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Dissertations / Theses on the topic 'Raman spectroscopy. Nanostructured materials'
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Osswald, Sebastian Gogotsi IU G. Scharff Peter. "In situ raman spectroscopy study of oxidation of nanostructured carbons /." Philadelphia, Pa. : Drexel University, 2008. http://hdl.handle.net/1860/2972.
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Calizo, Irene Gonzales. "Raman nanometrology of graphene." Diss., [Riverside, Calif.] : University of California, Riverside, 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3359892.
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Thesis (Ph. D.)--University of California, Riverside, 2009.Includes abstract. Available via ProQuest Digital Dissertations. Title from first page of PDF file (viewed March 8, 2010). Includes bibliographical references (p. 59-64). Also issued in print.
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White, Daniel Joshua. "Nanostructured optical fibre for use as miniature surface-enhanced raman scattering sensors." Swinburne Research Bank, 2008. http://hdl.handle.net/1959.3/42062.
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Thesis (PhD) - Swinburne University of Technology, Centre for Atom Optics and Ultrafast Spectroscopy, 2007.Thesis submitted in fulfilment for the degree of Doctor of Philosophy, Centre for Atom Optics and Ultrafast Spectroscopy, Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, 2008. Typescript. Bibliography: p. 151-160.
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Lee, Nam-Heui. "Extending Raman spectroscopy to the nanoscale." Akron, OH : University of Akron, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1172680006.
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Dissertation (Ph. D.)--University of Akron, Dept. of Polymer Science, 2007."May, 2007." Title from electronic dissertation title page (viewed 04/07/2008) Advisor, Mark D. Foster; Committee members, Alexei P. Sokolov, Darrell H. Reneker, Ali Dhinojwala, Rex D. Ramsier; Department Chair, Mark D. Foster; Dean of the College, George R. Newkome; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.
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Wieligor, Monika Katarzyna. "Characterization of planar defects in silicon carbide nanowires." [Fort Worth, Tex.] : Texas Christian University, 2010. http://etd.tcu.edu/etdfiles/available/etd-04292010-110338/unrestricted/Wieligor.pdf.
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Lawson, Thomas Ryan. "Micro-Raman spectroscopy and dry turning evaluations of nanostructured diamond films deposited on tungsten-carbide lathe inserts." Birmingham, Ala. : University of Alabama at Birmingham, 2008. https://www.mhsl.uab.edu/dt/2008m/lawson.pdf.
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Leyva, García Sarai. "Advanced nanostructured carbon materials for electrochemical energy storage devices: supercapacitors and micro-capacitors." Doctoral thesis, Universidad de Alicante, 2016. http://hdl.handle.net/10045/65694.
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Ghosh, Suchismita. "Thermal conduction in graphene and graphene multilayers." Diss., [Riverside, Calif.] : University of California, Riverside, 2009. http://proquest.umi.com/pqdweb?index=0&did=1957308711&SrchMode=2&sid=2&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1268427434&clientId=48051.
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Thesis (Ph. D.)--University of California, Riverside, 2009.Includes abstract. Available via ProQuest Digital Dissertations. Title from first page of PDF file (viewed March 12, 2010). Includes bibliographical references (p. 96-107). Also issued in print.
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Ben, Jaber Sultan Saeed. "Development of nanostructures materials for detection of ultra-trace levels of explosives based on Surface-Enhanced Raman Spectroscopy (SERS)." Thesis, University College London (University of London), 2017. http://discovery.ucl.ac.uk/10040377/.
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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.
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Zhou, Xuan. "Advances in hybrid plasmonics : from passive to active functions." Thesis, Troyes, 2013. http://www.theses.fr/2013TROY0015/document.
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La plasmonique hybride est un sujet d’actualité qui exploite des interactions physiques entre nano-objets métalliques et d’autres nanomatériaux. En bénéficiant des propriétés de chacun de leurs constituants, les nanostructures hybrides sont utilisées dans de nombreuses applications comme la détection d’espèces bio-chimiques. Dans cette thèse, nous présentons une nouvelle nanostructure hybride polymère/metal qui est non seulement utilisée comme nano-émetteur anisotrope qui s’avère aussi être un outil puissant de caractérisation du champ proche optique.La fabrication de cette nouvelle nanostructure est basée sur une approche de par photopolymérisation à l’échelle nanométrique. Cette technique, en comparaison aux méthodes traditionnelles de caractérisation, ne fournit pas seulement l’image de la distribution du champ, mais permet aussi des mesures quantitatives des plasmons de surface avec une résolution sub -5nm, incluant une description fine de la décroissance exponentielle des ondes évanescentes impliquées.A l’aide du mode plasmon dipolaire, une distribution anisotrope de matériau organique est intégrée dans le voisinage de la nanoparticule métallique. Avec une haute concentration de molécules de colorant dans le polymère, l’intensité des signaux de fluorescence et Raman du nano-émetteur hybride dépend de la polarisation incidente. À notre connaissance, il s’agit de la première réalisation d’un nano-émetteur dont le milieu à gain présente une distribution spatiale complexe le rendant sensible à la polarisationHybrid plasmonics has given rise to increasing interest in the context of the interaction between metal nano-objects and other materials. By benefiting from each of its constituents, hybrid nanostructures are commonly adopted in studies and optimization of biological and chemical sensors, nanoparticle with high plasmon resonance tunability, and nano-emitters. This PhD thesis presents a hybrid nanostructure of photopolymer/metal nanoparticle that is used as a near-field characterizing tool and as an anisotropic nano-emitter.The fabrication of this hybrid nanostructure is a near-field imprinting process based on nanoscale photopolymerization. This technique, compared with traditional near-field characterization methods, provides not only the image of the field distribution, but also enables quantification of the surface plasmon properties with sub-5nm resolution and reproduction of the exponential decay of the near-field.Under dipolar mode plasmon, the photopolymer was created anisotropically in the vicinity of the metal nanoparticle. With high concentration of dye molecules trapped in the polymer, the hybrid nano-emitter displays surface enhanced fluorescence and Raman signal that is dependent on the incident polarization. To our knowledge, this is the first achievement of the anisotropic nano-emitter based on the inhomogeneous distribution of the active molecule
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Domènech, i. Amador Núria. "Phonons in III-nitride thinfilms, bulk and nanowires: a closer look into InN vibrational properties." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/348867.
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This thesis is devoted to the study of the interactions of phonons in indium nitride (InN) and materials of the (In,Ga)N system with wurtzite structure. For this purpose, we present Raman spectroscopy on nanowires (NWs), thin films and bulk samples, in order to adress phonon interactions in these materials. We also present Brillouin spectrsocopy measurements of InN thin films, from which a reliable set of elastic constants is proposed.
We have studied the phonon anharmonic interactions and phonon decay channels of InN, both in thin films and NWs. The temperature dependence of Raman peak width of all the phonon modes has been studied using a model that considers the contribution of three- and four-phonon processes, taking into account the phonon density of states obtained by ab-initio calculations.
In InN thin films, we find that the E2h phonon mode mainly decays through 4-phonon processes, whereas the extremely narrow E2l mode can decay only through up-conversion processes. The LO and the TO modes are found to decay through 3-phonon and 4-phonon interactions. In InN NWs we found the same phonon decay channels but phonon linewidths are significantly reduced, indicating a higher crystalline quality. The lifetimes of the phonon modes are derived from the measured phonon linewidths. The long-lived E2l phonon exhibits the largest lifetime, which is mainly limited by impurity scattering. We also study the anharmonic decay of high-frequency LVMs H complexes in Mg-doped InN, which can be explained by considering dephasing due to quasi-elastic acoustic phonon scattering.
We have discussed the relevant electronic resonances that affect Raman scattering in the (In,Ga)N system. We show that the optical excitation of the longitudinal optical modes in InN occurs via the Martin's double resonance both in InN layers and nanostructures, even though the defect density of the latter is significantly lower. By performing wavelength-dependent measurements on InN thin films and NWs, the A1(LO) and the E1(LO) wave-vector dispersion close to zone-center have been obtained. We have also studied the impurity-mediated cascade mechanism of multiphonons in InGaN layers. To ascertain the role of the impurities we have studied as-grown samples in comparison with He+-implanted InGaN layers. UV Raman-scattering measurements allow us to measure up to fifth order multiphonon scattering due to cascade mechanism. Relative multiphonon intensities depend on the indium concentration and implantation dose.
