15, and 0.25 wt% of SDS (P-value = 0.001). With an increase in the SDS weight percentage to 0.65%, a reverse effect was observed in the nano-suspension distribution. 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 0.45wt% can be used to increase the stability of the nanoceria distribution. Also, 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.