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ZnO quantum dots-graphene composites: Formation mechanism and enhanced photocatalytic activity for degradation of methyl orange dye

Tayyebi, A ; Sharif University of Technology

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  1. Type of Document: Article
  2. DOI: 10.1016/j.jallcom.2015.12.169
  3. Publisher: Elsevier Ltd
  4. Abstract:
  5. The current study demonstrates homogenous decorating of zinc oxide quantum dots (QDs) onto graphene oxide (GO) surface via simple chemical method. The AFM image exhibited that the prepared graphene was 0.8 nm thick and hence practically monolayer. Average size of the ZnO QDs was estimated by transmission electron microscopy around 3 nm. Instrumental and chemical analyses demonstrated formation of a strong bond between ZnO QDs and GO, through C-O-Zn and C-Zn bridges. The UV-visible spectra displayed that the introduction of graphene sheets to ZnO QDs resulted in higher absorption intensity of UV as well as widening of adsorption window toward visible light for ZnO-Graphene due to chemical bond between ZnO QDS and graphene surface. Results showed that adding of graphene up to 30% can improve resistance of ZnO against acids however for keeping the activity of catalyst, the recommended pH is near neutral (pH ≥ 6-7.2). In addition, the presence of graphene on the surface of the ZnO could significantly suppress the photocorrosion effect. The ZnO-Graphene hybrids indicated enhanced photocatalytic activity for degradation of methyl orange (MO) with the following order: ZnO-5% Graphene > ZnO-10% Graphene > ZnO QDs > ZnO30% -Graphene. This enhancement of photocatalytic activity may be attributed to the extended absorption of visible light, reducing of electron-hole recombination rate, and adsorption of MO molecules onto the huge surface area of graphene, where they are kept at vicinity of ZnO for decomposition
  6. Keywords:
  7. Enhanced photocatalysis ; Formation mechanism ; Photocorrosion ; Visible photocatalytic activity ; ZnO-Graphene ; Azo dyes ; Catalyst activity ; Chemical analysis ; Citrus fruits ; Degradation ; High resolution transmission electron microscopy ; Light ; Nanocrystals ; Photocatalysis ; Quantum chemistry ; Semiconductor quantum dots ; Transmission electron microscopy ; Zinc ; Zinc oxide ; Absorption intensity ; Degradation of methyl oranges ; Electron hole recombination rate ; Formation mechanism ; Photocatalytic activities ; Photocorrosion ; Visible-photocatalytic activities ; ZnO ; Graphene
  8. Source: Journal of Alloys and Compounds ; Volume 663 , 2016 , Pages 738-749 ; 09258388 (ISSN)
  9. URL: http://www.sciencedirect.com/science/article/pii/S0925838815319605