Finally, we have studied the LO-Phonon-Plasmon Coupled Modes (LOPCMs) in InN and GaN using the Lindhard-Mermin model. We have determined the electron density in undoped, Si-doped and Mg-doped NWs. We have also studied a bulk, ammonothermally-grown Si-doped GaN sample. No evidence of LOPCMs was detected in the Ga-polar face, probably due to the higher defect density existing in this sample sector. We have detected both branches of the LOPCMs in the N-polar face, and we have made a study of the distribution of the free charge density by means of confocal micro-Raman measurements.Aquesta tesi està dedicada a l’estudi de les interaccions dels fonons en nitrur d'indi (InN) i en semiconductors del sistema (In.Ga)N amb estructura wurtzita. Amb aquest objectiu es presenten estudis d'espectroscòpia Raman en capes primes, nanofils (NWs), i mostres bulk, que han permès abordar de manera global les interaccions dels fonons en aquests materials. Hem estudiat les interaccions anharmòniques i els canals de decaïment dels fonons de InN, tant en capes primes com en NWs. La dependència de l’amplada del pic Raman amb la temperatura de tots els modes fonònics s’ha estudiat utilitzant un model anharmònic que considera la contribució dels processos de tres i quatre fonons, i tenint en compte la densitat d'estats de fonons obtinguda mitjançant càlculs ab-initio. L'anàlisi dels temps de vida fonònics i de la dependència amb temperatura de les freqüències permet afirmar que els NWs tenen una estructura més relaxada que les capes primes. També hem estudiat el decaïment anharmònic de modes locals de vibració corresponents a complexos d'H en InN fortament dopat amb Mg. Hem estudiat les ressonàncies en el sistema (In,Ga)N i la influència de la densitat d’impureses en l’eficiència dels mecanismes ressonants. Hem demostrat que la dispersió Raman de modes òptics longitudinals en el InN es produeix a través de la doble ressonància del Martin tant en capes primer com en nanoestructures, tot i que la densitat de defectes d'aquestes últimes és significativament menor. Hem estudiat també el mecanisme de cascada mediat per impureses, a través del qual es produeix la dispersió de multifonons, en capes primes de InGaN amb diferent composició i diferent grau d’implantació d'ions d'He, i hem comprovat que les intensitats relatives dels multifonons depenen de la concentració d’indi i de la dosi de la implantació. Finalment, hem estudiat l’acoblament de fonons polars amb els plasmons mitjançant el model dielèctric de Lindhard-Mermin, amb la finalitat d’investigar la densitat d’electrons lliures utilitzant espectroscòpia Raman. Hem determinat la concentració d'electrons en NWs de InN sense dopar, dopats amb Si i dopats amb Mg. També hem fet un estudi de la distribució de la densitat de càrrega en una mostra de GaN ammonotermal mitjançant mesures de micro-Raman confocal.
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Vanacore, Giovanni Maria. "INVESTIGATION OF Ge SURFACE DIFFUSION AND SiGe NANOSTRUCTURES BY SPECTRO-MICROSCOPY TECHNIQUES." Phd thesis, Ecole Polytechnique X, 2011. http://tel.archives-ouvertes.fr/tel-00725427.
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SiGe nanostructures on crystalline Si substrates with (001) orientation are among the most studied system in condensed matter physics and nanoscience. This interest has been mainly driven by the important potential applications in opto and nano-electronic devices thanks to the improvement of the optical and electronic properties compared to bulk systems. These features come essentially from the possibility of engineering the strain field within the nanostructures using the lattice mismatch of ~ 4 % between Ge and Si and from the spatial confinement, capable of modifying the electronic band structure leading to an increase of the charge carrier mobility. It is obvious that these applications largely depend on the control of surface processes during the growth of the nanostructures, and their performance are strongly dependent on strain relaxation and dislocation injection. Besides the technological interest, the SiGe/Si(001) system has received much attention since it is also a model for understanding the fundamental processes occurring during 3D island formation and self-organization phenomena. In fact, the lattice mismatch between Ge and Si introduces a stress field which has dramatic effects on the growth process and is responsible for a number of structural and electronic phenomena. In particular, the stored elastic energy can be partially relieved by spontaneous formation of 3D objects of nanometric size on top of a pseudomorphic SiGe wetting layer. This growth mode, called Stranski-Krastanov (SK), is a way of easily forming self-assembled nanostructures, which can be used to obtain quantum confinement of charge carriers in nanoelectronics device applications. In recent years, considerable efforts have been devoted to the growth of hetero-epitaxial SiGe nanostructures with well controlled size, shape and positioning, and with defined stoichiometry and strain state. However, some aspects still need to be addressed for a complete understanding of this system, including: (i) the competition between kinetic and thermodynamic factors for island formation, (ii) the mechanisms governing the relative growth of individual nanostructures, (iii) the interplay between SiGe intermixing and strain relaxation mechanisms. In the present work, we carry out an experimental investigation of the relationship between morphology, elemental composition, strain state and electronic structure of self-assembled and lithographically defined SiGe nanostructures by means of several spectro-microscopy techniques. The Si and Ge diffusion dynamics and the self-organization phenomena during the growth of SiGe islands have been studied by Scanning Auger Microscopy (SAM) and Atomic Force Microscopy (AFM). Micro-Raman, SAM and Scanning Transmission Electron Microscopy coupled with Electron Energy Loss Spectroscopy (STEM-EELS) techniques have been used for the investigation of the interplay between strain relaxation mechanisms and SiGe intermixing in self-assembled islands. The effects of strain and composition on the electronic band structure in lithographically defined SiGe nanostructures, in layout very close to those used in prototype devices, have been characterized with nanoscale spatial resolution joining information from Tip Enhanced Raman Spectroscopy (TERS), nanofocused X-Ray Diffraction (XRD) and Energy-Filtered PhotoElectron Emission Microscopy (PEEM). The thesis is conceptually divided in two main parts: the first, to which belong Chapters 1, 2 and 3, deals with the experimental investigation of the Ge surface diffusion and of the self-organization phenomena of SiGe islands grown in a bottom-up approach; the second, including Chapters 4 and 5, is based on the experimental characterization of the strain state and of the strain-induced effects on the electronic band structure of lithographically defined SiGe nanostructures obtained in a top-down approach Chapter 1 presents an overview on the basic processes occurring during hetero-epitaxial growth of thin solid films. In the Chapter 2 the surface diffusion of Ge on a clean and C covered Si(001) surface promoted by annealing at high temperatures in UHV of pure Ge stripes is experimentally investigated by means of in-situ Scanning Auger Microscopy. The influence of a controlled carbon coverage on the Ge surface diffusion is quantitatively studied, showing that the diffusion coefficient presents a strong dependence on carbon coverage (see Fig. 1(a)). Chapter 3 deals with the experimental investigation of the growth process of self-assembled SiGe islands on Si(001) (see Fig. 1(b)). From the size and density evolution exhibited by the nucleated islands, we propose a scenario where the island growth is essentially driven by kinetic factors within a diffusion limited regime. Finally, we investigated the interplay among SiGe intermixing and plastic relaxation, showing that the surface thermal diffusion growth method leads to the formation of coherent islands (dislocation-free), as shown in Fig. 1(c), larger than those attainable by MBE and CVD. Chapter 4 presents the mapping with nanoscale resolution of strain, composition, local work function and valence band structure of lithographically defined SiGe embedded nano-stripes using TERS and Energy-Filtered PEEM (see Fig. 1(d) showing the Ge concentration mapping of the nano-stripes as obtained by PEEM analysis). In Chapter 5 are presented the first results of a direct characterization of the strain state of lithographically defined SiGe nano-ridges using the recently developed nanofocused XRD technique. The work presented in this thesis is the outcome of an experimental PhD research project developed at the Politecnico di Milano (Milano, Italy) in co-tutorship with the École Polytechnique (Paris, France) and the French Atomic Energy Commission (CEA-Saclay, France). SAM and AFM have been performed at Department of Physics of the Politecnico di Milano. Micro-Raman Spectroscopy has been carried out at the Materials Science Department of the Università Milano-Bicocca. PEEM measurements have been realized at CEA and during two standard experimental runs at the TEMPO beamline of SOLEIL Synchrotron (France). TERS and preliminary TEM analysis have been performed at the École Polytechnique, while more extensive TEM and STEM-EELS measurements have been developed at IMM-CNR in Catania. The nano-XRD experiment has been carried out during a standard experimental run at ID13 beamline of the European Synchrotron Radiation Facility (ESRF). The close collaboration with the laboratory L-NESS in Como made available the set of the lithographically-defined investigated samples. The experimental results have been exploited in close collaboration with a theory group at the Materials Science Department of the Università Milano-Bicocca for a deeper insight into the atomic level mechanisms during island growth process.
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Hartschuh, Ryan D. "Optical Spectroscopy of Nanostructured Materials." University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1195016254.
