CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Nesse trabalho investigamos as propriedades vibracionais em monocristais D-Metionina, utilizando as espectroscopias Raman e Infravermelho. As medidas de espectroscopia Raman foram realizadas sob a variaÃÃo de pressÃo hidrostÃtica no intervalo de 0GPA atà 7GPa, mostraram duas transiÃÃes de fase, uma por volta 2.0GPa e outra em 2.5GPa, as quais foram detectadas no espectro Raman atravÃs das mudanÃas exibidas pelos picos associados principalmente Ãs vibraÃÃes atribuÃdas à carboxila (CO2-), amina (NH3+), , ligaÃÃes CS e CSC e grupos CH2 e CH3. Esses modos vibracionais tambÃm foram sensibilizados em baixas temperaturas, sendo que suas mudanÃas serviram como referÃncia para identificar a transiÃÃo de fase nas medidas de espalhamento infravermelho no intervalo de temperatura de 298K a 84K. Nas medidas de espalhamento Raman de 298K a 13K, a transiÃÃo foi identificada pelo surgimento do modo translacional em 91 cm-1 por volta de 84K. AlÃm disso, nesse trabalho comparamos o comportamento das mudanÃas apresentadas na rede cristalina dos monocristais de D-metionina de L-metionina sob condiÃÃes extremas de pressÃo. / In this work we have been investigated the vibrational properties of the D-methionine single crystals using the Raman and Infrared spectroscopies. The Raman spectroscopy measurements were performed under varying hydrostatic pressure from 0 GPa up to 7.0 GPa, indicated two transitions, one around 2.0 GPa and another in 2.5GPa, which were detected by changes of the vibrationals modes of the carboxilic (CO2-), amino (NH3+), CS, CSC, CH2 and CH3, respectively. These vibrationals modes also have been sensitized under low temperatures, whose changes have been helpful to identify the phase transition with the measurements of the infrared scattering from 298K up to 84K. In the measurements of the Raman scattering realized between 298K and 84K, the transition was identified by emerging of the translational mode in 91 cm-1 around 84K. Further, in this work we have been compared changes presented by crystal lattice between D-methionine and L-methionine under extremes conditions of the pressure.

The objective of this dissertation is to shed light on the physical properties of InN epilayers grown by High-Pressure Chemical Vapor Deposition (HPCVD) for optical device applications. Physical properties of HPCVD grown InN layers were investigated by X-ray diffraction, Raman scattering, infrared reflection spectroscopies, and atomic force microscopy. The dependencies of physical properties as well as surface morphologies of InN layers grown either directly on sapphire substrates or on GaN/sapphire templates on varied growth conditions were studied. The effect of crucial growth parameters such as growth pressure, V/III molar ratio, precursor pulse separation, substrate material, and mass transport along the flow direction on the optical and structural properties, as well as on the surface morphologies were investigated separately. At present, growth of high-quality InN material by conventional growth techniques is limited due to low dissociation temperature of InN (~600 ºC) and large difference in the partial pressures of TMI and NH3 precursors. In this research, HPCVD technique, in which ambient nitrogen is injected into reaction zone at super-atmospheric growth pressures, was utilized to suppress surface dissociation of InN at high temperatures. At high pressures, long-range and short-range orderings indicate that c-lattice constant is shorter and E2(high) mode frequency is higher than those obtained from low-pressure growth techniques, revealing that InN structure compressed either due to a hydrostatic pressure during the growth or thermal contraction during the annealing. Although the influence of varied growth parameters usually exhibit consistent correlation between long-range and short-range crystalline orderings, inconsistent correlation of these indicate inclination of InN anisotropy. InN layers, grown directly on α-sapphire substrates, exhibit InN (1 0 1) Bragg reflex. This might be due to a high c/a ratio of sapphire-grown InN epilayers compared to that of GaN/sapphire-grown InN epilayers. Optical analysis indicates that free carrier concentration, ne, in the range of 1–50 × 1018 cm–3 exhibits consistent tendency with longitudinal-optic phonon. However, for high ne values, electrostatic forces dominate over inter-atomic forces, and consistent tendency between ne and LO phonon disappears. Structural results reveal that growth temperature increases ~6.6 ºC/bar and V/III ratio affects indium migration and/or evaporation. The growth temperature and V/III ratio of InN thin films are optimized at ~850 ºC and 2400 molar ratio, respectively. Although high in-plane strain and c/a ratio values are obtained for sapphire-grown epilayers, FWHM values of long-range and short-range orderings and free carrier concentration value are still lower than those of GaN/sapphire-grown epilayers. Finally, vibrational and optical properties of chalcopyrite ZGP crystal on the (001), (110), and (10) crystalline planes were investigated by Raman scattering and infrared (IR) reflection spectroscopies. Raman scattering exhibits a nonlinear polarizability on the c-plane, and a linear polarizability on the a- and b-planes of ZGP crystal. Also, birefringence of ZGP crystal was calculated from the hydrostatic pressure difference between (110) and (10) crystalline planes for mid-frequency B2(LO) mode.

