{"id":{"repo_id":"qu-belfast","oai_identifier":"oai:pure.qub.ac.uk/portal:studenttheses/a3e277dd-0a10-49cf-9db5-88e63d02a4fd"},"canonical_url":"https://search.dev.ndltd.org/etd/qu-belfast/oai:pure.qub.ac.uk/portal:studenttheses/a3e277dd-0a10-49cf-9db5-88e63d02a4fd","repository":{"repo_id":"qu-belfast","name":"Queen's University Belfast","base_url":"https://pureadmin.qub.ac.uk/ws/oai"},"display":{"title":"Development of novel metal nanoparticle based methods for detection of bacteria using surface-enhanced Raman spectroscopy","abstract":"The principal aim of this Ph.D. thesis was to develop new enhancing substrates for use in Surface-enhanced Raman Spectroscopy (SERS) for the rapid detection of live bacteria by analysis of the headspace above bacterial cultures. It is knownt hat in-situ SERS can be used to detect vapour phase dimethyl disulphide (DMDS), which is a metabolic product of live bacteria. The test experiments in this thesis were carried out in a model system which was the headspace above DMDS solutions. The measurements actually detect the characteristic bands from chemisorbed methyl sulphide which is created by dissociation of adsorbed DMDS on the surface of Ag and Au nanoparticles. A variety of enhancing substrates were used, the first were arrays of Ag and Au nanoparticles which were deposited on a glass substrate from a layer of nanoparticles trapped at a liquid/liquid interface (a so-called metal-like liquid film or MeLLF). These were contrasted with surface-exposed nanoparticle sheets (SENS) where a layer of particles was fixed to a polymer backing. These films showed the expected rise in signal over a timescale of minutes although the rate of adsorption was faster than previously observed. The general observation has been that Ag films give larger signals but slower responses while Au films respond more rapidly but give lower signal intensities. In order to enhance the performance of AgSENS, two different general approaches were applied. The first approach was to deposit an Au layer on the AgSENS in an attempt to increase the rate of chemisorption while retaining the enhancement of the underlying silver substrate. Both sputtering and Galvanic replacement was attempted but neither gave the hoped-for increase. The second approach was to prepare different Ag nanoparticles whose performance has been claimed to be superior to those used in the original studies. For this approach, Ag nanoparticles were prepared using ethylene glycol rather than traditional citrate reduction, along with polyvinyl pyrrolidone (PVP). The product nanowires gave very good SERS results. Further studies showed that it was the PVP that improved the rate of adsorption rather than particle shape and the best results for all substrates were obtained by treating a standard AgSENS with PVP at a moderate concentration to introduce a functional surface layer.The second aspect of this work centred on applying the PVP-treated silver substrate with significantly enhanced performance for the detection of DMDS above live E. coli bacteria. The effects of the concentration of the bacteria, as measured by the optical density (O.D.) of the bacteria and PVP on the intensity of methyl sulphide band were investigated and data showing rapid detection of antibiotic action by Gentamicin was obtained. Studies were carried out using both the previously established method where colonies are grown on agar and then transferred to the broth for further growth and on direct measurement of the headspace above colonies being cultured on agar in petri dishes. The time-limiting step for the detection of antibiotic susceptibility using conventional methods is waiting for the colonies to grow sufficiently large that the effect of the treatment can be determined. In the current work it was found that detection time could be reduced to as little as15 minutes. This is a significant improvement and the fact that automated detection could be implemented rapidly and without the need for expert human operators to analyze and interpret the culture results means this is a very promising approach.A second use for SERS in studies of bacteria is to directly analyse the compounds present in, or excreted from, bacteria. This has been pursued for many years with the objective of using the characteristic spectra to identify the species and/or strain of bacteria in the sample. In the current study, the work was concerned with identifying the origin of the bands in a large dataset of SERS spectra of > 100 bacteria which were collected by a previous PhD student in the QUB. The work centred on identifying a puzzling band at 1050 cm-1 that appears in the SERS spectra of whole bacteria and has previously been misinterpreted as being due to a component of the bacteria. The current study identified the source as nitrate ions that are present in the enhancing colloid due to the use of silver nitrate in the preparation. Further work on identifying features arising from artefacts and comparing spectra of possible components to spectra of bacteria allowed other major components within the spectra to be identified.
Thesis embargoed until 31st July 2027.","abstract_html":"The principal aim of this Ph.D. thesis was to develop new enhancing substrates for use in Surface-enhanced Raman Spectroscopy (SERS) for the rapid detection of live bacteria by analysis of the headspace above bacterial cultures. It is knownt hat in-situ SERS can be used to detect vapour phase dimethyl disulphide (DMDS), which is a metabolic product of live bacteria. The test experiments in this thesis were carried out in a model system which was the headspace above DMDS solutions. The measurements actually detect the characteristic bands from chemisorbed methyl sulphide which is created by dissociation of adsorbed DMDS on the surface of Ag and Au nanoparticles. A variety of enhancing substrates were used, the first were arrays of Ag and Au nanoparticles which were deposited on a glass substrate from a layer of nanoparticles trapped at a liquid/liquid interface (a so-called metal-like liquid film or MeLLF). These were contrasted with surface-exposed nanoparticle sheets (SENS) where a layer of particles was fixed to a polymer backing. These films showed the expected rise in signal over a timescale of minutes although the rate of adsorption was faster than previously observed. The general observation has been that Ag films give larger signals but slower responses while Au films respond more rapidly but give lower signal intensities. In order to enhance the performance of AgSENS, two different general approaches were applied. The first approach was to deposit an Au layer on the AgSENS in an attempt to increase the rate of chemisorption while retaining the enhancement of the underlying silver substrate. Both sputtering and Galvanic replacement was attempted but neither gave the hoped-for increase. The second approach was to prepare different Ag nanoparticles whose performance has been claimed to be superior to those used in the original studies. For this approach, Ag nanoparticles were prepared using ethylene glycol rather than traditional citrate reduction, along with polyvinyl pyrrolidone (PVP). The product nanowires gave very good SERS results. Further studies showed that it was the PVP that improved the rate of adsorption rather than particle shape and the best results for all substrates were obtained by treating a standard AgSENS with PVP at a moderate concentration to introduce a functional surface layer.The second aspect of this work centred on applying the PVP-treated silver substrate with significantly enhanced performance for the detection of DMDS above live E. coli bacteria. The effects of the concentration of the bacteria, as measured by the optical density (O.D.) of the bacteria and PVP on the intensity of methyl sulphide band were investigated and data showing rapid detection of antibiotic action by Gentamicin was obtained. Studies were carried out using both the previously established method where colonies are grown on agar and then transferred to the broth for further growth and on direct measurement of the headspace above colonies being cultured on agar in petri dishes. The time-limiting step for the detection of antibiotic susceptibility using conventional methods is waiting for the colonies to grow sufficiently large that the effect of the treatment can be determined. In the current work it was found that detection time could be reduced to as little as15 minutes. This is a significant improvement and the fact that automated detection could be implemented rapidly and without the need for expert human operators to analyze and interpret the culture results means this is a very promising approach.A second use for SERS in studies of bacteria is to directly analyse the compounds present in, or excreted from, bacteria. This has been pursued for many years with the objective of using the characteristic spectra to identify the species and/or strain of bacteria in the sample. In the current study, the work was concerned with identifying the origin of the bands in a large dataset of SERS spectra of > 100 bacteria which were collected by a previous PhD student in the QUB. The work centred on identifying a puzzling band at 1050 cm-1 that appears in the SERS spectra of whole bacteria and has previously been misinterpreted as being due to a component of the bacteria. The current study identified the source as nitrate ions that are present in the enhancing colloid due to the use of silver nitrate in the preparation. Further work on identifying features arising from artefacts and comparing spectra of possible components to spectra of bacteria allowed other major components within the spectra to be identified.<br/><br/><i>Thesis embargoed until 31st July 2027.</i>","abstract_has_math":false,"creators":["Alqarni, Zarah"],"institution":"Queen's University Belfast","degree_name":"Doctor of Philosophy","degree_level":"Doctoral Thesis","degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Bell, Steven","Tunney, Michael"],"committee_chairs":[],"committee_members":[],"year":2022,"date_issued":"2022-7","date_published":"2022-7","updated_at":"2026-07-24T03:56:18Z","subjects":["Surface-enhanced raman spectroscopy","SENS","bacteria detection","bactericidal antibiotics","PVP"],"languages":["eng"],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["oai:pure.qub.ac.uk/portal:studenttheses/a3e277dd-0a10-49cf-9db5-88e63d02a4fd"],"render_values":[{"text":"oai:pure.qub.ac.uk/portal:studenttheses/a3e277dd-0a10-49cf-9db5-88e63d02a4fd","href":null,"code":true}]}]},"links":{"outbound_url":"https://pure.qub.ac.uk/en/studentTheses/a3e277dd-0a10-49cf-9db5-88e63d02a4fd","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Bell, Steven","Tunney, Michael"]},{"key":"dc:contributor.sponsor","label":"Sponsor","values":["University of Jeddah"]},{"key":"dc:creator","label":"Author","values":["Alqarni, Zarah"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2022-7"]},{"key":"dc:date.issued","label":"Date","values":["2022-7"]},{"key":"dc:publisher.department","label":"Dc Publisher Department","values":["School of Chemistry and Chemical Engineering"]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["Queen's University Belfast"]},{"key":"dc:relation.isreferencedby","label":"Dc Relation Isreferencedby","values":["https://pure.qub.ac.uk/en/studentTheses/a3e277dd-0a10-49cf-9db5-88e63d02a4fd"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["Doctoral Thesis"]},{"key":"dc:type.qualificationname","label":"Dc Type Qualificationname","values":["Doctor of Philosophy"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Surface-enhanced raman spectroscopy","SENS","bacteria detection","bactericidal antibiotics","PVP"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights.embargodate","label":"Dc Rights Embargodate","values":["2027-07-31"]},{"key":"dc:rights.embargoreason","label":"Dc Rights Embargoreason","values":["/dk/atira/pure/core/document/studentthesisembargoreason/publicationissues"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["oai:pure.qub.ac.uk/portal:studenttheses/a3e277dd-0a10-49cf-9db5-88e63d02a4fd","https://pure.qub.ac.uk/en/studentTheses/a3e277dd-0a10-49cf-9db5-88e63d02a4fd"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://pure.qub.ac.uk/files/284500141/Thesis_deposit_form_zarah.pdf"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["The principal aim of this Ph.D. thesis was to develop new enhancing substrates for use in Surface-enhanced Raman Spectroscopy (SERS) for the rapid detection of live bacteria by analysis of the headspace above bacterial cultures. It is knownt hat in-situ SERS can be used to detect vapour phase dimethyl disulphide (DMDS), which is a metabolic product of live bacteria. The test experiments in this thesis were carried out in a model system which was the headspace above DMDS solutions. The measurements actually detect the characteristic bands from chemisorbed methyl sulphide which is created by dissociation of adsorbed DMDS on the surface of Ag and Au nanoparticles. A variety of enhancing substrates were used, the first were arrays of Ag and Au nanoparticles which were deposited on a glass substrate from a layer of nanoparticles trapped at a liquid/liquid interface (a so-called metal-like liquid film or MeLLF). These were contrasted with surface-exposed nanoparticle sheets (SENS) where a layer of particles was fixed to a polymer backing. These films showed the expected rise in signal over a timescale of minutes although the rate of adsorption was faster than previously observed. The general observation has been that Ag films give larger signals but slower responses while Au films respond more rapidly but give lower signal intensities. In order to enhance the performance of AgSENS, two different general approaches were applied. The first approach was to