Preparation and characterization of BiFeO 3 @Ce-doped TiO 2 core-shell structured nanocomposites Lixiu Gong a , Zhufa Zhou a,b,n , Shumei Wang a,b,n , Ben Wang a a College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, PR China b National Engineering Laboratory of Modern Silk, Soochow University, Suzhou 215123, PR China article info Available online 13 November 2012 Keywords: Titania BiFeO 3 Ce-doped Synergistic effect Photocatalysts abstract BiFeO 3 @TiO 2 –Ce composite nanoparticles with a BiFeO 3 core and a Ce-doped TiO 2 shell structure were fabricated via a sol–gel method. The nanoparticles were characterized by scanning electron microscopy with energy dispersive spectroscopy, X-ray diffraction, transmission electron microscopy and UV–vis diffuse reflectance spectroscopy. The results reveal that core-shell structured BiFeO 3 @TiO 2 –Ce nanoparticles show a signifi- cant redshift in the UV–vis absorption spectra in comparison with both Ce-TiO 2 and BiFeO 3 @TiO 2 nanoparticles. The photocatalytic activities of the samples were tested in the degradation of methyl orange in aqueous solutions under visible light and UV light irradiations. The core-shell structured BiFeO 3 @TiO 2 –Ce sample exhibits higher photo- catalytic activity, which is attributed to the synergistic effects of BiFeO 3 and cerium. Crown Copyright & 2012 Published by Elsevier Ltd. All rights reserved. 1. Introduction Titanium dioxide (TiO 2 ) in different forms has attracted extensive interests in recent years owing to its high photo- catalytic effects on decomposing various organic pollutants [1–4], which offers a viable approach to solve the variety of environmental problems. But the band gap of TiO 2 (3.2 eV for anatase) is so wide that it can only absorb ultraviolet (UV) light, which is only 5% in the sun source [5]. In addition, the photogenerated electron–hole pair recombin- ing easily results in poor photocatalytic activity, and hence limits its applications. Several efforts have been made, such as replacing the oxygen position with nonmetallic or metal element to overcome the barriers [6–10]. Besides, various modifications have been performed to synthetize nanos- tructured composites such as Fe 3 O 4 /SiO 2 /TiO 2 , ZnO/TiO 2 and WO 3 /TiO 2 , which can efficiently hinder the recombina- tion of the photogenerated electron–hole pairs [11–13]. In particular, exploiting a core-shell structured nanoparti- cles in which TiO 2 acted as shell and magnetic materials (such as Fe 3 O 4 , MnFe 2 O 4 , BaFe 12 O 19 ) introduced as core is also an efficient way [14–16]. As we have known, BiFeO 3 has an excellent multiferro- electric properties at room temperature. In addition, It has been studied widely in the photocatalytic field due to its small bandgap. Zhang et al. synthesized TiO 2 /BiFeO 3 heterostructures, and their results indicated BiFeO 3 weaken the recombination of electrons generated [17]. Shun Li et al. had prepared BiFeO 3 @TiO 2 core-shell struc- ture and found that the core-shell nanoparticles had a higher photocatalytic activity in contrast to pure TiO 2 . BiFeO 3 act as electron carriers that can promote interfacial charge transfer in the composite systems [18]. Addition- ally the magnetic property of the composites helps recycle the photocatalysts from treated water. The core- shell BiFeO 3 @TiO 2 nanoparticles have a lower energy gap that enhances visible light absorption. In order to over- come the recombination of photogenerated electron–hole pairs of BiFeO 3 @TiO 2 , many groups have been involved in doping rare earth ions into TiO 2 [19,20], among which cerium has been received much attentions because of the Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/mssp Materials Science in Semiconductor Processing 1369-8001/$ - see front matter Crown Copyright & 2012 Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.mssp.2012.10.009 n Corresponding authors at: College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, PR China. Tel.: þ86 512 65880963; fax: þ86 512 65880089. E-mail address: zhouzhufa@suda.edu.cn (Z. Zhou). Materials Science in Semiconductor Processing 16 (2013) 288–294