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Malkovskiy, Andrey Victorovich. "Light Scattering of Nanostructured Materials." University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1303760576.
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Farhat, Hootan. "Raman spectroscopy of metallic carbon nanotubes." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/59217.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2010.Includes bibliographical references (p. 101-108).
Metallic carbon nanotubes are one dimensional conductors that are both technologically promising for electronic applications, and scientifically interesting for studying the physics of low dimensional materials. In this thesis, we present a detailed study of the inelastic light scattering (Raman) spectrum of individual metallic carbon nanotubes, with a focus on the influence of electronic excitations and charged carriers. We have demonstrated that the frequency and linewidth of certain phonon modes of metallic carbon nanotubes depend strongly the Fermi energy, because they couple strongly to low lying electron hole pairs. Next, we report the first experimental observation of electronic Raman scattering in carbon nanotubes. This observation demonstrates that the same electron-hole pairs that participate in damping the optical phonons of metallic carbon nanotubes, may themselves scatter light, thus giving rise to an electronic Raman spectrum. An analysis of the Fermi level and laser energy dependence of the electronic Raman and phonon Raman contributions allows us to explain the asymmetric lineshape of the G-band phonon modes in terms of a Fano interference. In another experiment, we have shown that the charge-induced expansion and contraction of the the graphitic C-C bond length is different for metallic and semiconducting nanotubes. Finally, we have measured the Stokes and antiStokes intensities of the Raman modes in electrically contacted metallic nanotubes in order to determine their phonon populations during high-field electrical transport. The experiments reported here, have helped to clarify the origin of several features in the Raman spectra of metallic carbon nanotubes that have been heavily debated in recent years. These result also shed light on the way electronic excitations and charged carriers affect the physical properties of metallic carbon nanotubes.
by Hootan Farhat.
Ph.D.
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Bowmar, Paul. "Optical spectroscopy of novel materials." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259758.
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Jones, Catherine Helen. "Fourier transform Raman spectroscopy of some polymeric materials." Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358428.
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Brooks, Thomas Michael Brinten. "Condition assessment of Kevlar composite materials using Raman spectroscopy." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/5052.
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Thesis (M.S.)--University of Missouri-Columbia, 2007.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 9, 2009) Includes bibliographical references.
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Malde, Nishil. "Raman spectroscopy of manganite (CMR) andcuprate (HTS) oxides." Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270622.
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Palinginis, Phedon. "Nonlinear optical spectroscopy of dipole and electron spin coherences in semiconductor nanostructures /." view abstract or download file of text, 2004. http://wwwlib.umi.com/cr/uoregon/fullcit?p3136437.
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Thesis (Ph. D.)--University of Oregon, 2004.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 136-141). Also available for download via the World Wide Web; free to University of Oregon users.
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El, Sachat Alexandros. "Characterization of nanostructured materials for thermal conduction and heat transfer control." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/405520.
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L'objectiu principal d'aquesta tesi és l'estudi de les propietats tèrmiques de materials nanoestructurats com un mitjà per controlar el transport de calor. Per a aquest propòsit s’han portat a terme mesures tèrmiques amb diferents tècniques experimentals a escales que cobreixen desenes de micròmetres fins a per sota de 50 nanòmetres. En aquest tesi s’estudien i es presenten dues tècniques experimentals en particular: (a) la microscòpia tèrmica d’escombrat (SThM) i (b) la termometria Raman amb dos làsers (2LRT). Aquestes tècniques s'han aplicat àmpliament per mesurar amb èxit propietats tèrmiques en diversos nanomaterials. En particular, s'investiguen dues configuracions del silici emprant 2LRT: (a) membranes de silici amb gruixos que van de 8 a 1000 nm i (b) membranes poroses periòdiques amb diferents paràmetres de xarxa i membranes amb patró desordenat. Els resultats obtinguts han mostrat que la conductivitat tèrmica en el pla de les membranes i la seva evolució en temperatura, des de la temperatura ambient a aproximadament 1000 K, es poden reduir i ajustar de manera eficaç per mitjà de (i) el gruix i (ii) el patró periòdic(forats). Atribuïm la reducció de la conductivitat tèrmica a l'escurçament del camí lliure dels fonons a causa de la dispersió difusa (incoherent) fonó en els límit de les superfícies. Hem demostrat a més que la dependència de la conductivitat tèrmica amb la temperatura en l’interval d'alta temperatura (400 a 1000 K) es regeix per fonons amb el camí lliure mitjà menor que 200 nm. Per investigar el transport tèrmic en nanoestructures suportades i a escala més petita, s’ha estudiat la transferència de calor entre sensors de sonda d’escombrat escalfats i els nanomaterials, com ara, (i) nanofils epitaxials en el pla d’aliatge Si1-xGex i (ii) nanoestructures basades en copolímer de blocs autoassemblats. En aquestes últimes estructures s’han aconseguit imatges tèrmiques d'alta resolució en estructures de mida per sota de 50 nm i amb resolució espacial per sota de 20 nm. La combinació de les dues tècniques experimentals ha estat crucial per a la caracterització tèrmica dels diferents sistemes de materials i la millor comprensió dels aspectes fonamentals del transport tèrmic.The main objective of this thesis is the study of thermal properties of nanostructured materials as a mean to control heat transport. For this purpose thermal measurements with different experimental techniques on length scales covering tens of microns to sub-50 have been performed. Two experimental techniques in particular have been studied and presented in this thesis: (a) the scanning thermal microscopy technique (SThM) and (b) the two-laser Raman thermometry (2LRT). These techniques have been extensively applied to successfully measure thermal properties in various nanomaterials. In particular, two configurations of Si based materials are investigated using 2LRT: (a) Si membranes with thicknesses ranging from to and (b) periodic porous membranes with different lattice parameters and disordered pattern. The results obtained showed that the in-plane thermal conductivity of silicon and its temperature evolution from room temperature to about 1000 can be effectively reduced and tuned by (i) thickness and (ii) periodic patterning (holes). We attribute the reduction of the thermal conductivity to the shortening of the phonon mean free path Λ due to diffuse (incoherent) phonon-boundary scattering. Furthermore, we showed that the temperature dependence of the thermal conductivity of Si membranes in the high temperature range from to is governed by phonons with mean free path smaller than 200 . To investigate thermal transport in supported nanostructures and in smaller length scale, we studied heat transfer between different heated scanning probe sensors and nanomaterials, such as, (i) in-plane epitaxial Si1-xGex alloy nanowires and (ii) self-assembled block copolymer nanostructures, provided high resolution thermal images of sub-50 structures with sub- spatial resolution. The combination of the two experimental techniques was crucial for the thermal characterization of different material systems and the better understanding of fundamental aspects of thermal transport.
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Freihofer, Gregory J. "Enhancing CNT-composites with Raman spectroscopy." Master's thesis, University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4763.
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Carbon Nanotubes (CNTs) have been the subject of intense research for their potential to improve a variety of material properties when developed as nano-composites. This research aims to address the challenges that limit the ability to transfer the outstanding nano-scale properties of CNTs to bulk nano-composites through Raman characterization.These studies relate the vibrational modes to microstructural characterization of CNT composites including stress, interface behavior, and defects. The formulation of a new fitting procedure using the pseudo-Voigt function is presented and shown to minimize the uncertainty of characteristics within the Raman G and D doublet. Methods for optimization of manufacturing processes using the Raman characterization are presented for selected applications in a polymer multiwalled nanotube (MWNT) composite and laser-sintered ceramic-MWNT composite. In the first application, the evolution of the MWNT microstructure throughout a functionalization and processing of the polymer-MWNT composite was monitored using the G peak position and D/G intensity ratio. Processing parameters for laser sintering of the ceramic-MWNT composites were optimized by obtaining maximum downshift in stress sensitive G-band peak position, while keeping disorder sensitive D/G integrated intensity ratio to a minimum. Advanced Raman techniques, utilizing multiple wavelengths, were used to show that higher excitation energies are less sensitive to double resonance Raman effects. This reduces their influence and allows the microstructural strain in CNT composites to be probed more accurately. The use of these techniques could be applied to optimize any processing parameters in the manufacturing of CNT composites to achieve enhanced properties.ID: 030646203; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (M.S.A.E.)--University of Central Florida, 2011.; Includes bibliographical references (p. 84-94).
M.S.A.E.
Masters
Mechanical and Aerospace Engineering
Engineering and Computer Science
Aerospace Engineering; Space System Design and Engineering Track
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Sharma, Narayan. "Solution Processable Surface Enhanced Raman Spectroscopy (SERS) Substrate." Bowling Green State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1434375587.
