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In situ Raman-Spektroskopie an Metallphthalocyaninen: Von ultradünnen Schichten zum organischen FeldeffekttransistorLudemann, Michael 01 July 2016 (has links)
Im ersten Teil der Arbeit werden Signalverstärkungsmechanismen für Raman-Spektroskopie erschlossen und evaluiert. Die als geeignet bewerteten Methoden finden im zweiten Teil ihre Anwendung zur Untersuchung der vibronischen Eigenschaften von dünnen Manganphthalocyaninschichten, die anschließend mit Kalium interkaliert werden. Hierbei sind verschiedene Phasen identifizierbar, die ein ganzzahliges Verhältnis von Kaliumatomen zu Manganphthalocyaninmolekülen besitzen. Im dritten Teil werden die elektrischen Eigenschaften durch die Verwendung dieses Materialsystems als aktives Medium eines Feldeffekttransistors untersucht.:1. Einleitung
2. Theoretische Grundlagen der angewendeten Effekte
3. Experimentelle Details
4. Herstellung, Charakterisierung und Optimierung von Substraten für Raman-Oberflächenverstärkungseffekte
5. Untersuchung zu Verstärkungsmechanismen des Raman-Effekts an dünnen organischen Schichten
6. Interkalation mit Kalium in dünne Schichten aus Manganphthalocyanin
7. MnPc unter Spannungs- und Stromeinfluss - Der Feldeffekttransistor
8. Zusammenfassung
Anhang
Literatur
Abbildungsverzeichnis
Eidesstattliche Versicherung
Lebenslauf
Liste wissenschaftlicher Leistungen
Danksagung
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Development of a Temperature Controlled Cell for Surface Enhanced Raman Spectroscopy for in situ Detection of GasesAppelblad, André January 2014 (has links)
This work describes a master’s thesis in engineering physics at Umeå University carried out during the spring semester of 2014. In the thesis the student has constructed and tested a temperature controlled cell for cooling/heating of surface-enhanced-Raman-spectroscopy (SERS) substrates for rapid detection of volatile substances. The thesis was carried out at the Swedish Defence Research Agency (FOI) in Umeå, Sweden. A Linkam Scientific Instruments TS1500 cell was equipped with a Peltier element for cooling/heating and a thermistor temperature sensor. A control system was constructed, based on an Arduino Uno microcontroller board and a pulse-width-modulated (PWM) H-bridge motor driver to control the Peltier element using a proportional-integral (PI) control algorithm. The temperature controlled cell was able to regulate the temperature of a SERS substrate within -15 to +110 °C and maintain the temperature over prolonged periods at ±0.22 °C of the set point temperature. Gas phase of 2-chloro-2-(difluoromethoxy)-1,1,1-trifluoro-ethane (isoflurane) was flowed through the cell and SERS spectra were collected at different temperatures and concentrations. This test showed that the signal is increased when the substrate is cooled and reversibly decreased when the substrate was heated. Keywords: temperature control, Raman scattering, surface enhanced Raman spectroscopy SERS, SERS substrate, volatile substances, Peltier module, thermistor, PWM, H-bridge, PI(D) control. / Detta dokument beskriver ett examensarbete för civilingenjörsexamen i teknisk fysik vid Umeå Universitet som utförts under vårterminen 2014. I examensarbetet har en kyl-/värmecell för temperaturkontroll av substratytor för ytförstärkt ramanspektroskopi (SERS) för snabb detektion av farliga flyktiga ämnen konstruerats och testats. Arbetet utfördes vid Totalförsvarets forskningsinstitut (FOI) i Umeå, Sverige. Utgångspunkten var ett Linkam Scientific Instruments TS1500 mikroskopsteg, vilket utrustades med ett Peltierelement för kylning/värmning och en termistor för temperaturövervakning. Ett styrsystem baserat på ett Arduino Uno mikrostyrenhetskort konstruerades med ett motordrivkort (H-brygga) vilket använder pulsbreddsmodulering (PWM) för att reglera spänningen till Peltierelementet utifrån en PI-regulator. Den färdiga cellen klarade att reglera temperaturen på ett SERS-substrat i ett temperaturspann på ungefär -15 till +110 °C med en temperaturstabilitet på ±0.22 °C av måltemperaturen. Cellen testades sedan på flyktiga ämnen för att visa dess funktion. Difluorometyl-2,2,2-trifluoro-1-kloroetyleter (isofluran) i gasfas, med instrumentluft som bärargas, flödades genom cellen och SERS-spektra erhölls vid olika koncentrationer och temperaturer. Vid samtliga koncentrationer visades att lägre temperatur ger ökad signalstyrka. När ytan sedan värmdes upp sjönk signalen reversibelt tillbaka till ursprungsvärdet. Nyckelord: temperaturkontroll, ytförstärkt ramanspektroskopi, SERS, flyktiga ämnen, Peltierelement, thermistor, PWM, H-brygga, PI(D)-regulator.
