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      Role of zinc interstitials and oxygen vacancies of ZnO in photocatalysis: a bottom-up approach to control the defect density

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      Author
      Kayaci, F.
      Vempati S.
      Donmez, I.
      Bıyıklı, Necmi
      Uyar, Tamer
      Date
      2014-06-09
      Source Title
      Nanoscale
      Print ISSN
      2040-3364
      Publisher
      Royal Society of Chemistry
      Volume
      6
      Issue
      17
      Pages
      10224 - 10234
      Language
      English
      Type
      Article
      Item Usage Stats
      127
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      204
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      Abstract
      Oxygen vacancies (VOs) in ZnO are well-known to enhance photocatalytic activity (PCA) despite various other intrinsic crystal defects. In this study, we aim to elucidate the effect of zinc interstitials (Zn i) and VOs on PCA, which has applied as well as fundamental interest. To achieve this, the major hurdle of fabricating ZnO with controlled defect density requires to be overcome, where it is acknowledged that defect level control in ZnO is significantly difficult. In the present context, we fabricated nanostructures and thoroughly characterized their morphological (SEM, TEM), structural (XRD, TEM), chemical (XPS) and optical (photoluminescence, PL) properties. To fabricate the nanostructures, we adopted atomic layer deposition (ALD), which is a powerful bottom-up approach. However, to control defects, we chose polysulfone electrospun nanofibers as a substrate on which the non-uniform adsorption of ALD precursors is inevitable because of the differences in the hydrophilic nature of the functional groups. For the first 100 cycles, Znis were predominant in ZnO quantum dots (QDs), while the presence of VOs was negligible. As the ALD cycle number increased, VOs were introduced, whereas the density of Zni remained unchanged. We employed PL spectra to identify and quantify the density of each defect for all the samples. PCA was performed on all the samples, and the percent change in the decay constant for each sample was juxtaposed with the relative densities of Znis and VOs. A logical comparison of the relative defect densities of Znis and VOs suggested that the former are less efficient than the latter because of the differences in the intrinsic nature and the physical accessibility of the defects. Other reasons for the efficiency differences were elaborated.
      Keywords
      Atomic layer deposition
      Defects
      Functional groups
      Nanostructures
      Oxygen vacancies
      Photocatalysis
      Zinc
      Zinc oxide
      Bottom up approach
      Decay constants
      Electrospun nanofibers
      Intrinsic nature
      Photocatalytic activities
      Relative density
      Zinc interstitials
      ZnO quantum dots
      Permalink
      http://hdl.handle.net/11693/12785
      Published Version (Please cite this version)
      https://doi.org/10.1039/c4nr01887g
      Collections
      • Institute of Materials Science and Nanotechnology (UNAM) 1831
      • Nanotechnology Research Center (NANOTAM) 1026
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