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Flexographic printed nanogranular LBZA derived ZnO gas sensors: Synthesis, printing and processing / ALED LEWIS

Swansea University Author: ALED LEWIS

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DOI (Published version): 10.23889/SUthesis.59435

Abstract

Within this document, investigations of the processes towards the production of a flexographic printed ZnO gas sensor for breath H2 analysis are presented. Initially, a hexamethylenetetramine (HMTA) based, microwave assisted, synthesis method of layered basic zinc acetate (LBZA) nanomaterials was in...

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Published: Swansea 2022
Institution: Swansea University
Degree level: Doctoral
Degree name: Ph.D
Supervisor: Maffeis, Thierry G.G.
URI: https://cronfa.swan.ac.uk/Record/cronfa59435
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fullrecord <?xml version="1.0"?><rfc1807><datestamp>2022-02-22T16:04:16.1623011</datestamp><bib-version>v2</bib-version><id>59435</id><entry>2022-02-22</entry><title>Flexographic printed nanogranular LBZA derived ZnO gas sensors: Synthesis, printing and processing</title><swanseaauthors><author><sid>63989aeca2ba64b7dd2245d10dc618fe</sid><firstname>ALED</firstname><surname>LEWIS</surname><name>ALED LEWIS</name><active>true</active><ethesisStudent>false</ethesisStudent></author></swanseaauthors><date>2022-02-22</date><abstract>Within this document, investigations of the processes towards the production of a flexographic printed ZnO gas sensor for breath H2 analysis are presented. Initially, a hexamethylenetetramine (HMTA) based, microwave assisted, synthesis method of layered basic zinc acetate (LBZA) nanomaterials was investigated. Using the synthesised LBZA, a dropcast nanogranular ZnO gas sensor was produced. The testing of the sensor showed high sensitivity towards hydrogen with response (Resistanceair/ Resistancegas) to 200 ppm H2 at 328 &#xB0;C of 7.27. The sensor is highly competitive with non-catalyst surface decorated sensors and sensitive enough to measure current H2 guideline thresholds for carbohydrate malabsorption (Positive test threshold: 20 ppm H2, Predicted response: 1.34). Secondly, a novel LBZA synthesis method was developed, replacing the HMTA by NaOH. This resulted in a large yield improvement, from a [OH-] conversion of 4.08 at% to 71.2 at%. The effects of [OH-]/[Zn2+] ratio, microwave exposure and transport to nucleation rate ratio on purity, length, aspect ratio and polydispersity were investigated in detail. Using classical nucleation theory, analysis of the basal layer charge symmetries, and oriented attachment theory, a dipole-oriented attachment reaction mechanism is presented. The mechanism is the first theory in literature capable of describing all observed morphological features along length scales. The importance of transport to nucleation rate ratio as the defining property that controls purity and polydispersity is then shown. Using the NaOH derived LBZA, a flexographic printing ink was developed, and proof-of-concept sensors printed. Gas sensing results showed a high response to 200 ppm H2 at 300 &#xB0;C of 60.2. Through IV measurements and SEM analysis this was shown to be a result of transfer of silver between the electrode and the sensing layer during the printing process. Finally, Investigations into the intense pulsed light treatment of LBZA were conducted. The results show that dehydration at 150 &#xB0;C prior to exposure is a requirement for successful calcination, producing ZnO quantum dots (QDs) in the process. SEM measurements show mean radii of 1.77-2.02 nm. The QDs show size confinement effects with the exciton blue shifting by 0.105 eV, and exceptionally low defect emission in photoluminescence spectra, indicative of high crystalline quality, and high conductivity. 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spelling 2022-02-22T16:04:16.1623011 v2 59435 2022-02-22 Flexographic printed nanogranular LBZA derived ZnO gas sensors: Synthesis, printing and processing 63989aeca2ba64b7dd2245d10dc618fe ALED LEWIS ALED LEWIS true false 2022-02-22 Within this document, investigations of the processes towards the production of a flexographic printed ZnO gas sensor for breath H2 analysis are presented. Initially, a hexamethylenetetramine (HMTA) based, microwave assisted, synthesis method of layered basic zinc acetate (LBZA) nanomaterials was investigated. Using the synthesised LBZA, a dropcast nanogranular ZnO gas sensor was produced. The testing of the sensor showed high sensitivity towards hydrogen with response (Resistanceair/ Resistancegas) to 200 ppm H2 at 328 °C of 7.27. The sensor is highly competitive with non-catalyst surface decorated sensors and sensitive enough to measure current H2 guideline thresholds for carbohydrate malabsorption (Positive test threshold: 20 ppm H2, Predicted response: 1.34). Secondly, a novel LBZA synthesis method was developed, replacing the HMTA by NaOH. This resulted in a large yield improvement, from a [OH-] conversion of 4.08 at% to 71.2 at%. The effects of [OH-]/[Zn2+] ratio, microwave exposure and transport to nucleation rate ratio on purity, length, aspect ratio and polydispersity were investigated in detail. Using classical nucleation theory, analysis of the basal layer charge symmetries, and oriented attachment theory, a dipole-oriented attachment reaction mechanism is presented. The mechanism is the first theory in literature capable of describing all observed morphological features along length scales. The importance of transport to nucleation rate ratio as the defining property that controls purity and polydispersity is then shown. Using the NaOH derived LBZA, a flexographic printing ink was developed, and proof-of-concept sensors printed. Gas sensing results showed a high response to 200 ppm H2 at 300 °C of 60.2. Through IV measurements and SEM analysis this was shown to be a result of transfer of silver