The objectives of the work presented were to 1) fabricate reproducible nanorod array SERS substrates, 2) detection of bacteria using nanorod substrates, 3) detection of DNA hybridization using nanorod substrates and 4) critically evaluate the sensing method. Important findings from this work are as follows. A novel method for batch fabrication of substrates for surface enhanced Raman scattering (SERS) has been developed using a modified platen machined to fit in a commercial electron beam evaporator. The use of this holder enables simultaneous deposition of silver nanorod (AgNR) arrays onto six microscope slide substrates utilizing glancing angle deposition. In addition to multiple substrate fabrication, patterning of the AgNR substrates with 36 wells allows for physical isolation of low volume samples. The well-to-well, slide-to-slide, and batch-to-batch variability in both physical characteristics and SERS response of substrates prepared via this method was nominal. A critical issue in the continued development of AgNR substrates is their stability over time, and the potential impact on the SERS response. The thermal stability of the arrays was investigated and changes in surface morphology were evaluated using scanning electron microscopy and x-ray diffraction and correlated with changes in SERS enhancement. The findings suggest that the shelf-life of AgNR arrays is limited by migration of silver on the surface. Continued characterization of the AgNR arrays was carried out using fluorescent polystyrene microspheres of two different sizes. Theory suggests that enhancement between nanorods would be significantly greater than at the tops due to contributing electromagnetic fields from each nanostructure. In contrast to the theory, SERS response of microspheres confined to the tops of the AgNR array was significantly greater than that for beads located within the array. The location of the microspheres was established using optical fluorescence and scanning electron microscopy. The application of SERS to characterizing pathogens such as bacteria and viruses is an active area of investigation. AgNR array-based SERS substrates have enabled detection of pathogens present in biofluids. Specifically, several publications have focused on determining the spectral bands characteristic of bacteria from different species and cell lines. Studies were carried out on three strains of bacteria as well as the medium in which the bacteria were grown. The spectra of the bacteria and medium were surprisingly similar, so additional spectra were acquired for commonly used bacterial growth media. In many instances, these spectra were similar to published spectra purportedly characteristic of specific bacterial species. In addition to bacterial samples, nucleic acid hybridization assays were investigated. Oligonucleotide pairs specifically designed to detect respiratory syncytial virus (RSV) in nasal fluids were prepared and evaluated. SERS spectra acquired on oligos, alone or in combination, contain the known spectral signatures of the nucleosides that comprise the oligo. However, spectra acquired on an oligo with a 5'- or 3' thiol were distinctly different from that acquired on the identical oligo without a thiol pendant group suggesting some control over the orientation of the oligo on the nanorod surface. The signal enhancement in SERS depends markedly upon the location of the probe relative to the substrate surface. By systematic placement of nucleotide markers along the oligo chain, the point at which the nucleotide disappears from the spectrum was identified. The overall findings for AgNR SERS substrates suggest that the applicability of SERS for detecting nucleic acid hybridization is limited. The strong distance dependence coupled with the lack of substrate stability at temperatures required for annealing oligos during hybridization suggest that AgNRs are not the platform to use for hybridization assays.

