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Influence of morphology on electrical and optical properties of graphene/Al-doped ZnO-nanorod composites
Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering. Halmstad Univ, Sweden.ORCID iD: 0000-0002-6850-1552
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.ORCID iD: 0000-0002-4547-6673
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2018 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 29, no 41, article id 415201Article in journal (Refereed) Published
Abstract [en]

The development of future 3D-printed electronics relies on the access to highly conductive inexpensive materials that are printable at low temperatures (amp;lt;100 degrees C). The implementation of available materials for these applications are, however, still limited by issues related to cost and printing quality. Here, we report on the simple hydrothermal growth of novel nanocomposites that are well suited for conductive printing applications. The nanocomposites comprise highly Al-doped ZnO nanorods grown on graphene nanoplatelets (GNPs). The ZnO nanorods play the two major roles of (i) preventing GNPs from agglomerating and (ii) promoting electrical conduction paths between the graphene platelets. The effect of two different ZnO-nanorod morphologies with varying Al-doping concentration on the nanocomposite conductivity and the graphene dispersity are investigated. Time-dependent absorption, photoluminescence and photoconductivity measurements show that growth in high pH solutions promotes a better graphene dispersity, higher doping levels and enhanced bonding between the graphene and the ZnO nanorods. Growth in low pH solutions yields samples characterized by a higher conductivity and a reduced number of surface defects. These samples also exhibit a large persistent photoconductivity attributed to an effective charge separation and transfer from the nanorods to the graphene platelets. Our findings can be used to tailor the conductivity of novel printable composites, or for fabrication of large volumes of inexpensive porous conjugated graphene-semiconductor composites.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2018. Vol. 29, no 41, article id 415201
Keywords [en]
graphene; zinc oxide; nanorods; nanocomposites; persistent photoconductivity; printing
National Category
Materials Chemistry
Identifiers
URN: urn:nbn:se:liu:diva-150196DOI: 10.1088/1361-6528/aad3ecISI: 000440632800001PubMedID: 30015332Scopus ID: 2-s2.0-85051665865OAI: oai:DiVA.org:liu-150196DiVA, id: diva2:1241121
Note

Funding Agencies|Knowledge Foundation; Linkoping University; Halmstad University

Available from: 2018-08-22 Created: 2018-08-22 Last updated: 2024-01-08Bibliographically approved
In thesis
1. Graphene-based nanocomposites for electronics and photocatalysis
Open this publication in new window or tab >>Graphene-based nanocomposites for electronics and photocatalysis
2019 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The development of future electronics depends on the availability of suitable functional materials. Printed electronics, for example, relies on access to highly conductive, inexpensive and printable materials, while strong light absorption and low carrier recombination rates are demanded in photocatalysis industry. Despite all efforts to develop new materials, it still remains a challenge to have all the desirable aspects in a single material. One possible route towards novel functional materials, with improved and unprecedented physical properties, is to form composites of different selected materials.

In this work, we report on hydrothermal growth and characterization of graphene/zinc oxide (GR/ZnO) nanocomposites, suited for electronics and photocatalysis application. For conductive purposes, highly Al-doped ZnO nanorods grown on graphene nanoplates (GNPs) prevent the GNPs from agglomerating and promote conductive paths between the GNPs. The effect of the ZnO nanorod morphology and GR dispersity on the nanocomposite conductivity and GR/ZnO nanorod bonding strength were investigated by conductivity measurements and optical spectroscopy. The inspected samples show that growth in high pH solutions promotes a better graphene dispersity, higher doping and enhanced bonding between the GNPs and the ZnO nanorods. Growth in low pH solutions yield samples characterized by a higher conductivity and a reduced number of surface defects.

In addition, different GR/ZnO nanocomposites, decorated with plasmonic silver iodide (AgI) nanoparticles, were synthesized and analyzed for solar-driven photocatalysis. The addition of Ag/AgI generates a strong surface plasmon resonance effect involving metallic Ag0, which redshifts the optical absorption maximum into the visible light region enhancing the photocatalytic performance under solar irradiation. A wide range of characterization techniques including, electron microscopy, photoelectron spectroscopy and x-ray diffraction confirm a successful formation of photocatalysts.