between the electrode and the sensing layer during the printing process. Finally, Investigations into the intense pulsed light treatment of LBZA were conducted. The results show that dehydration at 150 °C prior to exposure is a requirement for successful calcination, producing ZnO quantum dots (QDs) in the process. SEM measurements show mean radii of 1.77-2.02 nm. The QDs show size confinement effects with the exciton blue shifting by 0.105 eV, and exceptionally low defect emission in photoluminescence spectra, indicative of high crystalline quality, and high conductivity. Due to the high crystalline quality and amenity to printing, the IPL ZnO QDs have numerous potential uses ranging from sensing to opto-electronic devices. E-Thesis Swansea Flexographic printing, LBZA, Layered hydroxides, Layered Zinc Hydroxides, Layered Basic Zinc Acetate, Oriented attachment, Gas Sensing, Intense Pulsed Light, IPL, Nanomaterial Synthesis, Nanomaterial growth, ZnO, Zinc Oxide, Zinc Oxide gas sensor, Hydrogen breath test sensor 22 2 2022 2022-02-22 10.23889/SUthesis.59435 COLLEGE NANME COLLEGE CODE Swansea University Maffeis, Thierry G.G. Doctoral Ph.D Ser Cymru NRN Engineering; Research grant number: NRN 039 2022-02-22T16:04:16.1623011 2022-02-22T15:13:33.7627244 Faculty of Science and Engineering School of Engineering and Applied Sciences - Uncategorised ALED LEWIS 1 59435__22428__4233edfc007845188270c37c7484b25b.pdf Lewis_Aled_R_PhD_Thesis_Final_Redacted_Signature.pdf 2022-02-22T15:39:31.5408893 Output 31650986 application/pdf E-Thesis – open access true Flexographic printed nanogranular LBZA derived ZnO gas sensors: Synthesis, printing and processing © 2022 by Aled Rhodri Lewis is licensed under a CC-BY-SA license. Third party content is excluded for use under the license terms. true eng https://creativecommons.org/licenses/by-sa/4.0/
title Flexographic printed nanogranular LBZA derived ZnO gas sensors: Synthesis, printing and processing
spellingShingle Flexographic printed nanogranular LBZA derived ZnO gas sensors: Synthesis, printing and processing
ALED LEWIS
title_short Flexographic printed nanogranular LBZA derived ZnO gas sensors: Synthesis, printing and processing
title_full Flexographic printed nanogranular LBZA derived ZnO gas sensors: Synthesis, printing and processing
title_fullStr Flexographic printed nanogranular LBZA derived ZnO gas sensors: Synthesis, printing and processing
title_full_unstemmed Flexographic printed nanogranular LBZA derived ZnO gas sensors: Synthesis, printing and processing
title_sort Flexographic printed nanogranular LBZA derived ZnO gas sensors: Synthesis, printing and processing
author_id_str_mv 63989aeca2ba64b7dd2245d10dc618fe
author_id_fullname_str_mv 63989aeca2ba64b7dd2245d10dc618fe_***_ALED LEWIS
author ALED LEWIS
author2 ALED LEWIS
format E-Thesis
publishDate 2022
institution Swansea University
doi_str_mv 10.23889/SUthesis.59435
college_str Faculty of Science and Engineering
hierarchytype
hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Engineering and Applied Sciences - Uncategorised{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Engineering and Applied Sciences - Uncategorised
document_store_str 1
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description Within this document, investigations of the processes towards the production of a flexographic printed ZnO gas sensor for breath H2 analysis are presented. Initially, a hexamethylenetetramine (HMTA) based, microwave assisted, synthesis method of layered basic zinc acetate (LBZA) nanomaterials was investigated. Using the synthesised LBZA, a dropcast nanogranular ZnO gas sensor was produced. The testing of the sensor showed high sensitivity towards hydrogen with response (Resistanceair/ Resistancegas) to 200 ppm H2 at 328 °C of 7.27. The sensor is highly competitive with non-catalyst surface decorated sensors and sensitive enough to measure current H2 guideline thresholds for carbohydrate malabsorption (Positive test threshold: 20 ppm H2, Predicted response: 1.34). Secondly, a novel LBZA synthesis method was developed, replacing the HMTA by NaOH. This resulted in a large yield improvement, from a [OH-] conversion of 4.08 at% to 71.2 at%. The effects of [OH-]/[Zn2+] ratio, microwave exposure and transport to nucleation rate ratio on purity, length, aspect ratio and polydispersity were investigated in detail. Using classical nucleation theory, analysis of the basal layer charge symmetries, and oriented attachment theory, a dipole-oriented attachment reaction mechanism is presented. The mechanism is the first theory in literature capable of describing all observed morphological features along length scales. The importance of transport to nucleation rate ratio as the defining property that controls purity and polydispersity is then shown. Using the NaOH derived LBZA, a flexographic printing ink was developed, and proof-of-concept sensors printed. Gas sensing results showed a high response to 200 ppm H2 at 300 °C of 60.2. Through IV measurements and SEM analysis this was shown to be a result of transfer of silver between the electrode and the sensing layer during the printing process. Finally, Investigations into the intense pulsed light treatment of LBZA were conducted. The results show that dehydration at 150 °C prior to exposure is a requirement for successful calcination, producing ZnO quantum dots (QDs) in the process. SEM measurements show mean radii of 1.77-2.02 nm. The QDs show size confinement effects with the exciton blue shifting by 0.105 eV, and exceptionally low defect emission in photoluminescence spectra, indicative of high crystalline quality, and high conductivity. Due to the high crystalline quality and amenity to printing, the IPL ZnO QDs have numerous potential uses ranging from sensing to opto-electronic devices.
published_date 2022-02-22T04:16:44Z
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score 11.016481

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