Nanoscience dominates virtually every field of science and technology in the 21st century. Nanoparticles are of fundamental interest since they possess unique size- dependent properties (optical, electrical, mechanical, chemical, magnetic etc.), which are quite different from the bulk and the atomic state. Bimetallic nanoparticles are of particular interest since they combine the advantages of the individual monometallic counterparts. The present study focuses on bimetallic nanoparticles containing gold as one of the constituents. Au-Pd, Au-Pt and Au-Ag bimetallic/alloy nanoparticles have been prepared by four different synthetic methods, and characterised by a variety of techniques, with an emphasis on Au-Ag alloy systems in the solution phase as well as in the form of nanostructured films on solid substrates. Au- Ag alloy nanoparticles have been used to demonstrate two different applications. The first is the use of Au-Ag monolayer protected alloy clusters in demonstrating single electron charging events in the solution phase as well as in the dry state. Single electron transfer events involving nanosized particles are being probed extensively due to their potential applications in the field of electronics. The second is an analytical application, involving the use of trisodium citrate capped Au-Ag alloy hydrosols as substrates for surface enhanced Raman and resonance Raman scattering [SE(R)RS] studies. The sols have been used for single molecule detection purposes. Various organic molecules such as quinones, phthalocyanines and methyl violet have been self- assembled in a stepwise manner on the nanoparticulate as well as bulk Au, Ag and Au-Ag surfaces, and characterised extensively by spectroscopic, electrochemical and spectroelectrochemical techniques.

Το οξείδιο του ψευδαργύρου (ZnO) ανήκει στην κατηγορία των διάφανων αγώγιμων οξειδίων και θεωρείται ως το ανόργανο υλικό που επιδεικνύει τη μεγαλύτερη ποικιλία χαμηλοδιάστατων νανοδομών. Νανοδομές διαφόρων μορφολογιών του ZnO αναπτύσσονται με πλήθος μεθόδων – με κυριότερες την αέρια μεταφορά σε υψηλή θερμοκρασία (VLS) και τη χημεία διαλυμάτων – και παρουσιάζουν μεγάλο εύρος πιθανών εφαρμογών σε τομείς όπως η οπτική, η οπτικοηλεκτρονική, οι αισθητήρες, η παραγωγή ενέργειας, οι βιοϊατρικές επιστήμες, κ.α. Παρά τη συστηματική έρευνα σχετικά με την ανάπτυξη των νανοδομών αυτών για πάνω από μια δεκαετία, η καθιέρωση μιας πειραματικής μεθοδολογίας ικανής να παρέχει με επαναλήψιμο τρόπο συγκεκριμένες μορφολογίες νανοδομών του ZnO είναι ακόμα ένα ανοικτό ερώτημα. Αυτό αποτελεί και μια από τις τρέχουσες ερευνητικές προκλήσεις αφού οι παραγόμενες μορφολογίες χαρακτηρίζονται από διαφορετικές φυσικές ιδιότητες ενώ είναι αρκετά ευαίσθητες σε μικρές μεταβολές των πειραματικών συνθηκών. Στόχος της παρούσας εργασίας είναι η συστηματική μελέτη του ρόλου διαφόρων παραμέτρων της σύνθεσης στα μορφολογικά χαρακτηριστικά και τις οπτικές ιδιότητες των νανοδομών του ZnO. Η ανάπτυξη των νανοδομών πραγματοποιήθηκε τόσο με αέρια μεταφορά σε υψηλή θερμοκρασία (VLS) όσο και με τη μέθοδο της κρυστάλλωσης σε υδατικά διαλύματα (CBD). Σκοπός είναι να κατανοηθεί πως συγκεκριμένες παράμετροι επηρεάζουν τη μορφολογία των νανοδομών, το μέγεθος, τις κατανομές των διαμέτρων των μονοδιάστατων νανονημάτων και τον προσανατολισμό αυτών στο υπόστρωμα. Στην πρώτη