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ZnO and CuO Nanostructures: Low Temperature Growth, Characterization, their Optoelectronic and Sensing Applications
Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

One dimensional (1-D), zinc oxide (ZnO) and copper (II) oxide (CuO), nanostructures have great potential for applications in the fields of optoelectronic and sensor devices. Research on nanostructures is a fascinating field that has evolved during the last few years especially after the utilization of the hydrothermal growth method. Using this method variety of nanostructures can be grown from solutions, it is a cheap, easy, and environment friendly approach. These nanostructures can be synthesized on various conventional and nonconventional substrates such as silicon, plastic, fabrics and paper etc.

The primary purpose of the work presented in this thesis is to realize controllable growth of ZnO, CuO and nanohybrid ZnO/CuO nanostructures and to process and develop white light emitting diodes and sensor devices from the corresponding nanostructures.

The first part of the thesis deals with ZnO nanostructures grown under different hydrothermal conditions in order to gain a better understanding of the growth. Possible parameters affecting the growth such as the pH, the growth temperature, the growth time, and the precursors  concentration which can alter the morphology of the nanostructures were investigated (paper 1). Utilizing the advantage of the low temperature for growth we synthesized ZnO nanostructures on different substrates, specifically on flexible substrates, which are likely to be integrated with flexible organic substrates for future foldable and disposable electronics (paper 2, 3).

In the second part of the thesis, using the results and findings from the growth of ZnO nanostructures, it was possible to successfully implement ZnO nanostructures for white light emitting diodes (LEDs) on different flexible substrates (paper 4, 5).

In paper 4 we realized a ZnO/polymer LED grown on a paper substrate. In paper 5 we extended the idea to print the ZnO nanorods/polymer hybrid LEDs with potential application to large area flexible displays.

In the last part of the thesis, CuO and nanohybrid ZnO/CuO nanostructures were utilized to fabricate Ag+ detection and humidity sensors. In paper 6 we reported Ag+ selective electrochemical sensor based on the use of functionalized CuO nanopetals. To combine the advantages of both oxides nanostructures and to improve the performance we fabricated a pn-heterojuction using intrinsic n-ZnO nanorods and p-CuO nanostructures which were then utilized as an efficient humidity sensor (paper 7).

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2012. , 66 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1441
Keyword [en]
Zinc oxide, Copper (II) oxide, Nanostructures, Hydrothermal growth, Light emitting diodes.
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-76677ISBN: 978-91-7519-912-2OAI: oai:DiVA.org:liu-76677DiVA: diva2:515790
Public defence
2012-05-11, K3, Kåkenhus, Campus Norrköping, Linköpings universitet, Norrköping, 10:15 (English)
Opponent
Supervisors
Available from: 2012-04-16 Created: 2012-04-16 Last updated: 2014-01-15Bibliographically approved
List of papers
1. Influence of pH, Precursor Concentration, Growth Time, and Temperature on the Morphology of ZnO Nanostructures Grown by the Hydrothermal Method
Open this publication in new window or tab >>Influence of pH, Precursor Concentration, Growth Time, and Temperature on the Morphology of ZnO Nanostructures Grown by the Hydrothermal Method
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2011 (English)In: Journal of Nanomaterials, ISSN 1687-4110, no 269692Article in journal (Refereed) Published
Abstract [en]

We investigated the influence of the pH value, precursor concentration (C), growth time and temperature on the morphology of zinc oxide (ZnO) nanostructures. The pH of the starting solution was varied from1.8 to 12.5. It was found that the final pH reaches an inherent value of 6.6 independently of the initial pH solution. Various ZnO structures of nanotetrapod-like, flower-like, and urchin-like morphology were obtained at alkaline pH (8 to 12.5) whereas for pH solution lower than 8 rod-like nanostructures occurred. Moreover, we observed the erosion of the nanorods for a pH value less than 4.6. By changing the concentrations the density and size were also varied. On going from a high (C > 400mM) to lower (C < 25mM) C, the resulted ZnO nanostructures change from a film to nanorods (NRs) and finally nanowires (NWs). It was also found that the length and diameter of ZnO NRs follow a linear relation with time up to 10 hours, above which no further increase was observed. Finally the effect of growth temperature was seen as an influence on the aspect ratio.

Place, publisher, year, edition, pages
NY, USA: Hindawi Publishing Corporation, 2011
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-74729 (URN)10.1155/2011/269692 (DOI)000298424100001 ()
Note
funding agencies|advanced Functional Material project Sweden||Available from: 2012-02-06 Created: 2012-02-06 Last updated: 2014-01-15Bibliographically approved
2. 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: 2014-01-15
3. Current-transport studies and trap extraction of hydrothermally grown ZnO nanotubes using gold Schottky diode
Open this publication in new window or tab >>Current-transport studies and trap extraction of hydrothermally grown ZnO nanotubes using gold Schottky diode
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2010 (English)In: PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, ISSN 1862-6300, Vol. 207, no 3, 748-752 p.Article in journal (Refereed) Published
Abstract [en]

High-quality zinc oxide (ZnO) nanotubes (NTs) were grown by the hydrothermal technique on n-Si substrate. The room temperature (RT) current-transport mechanisms of Au Schottky diodes fabricated from ZnO NTs and nanorods (NRs) reference samples have been studied and compared. The tunneling mechanisms via deep-level states was found to be the main conduction process at low applied voltage but at the trap-filled limit voltage (V-TFL) all traps were filled and the space-charge-limited current conduction was the dominating current-transport mechanism. The deep-level trap energy and the trap concentration for; the NTs were obtained as similar to 0.27 eV and 2.1 x 10(16) cm(-3), respectively. The same parameters were also extracted for the ZnO NRs The deep-level states observed crossponds to zinc interstitials (Zn-i), which are responsible for the violet emission.

