TiO2- and CeO2-Based Biphasic Core–Shell Nanoparticles with Tunable Core Sizes and Shell Thicknesses

Abstract

A layer-by-layer methodology was used for synthesizing CeO2/TiO2 and TiO2/CeO2 core–shell nanoparticles supported in Vycor glass pores. The layers were deposited by cerium- or titanium-based metalloorganic precursor decomposition. Sequential depositions promoted linear mass increases of the Vycor pieces and a linear decrease of both total pore size and total surface area, confirmed by N2 adsorption–desorption isotherms. Alternation in the metalloorganic precursors used results in the formation of spherelike nanoparticles (as observed by HRTEM) with core–shell architecture. Raman spectroscopy data showed that CeO2 is crystallized in the fluorite structure and TiO2 in the anatase phase. Shifts in the frequency and changes in line width of TiO2 Eg and CeO2 T2g Raman bands were used for monitoring changes in core size and shell thickness based on the quantum size effect and on the phonon confinement theory. Our results show that nanoparticle core sizes and the shell thicknesses can be tuned by changing the nu...