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A comparative study of the electrodeposition and the aqueous chemical growth techniques for the utilization of ZnO nanorods on p-GaN for white light emitting diodes
Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
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2011 (English)In: Superlattices and Microstructures, ISSN 0749-6036, E-ISSN 1096-3677, Vol. 49, no 1, 32-42 p.Article in journal (Refereed) Published
Abstract [en]

Vertically well aligned zinc oxide nanorods (ZnO NRs) were grown on p-GaN by electrodeposition (ED) and aqueous chemical growth (ACG) techniques and the structures were employed to fabricate white light emitting diodes (LEDs). Room temperature current voltage (IV), photoluminescence (PL), and electroluminescence (EL) measurements were performed to investigate and compare both LEDs. In general, the IV characteristics and the PL spectra of both LEDs were rather similar. Nevertheless, the EL of the ED samples showed an extra emission peak shoulder at 730 nm. Moreover, at the same injection current, the EL spectrum of the ED light emitting diode showed a small UV shift of 12 nm and its white peak was found to be broader when compared to the ACG grown LED. The broadening of the EL spectrum of the LED grown by ED is due to the introduction of more radiative deep level defects. The presented LEDs have shown excellent color rendering indexes reaching a value as high as 95. These results indicate that the ZnO nanorods grown by both techniques possess very interesting electrical and optical properties but the ED is found to be faster and more suitable for the fabrication of white LEDs.

Place, publisher, year, edition, pages
Elsevier , 2011. Vol. 49, no 1, 32-42 p.
Keyword [en]
ZnO nanorods; GaN; Chemical growth; White light emitting diodes
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-71312DOI: 10.1016/j.spmi.2010.10.004OAI: oai:DiVA.org:liu-71312DiVA: diva2:447242
Available from: 2011-10-11 Created: 2011-10-11 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Device Fabrication and Photosensitizing Role of ZnO Nanostructures in Photodynamic Therapy of Cancer
Open this publication in new window or tab >>Device Fabrication and Photosensitizing Role of ZnO Nanostructures in Photodynamic Therapy of Cancer
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In nanoscience and nanotechnology, zinc oxide (ZnO) is gaining much research attention due to direct wide band gap (3.3 eV), large exciton binding energy (60 meV), and deep level defects emissions that cover the whole visible range. ZnO nanorods (NRs) in comparison to normal bio molecules and large surface area to volume ratio, allow them to interact within the cell thus are used as convincing intracellular carriers of photosensitizers. Vertical NRs are wave guiding cavities enhancing the light extraction efficiency from devices and are stable photosensitizing agents with their biophotonic, and biodegradation properties, therefore are appealing candidates for the photodynamic therapy of cancer.

The heterojunction LEDs of ZnO NRs/p-GaN are best choice to take the advantage of GaN ideal blue-light emission and fabricated LEDs explore the potential of white LEDs with superior performance. The main objective of this thesis is not only to fabricate ZnO NRs/p-GaN, or ZnO nanotubes (ZNTs)/p-GaN heterostructures, but also to investigate their optical properties for photodynamic therapy. These LEDs have showed enhanced EL intensity covering the visible band (425–750 nm).

ZnO nanorods are grown on the borosilicate glass capillaries (0.7 μm diameter) and then conjugated with photosensitizer. Such glass capillaries having ZnO nanorods complex with photosensitizer on them are used as pointer for intracellular mediated photochemistry in cells to achieve their necrosis. Mitochondrial staining of melanoma and foreskin fibroblast cells was done by Mitotracker Red with the aim of targeting the specific organelle with the prepared ZnO nanowires (NWs) Femtotip to see ROS production. Cytotoxic effects of nanometallic oxides e.g. ZnO-NRs, MnO2 NRs, and Fe2O3 NPs individually and their ligands with photosensitizers in osteosarcoma (U2OS) cells are also explored. Thus bare and ligands of nanometallic oxides, with particular focus of ZnO nanowires are having significant and convincing cytotoxic effects via the liberation of reactive oxygen species as well as Zn+2 ions in labeled cells, thus can be assigned as anticancer agents for breast cancer, melanoma cancer and osteosarcoma cells.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2011. 56 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1392
Keyword
Zinc oxide nanostructures, light emitting diodes, reactive oxygen species, photosensitizer, cancer cell, photodynamic therapy
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-71319 (URN)978-91-7393-083-3 (ISBN)
Public defence
2011-10-21, K2, Kåkenhus, Campus Norrköping, Linköpings universitet, Linköping, 10:15 (English)
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Available from: 2011-10-11 Created: 2011-10-11 Last updated: 2014-01-15Bibliographically approved

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Sultana, Kishwarul Hasan, KamranNur, OmerWillander, Magnus

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