περίπτωση δόθηκε έμφαση στο ρόλο του πάχους του υμενίου του καταλύτη (Au), αλλά και στον τρόπο ανόπτησης αυτού ώστε να δημιουργηθεί η κατάλληλη μορφολογία του καταλύτη η οποία μέσω της ανάπτυξης με τη μέθοδο VLS επηρεάζει κατ’ επέκταση και τη μορφολογία των νανοδομών του ZnO. Έτσι, επιχρυσωμένα υποστρώματα πυριτίου (Si) με πάχος καταλύτη (h) από 2 nm έως 15 nm χρησιμοποιήθηκαν μετά από ανόπτησή τους σε διάφορες θερμοκρασίες και για διαφορετικούς χρόνους για την ανάπτυξη νανονημάτων ZnO. Διαπιστώθηκε ότι για πολύ λεπτά υμένια Au (h ≤ 3 nm) δημιουργούνται σφαιρικά νανοσωματίδια χρυσού και ο χρόνος ανόπτησης δεν επηρεάζει τη μορφολογία και την κατανομή μεγεθών. Για παχύτερα υμένια (h ≥ 5 nm), ανόπτηση για σύντομο χρόνο δεν επαρκεί για την ανάπτυξη νανοσωματιδίων αντίστοιχα με αυτά των λεπτών υμενίων. Στην περίπτωση αυτή, η αύξηση του χρόνου ανόπτησης ή/και αύξηση της θερμοκρασίας ανόπτησης είναι επιβεβλημένη για την ελάττωση του μέσου μεγέθους. Εν γένει, ανόπτηση σε χαμηλότερη θερμοκρασία (400 °C) για μεγάλο χρονικό διάστημα (30 λεπτά) μετατρέπει τα υμένια του Au σε νανοσωματίδια με ευρείες κατανομές μεγεθών και υψηλές μέσες τιμές. Η ανάπτυξη νανονημάτων ZnO εξαρτάται από το μέσο μέγεθος των νανοσωματιδίων του Au. Η ανάπτυξη παρεμποδίζεται στα μεγάλα μεγέθη νανοσωματιδίων Au αφού ο υπερκορεσμός τους με Zn και O είναι αργός. Ως εκ τούτου, για τα υμένια Au με πάχος μεγαλύτερο από ~10 nm η ανάπτυξη νανονημάτων του ZnO είναι εξαιρετικά περιορισμένη. Στη δεύτερη περίπτωση, εξετάστηκε διεξοδικά ένα πλήθος παραμέτρων όπως η συγκέντρωση των αντιδρώντων στο διάλυμα, η παρουσία οργανικών ενώσεων για τον έλεγχο της διαμέτρου, οι ιδιότητες του πρόδρομου υμενίου κρυστάλλωσης στο υπόστρωμα, ο χρόνος κρυστάλλωσης, κ.α. Γυάλινα αγώγιμα υποστρώματα (FTO) στα οποία είχε εναποτεθεί πρόδρομο υμένιο πυρηνοποίησης, χρησιμοποιήθηκαν σε αυτή την περίπτωση για την ανάπτυξη νανονημάτων. Καλά προσανατολισμένες δομές κάθετες στο υπόστρωμα με διάμετρο ~30 nm και μήκος μέχρι ~7 μm δημιουργήθηκαν με χρήση 0.04 Μ ZnAc, 0.02 M HMTA, 0.16 M PEI και 0.04 M NH4OH σε υδατικό διάλυμα στους 95 οC. H χρονική διάρκεια των πειραμάτων κυμάνθηκε στο διάστημα 1 – 24 h. Η τιμή του pH του διαλύματος ήταν περίπου 7. Ο προσανατολισμός των νανοδομών χειροτέρευε με αύξηση του μήκους τους καθώς κάμπτονταν και ενώνονταν με τα γειτονικά τους. Επομένως, για την βελτίωση της δομής τους βρέθηκε ότι είναι απαραίτητη η ανανέωση του διαλύματος κάθε ~2.30 h. Οι παραχθείσες νανοδομές εξετάστηκαν με ηλεκτρονική μικροσκοπία σάρωσης (SEM) και περίθλαση ακτίνων – Χ (XRD). Για την μελέτη των ατελειών στους κρυστάλλους του ZnO χρησιμοποιήθηκε η φασματοσκοπία Raman και η φασματοσκοπία φωτοφωταύγειας (Photoluminescence). Με την φασματοσκοπία Raman μελετήθηκαν οι τρόποι δόνησης των μορίων του υλικού, ενώ με τη φασματοσκοπία φωτοφωταύγειας η ύπαρξη ατελειών στον κρύσταλλο, όπως έλλειψη οξυγόνου, αντικατάσταση ψευδαργύρου με οξυγόνο, κλπ. / Zinc oxide (ZnO) is one of the most important low dimensional semiconducting oxides owing to the amazing variety of the nanostructures it can form by means of various synthesis routes. The most important methods are the vapor deposition and the chemical bath deposition. ZnO nanostructures have attracted considerable attention in view of several applications they encounter such as optics – optoelectronics, sensors, energy