Loading...

The Photocatalytic and Photoluminescence Properties of Quasi Core-shell ZnO-graphene Oxide Nanoparticles

Pourseyed Haghshenas, Siamak | 2019

581 Viewed
  1. Type of Document: Ph.D. Dissertation
  2. Language: English
  3. Document No: 51931 (57)
  4. University: Sharif University of Technology, International Campus, Kish Island
  5. Department: Science and Engineering
  6. Advisor(s): Nemati, Ali; Simchi, Abdollreza; Kim, Choong-Un
  7. Abstract:
  8. In this report, a combination of in-situ chemical synthesis and electrolysis methods was applied for the preparation of zinc oxide/graphene quasi core-shell nanoparticles. Pure zinc oxide was also prepared using the same method at different temperatures. The degree of 100 ◦C was selected for synthesizing of ZnO-GO quasi core-shell (zinc oxide as a core and few layer of graphene oxide as a shell). The particle size was 15±2 nm in all samples. In both processes, oxygen was the main reason for the connection between the core and the shell. Unlike chemical process that has all kind of functions in electrolysis process, one kind of function was produced and confirmed by FTIR. XRD patterns also confirmed the formation of ZnO (with regular wurtzite structure) and ZnO-GO quasi core-shell structure. Raman spectroscopy results confirmed ZnO formation at various temperatures, but a little shift was observed for ZnO-GO quasi core-shell after conjugating. Although the HRTEM showed core and shell system, Raman and UV-Vis were able to define and confirm the conjugation and formation of the quasi core-shell structure as a bonding section and the mechanism of connection at the interface. Characterization of pure Zinc oxide showed that relation to synthesis process, the ZnO has specific sub levels of energy related to specific defect chemistry. Photoluminescence spectroscopy of core shell structure showed a few numbers of PL peaks that were not related to the presence of graphene. These sub-peaks depend on the kind of synthesis and creation of defects (based on defects chemistry). The results indicated that graphene just changed the intensity of PL peaks. Our data indicated that the rate of MB degradation for ZnO-GO core-shell structures was less than that of pure zinc oxide. After conjugating between ZnO and GO, two mechanisms are suggested at the interface. The first is the band structure modification in the boundary of the core and shell. The second is the diffusion of carbon atoms or functions as dopant in ZnO surface. The influence of functional groups of graphene oxide or specific function on luminescence property were discussed in this work. This report also addresses how band structure modification, defect chemistry, and microstructural features can affect the photocatalytic and photoluminescence behavior in a specific quasi core-shell structure. The results confirmed improvement of photoluminescence behavior in this kind of core shell structure but the catalytic performance of that is not better than pure zinc oxide. According to photoluminescence enhancement in these quasi core-shell quantum dots, it has potential for applying in optoelectronic devices, a hybrid polymer-quantum dot in light emitting diode (LED) device
  9. Keywords:
  10. Zinc Oxide ; Graphene ; Core-Shell Structure ; Photocatalyst ; Photoluminescence

 Digital Object List

 Bookmark

No TOC