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Dennenwaldt, Teresa. "Electron energy loss spectroscopy of novel oxide- and nitride-based nanostructured materials." Diss., Ludwig-Maximilians-Universität München, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-163047.
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Chong, K. K. R. "The characterisation of nanostructured magnetic materials using image spectroscopy and electron tomography." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597636.
Full textAbstract:
In this dissertation, two advanced TEM techniques, image spectroscopy and electron tomography, are applied to the quantitative structural and chemical characterisation of nanostructured magnetic materials, in both two and three dimensions (3D), at nanometre spatial resolution. In image spectroscopy, chemical information is obtained by acquiring extended energy-selected series of images, which are interpreted using a combination of computer processing and traditional electron energy-loss spectroscopy (EELS) analysis. In tomography, 3D microstructural and chemical information is obtained by acquiring ultra-high tilt series of high-angle-annular dark field (HAADF) or energy-filtered TEM (EFTEM) images, and subsequently applying tomographic reconstruction and visualisation algorithms to the data. The techniques are applied to the characterisation of materials that include closely-spaced FeNi nanoparticles coated in oxide shells, lithographically patterned Ni pillars, platinum nanoparticles, chromium carbides in stainless steel, titanomagnetite and an ALH meteorite sample. Biological samples include magnetotactic crystals and bacteria cells, greigite-containing bacterial cells and amyloid plaque cores. The chemical data from image spectroscopy and morphological data from electron tomography are cross-correlated. Furthermore, experimental tomographic data are compared with tomographic reconstructions of image simulations.
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Breucop, Justin Daniel. "In situ Raman spectroscopy of lanthanum-strontium-cobaltite thin films." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/76121.
Full textAbstract:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 29).
Raman spectroscopy is used to probe the structural change of Lanthanum Strontium Cobaltite (La1.xSrxCoO 3 -8) thin films across change in composition (0%-60% strontium) and temperature (30*C-520°C). Raman shift peaks were identified and correlated with specific vibrational modes. Results were consistent with relevant data, but no transition to the high spin state was observed above 200°C. Compositions were compared to oxygen catalytic data to investigate success in high temperature electrochemical applications. No structural phase changes were found in the research of this thesis, interesting effects in the surface regime were observed and possible explanations are offered. Future research should focus on resolving the surface regime via altered experimental set up. Keywords: LSC, LCO, Raman, in silu.
by Justin Daniel Breucop.
S.B.
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Wen, Xiaoming. "Ultrafast spectroscopy of semiconductor nanostructures." Australasian Digital Thesis Program, 2007. http://adt.lib.swin.edu.au/public/adt-VSWT20070426.110438/index.html.
Full textAbstract:
Thesis (PhD) - Swinburne University of Technology, Centre for Atom Optics and Ultrafast Spectroscopy, 2007.Thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy, Centre for Atom Optics and Ultrafast Spectroscopy, Swinburne University of Technology, 2007. Typescript. Bibliography: p. 122-144.
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Syed, Azfar A. "Surface enhanced Raman spectroscopy for ultra-sensitive detection of energetic materials." Thesis, Cranfield University, 2010. http://dspace.lib.cranfield.ac.uk/handle/1826/4644.
Full textAbstract:
The prospect of ultra-sensitive detection of molecular species, particularly those of energetic materials, has prompted the present research initiative. The combination of metal surface nano-technology and Raman spectroscopy has given rise to ‘Surface Enhanced Raman Spectroscopy’ (SERS). This is a very sensitive technique and has proved to be capable of detecting a single molecule. SERS was demonstrated by recording Raman spectra of the sample molecules adsorbed on various specially prepared SER-active surfaces both in the form of a colloidal suspension and on the solid roughened surfaces. Using a gold colloidal suspension, pyridine has been detected down to 10-11 molar (M) concentration. A silver slab was roughened to a dimension of a nano-scale by etching in nitric acid solution to make SER-active surface. Pentaerythritol Tetranitrate (PETN) explosive was detected using this surface after its 10-2 M solution was dropped, dried and washed (of any residue) from the surface. Lithographically engineered silver structures in the form of nanoarrays having a number of silver structures of approximately 106 in a region of 0.1 mm2 have been used for SERS. The major noise contribution to the scattering from impurities in an ordinary glass substrate has been eliminated by replacing glasses as substrates with pure quartz discs. The headspace vapours from peroxide explosives, Triacetone Triperoxide (TATP) and Hexamethylene Triperoxide Diamine (HMTD), were detected at approximately 70 parts per million (ppm) and 0.3 ppm concentrations respectively using a portable commercial Raman Spectrometer. PETN was also detected from its headspace vapour at about 18 parts per trillion (ppt) in spite of it having a much lower vapour pressure. The possibility of desorption of adsorbed molecules from a nano-structured surface by laser irradiation has been demonstrated experimentally with the aim of reusability of SER-active surfaces. Also demonstrated was the enhancement in Raman intensity through resonance Raman effect spectroscopy for the future use in surface enhanced resonance Raman spectroscopy (SERRS).
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Scherger, Jacob D. "Expanding Tip Enhanced Raman Spectroscopy: Blinking Measurements and Alternative Probe Materials." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1510657402180872.
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Syed, A. A. "Surface enhanced raman spectroscopy for ultra-sensitive detection of energetic materials." Thesis, Department of Materials and Applied Science, 2010. http://dspace.lib.cranfield.ac.uk/handle/1826/4644.
Full textAbstract:
The prospect of ultra-sensitive detection of molecular species, particularly those of
energetic materials, has prompted the present research initiative. The combination of
metal surface nano-technology and Raman spectroscopy has given rise to ‘Surface
Enhanced Raman Spectroscopy’ (SERS). This is a very sensitive technique and has
proved to be capable of detecting a single molecule.
SERS was demonstrated by recording Raman spectra of the sample molecules adsorbed
on various specially prepared SER-active surfaces both in the form of a colloidal
suspension and on the solid roughened surfaces. Using a gold colloidal suspension,
pyridine has been detected down to 10-11 molar (M) concentration. A silver slab was
roughened to a dimension of a nano-scale by etching in nitric acid solution to make
SER-active surface. Pentaerythritol Tetranitrate (PETN) explosive was detected using
this surface after its 10-2 M solution was dropped, dried and washed (of any residue)
from the surface. Lithographically engineered silver structures in the form of nanoarrays
having a number of silver structures of approximately 106 in a region of 0.1 mm2
have been used for SERS. The major noise contribution to the scattering from
impurities in an ordinary glass substrate has been eliminated by replacing glasses as
substrates with pure quartz discs. The headspace vapours from peroxide explosives,
Triacetone Triperoxide (TATP) and Hexamethylene Triperoxide Diamine (HMTD),
were detected at approximately 70 parts per million (ppm) and 0.3 ppm concentrations
respectively using a portable commercial Raman Spectrometer. PETN was also detected
from its headspace vapour at about 18 parts per trillion (ppt) in spite of it having a much
lower vapour pressure.
The possibility of desorption of adsorbed molecules from a nano-structured surface by
laser irradiation has been demonstrated experimentally with the aim of reusability of
SER-active surfaces. Also demonstrated was the enhancement in Raman intensity
through resonance Raman effect spectroscopy for the future use in surface enhanced
resonance Raman spectroscopy (SERRS).
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Hlaing, Oo Win Maw. "Infrared spectroscopy of zinc oxide and magnesium nanostructures." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Dissertations/Fall2007/w_hlaingoo_121107.pdf.
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Shi, Jian. "Horizontal zinc oxide nanomaterials growth and their application for surface enhanced raman scattering." Diss., Columbia, Mo. : University of Missouri-Columbia, 2008. http://hdl.handle.net/10355/6682.
Full textAbstract:
Thesis (M.S.)--University of Missouri-Columbia, 2008.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 19, 2009) Includes bibliographical references.
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Hansson, Freja. "Detection of Contaminants in Water Using Surface Enhanced Raman Spectroscopy." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-85943.
