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Synthesis of ZnO, CuO and their Composite Nanostructures for Optoelectronics, Sensing and Catalytic Applications
Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology. (Physical Electronics and Nanotechnology)
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Research on nanomaterials has become increasingly popular because of their unique physical, chemical, optical and catalytic properties compared to their bulk counterparts. Therefore, many efforts have been made to synthesize multidimensional nanostructures for new and efficient nanodevices. Among those materials, zinc oxide (ZnO), has gained substantial attention owing to many outstanding properties. ZnO besides its wide bandgap of 3.34 eV exhibits a relatively large exciton binding energy (60 meV) at room temperature which is attractive for optoelectronic applications. Likewise, cupric oxide (CuO), having a narrow band gap of 1.2 eV and a variety of chemo-physical properties that are attractive in many fields. Moreover, composite nanostructures of these two oxides (CuO/ZnO) may pave the way for various new applications.

This thesis can be divided into three parts concerning the synthesis, characterization and applications of ZnO, CuO and their composite nanostructures.

In the first part the synthesis, characterization and the fabrication of ZnO nanorods based hybrid light emitting diodes (LEDs) are discussed. The low temperature chemical growth method was used to synthesize ZnO nanorods on different substrates, specifically on flexible non-crystalline substrates. Hybrid LEDs based on ZnO nanorods combined with p-type polymers were fabricated at low temperature to examine the advantage of both materials. A single and blended light emissive polymers layer was studied for controlling the quality of the emitted white light.

The second part deals with the synthesis of CuO nanostructures (NSs) which were then used to fabricate pH sensors and exploit these NSs as a catalyst for degradation of organic dyes. The fabricated pH sensor exhibited a linear response and good potential stability. Furthermore, the catalytic properties of petals and flowers like CuO NSs in the degradation of organic dyes were studied. The results showed that the catalytic reactivity of the CuO is strongly depending on its shape.

In the third part, an attempt to combine the advantages of both ZnO and CuO NSs was performed by developing a two-step chemical growth method to synthesize the composite NSs. The synthesized CuO/ZnO composite NSs revealed an extended light absorption and enhanced defect related visible emission.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2012. , 59 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1467
Keyword [en]
ZnO, CuO, Nanostructures, Low temperature growth, Light emitting diodes, pH sensors
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-81120ISBN: 978-91-7519-818-7 (print)OAI: oai:DiVA.org:liu-81120DiVA: diva2:550644
Public defence
2012-09-28, K3, Kåkenhus, Campus Norrköping, Linköping University, Norrköping, 10:15 (English)
Opponent
Supervisors
Available from: 2012-09-07 Created: 2012-09-07 Last updated: 2014-01-15Bibliographically approved
List of papers
1. Deposition of Well-Aligned ZnO Nanorods at 50 degrees C on Metal, Semiconducting Polymer, and Copper Oxides Substrates and Their Structural and Optical Properties
Open this publication in new window or tab >>Deposition of Well-Aligned ZnO Nanorods at 50 degrees C on Metal, Semiconducting Polymer, and Copper Oxides Substrates and Their Structural and Optical Properties
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2010 (English)In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 10, no 7, 3250-3256 p.Article in journal (Refereed) Published
Abstract [en]

A two-step chemical bath deposition was utilized to synthesize ZnO nanorod arrays (ZNRAs) on metals, poly(3,4-ethylenedioxythiophene)/poly(strenesulfonate) (PEDOT/PSS) coated flexible plastic foils, and copper oxides coated glass substrates. The whole synthesis procedure was carried out at a low temperature of 50 degrees C, without any other substrate treatments. The low growth temperature showed improved influence on both the ZNRAs structural and optical properties. Scanning electron microscopy (SEM) images revealed well-aligned ZNRAs with large aspect ratios, and X-ray diffraction (X RI)) analysis indicated that single crystalline ZNRAs were achieved with high c-axial orientation tendency. Room temperature photoluminescence (PL) measurements demonstrated excellent optical properties of the as-grown ZNRAs with very low defect concentration contrary to what was believed to be achieved when lowering the growth temperature. The impact of the low deposition temperature on the ZNRAs structure is discussed in connection to the thermodynamics constraints, while the temperature effect on the defects formation and density in the as-deposited ZNRAs is elaborated and compared with recent theoretical calculations that appeared in the literature.

