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Adsorption of polyelectrolytes on ceria nanoparticles: stability and adsorption parameters

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 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 was 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. For that purpose, cerium oxide nanoparticles were synthesized [3] and characterized by means of XRD, DLS, BF – STEM, surface charge 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. Adsorption of PSS on ceria nanoparticles was also examined using the above mentioned methods. Mobility of ceria particles covered with PSS is determined as a function of ionic strength and DLS was used for determination of the hydrodynamic radius of ceria nanoparticles coated with PSS. On the basis of these results the electrophoretic softness parameter for ceria- PSS system and adsorption density value were determined using the modified Ohshima model for soft particles [4]. 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 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 was 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. For that purpose, cerium oxide nanoparticles were synthesized [3] and characterized by means of XRD, DLS, BF – STEM, surface charge 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. Adsorption of PSS on ceria nanoparticles was also examined using the above mentioned methods. Mobility of ceria particles covered with PSS is determined as a function of ionic strength and DLS was used for determination of the hydrodynamic radius of ceria nanoparticles coated with PSS. On the basis of these results the electrophoretic softness parameter for ceria- PSS system and adsorption density value were determined using the modified Ohshima model for soft particles [4]. References: [1] T. Xia et al, ACS Nano 2 (2008) 2121-2134. [2] J. Požar, K. Bohinc, V. Vlachy, D. Kovačević, Phys. Chem. Chem. Phys. 13 (2011) 15610-15618. [3] D. Namjesnik, S. Mutka, D. Iveković, A. Gajović, M. Willinger, T. Preočanin, Adsorption 22 (2016) 825–837. [4] S. Saraf et al, ACS Appl. Mater. Interfaces 6 (2014) 5472-5482.1] T. Xia et al, ACS Nano 2 (2008) 2121-2134. C2] J. Požar, K. Bohinc, V. Vlachy, D. Kovačević, Phys. Chem. Chem. Phys. 13 (2011) 15610-15618. [3] D. Namjesnik, S. Mutka, D. Iveković, A. Gajović, M. Willinger, T. Preočanin, Adsorption 22 (2016) 825–837. [4] S. Saraf et al, ACS Appl. Mater. Interfaces 6 (2014) 5472-5482.

adsorption, polyelectrolytes, ceria, nanoparticles, stability

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