Our findings show that the novel proposed GR-based nanocomposites can lead to further development of efficient photocatalyst materials with applications in removal of organic pollutants, or for fabrication of large volumes of inexpensive porous conjugated GR-semiconductor composites.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2019. p. 52
Series
Linköping Studies in Science and Technology. Licentiate Thesis, ISSN 0280-7971 ; 1847
Keywords
Graphene, Zinc oxide, Silver iodine, Plasmonics, Nanocomposites, Conjugated electronics, Photocatalysis, Photodegradation
National Category
Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-157095 (URN)10.3384/lic.diva-157095 (DOI)9789176850404 (ISBN)
Presentation
2019-06-13, K3, Kåkenhus, Norrköping, 14:15 (English)
Opponent
Supervisors
Available from: 2019-05-28 Created: 2019-05-28 Last updated: 2024-01-08Bibliographically approved
2. Synthesis and Characterization of ZnO/Graphene Nanostructures for Electronics and Photocatalysis
Open this publication in new window or tab >>Synthesis and Characterization of ZnO/Graphene Nanostructures for Electronics and Photocatalysis
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Recent rapid development of electronics and electro-optical devices demands affordable and reliable materials with enhanced performance. Forming nanocomposites of already well-known materials is one possible route towards novel functional materials with desirable synergistic enhanced properties. Incompatible chemical properties, mismatched crystal structures and weak bonding interactions between the substances, however, often limit the number of possible nanocomposites. Moreover, using an inexpensive, facile, large-area and flexible fabrication technique is crucial to employ the new composites in industrially viable applications.

This thesis focuses on the synthesis and characterization of different zinc oxide/graphene (ZnO/GR) nanocomposites, well suited for optoelectronics and photocatalysis applications. Two different approaches of i) substrate-free random synthesis, and ii) template-assisted selective area synthesis were studied in detail. In the first approach, ZnO nanoparticles/rods were grown on GR. The obtained nanocomposites were investigated for better GR dispersity, electrical conductivity and optical properties. Besides, by adding silver iodide to the nanocomposite, an enhanced plasmonic solar-driven photocatalyst was synthesized and analyzed. In the second approach, arrays of single, vertically aligned ZnO nanorods were synthesized using a colloidal lithography-patterned sol-gel ZnO seed layer. Our demonstrated nanofabrication technique with simple, substrate independent, and large wafer-scale area compatibility improved the alignment and surface density of ZnO nanorods over large selective growth areas. Eventually, we found a novel method to further enhance the vertical alignment of the ZnO nanorods by introducing a GR buffer layer between the Si substrate and the ZnO seed layer, together with the mentioned patterning technique.

The synthesized nanocomposites were analyzed using a large variety of experimental techniques including electron microscopy, photoelectron spectroscopy, x-ray diffraction, photoluminescence and cathodoluminescence spectroscopy for in-depth studies of their morphology, chemical and optical properties. Our findings show that the designed ZnO/GR nanocomposites with vertically aligned ZnO nanorods of high crystalline quality, synthesized with the developed low-cost nanofabrication technique, can lead to novel devices offering higher performance at a significantly lower fabrication cost.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2021. p. 128
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 2130
Keywords
zinc oxide, graphene, nanostructure, nanocomposite, conjugated electronics, photocatalysis, nanofabrication, colloidal lithography, chemical bath deposition, sol-gel
National Category
Composite Science and Engineering Nano Technology Materials Chemistry Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-174835 (URN)10.3384/diss.diva-174835 (DOI)9789179296827 (ISBN)
Public defence
2021-05-07, TPM55, Täppan, Campus Norrköping, Norrköping, 10:15 (English)
Opponent
Supervisors
Available from: 2021-04-08 Created: 2021-04-07 Last updated: 2024-01-08Bibliographically approved

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