Full textAbstract:
Due to deteriorating water quality and the world’s increasing demand for clean water, the need for cheap, easy and portable techniques to characterize and quantify pollutants in waters is urgent. Hence, surface-enhanced Raman spectroscopy (SERS) have gained considerable attention in this field. Atrazine and bentazon are two of the most occurring pesticides causing pollution in Sweden, and where therefore examined in this study, along with 4-mercaptopyridine (mpy) as a reference molecule. In this project, silver and gold nanoparticles where synthesised and used as SERS substrates for detection of contaminants in water by using a handheld Raman device provided by Serstech AB. Sodium chloride (NaCl) and magnesium sulfate (MgSO4) where used as aggregation agents allowing the nanoparticles to form hot spots. Mpy was detected to 0.5 nM and an enhancement factor of 108 using silver nanoparticles aggregated with NaCl was obtained. No Raman signal was obtained from atrazine nor bentazon using the handheld Raman device with silver nanoparticles aggregated with NaCl. Therefore the Raman cross-section of the probe molecules where investigated using the handheld Raman device and a conventional Raman device. Bentazon was not detectable using the handheld Raman device but detectable using a conventional Raman device. Atrazine was detectable at high concentrations i.e. atrazine powder using the handheld Raman device and detectable at 100 nM using a conventional Raman device. Since bentazon was not detectable with the handheld Raman device, more focus was put on getting a detectable signal from atrazine using the handheld Raman device. Investigation of the adsorption of atrazine and bentazon to the silver nanoparticle surface was performed. Due to the weaker adsorption to the nanoparticle surface, MgSO4 was used aggregation agent instead of NaCl with mpy, atrazine and bentazon. Mpy was detectable using MgSO4 as aggregation agent, atrazine and bentazon was not. Measurements of mpy, atrazine and bentazon without any salt was performed. For these measurements, no detectable signal from neither molecule was obtained, indicating that the formation of hot spots is necessary to obtained a detectable Raman signal. Measurements of mpy and atrazine with gold nanostars where performed. Enhancement factor using the gold nanostars was calculated to 107, and a detectrable signal from mpy was obtained, not from atrazine. Measurements of atrazine and mpy simultaneously was performed, where mpy peaks was observed but no atrazine peaks. The affinity of the probe molecule and the nanoparticle is crucial to obtain a detectable signal. This study inducates that both the chemical enhancement and electromagnetic enhancement are needed to obtain a detectable signal. For that, strongly binding species is necessary. Considering the simplicity of this method and the limited optimization efforts, there is plenty of room for improvements, including different probe molecules and different SERS substrates. With the right conditions, the evaluated technique reveals a promising and accessible method using a commercially available handheld Raman spectrometer for detection and quantification of contaminants in water.
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Villalpando, Páez Federico. "Raman spectroscopy of double walled carbon nanotubes with different metallic and semiconducting configurations." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/59238.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2010.Includes bibliographical references (p. 117-125).
A double-walled carbon nanotube (DWNT) provides the simplest system to study the interaction between concentric tubes in carbon nanotubes. The inner and outer walls of a DWNT can be metallic (M) or semiconducting (S), and each of the four possible configurations (MUM, M©S, SUS, S©M) has different electronic properties. We analyze the Raman spectra from undoped and boron-doped chemical vapor deposition-derived DWNT bundles (CVD-DWNTs) that exhibit the "coalescence inducing mode" (CIM) as they are heat treated at temperatures between 12000C and 2000'C. We then report, for the first time, detailed Raman spectroscopy experiments carried out on individual DWNTs, where both concentric tubes of the same DWNT are measured under resonance conditions. A technique is developed that combines tunable Raman spectroscopy with Raman mapping procedures and electron beam lithography to enable the acquisition of Raman spectra from the individual constituents of the same isolated DWNT. By using the technique mentioned above, we measure resonant Raman scattering from 11 individual C60-derived double wall carbon nanotubes all having inner semiconducting (6,5) tubes and various outer metallic tubes. We report that in an individual DWNT an increase in the RBM frequency of the inner tube is related to an increase in the RBM frequency of the outer tube due to a decrease in the wall to wall distance. Finally, we use 40 laser excitation energies to analyze the differences in the Raman spectra from chemical vapor deposition-derived DWNT bundles (CVD-DWNTs), fullerene-derived DWNT bundles (C₆₀-DWNTs) and individual fullerene-derived DWNTs with inner type I and type II semiconducting tubes paired with outer metallic tubes.
by Federico Villalpando Páez.
Ph.D.
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Cheng, Weifeng. "Development of High-Performance Optofluidic Sensors on Micro/Nanostructured Surfaces." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/103873.
Full textAbstract:
Optofluidic sensing utilizes the advantages of both microfluidic and optical science to achieve tunable and reconfigurable high-performance sensing purpose, which has established itself as a new and dynamic research field for exciting developments at the interface of photonics, microfluidics, and the life sciences. With the trend of developing miniaturized electronic devices and integrating multi-functional units on lab-on-a-chip instruments, more and more desires request for novel and powerful approaches to integrating optical elements and fluids on the same chip-scale system in recent years. By taking advantage of the electrowetting phenomenon, the wettability of liquid droplet on micro/nano-structured surfaces and the Leidenfrost effect, this doctoral research focuses on developing high-performance optofluidic sensing systems, including optical beam adaptive steering, whispering gallery mode (WGM) optical sensing, and surface-enhanced Raman spectroscopy (SERS) sensing.
A watermill-like beam steering system is developed that can adaptively guide concentrating optical beam to targeted receivers. The system comprises a liquid droplet actuation mechanism based on electrowetting-on-dielectric, a superlattice-structured rotation hub, and an enhanced optical reflecting membrane. The specular reflector can be adaptively tuned within the lateral orientation of 360°, and the steering speed can reach ~353.5°/s. This work demonstrates the feasibility of driving a macro-size solid structure with liquid microdroplets, opening a new avenue for developing reconfigurable components such as optical switches in next-generation sensor network.
Furthermore, the WGM sensing system is demonstrated to be stimulated along the meridian plane of a liquid microdroplet, instead of equatorial plane, resting on a properly designed nanostructured chip surface. The unavoidable deformation along the meridian rim of the sessile microdroplet can be controlled and regulated by tailoring the nanopillar structures and their associated hydrophobicity. The nanostructured superhydrophobic chip surface and its impact on the microdroplet morphology are modeled by Surface Evolver (SE), which is subsequently validated by the Cassie-Wenzel theory of wetting. The influence of the microdroplet morphology on the optical characteristics of WGMs is further numerically studied using the Finite-Difference Time-Domain method (FDTD) and it is found that meridian WGMs with intrinsic quality factor Q exceeding 104 can exist. Importantly, such meridian WGMs can be efficiently excited by a waveguiding structure embedded in the planar chip, which could significantly reduce the overall system complexity by eliminating conventional mechanical coupling parts. Our simulation results also demonstrate that this optofluidic resonator can achieve a sensitivity as high as 530 nm/RIU. This on-chip coupling scheme could pave the way for developing lab-on-a-chip resonators for high-resolution sensing of trace analytes in various applications ranging from chemical detections, biological reaction processes to environmental protection.
Lastly, this research reports a new type of high-performance SERS substrate with nanolaminated plasmonic nanostructures patterned on a hierarchical micro/nanostructured surface, which demonstrates SERS enhancement factor as high as 1.8 x 107. Different from the current SERS substrates which heavily relies on durability-poor surface structure modifications and various chemical coatings on the platform surfaces which can deteriorate the SERS enhancement factor (EF) as the coating materials may block hot spots, the Leidenfrost effect-inspired evaporation approach is proposed to minimize the analyte deposition area and maximize the analyte concentration on the SERS sensing substrate. By intentionally regulating the temperature of the SERS substrate during evaporation process, the Rhodamine 6G (R6G) molecules inside a droplet with an initial concentration of 10-9 M is deposited within an area of 450 μm2, and can be successfully detected with a practical detection time of 0.1 s and a low excitation power of 1.3 mW.Doctor of Philosophy
Over the past two decades, optofluidics has emerged and established itself as a new and exciting research field for novel sensing technique development at the intersection of photonics, microfluidics and the life sciences. The strong desire for developing miniaturized lab-on-a-chip devices and instruments has led to novel and powerful approaches to integrating optical elements and fluids on the same chip-scale systems. By taking advantage of the electrowetting phenomenon, the wettability of liquid droplet on micro/nano-structured surfaces and the Leidenfrost effect, this doctoral program focuses on developing high-performance optofluidic sensing systems, including optical beam adaptive steering, whispering gallery mode (WGM) optical sensing, and surface-enhanced Raman spectroscopy (SERS) sensing. During this doctoral program, a rotary electrowetting-on-dielectric (EWOD) beam steering system was first fabricated and developed with a wide lateral steering range of 360° and a fast steering speed of 353.5°/s, which can be applied in telecommunication systems or lidar systems. Next, the meridian WGM optical sensing system was optically simulated using finite difference time domain (FDTD) method and was numerically validated to achieve a high quality-factor Q exceeding 104 and a high refractive index sensitivity of 530 nm/RIU, which can be applied to the broad areas of liquid identification or single molecule detection. Lastly, a SERS sensing platform based on a hierarchical micro/nano-structured surface was accomplished to exhibit a decent SERS enhancement factor (EF) of 1.81 x 107. The contact angle of water droplet on the SERS substrate is 134° with contact angle hysteresis of ~32°. Therefore, by carefully controlling the SERS surface temperature, we employed Leidenfrost evaporation to concentrate the analytes within an extremely small region, enabling the high-resolution detection of analytes with an ultra-low concentration of ~10-9 M.
