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Electro-optical and Cathodoluminescence properties of low temperature grown ZnO nanorods/p-GaN 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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2010 (English)In: PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, ISSN 1862-6300, Vol. 207, no 1, 67-72 p.Article in journal (Refereed) Published
Abstract [en]

Vertically aligned ZnO nanorods (NRs) with a diameter in the range of 160-200 nm were grown on p-GaN/sapphire substrates by aqueous chemical growth technique and white light emitting I diodes (LEDs) are fabricated. The properties of this LED were investigated by parameter analyzer, cathodoluminescence (CL), electroluminescence (EL), and photoluminescence (PL). The I-V characteristics of the fabricated ZnO/GaN heterojunction revealed rectifying behavior and the LED emits visible EL when bias is applied. From the CL it was confirmed that both the ZnO NRs and the p-GaN are contributing to the observed peaks. The observed EL measurements showed two emission hands centered at 450 nm and a second broad deep level defect related emission centered at 630 nm and extending from 500 rim and up to over 700 rim. Moreover, the room temperature PL spectrum of the ZnO NRs/p-GaN reveals an extra peak at the green color wavelength centered at 550 nm. Comparison of the PL, CL, and EL data suggest that the blue and near red emissions in the EL spectra are originating from Mg acceptor levels in the p-GaN and from the deep levels defects present in the ZnO NRs, respectively. The mixture of high and low energy colors, i.e., blue, green, and red, has led to the white observed luminescence.

Place, publisher, year, edition, pages
2010. Vol. 207, no 1, 67-72 p.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-54058DOI: 10.1002/pssa.200925393ISI: 000274280900010OAI: oai:DiVA.org:liu-54058DiVA: diva2:298318
Available from: 2010-02-22 Created: 2010-02-22 Last updated: 2014-01-15
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)
Opponent
Supervisors
Available from: 2011-10-11 Created: 2011-10-11 Last updated: 2014-01-15Bibliographically approved
2. Graphene and ZnO Nanostructures for Nano- Optoelectronic & Biosensing Applications
Open this publication in new window or tab >>Graphene and ZnO Nanostructures for Nano- Optoelectronic & Biosensing Applications
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

There has been a remarkable excitement in graphene research since the famous discovery in 2004 by isolating a monolayer with the help of scotch tape. Graphene, merely a single layer of carbon atoms, is progressively making inroads into a wide range of applications, from ballistic electronics to biosensors to flexible/transparent displays. Graphene is a matchless material that is strong, light, transparent, and an excellent conductor of heat and electricity. On the other hand, zinc oxide (ZnO) is a wide band semiconductor that demonstrates excellent electrical, optical, catalytic and sensing properties and has numerous applications in various fields. ZnO is a natural n-type semiconductor due to the presence of intrinsic defects such as Zn interstitials and O vacancies that also contribute strongly to optical emissions in the visible region.

The amalgamation of the exceptional properties of graphene with good semiconducting properties of ZnO can pave the way towards the realization of future devices (LED, biosensors, photovoltaics etc.).

In this thesis, graphene nanosheets and zinc oxide (ZnO) nanostructures have beensuccessfully synthesized by using chemical vapor deposition (CVD), vapor liquidsolid (VLS) or wet chemistry routines. These nanostructures were used to fabricatenano and optoelectronic devices, including field effect transistors (FETs), lightemitting diodes (LEDs), UV detectors and biosensors. Both nanomaterial’s propertiesand performances of the devices have been characterized and reported.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2012. 80 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1458
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-78697 (URN)978-91-7519-869-9 (ISBN)
Public defence
2012-05-29, K3, Kåkenhus, Campus Norrköping, Linköpings universitet, Norrköping, 10:15 (English)
Opponent
Supervisors
Available from: 2012-06-18 Created: 2012-06-18 Last updated: 2014-01-15Bibliographically approved

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