1290 host SBA-15 template [26]. By using a facile sol–gel AAO template method, Zhang and Liu et al. got highly ordered ZnFe2O4 nanotube arrays, which displayed low-energy consumption and high sensitivity to organics as gas sensor materials and exhibited unusual photovoltaic behavior [7, 27]. However, all these 1D ZnFe2O4 nanostructures have no orientation, where Kim et al. demonstrated that ordered ZnO microrod arrays with the preferred orientation of [0001] direction showing a strong free-exciton emission at 3.23 eV and a weak deep level emission at 2.2 eV reveals the high optical quality than that of the ZnO nanowire arrays with no orientation [28, 29]. Recently, Zhang and Zhu et al. demonstrated that the properties of 1D nanostructures depend strongly not only on the ordered arrangement but also on the crystal orien- tation as well [30, 31]. In our previous, the ordered CoFe2O4 nanowire arrays with preferred crystal orientation were prepared by using the template synthesis in con- junction with electrochemical deposition [32]. Here, ordered ZnFe2O4 nanowire arrays with preferred crystal orientation of [110] direction were prepared by spatial conﬁnement oxidation of preferred [110] crystal orienta- tion ZnFe2 alloy nanowires in AAO templates. The mag- netic and optical properties of ZnFe2O4 nanowire arrays were studied. Experiment AAO was used as the template to synthesize ZnFe2O4 nanowire arrays. The AAO templates were prepared through two anodizing steps as our report previously [33]. Brieﬂy, high purity (99.999%) aluminum foil was polished in the mixed solution of ethanol and choric acid (HClO4) in the constant current of 1.5 A for 5 min. The two-step anodization process was carried out in constant voltage mode to improve the arrangement of the ordered nanopore arrays. In the ﬁrst step of the anodization, aluminum foil was anodized in 0.3 M H2SO4 aqueous solution under the constant voltage of 13 V at 0 C for 0.5 h resulting in the textured surface, and then the formed anodic alumina layer was removed in the mixed solution of 0.4 M phosphoric acid and 0.2 M chromic acid at 60 C. Subsequently, the foil was re-anodized for 4 h using the same parameters in the ﬁrst step. The electrolyte contained FeSO4 7H2O (22 g/l), ZnSO4 7H2O (10 g/l), H3BO3 (10 g/l) with the pH value of 3.2. The alternating current electrodeposition was conducted at 200 Hz and 13 V for the duration of 5 min. The compositions in the ZnFe alloy nanowires were ana- lyzed by energy dispersive X-ray spectroscopy (EDS) and inductively coupled plasma-atomic emission spectrometer (IRIS, ER/S). The results indicate the atom ratio of Fe:Zn is about 2. Because of the conﬁnement of the nanopore size, 123 Nanoscale Res Lett (2010) 5:1289–1294 after heat treating the well orientation ZnFe2 alloy nano- wire arrays in tube furnace at 460 C for 21 h in atmo- sphere, the arrays of ZnFe2O4 nanowires inside the AAO templates with preferred crystallite orientation were obtained. The morphologies of the nanowires were obtained by using the scanning electron microscope (SEM, Hitachi S-4800) and transmission electron microscopy (TEM, JEM-2010), where the nanowires were separated from the AAO templates by dissolving the aluminium oxide tem- plates in the mixed solution of 0.2 M H2CrO4 and 0.4 M H3PO4. The selected area electron diffraction (SAED) and X-ray diffraction (XRD, X’ Pert PRO PHILIPS with Cu Ka radiation) were employed to study the structure of the nanowires. The measurements of magnetic properties were made using Quantum Design MPMS magnetometer based on superconducting quantum interference device (SQUID) and vibrating sample magnetometer (VSM, Lakeshore 7304). Micro photoluminescence (PL) measurement was carried out at room temperature (RT) using a He-Cd laser with the wavelength of 325 nm and output power of 15 W as the excitation source. Light absorption property was measured using a UV–vis spectrophotometer (JASCO, UV-550). Results and Discussion Figure 1a shows the cross-sectional SEM image of ZnFe2O4 nanowires within AAO template. It is found that the nanowire arrays are ordered in AAO templates, and the average diameter is about 16 nm with the aspect ratio of 125. The EDS spectrum of the sample is shown in the inset of Fig. 1a, which reveals that the atom ratio of Zn: Fe is 32.3:67.7 (about 1:2), the same as the result of ICP. Shown in Fig. 1b is the TEM image of ZnFe2O4 nanowires, which has a diameter consistent with the result of SEM. Figure 1c shows the high resolution TEM image of the corresponding ZnFe2O4 nanowires. The lattice fringe between the two adjacent planes is about 0.30 nm apart, which is equal to the lattice fringes of the standard ZnFe2O4, growing along the [220] direction. The SAED pattern taken from the nanowires is shown in Fig. 1d, consisting of ﬁve obvious rings, which are corresponding to (220), (311), (400), (511), and (440) planes of polycrystalline ZnFe2O4 with a cubic spinel-type lattice structure [34]. XRD patterns of the ZnFe2 and ZnFe2O4 nanowire arrays within AAO templates are shown in Fig. 2a, b, respectively. Besides the smooth amorphous broad peak which comes from the AAO template, there is a sharp peak in XRD pattern of ZnFe2 nanowire arrays implying that orientation of [110] is perfect preferred. Similarly, the diffraction peaks of ZnFe2O4 nanowire arrays shown in