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Hunter-Saphir, S. A. "An investigation by Raman spectroscopy and other methods of some industrially relevant materials." Thesis, University of Kent, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324711.
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Makiabadi, Tahereh. "Etude de surfaces nanostructurées : applications à la spectroscopie Raman exaltée de surface et à la résonance de plasmons localisés." Phd thesis, Université de Nantes, 2010. http://tel.archives-ouvertes.fr/tel-00467582.
Full textAbstract:
Cette recherche porte sur la réalisation, la caractérisation et l'optimisation de surfaces nanostructurées comme substrats pour la spectroscopie Raman exaltée et la résonance de plasmons de surface. Plusieurs voies sont proposées et comparées. La première s'intéresse au greffage de nanoparticules d'or et d'argent sur des supports préalablement fonctionnalisés. Cette approche de type « top-down » nous permet de mettre en évidence les conditions optimales pour obtenir une monocouche homogène et dense de nanoparticules. Les courbes d'extinction et les facteurs d'exaltation sont quantifiés et modélisés avec des temps de fabrication minimisés. La seconde voie étudiée, de type « bottom-up » consiste à synthétiser des nanostructures par dissolution-déposition de films minces d'or ou d'argent, ces derniers étant réalisés par dépôt physique en phase vapeur. Ce procédé s'appuie sur l'optimisation de cycles d'oxydation-réduction qui permet de concevoir successivement des films rugueux et des nanostructures métalliques. La présence de ces nanostructures et de nano cavités sur les substrats est appréciée et mesurée par microscopies à force atomique et à balayage. La limite de détection de molécules par spectrométrie Raman est ainsi évaluée et comparée aux valeurs rapportées dans la littérature. Les conditions optimales déterminées à partir des courbes d'extinction et de diffusion Raman permettent de converger vers un protocole de fabrication fiable et reproductible. Pour finir, le greffage de nanoparticules a été réalisé sur fibres optiques et la sensibilité de la résonance des plasmons de surface localisés (LSPR) est évaluée
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Patrick, Christopher Edward. "Photoemission spectra of nanostructured solar cell interfaces from first principles." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:fa2333ea-7016-4d6f-8d55-aee4178482a6.
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Photovoltaic (PV) technologies could provide abundant, clean and secure energy through the conversion of sunlight into electricity, but currently are too expensive to compete with conventional sources of power. Novel PV devices incorporating nanostructured materials, such as the dye-sensitized solar cell (DSC), have been identified as viable, low-cost alternatives to traditional solar cell designs. In spite of technological progress in the field over the last twenty years, the underlying physics governing DSC operation is still not well understood. In this thesis, first-principles (i.e. parameter-free) calculations are performed with the aim of connecting experimentally-measured photoemission data to the underlying atomistic and electronic structure of interfaces found in DSCs. The principal system under study is the interface between anatase titanium dioxide (TiO2) and the "N3" dye molecule, one of the most widely-investigated device designs in DSC research. Atomistic models of the interface are determined within density-functional theory. Core-level spectra of these interface models are then calculated using a ∆SCF approach. Comparison of the calculations to published experimental data finds that intermolecular interactions have a significant effect on the spectra. Next, the electronic structure of bulk TiO2 and of isolated N3 molecules is calculated using the GW approximation and ∆SCF method respectively. For the former, it is shown that including Hubbard U corrections in the initial Hamiltonian reduces the GW gap by 0.4 eV. These calculations are then used to determine the valence photoemission spectrum of the full interface. By including image-charge effects, thermal broadening and configurational disorder, quantitative agreement with experimentally-measured spectra is demonstrated. In addition to the N3/TiO2 system, calculations of the core-level spectra of the interfaces between TiO2 and H2O and bi-isonicotinic acid are also presented. The thesis concludes with a study of the X2Y3/TiO2 interfaces (X=Sb, Bi; Y=S, Se) found in recently-developed semiconductor-sensitized solar cells.
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Massoud, Mouhannad. "Experimental characterization of heat transfer in nanostructured silicon-based materials." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI063/document.
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Ce mémoire de thèse aborde la caractérisation expérimentale du transfert thermique à l’échelle nanométrique dans des matériaux compatibles avec les procédés de la micro-électronique. Pour cela deux techniques de caractérisation sont appliquées chacune à deux différents systèmes, le silicium mésoporeux irradié et les membranes de silicium suspendues. La première technique de caractérisation est la thermométrie micro-Raman. La puissance du laser chauffe l'échantillon exposé. La détermination de la conductivité thermique nécessite la modélisation de la source de chaleur par la méthode des éléments finis. Dans les cas considérés la modélisation de la source de chaleur repose sur différents paramètres qui doivent être soigneusement déterminés. La seconde technique de caractérisation est la microscopie à sonde locale (d’acronyme anglais SThM), basée sur le principe de la microscopie à force atomique (d’acronyme anglais AFM). Utilisée en mode actif, la sonde AFM est remplacée par une sonde résistive de type Wollaston qui est chauffée par effet Joule. Utilisée en mode AFM contact, cette technique permet une excitation thermique locale du matériau étudié. La détermination de la conductivité thermique nécessite l'analyse de la réponse thermique de la sonde au moyen d'échantillons d'étalonnage et également via la modélisation dans le cas des géométries complexes. L'effet de la position de la pointe sur le transfert de chaleur entre la pointe et l'échantillon est étudié. Une nouvelle méthode de découplage entre le transfert de chaleur entre la pointe et l'échantillon, respectivement à travers l'air et au contact, est proposée pour la détermination de la conductivité thermique des géométries complexes. Les résultats obtenus avec les deux techniques pour les échantillons de silicium mésoporeux irradiés à l’aide d’ions lourds dans le régime électronique sont en bon accord. Ils montrent la dégradation de la conductivité thermique du silicium mésoporeux suite à une augmentation dans la phase d’amorphe lorsque la dose d’irradiation croît. Les résultats obtenus sur les membranes de silicium suspendues montrent une réduction de la conductivité thermique de plus de 50 % par rapport au silicium massif. Lorsque la membrane est perforée périodiquement afin de réaliser une structure phononique de période inférieure à 100 nm, cette réduction est approximativement d’un ordre de grandeur. Un chapitre introduisant un matériau prometteur à base de silicium pour observer des effets de cohérence phononique conclut le manuscritThis PhD thesis deals with the experimental characterization of heat transfer at the nanoscale in materials compatible with microelectronic processes. Two characterization techniques are applied to two different systems, irradiated mesoporous silicon and suspended silicon membranes. The first characterization technique is micro-Raman thermometry. The laser power heats up the exposed sample. The determination of the thermal conductivity requires the modeling of the heat source using finite element simulations. The modeling of the heat source relies on different parameters that should be carefully determined. The second characterization technique is Scanning Thermal Microscopy (SThM), an Atomic Force Microscopy (AFM)-based technique. Operated in its active mode, the AFM probe is replaced by a resistive Wollaston probe that is heated by Joule heating. Used in AFM contact mode, this technique allows a local thermal excitation of the studied material. The determination of the thermal conductivity requires the analysis of the thermal response of the probe using calibration samples and modeling when dealing with complicated geometries. The effect of the tip position on heat transfer between the tip and the sample is studied. A new method decoupling the heat transfer between the tip and the sample, at the contact and through air, is proposed for determining the thermal conductivity of complicated geometries. The results obtained from the two techniques on irradiated mesoporous silicon samples using heavy ions in the electronic regime are in good agreement. They show a degradation of the thermal conductivity of mesoporous silicon due to the increase in the amorphous phase while increasing the ion fluence. The results obtained on suspended silicon membrane strips show a decrease in the thermal conductivity of more than 50 % in comparison to bulk silicon. When perforated into a phononic structure of sub-100 nm period, the membrane thermal conductivity is about one order of magnitude lower than the bulk. A chapter introducing a promising silicon-based material for the evidence of phonon coherence concludes the manuscript
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Eriksen, Tell Andreas. "Structural Investigations of HiPIMS-deposited Diamond-Like Carbon Thin Films using Raman Spectroscopy." Thesis, Uppsala universitet, Fasta tillståndets elektronik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-322376.
