Amorphous to Tetragonal Zirconia Nanostructures and Evolution of Valence and Core Regions

Abstract

In this report, we study the evolution of valence band (VB) structure during a controlled amorphous to tetragonal transformation of ZrO2 core-shell nanostructures fabricated from electrospun nanofiber template (at 130, 200, and 250 °C). Shell-ZrO2 was formed with atomic layer deposition. X-ray diffraction and transmission electron microscopy are employed to unveil the transformation of amorphous to crystalline structure of ZrO2. O 1s core-level spectra indicated chemisorbed oxygen (OCh) of almost invariant fraction for the three samples. Zr 3s level suggested that the sample deposited at 130 °C has depicted a peak at relatively higher binding energy. Analyses on Zr 3d spectra indicated the presence of metallic-Zr (Zr+ζ, 0 ≤ |ζ| < 4), the fraction of which decreases with increasing template temperature. VB region is analyzed until ∼64 eV below the Fermi level (EF). The region close to EF depicted features that are dissimilar to the literature. This discrepancy is explained on the basis of the analyses from O 1s, Zr 3d, and Zr 4p levels including hybridization of orbitals from chemisorbed species. These levels were analyzed in terms of peak characteristics such as spectral position, area under the peak, etc. The results of this study would enhance the understanding of the evolution of various bands in the presence of OCh and changes to the crystallinity enabling the functionalities that are not available in the single-phase ZrO2. © 2015 American Chemical Society

Insights Into the Sunlight-Driven Water Oxidation by Ce and Er-Doped ZrO2

“…As reported in Figure S6B , the two VBM values (extrapolated by a linear fit in the descending side of the curve toward the Fermi Level at 0 eV) are: 1.53 eV for t-ZrO 2 and 1.72 eV for m-ZrO 2 , which also confirm the relative positions of the valence bands reported in the Figure 10 . This difference in the VBM, even if not so huge, represents a hint that the t-ZrO 2 is more conductive on its surface, electronically speaking, than the monoclinic one, as reported by Dash et al ( 2004 ) This behavior has also been observed in theoretical studies in which the electronic structure and density of states (DOS) of ZrO 2 polymorphs have been investigated by DFT or LCAO calculations (Zandiehnadem et al, 1988 ; Vempati et al, 2015 ; Sinhamahapatra et al, 2016 ). The main result is that both materials possess a flat valence band, which is in accordance with the semiconducting behavior, however, the t-ZrO 2 polymorph presents a higher amount of unoccupied states than m-ZrO 2 (at around 5 eV above the Fermi level) and the O deficiency creates new available states in the gap region (Dash et al, 2004 ).…”

“…This phenomenon has been observed for the water splitting reaction on commercial P25 TiO 2 with mixed anatase and rutile crystalline phases (Masolo et al, 2015 ), in which the creation of a heterostructure between the two polymorphs leads on an improved interface that allow a fast separation of the photogenerated charges with a consequent reduction of recombination processes. In the present case, although the band gap values of the various phases of ZrO 2 are quite similar (Dash et al, 2004 ), the VB and CB potentials of ZrO 2 polymorphs are different, as shown in Figure 10 , where a schematic representation of the relative VB and CB positions of m-ZrO 2 vs. the t-ZrO 2 and c-ZrO 2 were drawn considering the VBM experimentally obtained by XPS (Figures S6 ) and theoretical works (Zandiehnadem et al, 1988 ; Hernández et al, 2015 ; Vempati et al, 2015 ).…”

Ultrathin Zirconium Hydroxide Nanosheet‐Assembled Nanofibrous Membranes for Rapid Degradation of Chemical Warfare Agents

“…[ 38 ] The O 1s spectrum was fitted with three peaks (Figure S12b, Supporting Information) corresponding to terminal hydroxyls, bridging hydroxyls, and physisorbed water. [ 39 ] Notably, Zr–O(H)–Zr species were the key components of NANMs.…”

First Proposal of Minimum Information About a Cellular Assay for Regenerative Medicine

“…To control proper curation terms in MIACARM, we collected and assigned necessary IDs and technical and ontological terms from 13 existing collections: BioAssay Ontology [23]; Cell: Expression, Localization, Development, Anatomy [24]; Chemical Entities of Biological Interest Ontology [25]; Cell Ontology [26]; EDAM Bioinformatics Operations, Data Types, Formats, Identifiers, and Topics [27]; Experimental Factor Ontology [28]; Biological Imaging Methods Ontology [29]; Foundational Model of Anatomy [30]; Medical Subject Headings [31]; Microarray and Gene Expression Data Ontology [32]…”