Fe-incorporated TiO2 nanotube arrays: Electronic structure and magnetic response

Abstract

Incorporating Fe atoms into the lattice is shown to significantly alter electronic and magnetic properties of TiO 2 nanotubes synthesized by electrochemical anodization of Ti-Fe alloy sheets. The effects of Fe incorporation on the nanotube morphology, crystallinity, crystal structure, magnetic behavior and electronic structure were investigated with crystallographic and magnetic probes, including synchrotronbased spectroscopy. Results indicate that the iron cations predominately adopt the Fe 3+ configuration, leading to a large increase of the electronic density of states at the Fermi energy. This increase is anticipated to provide enhanced catalytic action, for instance, in the degradation of water and of air pollutants. These results provide insight for tailoring the functionality of these nanostructures for energyrelated applications.

Enhanced Photodegradation in Metal Oxide Nanowires with Co-Doped Surfaces under a Low Magnetic Field

“…First, we employed ultraviolet−visible spectroscopy (UV−vis) optical absorption (OA) spectra to reveal changes in the electronic structures of the bare ZnO NWs and the Co 2+ /ZnO NWs (Figure 2a). The amplitude of the OA spectrum near the ZnO band gap significantly increased, and a band tail was induced after the Co 2+ atoms were incorporated into the ZnO surfaces, possibly because the Co ions substituted some of the Zn ions in the crystal structure, increasing the unoccupied DOS near the ZnO's Fermi level 17 and thereby improving catalytic activity.…”

“…Complementary Co K-edge XANES measurements were taken during PD to determine the role of Co 2+ -rich doping in improved PD activity. 17,22 Figure 3a illustrates the Co K-edge XANES spectra of Co 2+ /ZnO NWs exposed to UV irradiation for various periods during PD, the spectra of which differed slightly depending on UV irradiation duration. In general, the valence states of the element can be quantified according to the half-height energy on the XANES edge.…”

“…The efficiency of PD activity is sensitive to changes in electronic structure. Complementary Co K-edge XANES measurements were taken during PD to determine the role of Co 2+ -rich doping in improved PD activity. , Figure a illustrates the Co K-edge XANES spectra of Co 2+ /ZnO NWs exposed to UV irradiation for various periods during PD, the spectra of which differed slightly depending on UV irradiation duration. In general, the valence states of the element can be quantified according to the half-height energy on the XANES edge. , The inset demonstrates that the half-height energy on the Co K-edge XANES shifted as UV irradiation duration increased, indicating that the energy level of the Co doping was near the Fermi level of the ZnO NWs; therefore, electrons could transfer from the Co 2+ /ZnO NWs to the MB solution and participate in PD as a function of UV irradiation duration .…”

“…The intrinsic characteristics (e.g., the d-orbitals) of transition metals (TMs) may extend the optical absorption range and increase a semiconductor’s density of states (DOS) to near its Fermi level because of the naturally sharp electronic band structures of TMs. − Additionally, the d or f electrons in TMs induce a strong spin–orbit interaction, generating the spin-polarized semiconductor band in spintronic applications. Essentially, the successful incorporation of TMs into the nanostructure of a photocatalytic system has indicated that enhanced spin polarization can be achieved using a low magnetic field, which is essential for environmental reasons.…”

Manipulated Optical Absorption and Accompanied Photocurrent Using Magnetic Field in Charger Transfer Engineered C/ZnO Nanowires

“…Typically, the magnetic‐field‐controlled optical phenomena in nano‐heterostructures consisting of magnetic‐components arises from the interactions between magnetic moment of an electron and applied magnetic field. [ 19,20 ] As the functions underlying these potential applications are determined by the density of states (DOSs), it is important to elucidate interrelations between the band structure and the magnetic response.…”