Moreover, the interstitial defect in this case is highly charged, which is another detrimental factor [32]. Figure 5 XRD patterns of undoped and TM-doped TiO 2 films. Figure 6 Change in the rutile and anatase lattice constant and rutile fraction. (a,b) The rutile/anatase TiO2 c-axis length changed monotonously with increasing TM content following Vegard’s law. The solid lines are the linear fitting

results VS-4718 cell line to guide the eyes. (c) Fractions of the rutile content as a function of dopant content for the TM-doped TiO2 films (left); evolution of the optical band gap of TM-doped TiO2 films with dopant content with error bar (right). With increasing dopant content, rutile-related peaks gradually increased. For the Co- and CP673451 Ni-doped TiO2 films, when dopant content reaches 0.03, the diffraction patterns of the rutile phase become predominant. On the contrary, for the Fe-doped TiO2 films, the diffraction patterns of the anatase phase are still dominant. These results indicate that the addition of dopant catalyzes the anatase-to-rutile transformation (ART), which are similar to those of the Co-doped [23, 33], Ni-doped [34, 35], and Fe-doped [36–39] TiO2 powders. The fraction of rutile phase in these films can be estimated from the XRD peak OICR-9429 clinical trial intensities

by the following equation: X R = 1/[1 + 0.884(I A/I R)], where X R is the weight fraction of rutile phase in the samples, and I A and I R are the x-ray-integrated intensities of the A(101) and R(110) peaks, respectively [20]. The rutile fraction against dopant content of the TM-doped TiO2 films is presented in Figure 6c. It can be seen selleck antibody inhibitor that the contents of the rutile phase enhance with increasing dopant content. The influence of the Co and Ni dopants on the ART of the TiO2 films is conspicuous, but minimal for the Fe dopant. At the same dopant content, the rutile content of the Co-doped

TiO2 films is the highest, and that of Fe-doped TiO2 films is the lowest. The ART is a nucleation and growth process at the expense of consuming the surrounding anatase in undoped TiO2[23, 33]. The nuclei were formed at the anatase 112 twin boundaries. Half of the titanium cations in the twin slab displace and the rutile phase nucleates [40, 41]. The transformation of bulk anatase ruptures 7 out of the 24 Ti-O bonds per unit cell and leads to the cooperative displacement of both Ti and O. After Ti4+ is replaced by Co2+, Ni2+, and Fe3+ ions, oxygen vacancies are introduced to keep the crystal charge neutrality. During the course of the ART, the presence of oxygen vacancies makes the number of Ti-O bond rupture less than 7/24 per anatase unit cell. In other words, oxygen vacancies make the ART [24].