Place, publisher, year, edition, pages
The American Chemical Society, 2010
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-58270 (URN)10.1021/cg100390x (DOI)000279422700059 ()
Available from: 2010-08-10 Created: 2010-08-09 Last updated: 2017-12-12
2. ZnO nanorods-polymer hybrid white light emitting diode grown on a disposable paper substrate
Open this publication in new window or tab >>ZnO nanorods-polymer hybrid white light emitting diode grown on a disposable paper substrate
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2011 (English)In: Physica Status Solidi. Rapid Research Letters, ISSN 1862-6254, E-ISSN 1862-6270, Vol. 5, no 2, 71-73 p.Article in journal (Refereed) Published
Abstract [en]

We demonstrate intrinsic white light emission from hybrid light emitting diodes fabricated using an inorganic-organic hybrid junction grown at 50 C on a paper substrate. Cyclotene was first spin coated on the entire substrate to act as a surface barrier layer for water and other nutrient solutions. The active area of the fabricated light emitting diode (LED) consists of zinc oxide nanorods (ZnO NRs) and a poly(9,9-dioctylfluorene) (PFO) conducting polymer layer. The fabricated LED shows clear rectifying behavior and a broad band electroluminescence (EL) peak covering the whole visible spectrum range from 420 nm to 780 nm. The color rendering index (CRI) was calculated to be 94 and the correlated color temperature (CCT) of the LED was 3660 K. The low process temperature and procedure in this work enables the use of paper substrate for the fabrication of low cost ZnO-polymer white LEDs for applications requiring flexible/disposable electronic devices.

Place, publisher, year, edition, pages
John Wiley and Sons, Ltd, 2011
Keyword
ZnO, PFO, LED, hybrid materials
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-67009 (URN)10.1002/pssr.201004446 (DOI)000288178300009 ()
Available from: 2011-03-25 Created: 2011-03-25 Last updated: 2017-12-11Bibliographically approved
3. Influence of the polymer concentration on the electroluminescence of ZnO nanorod/polymer hybrid light emitting diodes
Open this publication in new window or tab >>Influence of the polymer concentration on the electroluminescence of ZnO nanorod/polymer hybrid light emitting diodes
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2012 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 112, no 6, 064324- p.Article in journal (Refereed) Published
Abstract [en]

The effects of the polymer concentration on the performance of hybrid light emitting diodes (LEDs) based on zinc oxide nanorods (ZnO NRs) and poly(9,9-dioctylfluorene) (PFO) was investigated. Various characterization techniques were applied to study the performance of the PFO/ZnO NR hybrid LEDs fabricated with various PFO concentrations. The fabricated hybrid LEDs demonstrated stable rectifying diode behavior, and it was observed that the turn-on voltage of the LEDs is concentration dependent. The measured room temperature electroluminescence (EL) showed that the PFO concentration plays a critical role in the emission spectra of the hybrid LEDs. At lower PFO concentrations of 2-6 mg/ml, the EL spectra are dominated by blue emission. However, by increasing the concentration to more than 8 mg/ml, the blue emission was completely suppressed while the green emission was dominant. This EL behavior was explained by a double trap system of excitons that were trapped in the β-phase and/or in the fluorenone defects in the PFO side. The effects of current injection on the hybrid LEDs and on the EL emission were also investigated. Under a high injection current, a new blue peak was observed in the EL spectrum, which was correlated to the creation of a new chemical species on the PFO chain. The green emission peak was also enhanced with increasing injection current because of the fluorenone defects. These results indicate that the emission spectra of the hybrid LEDs can be tuned by using different polymer concentrations and by varying the current injected into the device.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2012
Keyword
Hybrid light emitting diodes, ZnO nanorods, PFO, electroluminescence
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-81426 (URN)10.1063/1.4754542 (DOI)000309423200142 ()
Available from: 2012-09-14 Created: 2012-09-14 Last updated: 2017-12-07Bibliographically approved
4. Effect of the polymer emission on the electroluminescence characteristics of n-ZnO nanorods/p-polymer hybrid light emitting diode
Open this publication in new window or tab >>Effect of the polymer emission on the electroluminescence characteristics of n-ZnO nanorods/p-polymer hybrid light emitting diode
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2011 (English)In: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 104, no 4, 1203-1209 p.Article in journal (Refereed) Published
Abstract [en]

Hybrid light emitting diodes (LEDs) based on zinc oxide (ZnO) nanorods and polymers (single and blended) were fabricated and characterized. The ZnO nanorods were grown by the chemical bath deposition method at 50A degrees C. Three different LEDs, with blue emitting, orange-red emitting or their blended polymer together with ZnO nanorods, were fabricated and studied. The current-voltage characteristics show good diode behavior with an ideality factor in the range of 2.1 to 2.27 for all three devices. The electroluminescence spectrum (EL) of the blended device has an emission range from 450 nm to 750 nm, due to the intermixing of the blue emission generated by poly(9,9-dioctylfluorene) denoted as PFO with orange-red emission produced by poly(2-methoxy-5(20-ethyl-hexyloxy)-1,4-phenylenevinylene) 1,4-phenylenevinylene) symbolized as MEH PPV combined with the deep-band emission (DBE) of the ZnO nanorods, i.e. it covers the whole visible region and is manifested as white light. The CIE color coordinates showed bluish, orange-red and white emission from the PFO, MEH PPV and blended LEDs with ZnO nanorods, respectively. These results indicate that the choice of the polymer with proper concentration is critical to the emitted color in ZnO nanorods/p-organic polymer LEDs and careful design should be considered to obtain intrinsic white light sources.