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Détection de protéines par diffusion Raman exaltée par effet de pointe (TERS)Faid, Rita 07 1900 (has links)
La concentration locale des messagers chimiques sécrétés par les cellules peut être mesurée afin de mieux comprendre les mécanismes moléculaires liés à diverses maladies, dont les métastases du cancer. De nouvelles techniques analytiques sont requises pour effectuer ces mesures locales de marqueurs biologiques à proximité des cellules. Ce mémoire présentera le développement d’une nouvelle technique basée sur la réponse plasmonique sur des leviers AFM, permettant d’étudier les réactions chimiques et biologiques à la surface des leviers grâce au phénomène de résonance des plasmons de surface (SPR), ainsi qu’à la diffusion Raman exaltée par effet de pointe (TERS). En effet, il est possible de localiser l’amplification du signal Raman à la pointe d’un levier AFM, tout comme le principe de la diffusion Raman exaltée par effet de surface (SERS) basée sur la diffusion de la lumière par des nanoparticules métalliques, et permettant une large amplification du signal Raman. La surface du levier est recouverte d’une nano-couche métallique d’or, suivi par des réactions biologiques pour l’immobilisation d’un récepteur moléculaire, créant ainsi un biocapteur sur la pointe du levier. Une détection secondaire utilisant des nanoparticules d’or conjuguées à un anticorps secondaire permet également une amplification du signal SPR et Raman lors de la détection d’antigène. Ce mémoire démontrera le développement et la validation de la détection de l’immunoglobuline G (IgG) sur la pointe du levier AFM.Dans des projets futurs, cette nouvelle technique d’instrumentation et d’imagerie sera optimisée grâce à la création d’un micro-détecteur protéique généralement adapté pour l’étude de la communication cellulaire. En intégrant le signal SPR à la microscopie AFM, il sera alors possible de développer des biocapteurs SPR couplés à une sonde à balayage, ce qui permettra d’effectuer une analyse topographique et de l’environnement chimique d’échantillons cellulaires en temps réel, pour la mesure des messagers moléculaires sécrétés dans la matrice extracellulaire, lors de la communication cellulaire. / Measurement of the local concentration of chemical messengers secreted by cells may give a better understanding of molecular mechanisms related to different diseases, such as cancer metastasis. Current techniques are not suited to perform such measurements and thus, new analytical techniques must be developed. This Master’s thesis reports the development of a new technique based on the plasmonic response of atomic force microscopy (AFM) tips, which will ultimately allow monitoring of chemical and biological molecules on the surface of a cantilever by use of surface plasmon resonance (SPR) and tip-enhanced Raman scattering (TERS). Indeed, it is possible to localize the enhancement of the Raman signal on the AFM tip using principles associated to surface-enhanced Raman spectroscopy (SERS), based on the absorption of light by nanometer-sized metal particles, resulting in a large enhancement of the Raman signal. The AFM tip was constructed by the deposition of a nanometer-size gold layer, followed by the assembly of a biosensor with a biomolecular receptor. Gold nanoparticles (AuNPs) conjugated with a secondary antibody served as the secondary detection step. In addition, the use of the gold nanoparticles for antigen detection allows an amplification of the SPR and Raman signals. This Master’s thesis will demonstrate the development and validation of a biosensor for immunoglobuline G (IgG) at the tip of an AFM cantilever.This thesis sets the basis for future projects, where this new imaging technique will be developed for monitoring cellular communication by exploiting the plasmonic signal at the AFM tip. Different biosensors will then be developed and coupled to an AFM probe for scanning the chemical environment and detect in real-time chemical messengers secreted in the extracellular matrix in cellular communication.
