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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
441

Applications of Raman spectroscopic techniques in forensic and security contexts : the detection of drugs of abuse and explosives in scenarios of forensic and security relevance using benchtop and portable Raman spectroscopic instrumentation

Ali, Esam Mohamed Abdalla January 2010 (has links)
Drug trafficking and smuggling is an ongoing challenge for law enforcement agencies. Cocaine smuggling is a high-value pursuit for smugglers and has been attempted using a variety of concealment methods including the use of bottled liquids, canned milk, wax and suspensions in cans of beer. In particular, traffickers have used clothing impregnated with cocaine for smuggling. Handling, transportation or re-packaging of drugs of abuse and explosives will inevitably leave residual material on the clothing and other possessions of the involved persons. The nails and skin of the person may also be contaminated through the handling of these substances. This research study describes the development of Raman spectroscopic techniques for the detection of drugs of abuse and explosives on biomaterials of forensic relevance including undyed natural and synthetic fibres and dyed textile specimens, nail and skin. Confocal Raman microscopy has been developed and evaluated for the detection and identification of particulates of several drugs of abuse and explosives on different substrates. The results show that excellent spectroscopic discrimination can be achieved between single particles and substrate materials, giving a ubiquitous non-destructive approach to the analysis of pico-gram quantities of the drugs and explosives in-situ. Isolating the particle in this way corresponds with an analytical sensitivity comparable with the most sensitive analytical techniques currently available e.g. the highly sensitive, yet destructive ionization desorption mass spectrometry. With the confocal Raman approach, this work demonstrates that definitive molecular-specific information can be achieved within seconds without significant interference from the substrate. The potential for the application of this technique as a rapid preliminary, forensic screening procedure is obvious and attractive to non-specialist operators as it does not involve prior chemical pretreatment ii or detachment of the analyte from the substrate. As a result, evidential materials can be analysed without compromising their integrity for future investigation. Also, the applications of benchtop and portable Raman spectroscopy for the in-situ detection of drugs of abuse in clothing impregnated with the drugs have been demonstrated. Raman spectra were obtained from a set of undyed natural and synthetic fibres and dyed textiles impregnated with these drugs. The spectra were collected using three Raman spectrometers; one benchtop dispersive spectrometer coupled to a fibre-optic probe and two portable spectrometers. High quality spectra of the drugs could be acquired in-situ within seconds and without any sample preparation or alteration of the evidential material. A field-portable Raman spectrometer is a reliable instrument that can be used by emergency response teams to rapidly identify unknown samples. This method lends itself well to further development for the in-situ examination by law enforcement officers of items associated with users, handlers and suppliers of drugs of abuse in the forensics arena. In the last section of this study, a portable prototype Raman spectrometer ( DeltaNu Advantage 1064) equipped with 1064 nm laser excitation has been evaluated for the analysis of drugs of abuse and explosives. The feasibility of the instrument for the analysis of the samples both as neat materials and whilst contained in plastic and glass containers has been investigated. The advantages, disadvantages and the analytical potential in the forensics arena of this instrument have been discussed.
442

Raman spectroscopic application for the analysis of organic compounds and minerals of astrobiological significance : the detection and discrimination of organic compounds and mineral analogues in pure and mixed samples of astrobiological significance using raman spectroscopy, XRD and scanning electron microscopy