Place, publisher, year, edition, pages
Springer Verlag (Germany), 2011
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-70328 (URN)10.1007/s00339-011-6411-3 (DOI)000293972100029 ()
Available from: 2011-09-02 Created: 2011-09-02 Last updated: 2017-12-08
5. CuO nanoflowers as an electrochemical pH sensor and the effect of pH on the growth
Open this publication in new window or tab >>CuO nanoflowers as an electrochemical pH sensor and the effect of pH on the growth
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2011 (English)In: JOURNAL OF ELECTROANALYTICAL CHEMISTRY, ISSN 1572-6657, Vol. 662, no 2, 421-425 p.Article in journal (Refereed) Published
Abstract [en]

Well-crystallized flower-shaped cupric oxide (CuO) nanostructures composed of thin leaves have been synthesized by simple low-temperature chemical bath method and used to fabricate pH sensor. We examined the effect of the pH on the growth of the CuO nanostructures, by changing the pH of the precursor solutions different morphologies of the CuO nanostructures were obtained. CuO nanoflowers have recently become important as a material that provides an effective surface for electrochemical activities with enhanced sensing characteristics. The proposed sensor exhibited a linear electrochemical response within a wide pH range of (2-11). The experimental results (time response, electrochemical activity, reproducibility, absorption spectra, and XRD) indicate that the CuO nanoflowers can be used in pH sensor applications with enhanced properties.

Place, publisher, year, edition, pages
Elsevier, 2011
Keyword
CuO nanoflower; Morphological effect; Electrochemical; pH sensor; Repeatability
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-73334 (URN)10.1016/j.jelechem.2011.09.015 (DOI)000297881200020 ()
Available from: 2012-01-03 Created: 2012-01-02 Last updated: 2014-01-15
6. Efficient catalytic effect of CuO nanostructures on the degradation of organic dyes
Open this publication in new window or tab >>Efficient catalytic effect of CuO nanostructures on the degradation of organic dyes
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2012 (English)In: Journal of Physics and Chemistry of Solids, ISSN 0022-3697, E-ISSN 1879-2553, Vol. 73, no 11, 1320-1325 p.Article in journal (Refereed) Published
Abstract [en]

An efficient catalytic effect of petals and flowers like CuO nanostructures (NSs) on the degradation of two organic dyes, methylene blue (MB) and rhodamine B (RB) were investigated. The highest degradation of 95% in CuO petals and 72% in flowers for MB is observed in 24 h. For RB, the degradation was 85% and 80% in petals and flowers, respectively for 5 h. It was observed that CuO petals appeared to be more active than flowers for degradation of both dyes associated to high specific surface area. The petals and flower like CuO NSs were synthesized using the chemical bath method at 90 °C. The grown CuO NSs were characterized using scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD).

Keyword
A. Nanostructures; B. Chemical synthesis; C. X-ray diffraction; D. Crystal structure
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-81427 (URN)10.1016/j.jpcs.2012.07.005 (DOI)000308778900012 ()
Note

funding agencies|Advanced Functional Materials (AFT) grant at Linkoping University, Sweden||MUST University AJK, Pakistan||

Available from: 2012-09-14 Created: 2012-09-14 Last updated: 2017-12-07Bibliographically approved
7. Synthesis and Characterization of CuO/ZnO Composite Nanostructures: Precursor’s Effects, and their Optical Properties
Open this publication in new window or tab >>Synthesis and Characterization of CuO/ZnO Composite Nanostructures: Precursor’s Effects, and their Optical Properties
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2012 (English)Manuscript (preprint) (Other academic)
Abstract [en]

A two steps hydrothermal method was developed to synthesize CuO/ZnO composite nanostructures (NSs) on glass substrate. The CuO NSs were selectively assembled on the lateral surface of ZnO nanorods (NRs) upon short growth duration. While the CuO NSs were entirely covered the surface of ZnO NRs at extended growth durations. The growth kinetics of CuO NSs is strongly dependent on the nature and the pH value of the precursor solution. When a single precursor solution of copper nitrate was applied in the synthesis process, a coral-like CuO/ZnO NSs were obtained. However, by adding a pH controlling agent to the precursor solution significant increase in the size of the grown CuO NSs was observed. The results revealed that the grown CuO NSs were robustly adhered to ZnO NRs, however, no explicit epitaxial relationship was found. The ZnO NRs band to band and defects emissions ratio was decreased compared to that of pure ZnO NRs, suggesting that oxygen vacancies are the probable growth sites of CuO NSs. The CuO/ZnO composite NSs exhibited a broad light absorption covering the whole visible range compared to the constituent materials. The low growth temperatures along with the optical properties of CuO/ZnO suggest these composite NSs may carry great potentials in light harvesting, sensing and emitting applications.

Keyword
Hydrothermal, ZnO nanorods, CuO nanostructures, deep level defects, composite
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-81428 (URN)
Available from: 2012-09-14 Created: 2012-09-14 Last updated: 2014-01-15Bibliographically approved

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