production, biomedical sciences, etc. Despite systematic research concerning the rational growth of ZnO nanostructures for over a decade, the establishment of an experimental methodology capable of providing specific morphologies of ZnO nanostructures in a reproducible way is still an open question. This is also one of the current research challenges because the resulting morphologies are characterized by different physical properties and are quite sensitive to small changes in experimental conditions. The current work is aimed at providing a systematic study of the role of various growth parameters on the morphological features and the optical properties of ZnO nanostructures. Growth was achieved by catalyst-assisted (Au) vapor transport at high temperature (VLS) and by solution chemistry (CBD). It is important to gain understanding about how certain parameters affect the morphology of the nanostructures, the size distributions of the diameters and their orientation relative to the substrate. High temperature evaporation methods, such as the vapor-liquid-solid mechanism, have been exploited for the controlled growth of ZnO nanostructures on various substrates. While Au is the most frequently used catalyst for growing ZnO nanowires, its morphological features on the substrate, which determine the size and shape of the nanostructures grown, are not yet methodically explored. In the current work, we investigated the details of thermal dewetting of Au films into nanoparticles on Si substrates. Au films of various thicknesses, h, ranging from 2 to 15 nm, were annealed under slow and fast rates at various temperatures and the morphological details of the nanoparticles formed were investigated. The vapor-liquid-solid method was employed to investigate the role of the Au nanoparticles on the growth details of ZnO nanowires. Efficient and high throughput growth of ZnO nanowires, for a given growth time, is realized in cases of thin Au films, i.e. when the thickness is lower than 10 nm. In the second case, the influence of a number of parameters such as the thickness of the seed layer, the reactants concentration, the existence of organic compounds, the growth time, etc. on the growth of ZnO nanowires on conducting glass substrates (FTO) was examined. After parameter optimization it was found that ZnO nanowires grown have excellent orientation, perpendicular to the substrate, while their diameter and length were found to be ~30 nm and ~7 μm, respectively. The best growth conditions were achieved using 0.04 Μ ZnAc, 0.02 M HMTA, 0.16 M PEI and 0.04 M NH4OH. The reaction temperature was kept at 95 οC for 1 h to 24 h. The pH value was ~ 7. The alignment of ZnO nanowires deteriorates when their length increases; therefore neighboring nanowires bend forming bundles. This shortcoming has been overcome by employing the renewal of the solution every 2.30 h. The structure of ZnO nanowires was investigated by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). Raman scattering was used to study defects of ZnO nanostructures. New Raman modes, in comparison to the bulk crystal, have been assigned to finite size effects and phonon confinement in the nanostructures. Photoluminescence spectroscopy provides evidence for the type of the defects such as oxygen vacancies, zinc interstitials etc.

