Experimental and Theoretical Study of Morphological and Charging Properties of Truncated Octahedron and Cubic Ceria Nanoparticles: Implications for Biomedical Applications

Klemen Bohinc,Marijana Đaković,Karla Korade,Goran Dražić,Nikolina Lešić,Davor Kovačević,Jean-François Dufrêche,Katarina Jerin

doi:10.1021/acsanm.0c02960

Abstract

Ceria (CeO2) nanoparticles are known to be very often used in various applications from biomedicine to fuel cells. To optimize the applications, detailed information about the physicochemical properties such as size, shape, and charge of nanoparticles should be available. Therefore, in our study we performed a systematic study of ceria nanoparticles ranging from synthesis to comprehensive experimental and theoretical characterization. We synthesized ceria nanoparticles using two synthesis paths which led to the formation of two types of ceria nanoparticles. The structure and charging properties of both types of ceria nanoparticles were studied by using X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), particle charge detector (PCD) for surface charge density, and a ZetaPlus instrument for electrophoretic mobility measurements. The results suggested that in the case where hydrolysis of Ce(NO3)3 at room temperature was applied nanoparticles with morphology close to a spherical, more exactly truncated octahedron were synthesized. On the other hand, nanoparticles obtained by hydrothermal synthesis had characteristic cube-like morphology. Finally, for more complete understanding and interpretation of the studied system, we prepared a theoretical model based on the classical density functional theory for electrolyte solutions coupled with the surface charge regulation via the law of mass action. Even without using fitting parameters, the theory adequately describes the experimental data. All the results obtained in our study could serve as a basis for obtaining tuned and engineered ceria nanoparticles with optimized physicochemical properties which could lead to the improved applications of the nanotechnology in the biomedical research.

Highlights

In recent years we have witnessed rapid advances in the field of synthesis and applications of cerium oxide (CeO2, ceria) nanoparticles
A systematic experimental investigation enabled us to find out the exact morphology of the investigated CeO2 NPs
Surface charge and mobility measurements allowed us to determine the charging properties of the studied nanoparticles as well as the ionic strength and cation type effect which was not found to be significant. This systematic approach has allowed us to continue with the theoretical approach for which experimentally obtained properties of CeO2 NPS are needed

Summary

INTRODUCTION

In recent years we have witnessed rapid advances in the field of synthesis and applications of cerium oxide (CeO2, ceria) nanoparticles (shortened CeO2 NPs). That is attributed to their specific physicochemical properties like nano size, good crystallinity, morphology, and charge. The surface charge density can be determined by polyelectrolyte titration with streaming potential measurement.[28] From electrophoretic mobility measurements, the isoelectric point can be determined as well as the mobilities of uncoated and coated nanoparticles as a function of pH. It is well-known that for obtaining the complete picture of the studied systems the holistic approach which combines experiments and theoretical results is required. To make a long story short, we decided to systematically study the surface properties of ceria nanoparticles and apply a combined approach based on experimental and theoretical investigations. The surface charge density of the particles was experimentally obtained by polyelectrolyte neutralization and compared with the theoretical predictions

EXPERIMENTAL SECTION

Ceria Nanoparticles Morphology

CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES