Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.747148
Title: Development of nanostructures materials for detection of ultra-trace levels of explosives based on Surface-Enhanced Raman Spectroscopy (SERS)
Author: Ben Jaber, Sultan Saeed
ISNI:       0000 0004 7228 601X
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2017
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Abstract:
The detection of explosives and their derivatives is crucial for security, defence and safety. However, detection of low levels and vapour phase of explosives are a serious challenge for forensic practitioners. Scientists and researchers continue to improve sensitive detection methods with reasonable cost and portability. One of the promising techniques for such applications is Surface Enhanced Raman spectroscopy (SERS) due to its high sensitivity and ease of use. Several approaches were applied to improve the sensitivity of explosives detection based on the SERS technique. A wide range of materials were prepared, characterized and used as SERS substrates, including metals such as gold, silver, copper nanostructures, and semiconductors such as TiO2, ZnO. SERS activity of these materials was evaluated, and high quality detection of explosives was achieved at ultra-trace levels. Sensors with high selectivity, reproducibility, reusability and low limit of detection LOD were made. A new sensitive method for enhancement of Raman signals was demonstrated, whereby pre-irradiation (photo-excitation) of a semiconductor such as TiO2 coated with gold/silver nanoparticles, enables strong Raman enhancement at the nanoparticle sites, increasing sensitivity beyond the normal SERS effect. We call this effect photo-induced enhanced Raman spectroscopy— PIERS. In this system the molecules can be directly adsorbed onto the metallic particle, allowing controlled enhancement by both the electromagnetic and chemical enhancement factor. Various analytes were detected by PIERS including dyes, explosives and biomolecules with high sensitivity, reproducibility, and the substrate was reusable for self-cleaning by UV-irradiation. Further investigations were carried out for photo-induced enhancement including creation of oxygen vacancies on semiconductors surface by annealing in vacuum and etching, and a series of SERS measurements were performed of molecules on treated substrates. Silver nanocubes showed high SERS sensitivity of explosives with good specificity, and showed an important role for the preparation of SERS samples. The shape of AgNC contributed significantly to obtained high SERS enhancement. SERS measurements of vapour explosives were performed and showed to be an order of magnitude greater than reported enhancement, where the detection specificity was strongly improved. Free-metal ZnO nanostructures showed charge transfer enchantment, where ZnO nanocrystals exhibited better enhancement than ZnO thin films. The enhancement is further improved in the presence of copper species in the ZnO thin film structure.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.747148  DOI: Not available
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