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Graphene-based nanocomposites for electronics and photocatalysis
Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS). Linköping University, Linköping, Sweden.ORCID iD: 0000-0002-6850-1552
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
Norrköping: Linköping University Electronic Press, 2019. , p. 52
Series
Linköping Studies in Science and Technology. Licentiate Thesis, ISSN 0280-7971 ; 1847
Keywords [en]
Graphene, Zinc oxide, Silver iodine, Plasmonics, Nanocomposites, Conjugated electronics, Photocatalysis, Photodegradation
National Category
Other Physics Topics
Identifiers
URN: urn:nbn:se:hh:diva-40638Libris ID: x74jqjpfvk0qx5j5ISBN: 9789176850404 (print)OAI: oai:DiVA.org:hh-40638DiVA, id: diva2:1355258
Presentation
2019-06-13, K3, Kåkenhus, Norrköping, 14:15 (English)
Opponent
Supervisors
Available from: 2019-09-27 Created: 2019-09-27 Last updated: 2019-09-30Bibliographically approved
List of papers
1. Influence of morphology on electrical and optical properties of graphene/Al-doped ZnO-nanorod composites
Open this publication in new window or tab >>Influence of morphology on electrical and optical properties of graphene/Al-doped ZnO-nanorod composites
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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 (<100 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 graphenedispersity 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. © 2018 IOP Publishing Ltd.

Place, publisher, year, edition, pages
Bristol: Institute of Physics Publishing (IOPP), 2018
Keywords
grapheme, nanocomposites, nanorods, persistent photoconductivity, printing, zinc oxide
National Category
Nano Technology
Identifiers
urn:nbn:se:hh:diva-38250 (URN)10.1088/1361-6528/aad3ec (DOI)000440632800001 ()30015332 (PubMedID)2-s2.0-85051665865 (Scopus ID)
Available from: 2018-11-02 Created: 2018-11-02 Last updated: 2019-09-30Bibliographically approved
2. Graphene-based plasmonic nanocomposites for highly enhanced solar-driven photocatalytic activities
Open this publication in new window or tab >>Graphene-based plasmonic nanocomposites for highly enhanced solar-driven photocatalytic activities
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2019 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 9, no 52, p. 30585-30598Article in journal (Refereed) Published
Abstract [en]

High-efficiency photocatalysts are crucial for the removal of organic pollutants and environmental sustainability. In the present work, we report on a new low-temperature hydrothermal chemical method, assisted by ultrasonication, to synthesize disruptive plasmonic ZnO/graphene/Ag/AgI nanocomposites for solar-driven photocatalysis. The plasmonic nanocomposites were investigated by a wide range of characterization techniques, confirming successful formation of photocatalysts with excellent degradation efficiency. Using Congo red as a model dye molecule, our experimental results demonstrated a photocatalytic reactivity exceeding 90% efficiency after one hour simulated solar irradiation. The significantly enhanced degradation efficiency is attributed to improved electronic properties of the nanocomposites by hybridization of the graphene and to the addition of Ag/AgI which generates a strong surface plasmon resonance effect in the metallic silver further improving the photocatalytic activity and stability under solar irradiation. Scavenger experiments suggest that superoxide and hydroxyl radicals are responsible for the photodegradation of Congo red. Our findings are important for the fundamental understanding of the photocatalytic mechanism of ZnO/graphene/Ag/AgI nanocomposites and can lead to further development of novel efficient photocatalyst materials. © 2019 Elsevier B.V.

Place, publisher, year, edition, pages
Cambridge: Royal Society of Chemistry, 2019
National Category
Materials Chemistry
Identifiers
urn:nbn:se:hh:diva-40639 (URN)10.1039/C9RA06273D (DOI)2-s2.0-85065782272 (Scopus ID)
Funder
Linköpings universitetKnut and Alice Wallenberg Foundation
Available from: 2019-09-27 Created: 2019-09-27 Last updated: 2019-09-30Bibliographically approved

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