In this study some of the first row transition metal oxides were transformed to metal sulfides by new solid gas reaction system. Transition metal sulfides have wide application area in industry and technology. Several techniques are known for the production of metal sulfides. Such as reactions between metal or metal oxide with H2S, precipitation in several liquid medium, reaction between metal and sulfur in closed vessel, chemical vapor deposition (CVD) technique. These techniques will have some disadvantages / for example, reactants are rarely available or expensive materials, their production systems are complicated and hard to set up these systems, products contain oxygen or hydrogen or corresponding metal sulfate as impurities. In our new sulfidizing system the reactants are metal oxides, carbon and SO2. These materials can be found easily. Especially, SO2 usage in this system is a big advantage of giving possibility of usage the hazardous waste product of SO2 in industry. The sulfidizing gas mixture was obtained by passing SO2 over activated carbon at 750 OC in a vertical tubular furnace. The obtained gas contains, mainly, CS2, CO and COS. The sulfidizing reactions took place in the horizontal tubular furnace at 450OC-1250 OC. The duration of the reaction, (three hours), and flow rate (60ml/min) of the SO2 gas were kept constant. The products were examined by X-ray powder diffraction and Raman scattering spectroscopy. All examined metal oxides were transformed to metal sulfides by sulfidizing gas mixture successfully. Ti3S5 was obtained from TiO2. Cr2S3 was obtained from Cr2O3. MnS (Alabandite) was obtained from MnO2. FeS and Fe1-xS (Pyrrhotite) were obtained from Fe2O3. Co9S8 (Cobaltpentlandite) and CoS (Jaipurite) were obtained from Co3O4. NiS was obtained from NiO. Cu7.2S, Cu1.6S (Calcocite-Q), Cu1.81S, Cu7S4 (Anilite) Cu9S5 (Digenite), Cu8S5 (Geerite) were obtained from CuO, ZnS was obtained from ZnO. The electrical conductivity character of each product obtained by sulfidizing reaction was analyzed in the temperature range of 77 K-300 K. Titanium sulfide, cobalt sulfide and nickel sulfide showed metallic conductivity, cupper sulfide and iron sulfide showed semiconductor behavior in this temperature range.

A novel combustor design, referred to as the Stagnation Point Reverse-Flow (SPRF) combustor, was recently developed that is able to operate stably at very lean fuel-air mixtures and with low NOx emissions even when the fuel and air are not premixed before entering the combustor. The primary objective of this work is to elucidate the underlying physics behind the excellent stability and emissions performance of the SPRF combustor. The approach is to experimentally characterize velocities, species mixing, heat release and flame structure in an atmospheric pressure SPRF combustor with the help of various optical diagnostic techniques: OH PLIF, chemiluminescence imaging, PIV and Spontaneous Raman Scattering. Results indicate that the combustor is primarily stabilized in a region downstream of the injector that is characterized by low average velocities and high turbulence levels; this is also the region where most of the heat release occurs. High turbulence levels in the shear layer lead to increased product entrainment levels, elevating the reaction rates and thereby enhancing the combustor stability. The effect of product entrainment on chemical timescales and the flame structure is illustrated with simple reactor models. Although reactants are found to burn in a highly preheated (1300 K) and turbulent environment due to mixing with hot product gases, the residence times are sufficiently long compared to the ignition timescales such that the reactants do not autoignite. Turbulent flame structure analysis indicates that the flame is primarily in the thin reaction zones regime throughout the combustor, and it tends to become more flamelet like with increasing distance from the injector. Fuel-air mixing measurements in case of non-premixed operation indicate that the fuel is shielded from hot products until it is fully mixed with air, providing nearly premixed performance without the safety issues associated with premixing. The reduction in NOx emissions in the SPRF combustor are primarily due to its ability to stably operate under ultra lean (and nearly premixed) condition within the combustor. Further, to extend the usefulness of this combustor configuration to various applications, combustor geometry scaling rules were developed with the help of simplified coaxial and opposed jet models.

