engleski

Adsorption of polyelectrolytes on cerium oxide nanoparticles

The research interest in cerium(IV) oxide (ceria) nanoparticles has been increasing recently due to their potential applications in various fields such as biomedicine and catalysis. In that sense, the biocompatibility of ceria nanoparticles should be stressed since there are no reports on health risks which may be associated with such particles. In many cases a stable dispersion of cerium oxide nanoparticles in a biological environment is needed and for reaching that aim polyelectrolyte coated particles are very promising. Therefore, the objective of this study was to synthesize and characterize ceria nanoparticles and to systematically investigate their interactions with polyelectrolytes. As a model polyelectrolyte negatively charged strong polyelectrolyte sodium poly(styrene sulfonate) (PSS) was used. For that purpose, cerium oxide nanoparticles were synthesized and, after rinsing and drying procedure, characterized by means of X-ray powder diffraction (XRD), dynamic light scattering (DLS) and zeta- potential measurements. Average diameter of ceria nanocrystals was estimated from XRD measurements using Scherrer equation and it was found to be 6 nm. Isoelectric point of ceria nanoparticles was measured at two ionic strength values (Ic = 1x10-2 mol dm-3 and 1x10- 3 mol dm-3) and the obtained values were pHiep = 5.8 ± 0.2 and pHiep = 5.9 ± 0, 1, respectively. Hydrodynamic radius of the synthesized cerium oxide nanoparticles was obtained by dynamic light scattering at various experimental conditions. It was shown that the particle size depends on pH and on ceria mass concentration and obtained results were in the range between 40 and 70 nm. Adsorption of sodium poly(styrene sulfonate) on ceria nanoparticles was also examined using zeta- potential and DLS measurements. As expected, at pH = 3 adsorption of negatively charged PSS on positively charged ceria nanoparticles leads to overcharging of the surface. The influence of PSS concentration on zeta-potential was tested and it was shown that already at c(PSS) = 5∙10- 4 mol dm-3 overcharging took place. DLS was used for determination of the particle size of ceria nanoparticles coated with PSS and it was shown that in the examined pH range measurable difference in particle size between uncoated and coated samples was obtained.

Polyelectrolytes ; Adsorption ; Cerium oxide

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