Alajtal, Adel Imhemed January 2010 (has links)
Raman spectroscopy has been used to characterise both organic and geological samples in order to build a database for the future characterization of biomarker molecules that are of astrobiological relevance. Characteristic geological features and hydrated minerals recently found on the surface of Mars by the NASA planetary rovers Spirit and Opportunity suggest that a possible biosphere could have once existed there. Analytical instrumentation protocols for the unequivocal detection of biomarkers in suitable geological matrices are critical for future unmanned explorations, including the forthcoming ESA ExoMars mission scheduled for 2018. Several geological features found on the surface of Mars by planetary rovers suggest that a possible extinct biosphere could exist based on similar sources of energy as occurred on Earth. For this reason, analytical instrumental protocols for the detection of isolated biomarkers preserved in suitable geological matrices unequivocally and non-destructively have to be evaluated for future unmanned missions. Raman spectroscopy is currently part of the Pasteur instrumentation suite of the ExoMars mission for the remote detection of extant or extinct life signatures in the Martian surface and subsurface. Terrestrial analogues of Martian sites have been identified and the biogeological modifications resulting from extremophilic survival activity have been studied. Here we present the Raman spectral characterization of several examples of organic compounds which have been recorded using 785 nm, 633 nm and 514 nm laser excitation -polycyclic aromatic hydrocarbons (PAHs), organic acids, chlorophyll and carotenoids. Experimental mixtures of ß-carotene in usnic acid, PAHs in usnic acid and PAHs in mineral matrices have also been investigated. Organic compounds and PAHs located under crystalline minerals samples were identified using a 5x objective lens and 785 nm III excitation. The pure compounds and compound mixtures were also analysed using X-ray powder diffraction and scanning electron microscopy (SEM). The results of this study indicate that near infrared laser at 785 nm provided the clearest and the most informative spectra due to the reduction of fluorescence emission. Higher energy lasers operating in the visible region have resulted in the emission of significant background fluorescence. Few samples fluoresce even with the use of 785 nm excitation and FT-Raman spectroscopy remains the instrument of choice for the analysis of these samples.
443

Time-resolved resonance Raman investigation of selected para-substituted phenylnitrenium ions and the 2-fluorenylnitrenium ionreaction with guanosine

Chan, Pik-ying., 陳碧瑩. January 2005 (has links)
published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy
444

Time-resolved resonance raman and density functional theory studies ofselected arylnitrenium ions and their reactions with guanosinederivatives and aryl azides

Xue, Jiadan., 薛佳丹. January 2008 (has links)
published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy
445

Development of new polymer-supported reagents for organic synthesis, solvent effects in samarium promoted allylic alcohol cyclopropanationreactions and time resolved resonance studies of the photodeprotectionof p-hydroxyphenacyl caged phototrigger compounds

Kan, Tze-wai, Jovi., 簡紫慧. January 2006 (has links)
published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy
446

Time-resolved resonance raman and density functional theory studies ofthe photochemistry of (S)-ketoprofen

Chuang, Yung-ping., 莊蓉萍. January 2008 (has links)
published_or_final_version / Chemistry / Master / Master of Philosophy
447

Coherent Raman studies of optical nonlinearities in conjugated molecules and polymers

Atherton, Kathryn Jane January 1997 (has links)
No description available.
448

Investigation of Deterioration Mechanisms of Cellulose Acetate Compounded with Triphenyl Phosphate

McGath, Molly Kathleen January 2012 (has links)
The mechanisms of the deterioration of cellulose acetate compounded with triphenyl phosphate were investigated. A key peak shift of 726cm⁻¹ to 718cm⁻¹ in the Raman spectrum of triphenyl phosphate (726cm-1 uncompounded) when compounded in cellulose acetate (718cm⁻¹) was tied to the action of C-O bonds in triphenyl phosphate. The molecular bonds responsible for the 726cm⁻¹ peak were identified by collecting and examining spectra of chemicals with functional groups similar to triphenyl phosphate. Initially it was hypothesized that triphenyl phosphate acts as nucleophilic catalyst of deacetylation. This mechanism was evaluated by dissolving triphenyl phosphate in solvents that served as functional group analogues of cellulose acetate. These liquid-solution systems have a faster rate of reaction and complete mixing with triphenyl phosphate compared with what is seen in cellulose acetate solid-solution systems. The results of the cellulose acetate analogue experiments did not support the hypothesis of triphenyl phosphate acting as a nucleophilic catalyst of deacetylation. The results instead support a new theory of deterioration induced by the recrystallization of triphenyl phosphate. Additionally, the prevailing theory of triphenyl phosphate induced deterioration as proposed by Shinagawa et al. in 1992 was reviewed. The experiments conducted here do not support Shinagawa's theory.
449

Nucleation, growth and acoustic properties of thin film diamond

Whitfield, Michael David January 1999 (has links)
No description available.
450

Application of a charge coupled device Raman microscope imaging system for quantitative analysis of aqueous surfactant phases

Millichope, Allen John January 2000 (has links)
No description available.

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