deposit an Au layer on the AgSENS in an attempt to increase the rate of chemisorption while retaining the enhancement of the underlying silver substrate. Both sputtering and Galvanic replacement was attempted but neither gave the hoped-for increase. The second approach was to prepare different Ag nanoparticles whose performance has been claimed to be superior to those used in the original studies. For this approach, Ag nanoparticles were prepared using ethylene glycol rather than traditional citrate reduction, along with polyvinyl pyrrolidone (PVP). The product nanowires gave very good SERS results. Further studies showed that it was the PVP that improved the rate of adsorption rather than particle shape and the best results for all substrates were obtained by treating a standard AgSENS with PVP at a moderate concentration to introduce a functional surface layer.The second aspect of this work centred on applying the PVP-treated silver substrate with significantly enhanced performance for the detection of DMDS above live E. coli bacteria. The effects of the concentration of the bacteria, as measured by the optical density (O.D.) of the bacteria and PVP on the intensity of methyl sulphide band were investigated and data showing rapid detection of antibiotic action by Gentamicin was obtained. Studies were carried out using both the previously established method where colonies are grown on agar and then transferred to the broth for further growth and on direct measurement of the headspace above colonies being cultured on agar in petri dishes. The time-limiting step for the detection of antibiotic susceptibility using conventional methods is waiting for the colonies to grow sufficiently large that the effect of the treatment can be determined. In the current work it was found that detection time could be reduced to as little as15 minutes. This is a significant improvement and the fact that automated detection could be implemented rapidly and without the need for expert human operators to analyze and interpret the culture results means this is a very promising approach.A second use for SERS in studies of bacteria is to directly analyse the compounds present in, or excreted from, bacteria. This has been pursued for many years with the objective of using the characteristic spectra to identify the species and/or strain of bacteria in the sample. In the current study, the work was concerned with identifying the origin of the bands in a large dataset of SERS spectra of > 100 bacteria which were collected by a previous PhD student in the QUB. The work centred on identifying a puzzling band at 1050 cm-1 that appears in the SERS spectra of whole bacteria and has previously been misinterpreted as being due to a component of the bacteria. The current study identified the source as nitrate ions that are present in the enhancing colloid due to the use of silver nitrate in the preparation. Further work on identifying features arising from artefacts and comparing spectra of possible components to spectra of bacteria allowed other major components within the spectra to be identified.
Thesis embargoed until 31st July 2027."]},{"key":"dc:title","label":"Title","values":["Development of novel metal nanoparticle based methods for detection of bacteria using surface-enhanced Raman spectroscopy"]}]}],"canonical_facts":{"dc:contributor.advisor":["Bell, Steven","Tunney, Michael"],"dc:contributor.sponsor":["University of Jeddah"],"dc:creator":["Alqarni, Zarah"],"dc:date":["2022-7"],"dc:date.issued":["2022-7"],"dc:description.abstract":["The principal aim of this Ph.D. thesis was to develop new enhancing substrates for use in Surface-enhanced Raman Spectroscopy (SERS) for the rapid detection of live bacteria by analysis of the headspace above bacterial cultures. It is knownt hat in-situ SERS can be used to detect vapour phase dimethyl disulphide (DMDS), which is a metabolic product of live bacteria. The test experiments in this thesis were carried out in a model system which was the headspace above DMDS solutions. The measurements actually detect the characteristic bands from chemisorbed methyl sulphide which is created by dissociation of adsorbed DMDS on the surface of Ag and Au nanoparticles. A variety of enhancing substrates were used, the first were arrays of Ag and Au nanoparticles which were deposited on a glass substrate from a layer of nanoparticles trapped at a liquid/liquid interface (a so-called metal-like liquid film or MeLLF). These were contrasted with surface-exposed nanoparticle sheets (SENS) where a layer of particles was fixed to a polymer backing. These films showed the