We found that appropriate doping amount of V and N does not change the diameter of nanotubes. However, excessive dopants may lead to some particles or aggregates on the surface of nanotube arrays and some even block the pores and channels. Figure 1 FESEM top views and side views for N-TiO 2 (a, b), VN0 (c, d), and VN5 (e, f). Crystal structure The structural analysis of doped TiO2 nanotube arrays was usually carried out by using X-ray diffraction (XRD) and Raman spectroscopy [14]. Here, XRD measurements were performed to investigate the changes selleck inhibitor of phase structures of N-TiO2 sample and V, N co-doped TNAs with various

doping amounts. As shown in Figure  2, diffraction peaks of all samples were ascribed to pure anatase TiO2 diffraction pattern consistent with the values in the standard card (JCPDS card no. 21-1272) [15]. No significant characteristic peak of vanadium species is found in corresponding XRD patterns. Numerous reports showed that the incorporation Bucladesine solubility dmso of transition metal ions into other compounds as dopant could distort the original crystal lattice of the doped materials [16]. A detail analysis of XRD patterns was performed by enlarging the anatase (101) plane of the samples as shown in the inset of Figure  2. Compared with N-TiO2, the peak position of the V, N co-doped TNA samples gradually shifted toward a higher diffraction angle. It suggests that the V ions might be successfully incorporated

into the crystal lattice of anatase TiO2 as

vanadyl groups (V4+) or polymeric vanadates (V5+) and substituted for Ti4+ because the ionic radii of V4+(0.72 Å) and V5+(0.68 Å) were both slightly smaller than that of Ti4+(0.75 Å) [17]. However, peak position change of VN5 was not obvious, indicating that the doped V ions might be excessive and aggregate on the surface of TNAs and then inhibit the incorporation of ions into crystal lattice. For VN0 sample without co-doping, its crystal lattice did not change through the Proteases inhibitor hydrothermal process and kept the similar peak position with N-TiO2 sample. Figure 2 XRD patterns for N-TiO 2 , VN0, VN0.5, VN1, VN3, and VN5. The inset is an enlargement of the anatase (101) peaks for the above samples. Adenosine triphosphate XPS analysis Figure  3 shows the high-resolution XPS spectra of Ti 2p, O 1 s, N 1 s, and V 2p regions for N-TiO2, VN0, and VN3 samples. A significant negative shift is found for Ti 2p in Figure  3a and O 1 s in Figure  3b when V and N were co-doped into TiO2 by hydrothermal process. The measured binding energies of Ti 2p3/2 and O 1 s for N-TiO2 and VN0 are 458.7 and 529.9 eV, respectively. As compared to N-TiO2 and VN0, the binding energy of Ti 2p3/2 for the VN3 sample is shifted to 458.5 eV. The lower binding energy of Ti 2p in co-doped TiO2 suggests the different electronic interactions of Ti with ions and substitutes for Ti [9], which further justifies the incorporation of vanadium and nitrogen into the TiO2 lattice.