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Design, characterisation and biosensing applications of nanoperiodic plasmonic metamaterials / Conception, caractérisation et applications de métamatériaux nanopériodiques plasmoniques pour biocapteursDanilov, Artem 11 April 2018 (has links)
Cette thèse considère de nouvelles architectures prometteuses des métamatériaux plasmoniques pour biosensing, comprenant: (I) des réseaux périodiques 2D de nanoparticules d'Au, qui peuvent supporter des résonances des réseaux de surface couplées de manière diffractive; (II) Reseaux 3D à base de cristaux plasmoniques du type d'assemblage de bois. Une étude systématique des conditions d'excitation plasmonique, des propriétés et de la sensibilité à l'environnement local dans ces géométries métamatérielles est présentée. On montre que de tels réseaux peuvent combiner une très haute sensibilité spectrale (400 nm / RIU et 2600 nm / RIU, ensemble respectivement) et une sensibilité de phase exceptionnellement élevée (> 105 deg./RIU) et peuvent être utilisés pour améliorer l'état actuel de la technologie de biosensing the-art. Enfin, on propose une méthode de sondage du champ électrique excité par des nanostructures plasmoniques (nanoparticules uniques, dimères). On suppose que cette méthode aidera à concevoir des structures pour SERS (La spectroscopie du type Raman à surface renforcée), qui peut être utilisée comme une chaîne d'information supplémentaire à un biocapteur de transduction optique. / This thesis consideres novel promissing architechtures of plasmonic metamaterial for biosensing, including: (I) 2D periodic arrays of Au nanoparticles, which can support diffractively coupled surface lattice resonances; (II) 3D periodic arrays based on woodpile-assembly plasmonic crystals, which can support novel delocalized plasmonic modes over 3D structure. A systematic study of conditions of plasmon excitation, properties and sensitivity to local environment is presented. It is shown that such arrays can combine very high spectral sensitivity (400nm/RIU and 2600 nm/RIU, respectively) and exceptionally high phase sensitivity (> 105 deg./RIU) and can be used for the improvement of current state-of-the-art biosensing technology. Finally, a method for probing electric field excited by plasmonic nanostructures (single nanoparticles, dimers) is proposed. It is implied that this method will help to design structures for SERS, which will later be used as an additional informational channel for biosensing.
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Application of Raman and Fluorescence Spectroscopy to Single Chromatographic BeadsLarsson, Mina January 2005 (has links)
<p>Chromatography is a powerful technique, essential in chemical analyses and preparative separation in industry and research. Many different kinds of chromatographic material are needed, due to the large variety of applications. Detailed methods of characterisation are needed to design new chromatographic materials and understand their properties. In this thesis, confocal Raman spectroscopy and surface enhanced Raman spectroscopy (SERS) have been applied to micrometer-size chromatographic beads, for which these techniques have not been used earlier. New methodology, optimized for use with the chromatographic beads, has been developed and evaluated. </p><p>Confocal spectroscopy has been used to determine distributions of functional groups within single chromatographic beads. This distribution is of great importance in determining the chromatographic properties, since the material is porous and the solute molecules can diffuse inside the beads. Most of the confocal experiments have been performed with Raman spectroscopy; fluorescence spectroscopy, using Nd<sup>3+</sup> ions or dye-labelled proteins as fluorescence probes, has been used for comparison. </p><p>The concentration of adsorbed analytes is very low within the beads. SERS was therefore used to enhance the Raman signal. SERS-active surfaces were prepared by incorporating gold nano-particles into the interior of the bead. TEM measurements showed that the gold nano-particles could be observed throughout, and it was possible to record analyte spectra from different positions within the bead. Enhanced spectra could be obtained both for small test molecules and for larger bio-molecules, although the spectra for the smaller analytes were much more intense.</p>