expected rise in signal over a timescale of minutes although the rate of adsorption was faster than previously observed. The general observation has been that Ag films give larger signals but slower responses while Au films respond more rapidly but give lower signal intensities. In order to enhance the performance of AgSENS, two different general approaches were applied. The first approach was to deposit an Au layer on the AgSENS in an attempt to increase the rate of chemisorption while retaining the enhancement of the underlying silver substrate. Both sputtering and Galvanic replacement was attempted but neither gave the hoped-for increase. The second approach was to prepare different Ag nanoparticles whose performance has been claimed to be superior to those used in the original studies. For this approach, Ag nanoparticles were prepared using ethylene glycol rather than traditional citrate reduction, along with polyvinyl pyrrolidone (PVP). The product nanowires gave very good SERS results. Further studies showed that it was the PVP that improved the rate of adsorption rather than particle shape and the best results for all substrates were obtained by treating a standard AgSENS with PVP at a moderate concentration to introduce a functional surface layer.The second aspect of this work centred on applying the PVP-treated silver substrate with significantly enhanced performance for the detection of DMDS above live E. coli bacteria. The effects of the concentration of the bacteria, as measured by the optical density (O.D.) of the bacteria and PVP on the intensity of methyl sulphide band were investigated and data showing rapid detection of antibiotic action by Gentamicin was obtained. Studies were carried out using both the previously established method where colonies are grown on agar and then transferred to the broth for further growth and on direct measurement of the headspace above colonies being cultured on agar in petri dishes. The time-limiting step for the detection of antibiotic susceptibility using conventional methods is waiting for the colonies to grow sufficiently large that the effect of the treatment can be determined. In the current work it was found that detection time could be reduced to as little as15 minutes. This is a significant improvement and the fact that automated detection could be implemented rapidly and without the need for expert human operators to analyze and interpret the culture results means this is a very promising approach.A second use for SERS in studies of bacteria is to directly analyse the compounds present in, or excreted from, bacteria. This has been pursued for many years with the objective of using the characteristic spectra to identify the species and/or strain of bacteria in the sample. In the current study, the work was concerned with identifying the origin of the bands in a large dataset of SERS spectra of > 100 bacteria which were collected by a previous PhD student in the QUB. The work centred on identifying a puzzling band at 1050 cm-1 that appears in the SERS spectra of whole bacteria and has previously been misinterpreted as being due to a component of the bacteria. The current study identified the source as nitrate ions that are present in the enhancing colloid due to the use of silver nitrate in the preparation. Further work on identifying features arising from artefacts and comparing spectra of possible components to spectra of bacteria allowed other major components within the spectra to be identified.
Thesis embargoed until 31st July 2027."],"dc:identifier":["oai:pure.qub.ac.uk/portal:studenttheses/a3e277dd-0a10-49cf-9db5-88e63d02a4fd","https://pure.qub.ac.uk/en/studentTheses/a3e277dd-0a10-49cf-9db5-88e63d02a4fd"],"dc:identifier.uri":["https://pure.qub.ac.uk/files/284500141/Thesis_deposit_form_zarah.pdf"],"dc:language":["eng"],"dc:publisher.department":["School of Chemistry and Chemical Engineering"],"dc:publisher.institution":["Queen's University Belfast"],"dc:relation.isreferencedby":["https://pure.qub.ac.uk/en/studentTheses/a3e277dd-0a10-49cf-9db5-88e63d02a4fd"],"dc:rights.embargodate":["2027-07-31"],"dc:rights.embargoreason":["/dk/atira/pure/core/document/studentthesisembargoreason/publicationissues"],"dc:subject":["Surface-enhanced raman spectroscopy","SENS","bacteria detection","bactericidal antibiotics","PVP"],"dc:title":["Development of novel metal nanoparticle based methods for detection of bacteria using surface-enhanced Raman spectroscopy"],"dc:type":["Thesis"],"dc:type.qualificationlevel":["Doctoral Thesis"],"dc:type.qualificationname":["Doctor of Philosophy"]},"updated_at":"2026-07-24T03:56:18Z"}