Full textAbstract:
Diamond-like carbon (DLC) is a versatile material which exhibits excellentmechanical, electrical and optical properties making it suitable for applications rangingfrom biomedical implants to engine components. The properties of DLC thin films aredetermined by the bonding configuration (sp3/sp2 fraction) of its carbon atoms. Inorder to prepare DLC thin films for desired applications, it is essential to control andestimate the sp3/sp2 fraction precisely. Raman spectroscopy is widely employed for the estimation of sp3/sp2 fraction due toits non-destructive nature, high probing depth and possibility of quick acquisition. Thequality of information obtained from Raman analysis depends largely on the structureof DLC thin films, which varies from one deposition method to another. Using theexisting approaches for the estimation of sp3/sp2 fraction for a particular type of DLCthin films could entail large errors and thereby result in misleading conclusions. For anaccurate analysis of the film structure, it is therefore important that a carefullydesigned strategy is employed. In this work, Raman spectroscopy is employed forstructural investigation of DLC thin films deposited by High Power ImpulseMagnetron Sputtering (HiPIMS). Owing to the unique DLC film properties obtainedfrom HiPIMS, Raman spectroscopic investigations were made by developing ananalysis routine relevant for HiPIMS-deposited films. The developed approach isvalidated by complementary analysis of film density. The method is further employedfor investigating the compressive stress and thermal stability of the resulting films. Theanalyzed films were deposited using different buffer gas (Ar and Ne) and ion energy toproduce a range of sp2/sp3 ratios. Raman measurements were performed using visible(532 nm) and UV (325 nm) lasers. Film density was determined using X-RayReflectivity (XRR) and chemical composition using Elastic Recoil Detection Analysis(ERDA). The compressive stresses of the films were determined usingwafer-curvature method and thermal stability of the films was investigated byperforming Raman measurements on films annealed from 100 degrees C to 600degrees C. By developing an analysis routine and employing appropriate fitting method, it wasshown that the Full Width at Half Maximum (FWHM) of the G peak in the Ramanspectrum is the most relevant parameter for estimating the sp3/sp2 fraction. Theaccuracy of the analysis routine was verified by studying the evolution of sp3/sp2fraction and film density with respect to ion energy. The correlation between sp3/sp2fraction and film density was good. The differences in mass density and compressivestresses between Ar- and Ne-HiPIMS deposited films were also found to beconsistent with the estimated sp3/sp2 fractions. The structural evolution of theannealed films, investigated by Raman spectroscopy, showed that the Ne-HiPIMS filmsexhibit a transition from sp3 rich structure to sp2 rich structure at ~450 degrees Cwhereas the transition for the Ar-HiPIMS films occurs at ~300 degrees C. This impliesthat the Ne-HiPIMS films are thermally more stable than the Ar-HiPIMS films.
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Lin, Sally S. B. Massachusetts Institute of Technology. "Investigation into the use of surface-enhanced Raman spectroscopy (SERS) for organic dye analysis." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98657.
Full textAbstract:
Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 48-49).
In art conservation, color is essential to understanding a society's culture and history-as an indicator of beauty, status, religion, and more-but has a tendency to fade and diminish over time. Analytical techniques, particularly that of pigment identification, can reveal the artifact's original color and appearance and give new insights to an artist's intentions, techniques, date of creation, and more. However, most identification procedures are invasive and destroy the samples in the process. Surface-enhanced Raman spectroscopy (SERS) has recently been identified as a technique that is minimally invasive and also solves the issue of fluorescence that is found in many other techniques. In this paper, a specific SERS procedure has been developed for the identification of yellow organic dyes from 18th century Japanese Woodblock prints. Several SERS spectra of nine dyes both in solution and applied on artist paper have also been documented in hopes of assisting with pigment identification in the future.
by Sally Lin.
S.B.
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Ohlhaver, Christopher M. "Use of Surface Enhanced Raman Spectroscopy for the Detection of Bioactive Lipids." VCU Scholars Compass, 2018. https://scholarscompass.vcu.edu/etd/5551.
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The detection and analysis of lipids in biological matrices for clinical applications poses many challenges, but rapid and reliable detection will prove invaluable for clinical diagnosis. Herein, we report the application of drop-casted Ag nanoplatelets as surface enhanced Raman scattering (SERS) substrates for qualitative detection of 20-hydroxyeicosatetraenoic acid (20-HETE), which is a potential biomarker for diagnosis of hypertensive disorders. Biomarker peaks of 20-HETE can be reliably detected and differentiated from those of the structurally similar lipids (arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid) commonly found in human blood, even 1 pM concentrations. Additionally, one study mixed 20-HETE with three structurally similar lipids at concentrations several orders of magnitude greater than the target lipid and 20-HETE could still be detected under these conditions. These experiments demonstrate the viability of SERS for the rapid and reliable detection of endogenous bioactive lipids, which has significant clinical impact in enabling point of care diagnostics.
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Bassi, Andrea Li. "X-ray and light scattering from nanostructured thin films." Thesis, Durham University, 2000. http://etheses.dur.ac.uk/4631/.
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The object of this thesis is the study of nanostructured thin films using inelastic fight scattering and elastic x-ray scattering techniques. Their use in combination with other techniques is a powerful tool for the investigation of nanostructured materials. X-ray, Raman and Brillouin characterisation of cluster-assembled carbon films, promising for applications in the field of catalysis, hydrogen storage and field emission, is here presented. X-ray reflectivity (XRR) provided a measure of the density. Raman spectroscopy showed that the local bonding in these amorphous films depends on the size distribution of the clusters and that it is possible to select the cluster size in order to grow films with tailored properties. Brillouin scattering provided a characterisation at the mesoscopic scale and an estimate of the elastic constants, revealing a very soft material. XRR was employed to study density, layering and roughness of a wide range of amorphous carbon films grown with different techniques. Some films possess an internal layering due to plasma instabilities in the deposition apparatus. By comparing XRR with Electron Energy Loss Spectroscopy, a unique value for the electron "effective mass" was deduced and a general relationship between sp(^3)-content and density was found. XRR and H effusion were used to determine the hydrogen content. A study of the size-dependent melting temperature in tin nanoparticle thin films was undertaken with a combined use of X-Ray Diffraction (XRD) and light scattering. A redshift in the position of a Rayleigh peak in the temperature-dependent Brillouin measurements was shown to be related to the melting of the nanoparticles and explained by an effective medium model. XRD also provided information on the low-level of stress in the particles. Low-frequency Raman scattering was used to study the behaviour of the acoustic modes of a single particle as a function of temperature.
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Page, Kristian. "Evaluation of Raman spectroscopy for application in analytical astrobiology : the application of Raman spectroscopy for characterisation of biological and geological materials of relevance to space exploration." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5716.
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In 2018 ESA and NASA plan to send the ExoMars rover to the Martian surface. This rover is planned to have a suite of analytical equipment that includes a Raman spectrometer. In this context, an evaluation of Raman spectroscopy as an analytical tool for interplanetary studies is investigated. The preparation techniques for appropriate inorganic and organic mixtures are interrogated. Methods are investigated to optimize the homogeneity of over 50 samples involving mineral phases; calcite, gypsum and goethite and selected organic biomolecular systems; anthracene, naphthalene and beta-carotene. From mixtures produced of these organic and inorganic materials differences between homogeneity of the samples is observed. Different mixing techniques are investigated to reduce this, however all the samples display variation on a micron scale. To resolve this issue a grid system of 9 points is implemented on solid samples and solutions are used to produce standards. The standards are devised using a range of instrument validation parameters for comparison between commercially available spectrometers and the prototype instrument. From these standards a prototype instrument is optimized for data acquisition and an evaluation procedure for instrument performance is established. The prototype Raman spectrometer is evaluated to match the specifications of the spectrometer on board ExoMars rover. A range of astrobiological relevant samples are interrogated; geological samples, biomarkers, cellular systems and bio-geological inclusions. From these samples detection of organics is observed to be only possible, with Raman spectroscopy where organics are localised in high concentrations, upon grinding and mixing geological inclusions Raman spectroscopy is unable to detect the organic components.
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Sanzenbacher, Lindsay M. "Raman Spectroscopic Studies of Single Crystal Diamond." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1313440154.
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Nguyen, Van Tang. "Nanostructured soft-hard magnetic materials with controlled architecture." Thesis, Le Mans, 2018. http://www.theses.fr/2018LEMA1007.
