Synthesis and characterization of core@shell (ZnO@γ-Fe_2O_3) structured nanoparticles with two morphologies

摘要

Core-shell ZnO/y-Fe_2O_3 nanoparticles were prepared via a simple method using forced hydrolysis of acetate metallic salts in a polyol medium. Two types of morphologies can be easily obtained: (ⅰ) quasi-spherical ZnO core 20 ran in diameter coated with a continuous shell with 3 nm in length, (ⅱ) rod-like ZnO decorated with y-Fe_2O_3 nanoparticles. The ZnO nanorods are 80 nm in diameter and 400 nm in length. The maghemite (γ-Fe_2O_3) nanoparticles with 5 nm in diameter are strongly bonded to ZnO, well separated from each other and form a monolayer on the surface of ZnO nanorods. In both systems, coating ZnO by y-Fe_2O_3 inhibits the surface defects and thus enhances the UV luminescence. The two systems present a superparamagnetic behavior with blocking temperature depending on the morphology: the decorated ZnO nanorods present a blocking temperature around 6 K whereas this temperature is significantly higher (300 K) for spherical core-shell nanoparticles.