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Application of Raman and Fluorescence Spectroscopy to Single Chromatographic BeadsLarsson, Mina January 2005 (has links)
Chromatography is a powerful technique, essential in chemical analyses and preparative separation in industry and research. Many different kinds of chromatographic material are needed, due to the large variety of applications. Detailed methods of characterisation are needed to design new chromatographic materials and understand their properties. In this thesis, confocal Raman spectroscopy and surface enhanced Raman spectroscopy (SERS) have been applied to micrometer-size chromatographic beads, for which these techniques have not been used earlier. New methodology, optimized for use with the chromatographic beads, has been developed and evaluated. Confocal spectroscopy has been used to determine distributions of functional groups within single chromatographic beads. This distribution is of great importance in determining the chromatographic properties, since the material is porous and the solute molecules can diffuse inside the beads. Most of the confocal experiments have been performed with Raman spectroscopy; fluorescence spectroscopy, using Nd3+ ions or dye-labelled proteins as fluorescence probes, has been used for comparison. The concentration of adsorbed analytes is very low within the beads. SERS was therefore used to enhance the Raman signal. SERS-active surfaces were prepared by incorporating gold nano-particles into the interior of the bead. TEM measurements showed that the gold nano-particles could be observed throughout, and it was possible to record analyte spectra from different positions within the bead. Enhanced spectra could be obtained both for small test molecules and for larger bio-molecules, although the spectra for the smaller analytes were much more intense.
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Spectroelectrochemistry of self-assembled monolayers of 2- and 4-mercaptopyridinesHassan, Nazly 10 July 2007 (has links) (PDF)
Die Elektrochemie und die Spektroelektrochemie von selbst-organisiererten Monoschichten (selfassembled
monolayers, SAMs) gebildet aus 2-Mercaptopyridin (2MP) und 4-Mercaptopyridin
(4MP) wurden an polykristallinen Goldelektroden in wässrigen Elektrolytlösungen untersucht.
Folgende Untersuchungsmethoden wurden angewandt: zyklische Voltammetrie, elektrochemische
Impedanzmessungen (EIM) und oberflächenverstärkte Raman Streuung (surface-enhanced Raman
scattering, SERS).
Die elektrochemischen Untersuchungen von 2MP und 4MP in wässriger saurer Lösung (0.5 M
H2SO4) zeigten, dass 2MP stärker adsorbiert wird als 4MP aufgrund der Bildung eines S-Au-N Chelates,
wobei die S-Au-Interaktionen bei 4MP stärker sind. Die Bildung eines Chelates im Falle
von 2MP verringert die Wahrscheinlichkeit der Bildung eines Dimers. In sauren Lösungen wird
das N-Atom von 2MP protoniert, was zu einer schwächeren Bindung von 2MP-Molekülen zur
Substratoberfläche führt. Die Ergebnisse der SERS-Untersuchungen stimmen mit den Resultaten
aus der zyklischen Voltammetrie überein. Man erhält eine Au-S-Streckschwingungsbande für
2MP zwischen 225 bis 250 cm-1 bei Abscheidung aus wässriger oder saurer Lösung und für 4MP
bei ca. 263 cm-1 in beiden Lösungen. Die SERS-Experimente ergaben eine senkrechte Orientierung
zur Goldoberfläche sowohl für 2MP als auch für 4MP. Die Thion-Thiol-Tautomerie von 2-
Mercaptopyridinen wurde ebenfalls in Betracht gezogen.