Optical assays to detect cancer-associated molecular biomarkers in biological substrates are commonly performed with antibody-targeted organic dye contrast agents but the potential for precise quantification, long-term imaging, and multiplexed readouts is limited by chemical and optical instability, non-optimal spectral characteristics, and complicated synthetic chemistry of the dyes. This dissertation tested the hypothesis that a novel class of optical contrast agents termed polymer-protected Raman-encoded nanoparticle tags (PRENTs) provides practical advantages over existing optical technologies for molecular diagnostic applications. First, PRENTs were developed through a modular design utilizing gold-nanoparticle-Raman reporter complexes protected and functionalized by polyethylene glycol derivatives. PRENTs produced optical readouts through surface enhanced Raman scattering (SERS) that were brighter and more photostable than the fluorescence of semiconductor quantum dots under identical experimental conditions. Unique spectral signatures were produced with a broader class of Raman reporters than is possible with silica coated Raman tags. Spectral signatures and colloidal stability of PRENTs were unaffected by harsh chemical conditions that cause spectral changes and aggregation of dyes, quantum dots, and protein coated Raman tags. Antibody-targeted PRENTs specifically tagged cell surface cancer biomarkers on living cells at reasonable integration times. PRENTs were non-toxic to cells under conditions exceeding those required for sensitive molecular detection. Next, PRENTs were efficiently optimized for excitation with near-infrared light through inclusion of near-infrared chromophores as Raman reporters and exploitation of the size-dependent optical enhancement of gold nanoparticles. Third, the development of a slide-based Raman-linked immunosorbent assay using antibody-conjugated PRENTs enabled quantification of protein biomarkers with a dynamic range of 3 to 4 logs. In summary, this dissertation establishes PRENTs as novel optical tags with unique features useful for biomedical applications and provides insights for further assay development.

Διανύουμε μια εποχή, όπου οι ανάγκες για μετάδοση πληροφορίας αυξάνονται ταχύτατα, με αποτέλεσμα τα χάλκινα καλώδια να μην αρκούν για να μεταδώσουν το πλήθος αυτό της πληροφορίας. Έτσι, περάσαμε στις Οπτικές Τηλεπικοινωνίες, όπου τα χάλκινα καλώδια αντικαταστάθηκαν από οπτικές ίνες και φορείς μετάδοσης της πληροφορίας δεν είναι πλέον τα ηλεκτρόνια αλλά τα φωτόνια. Κατά τη μετάδοση της πληροφορίας υπάρχουν όμως, φαινόμενα εξασθένησης και παραμόρφωσης του σήματος. Τη λύση σε αυτά τα προβλήματα καλείται να δώσει η χρήση σολιτονίων. Στην παρούσα διπλωματική εργασία, θα μελετήσουμε τον τρόπο με τον οποίον επηρεάζουν τα φαινόμενα ανώτερης τάξης την αλληλεπίδραση δύο γειτονικών σολιτονιακών παλμών που διαδίδονται μέσα σε μία οπτική ίνα. Πιο συγκεκριμένα, με τη χρήση αλγόριθμου της Fortran θεωρήσαμε δύο θεμελιώδεις σολιτονιακούς παλμούς και μελετήσαμε πως επηρεάζεται η διάδοσή τους κατά μήκος μιας οπτικής ίνας, αλλά και η μεταξύ τους αλληλεπίδρασή, από τη μεταξύ τους απόσταση, το σχετικό τους πλάτος καθώς και από τη διαφορά φάσης. Επιπλέον περιορίζοντας τη μεταξύ τους αλληλεπίδραση μελετήσαμε το πώς επηρεάζουν τη διάδοσή τους φαινόμενα ανώτερης τάξης όπως η σκέδαση Raman, η αυτό-διαμόρφωση απότομων άκρων (self-steepening) και η διασπορά τρίτης τάξης. / We are in an era where the need to transmit information rapidly increases, making the copper wires not enough to convey the multitude of this information. Thus, we moved on Optical Communications, where the copper cables were replaced by optical fibers and broadcasters of information are no longer electrons but photons. During the transmission of information we come across with problems such as attenuation and signal distortion. The use of solitons has come to give the solution to these problems. In this paper, we studied how the higher order phenomena, affects the interaction of two neighboring soliton pulses propagating through an optical fiber. More specifically, using a Fortran algorithm considering two fundamental soliton pulses we have studied how the propagation and their interaction is affected by their relative amplitude and phase difference. Also limiting the interaction between them, we have studied how the propagation is affected by higher order phenomena such as Stimulated Raman Scattering, Self Steepening and third order dispersion.

