engleski

Polyelectrolyte-coated cerium oxide nanoparticles

The research interest in cerium oxide (ceria) nanoparticles has been increasing recently due to their potential applications in various fields such as biomedicine and catalysis. In that sense, one of the main advantages is the biocompatibility of ceria nanoparticles [1]. In the field of environment and energy related applications cerium oxide’s catalytic ability, which is largely affected by redox behaviour and is related to cerium’s redox state, gets more and more attention. In many cases a stable dispersion of cerium oxide nanoparticles in a biological environment is needed. For reaching that aim particles coated with various polyelectrolytes are very promising. Therefore, the objective of this study is to synthesize and characterize ceria nanoparticles and to systematically investigate their interactions with polyelectrolytes. As a model polyelectrolyte strongly charged polyanion sodium poly(styrene sulfonate) (PSS) [2] was used. Cerium oxide nanoparticles were synthesized [3] and characterized by means of XRD, BF – STEM, DLS and zeta-potential measurements. Average diameter of ceria nanocrystals was estimated to be ≈5 nm. Isoelectric point of uncoated ceria nanoparticles was measured at two ionic strength values (Ic = 0.01 mol dm-3 and 0.001 mol dm-3) and the obtained value was in both cases pH(iep) = 6.7 ± 0.1. Hydrodynamic radius of the synthesized cerium oxide nanoparticles was investigated by dynamic light scattering at various experimental conditions. It was shown that the particle size depends on pH and on ceria mass concentration. After adsorption of PSS, polyelectrolyte-coated ceria nanoparticles were also examined using the above-mentioned methods. In order to interpret the obtained experimental results by means of the modified Ohshima model for soft particles [4], mobility of ceria particles covered with PSS was determined as a function of ionic strength. DLS was used for determination of the hydrodynamic radius of ceria nanoparticles coated with PSS. Finally, on the basis of these results the electrophoretic softness parameter for ceria- PSS system and adsorption density value were determined and compared with the results obtained by classical adsorption experiments.

Polyelectrolytes, cerium oxide, nanoparticles

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