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Parmi les aimants sans terres raresactuellement étudiés, τ-MnAl ferromagnétique est uncandidat à haut potentiel, car il possède despropriétés magnétiques intrinsèques prometteuses.Dans cette thèse, Mn(Fe)AlC a été synthétisé parbroyage mécanique. Les effets du carbone sur lamicrostructure et les propriétés magnétiques ont étéétudiés. Les résultats montrent qu’une pureté élevéede τ-MnAl(C) pouvait être obtenue avec un dopage à2% en atomes de carbone, montrant clairement l’effetstabilisant du carbone. L’alliage Mn54.2Al43.8C2possède les meilleures propriétés magnétiques :aimantation à 2T M2T = 414 kAm-1, aimantationrémanente Mr = 237 kAm-1, coercivité HC = 229 kAm-1et |BH|max = 11,2 kJm-3. HC augmente inversementproportionnellement avec la taille des cristallites de laphase τ et proportionnellement à la teneur en C. Descalculs ab initio confirment l’effet stabilisant etindiquent les positions interstitielles préférentielles ducarbone dans la maille quadratique de la phase τ-MnAl.Les alliages Mn51-xFexAl47C2 (x = 0,25, 0,5, 1, 2, 4, 6)ont également été synthétisés par broyagemécanique, montrant une pureté élevée de la phaseτ jusqu'à un taux de substitution de 2% du Mn par duFe. L'ajout de Fe dans MnAl(C) réduit l'aimantationet TC, mais augmente légèrement la valeur de HC. Laspectrométrie 57Fe Mössbauer à 300K a été utiliséepour sonder l'environnement local dans ε-, τ-, β- etγ2-MnFeAl(C). γ2-, ε- et β-MnFeAl(C) présentent unestructure hyperfine quadripolaire alors que τ-Mn50.5Fe0.5Al47C2 montre une structutr hyperfinemagnétique assez complexe. Une expérience despectrométrie Mössbauer effectuée à bassetempérature (10K) et sous champ magnétique (8T)montre un ordre ferromagnétique local non colinéairedes moments magnétiques de Fer par rapport à ladirection du champ appliqué. Le champ hyperfin del’alliage MnFeAl calculé par Wien2k confirme lespropriétés magnétiques et les résultats despectrométrie MössbauerAmong currently investigated rare-earth-free magnets, ferromagnetic τ-MnAl is a highly potential candidate as having promising intrinsic magnetic properties. In my thesis, Mn(Fe)AlC was synthesized by mechanical alloying method. Effects of carbon on microstructure and magnetic properties were systematically investigated. It was found that high purity of τ-MnAl(C) could be obtained at 2 at.% C doping, showing clearly stabilizing effect of carbon. Mn54.2Al43.8C2 has the best magnetic properties: magnetization at 2T M2T = 414 kAm-1, remanent magnetization Mr = 237 kAm-1, coercivity HC = 229 kAm-1, and |BH|max = 11.2 kJm-3. HC increased inversely with the crystallite size of τ phase and proportionally with C content. Moreover, first principle calculation showed both stabilizing effect and preferable interstitial positions of carbon in tetragonal τ-MnAl. Mn51-xFexAl47C2 (x= 0.25, 0.5, 1, 2, 4, 6) alloys were also synthesized by mechanical alloying method, showing high purity of τ phase up to 2 at.% Fe doping. Adding of Fe on MnAl(C) reduced both magnetization and TC but likely increased slightly HC. 57Fe Mössbauer spectrometry at 300K was used to probe local enviroment in ε-, τ-, β-, and γ2-MnFeAl(C). In which, γ2-, ε-, and β-MnFeAl(C) exhibited a quadrupolar structure while τ -Mn50.5Fe0.5Al47C2 spectrum showed a rather complex magnetic hyperfine splitting. The interaction between Fe and Mn examined by in-field Mössbauer measurement at 10 K and 8 T showed a non-collinear magnetic structure between Fe and Mn with different canting angles at different sites. Hyperfine field of MnFeAl alloy calculated by Win2k supported both magetic properties and Mossbauer results
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Mavumengwana, Bongeka Nomakhephu. "The evaluation of a handheld Raman Analyser for the good laboratory practise (glp) compliant identification of paracetamol raw materials, in a pharmaceutical manufacturing environment." Thesis, Nelson Mandela Metropolitan University, 2015. http://hdl.handle.net/10948/4243.
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The use of a handheld Raman analyser for the positive identification of raw materials in a manufacturing pharmaceutical company was evaluated using paracetamol as test raw material to evaluate whether such a system would meet Aspen’s regulatory requirements. The approach involved subjecting the chosen raw material to identification tests under a variety of conditions so as to evaluate robustness, and specificity of the system. Thus, raw material provided by different suppliers, different packages of one manufacturing batch, and raw materials subjected to different storage conditions were evaluated. Specificity was evaluated by deliberately contaminating a sample of paracetamol with either acetanilide, or 4-aminophenol, or both at varying concentration levels. The results obtained from these investigations showed that the handheld Raman analyser can correctly identify the selected raw material (paracetamol) under a wide range of conditions, but could not correctly identify the presence of the selected contaminants at lower concentration levels (< 10 – 20 mass percent). Finally, a cost-benefit analysis was carried out in which a scenario of an existing FTIR-ATR system is used for the analysis of a specific number of raw material samples per year as opposed to a scenario in which a new handheld Raman analyser has to be purchased, set up, and used for the analysis of the same number of raw material samples. This comparison showed that the handheld Raman analyser had a pay-back time of approximately 6 months and gave a return on investment of approximately the same value as the actual purchase cost.
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Israelsen, Nathan. "Surface-Enhanced Raman Spectroscopy-Based Biomarker Detection for B-Cell Malignancies." DigitalCommons@USU, 2015. https://digitalcommons.usu.edu/etd/4605.
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This thesis presents a light scattering-based method for biomarker detection, which could potentially be used for the quantification of multiple biomarkers specific to B-cell malignancies. This method uses fabricated gold nanoparticle probes to amplify inelastic light scattering in a process referred to as surface-enhanced Raman scattering. These gold nanoparticle probes were conjugated to antibodies for specific and targeted molecular binding. The spectrum of the amplified inelastic light scattering was detected using a spectrometer and a detector. To detect the light scattering signal from the gold nanoparticle probes, several commercial Raman spectrometer instruments were evaluated. Initial results from these evaluations are presented in this thesis. After system evaluation, a custom Raman microscope system was designed, built, and tested. This system was used for the development of a surface-enhanced Raman spectroscopy-based immunoassay. The development of this assay confirms the successful design of gold nanoparticle probes for the specific targeting and detection of immunoglobulins. The immunoassay also shows promise for the simultaneous detection of multiple biomarkers specific to B-cell malignancies.
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Kharkov, Boris. "Molecular Order and Dynamics in Nanostructured Materials by Solid-State NMR." Doctoral thesis, KTH, Tillämpad fysikalisk kemi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-160636.
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Organic-inorganic nanostructured composites are nowadays integrated in the field of material science and technology. They are used as advanced materials directly or as precursors to novel composites with potential applications in optics, mechanics, energy, catalysis and medicine. Many properties of these complex materials depend on conformational rearrangements in their inherently dynamic organic parts. The focus of this thesis is on the study of the molecular mobility in ordered nanostructured composites and lyotropic mesophases and also on the development of relevant solid-state NMR methodologies. In this work, a number of new experimental approaches were proposed for dipolar NMR spectroscopy for characterizing molecular dynamics with atomic-level resolution in complex solids and liquids. A new acquisition scheme for two-dimensional dipolar spectroscopy has been developed in order to expand the spectral window in the indirect dimension while using limited radio-frequency power. Selective decoupling of spin-1 nuclei for sign-sensitive determination of the heteronuclear dipolar coupling has been described. A new dipolar recoupling technique for rotating samples has been developed to achieve high dipolar resolution in a wide range of dipolar coupling strength. The experimental techniques developed herein are capable of delivering detailed model-independent information on molecular motional parameters that can be directly compared in different composites and their bulk analogs. Solid-state NMR has been applied to study the local molecular dynamics of surfactant molecules in nanostructured organic-inorganic composites of different morphologies. On the basis of the experimental profiles of local order parameters, physical motional models for the confined surfactant molecules were put forward. In layered materials, a number of motional modes of surfactant molecules were observed depending on sample composition. These modes ranged from essentially immobilized rigid states to highly flexible and anisotropically tumbling states. In ordered hexagonal silica, highly dynamic conformationally disordered chains with restricted motion of the segments close to the head group have been found. The results presented in this thesis provide a step towards the comprehensive characterization of the molecular states and understanding the great variability of the molecular assemblies in advanced nanostructured organic−inorganic composite materials.QC 20150225
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Kollins, Kaitlin Noelle. "Investigation of Residual Stresses in Melt Infiltrated SiC/SiC Ceramic Matrix Composites using Raman Spectroscopy." Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright1513591335033283.
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