La diffusion Raman exaltée de surface (SERS) est utilisée pour la mise au point d’un biocapteur capable de détecter des pesticides dans l’eau, en se basant sur le suivi de l’activité enzymatique de l’Acétylcholinestérase (ACHE). Les nanoparticules d’or sont utilisées comme substrats SERS actifs. Le signal Raman exalté de l’analyte est optimisé en testant plusieurs types de nanoparticules.Le Raman SERS a permis la détection directe du Paraoxon (PO) et du carbaryl (CA) et la possibilité de suivi de l’activité de l’ACHE. En absence d'inhibiteurs, la molécule d’acétylcholine (ATC) est transformée en acide acétique et en choline par l’enzyme ACHE. La mesure de l’activité de l’ACHE repose sur le suivi des concentrations en ATC car sa transformation est inhibée en présence de pesticides. Il a été ainsi possible d’établir une relation linéaire entre la concentration de pesticides et l’exaltation du signal Raman de l’ATC non transformé. La méthode a permis la détection du PO et du CA, avec une limite de détection beaucoup plus faible que la détection directe. Ce biocapteur basé sur l’activité de l’ACHE a ensuite été utilisé pour l'évaluation d’autres polluants (inhibiteurs d’ACHE) comme les additifs contenus dans les plastiques notamment. Enfin, nous avons développé une seconde approche qui consistait à mesurer l’activité de l’ACHE en utilisant la diffusion dynamique de la lumière. En effet, nous avons montré que les paramètres physicochimiques (agrégation) des AuNPs en contact avec certaines molécules, sont fortement influencés par l’activité enzymatique de l’ACHE. C’est ce phénomène d’instabilité qui nous a permis de distinguer entre les deux cas : absence et présence de PO. / Surface-enhanced Raman scattering (SERS) was used to develop a biosensor for the detection of pesticides through the monitoring of the enzymatic activity of acetylcholinesterase (ACHE). Gold nanoparticles (AuNPs) were used as an active SERS substrate. The enhanced Raman signal of the analyte is optimized by testing several types of nanoparticles. Raman SERS allowed the direct detection of Paraoxon (PO) and carbaryl (CA) pesticides and the possibility of follow-up of the activity of the ACHE. In the absence of inhibitors, the acetylcholine (ATC) is transformed into acetic acid and choline by the enzyme ACHE. The measurement of ACHE activity is performed through the monitoring of ATC concentrations because its transformation is inhibited in the presence of pesticides. Results showed a linear correlation between the concentration of pesticides and the SERS signal of the untransformed ATC. The method was optimized for the quantification of paraoxon and carbaryl with a limit of quantification much lower than the one obtained with a direct detection. Their identification was also possible using chemometrics. This biosensors, based on the ACHE activities, was applied to the evaluation of emergent pollutants: additives of commercial polymers. Our results suggested that most of the tested polymers contained molecules that act as inhibitors of the ACHE. Finally, we propose another very simple approach to measure the ACHE activity using dynamic light scattering measurements. We found that the physicochemical parameters (aggregation) of AuNPs were strongly influenced by the enzymatic activity of ACHE when in contact with specified molecules, allowing to detect the presence of PO.