In situ growth of Au@CeO2core–shell nanoparticles and CeO2nanotubes from Ce(OH)CO3nanorods

Abstract

Core–shell (CS) nanoparticles (NPs) have many applications in areas such as catalysis and sensing. The utilization of hollow nanostructured materials as the supports, such as nanotubes (NT), is a growing interest to anchor NPs. Generally, several steps are necessary to prepare CS NP–NT nanocomposites, including: (i) the synthesis of CS NPs; (ii) the preparation of NTs; and (iii) the combination of CS NPs and NTs. Moreover, surface modifications with organic ligands are often involved during the synthesis of CS NPs and/or the step combining CS NPs and supports. Here we report a facile method for in situ growth of Au@CeO2 CS NPs and CeO2 NTs by mixing HAuCl4 and Ce(OH)CO3 nanorods under mild conditions. The formation of Au–CeO2 nanocomposite is due to the interfacial oxidation–reduction reaction between HAuCl4 and Ce(OH)CO3, where Au(III) in HAuCl4 is reduced to Au(0) by Ce(III) in Ce(OH)CO3, while Ce(III) is oxidized into Ce(IV), followed by hydrolysis to generate CeO2. The slow hydrolysis rate of Ce(IV) leads to the coverage of CeO2 on the Au NPs, and on the residual Ce(OH)CO3 surface, developing into Au@CeO2 and Ce(OH)CO3@CeO2 CS structures. Further depletion/dissolution of Ce(OH)CO3 results in Au@CeO2 CS NP–CeO2 NT nanocomposite eventually. The advantages of our synthetic strategy are independent of foreign reducing agents and additional surface modification. And, such CS NP–NT nanocomposite can be obtained in one step, simplifying the synthesis procedures greatly. This method based on interfacial oxidation–reduction may be employed as a unique entry to other nanocomposites.