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH, PO BOX 10 11 61, D-69451 WEINHEIM, GERMANY, 2010
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-55049 (URN)10.1002/pssa.200925547 (DOI)000276339800054 ()
Available from: 2010-04-28 Created: 2010-04-28 Last updated: 2014-01-15
4. 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, 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: 2014-01-15Bibliographically approved
5. Scale-up synthesis of ZnO nanorods for printing inexpensive ZnO/polymer white light-emitting diode
Open this publication in new window or tab >>Scale-up synthesis of ZnO nanorods for printing inexpensive ZnO/polymer white light-emitting diode
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2012 (English)In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 47, no 11, 4726-4731 p.Article in journal (Refereed) Published
Abstract [en]

In this study, possibilities of scaling up the synthesis of zinc oxide (ZnO) nanorods (NRs) by the hydrothermal method have been explored. It was found that batches yielding several grams can easily be made using common and easily available materials. Further, a printable composition was fabricated by mixing the obtained ZnO NRs into a common solvent-based screen printable varnish. Scanning electron microscope, high-resolution transmission electron microscope, X-ray diffraction, UV–vis spectroscopy analysis of the scaled up batch indicated that the ZnO nanostructures were of NRs shape, well crystalline and having less defects. Using the ZnO NRs-based printable composition a device fabrication on a flexible substrate was demonstrated, producing a flexible light-emitting device being highly tolerant to bending.

Place, publisher, year, edition, pages
Springer, 2012
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-76674 (URN)10.1007/s10853-012-6342-1 (DOI)000302244500026 ()
Available from: 2012-04-16 Created: 2012-04-16 Last updated: 2014-01-15Bibliographically approved
6. CuO Nanopetals Based Electrochemical Sensor for Selective Ag+ Measurements
Open this publication in new window or tab >>CuO Nanopetals Based Electrochemical Sensor for Selective Ag+ Measurements
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

The electrochemical sensing activity of cupric oxide (CuO) nanopetals was investigated for the detection of silver (I) ions (Ag+. The CuO nanopetals were synthesized on a large area glass substrate by a low-temperature hydrothermal growth process. Structural morphological investigations were carried out using field emission scanning electron microscopy, high resolution transmission electron microscopy, and X-ray diffraction. To check the sensing application of the CuO nanopetals, it was functionalized for selectivity of Ag+. A polymeric membrane with Ag+-selective ionophore was coated on the surface of the CuO nanopetals. CuO nanopetals reveal excellent electrochemical sensing behavior in aqueous solution to selectively detect Ag+. The CuO based sensor exhibits a linear electrochemical response within the concentration range of 1 μM to 100 mM. The functionalized CuO nanopetal based sensor show stable, fast response and high sensitivity for [Ag+]. This work demonstrates a simple technique for sensitive detection of Ag+ and other biochemical species.

Keyword
CuO, Nanopetals, Hydrothermal Method, Ag+-Selective Membrane, Electrochemical Sensor
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-76675 (URN)
Available from: 2012-04-16 Created: 2012-04-16 Last updated: 2014-01-15Bibliographically approved
7. CuO/ZnO Nanocorals synthesis via hydrothermal technique: growth mechanism and their application as Humidity Sensor
Open this publication in new window or tab >>CuO/ZnO Nanocorals synthesis via hydrothermal technique: growth mechanism and their application as Humidity Sensor
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2012 (English)In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 22, no 23, 11583-11590 p.Article in journal (Refereed) Published
Abstract [en]

We demonstrate hydrothermal synthesis of coral-like CuO nanostructures by selective growth on ZnO nanorods (NR) at low temperatures. During the hydrothermal processing the resultant hydroxylated and eroded surface of ZnO NR becomes favorable for the CuO nanostructures growth via oriented attachments. Heterojunction p-n diodes fabricated from the CuO/ZnO nanocorals (NC) reveal stable and high rectification diode properties with a turn-on voltage ~1.52 V and negligible reverse current. The humidity sensing characteristics of the CuO/ZnO NC diodes exhibit a remarkable linear (in a semilogarithmic scale) decrease in the DC resistance by more than three orders when the relative humidity is changed from 30 – 90 %. The NC humidity sensor is also found to reveal the highest sensitivity factor ~6045 among available data for the constituent material’s and a response and recovery time of 6 s and 7 s, respectively.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2012
Keyword
Zinc oxide nanorods, copper oxide nanostructures, nanocorals, relative humidity, sensitivity factor
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-76676 (URN)10.1039/c2jm16597j (DOI)000304351400026 ()
Note
funding agencies|Swedish government||Available from: 2012-04-16 Created: 2012-04-16 Last updated: 2014-01-15Bibliographically approved

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