Die Unter- und Überpotentialabscheidung von Kupfer auf einer polykristallinen Goldelektrode in
wässriger 0.1 M Schwefelsäure in An- und Abwesenheit von SAMs von 2- und 4-
Mercaptopyridin wurde mit zyklischer Voltammetrie untersucht. Es zeigte sich, daß bei Vorhandensein
der SAMs die Elektrodeposition von Kupfer verhindert wird, was auf starke Wechselwirkungskräfte
zwischen dem Adsorbat (MP) und der Goldoberfläche zurückzuführen ist. 2MP zeigt
eine grössere Inhibierung, was höchstwahrscheinlich auf die Bildung der Chelatstruktur zurückzuführen
ist. Es wurden ebenso Untersuchungen zum Einfluss von 2MP und 4MP auf die abgeschiedene
Kupfermonolage auf der Goldelektrode durchgeführt. Es zeigte sich, daß die Kupfermonolage
teilweise durch 2MP oder 4MP ersetzt wird.
Die Elektronenaustauschgeschwindigkeit für das Fe2+/Fe3+-Redoxsystem in An- und Abwesenheit
von 2MP- oder 4MP-Monolagen wurde mit zyklischer Voltammetrie und elektrochemischen Impedanzmessungen
(EIM) untersucht. Es stellte sich heraus, dass der Elektronenaustausch höchstwahrscheinlich
über Defektstellen in der Monolage (Pinholes) erfolgt. In einer wässrigen Lösung
verringert 4MP den Elektronenaustausch stärker als 2MP. Da die Packungsdichte bei 4MP größer
ist als bei 2MP ist wahrscheinlich auch die Zahl der Pinholes geringer in der 4MP-Monolage. In
saurer Lösung liegen die N-Atome protoniert vor. Man kann davon ausgehen, dass in saurer Lösung
zwei Prozesse gleichzeitig ablaufen, die für den Elektronenaustausch entscheidend sind. Erstens
kommt es zu einer Abstoßung zwischen der positiv geladenen Monolage und den positiv geladenen
Redoxionen. Und zweitens erfolgt eine Abstoßung zwischen den positiv geladenen Molekülen
der SAMs, was zu einer geringeren Packungsdichte führt. Der Ladungsaustausch wird dominiert
durch den zweiten Effekt.
Mit Hilfe von EIM wurden die Elektronenaustauschgeschwindigkeit und der Bedeckungsgrad bestimmt.
Die korrosionshemmende Wirkung von 2MP und 4MP auf Stahl in 3.5 % wässriger NaCl-Lösung
wurde mit Hilfe der EIM untersucht. 2MP zeigte eine grössere Hemmung als 4MP. / The electrochemistry and spectroelectrochemistry of the self-assembled
monolayers (SAMs) prepared of 2-mercaptopyridine (2MP) and 4-mercaptopyridine
(4MP) dissolved either in water or 0.1 M H2SO4 have been investigated at polycrystalline
gold electrodes in aqueous electrolyte solutions using cyclic voltammetry, electrochemical
impedance measurements (EIM) and surface enhanced Raman spectroscopy
(SERS).
Electrochemical studies of 2MP and 4MP monolayers in aqueous acidic solution
(0.5 M H2SO4) suggest that 2MP is adsorbed more strongly than 4MP due to the
formation of S-Au-N chelate. However, the S-Au bond was found to be stronger in
4MP as compared with 2MP. The formation of the chelate in case of 2MP diminishes
the probability of dimer formation. In the acidic solvent, the N-atom of 2MP molecule
will be protonated leading to a weaker interaction of 2MP molecules with the substrate
surface. The SERS results are in good agreement with the cyclic voltammetry
results. The Au-S stretching band was obtained in the region from 215 to 245 cm-1 for
2MP deposited from water and acidic solvent and around 263 cm-1 for 4MP in both
solvents. The SERS measurements showed also a perpendicular orientation of both
2MP and 4MP on the gold surface. In explaining the SERS results, the thione-thiol
tautomerisations of the mercaptopyridines were also taken into consideration.
The under- and overpotential deposition of copper on a polycrystalline gold
electrode in aqueous 0.1 M sulfuric acid in the presence and in the absence of SAMs
of 2- and 4-mercaptopyridine has been studied using cyclic voltammetry. In general,
the presence of these SAMs has been found to inhibit the electrodeposition process of
copper, suggesting very strong interactions between these adsorbates and the Au surface.
2MP shows a higher degree of inhibition, which is due to a stronger interaction
probably due to the formation of the chelate structure. Studies have also been made of
the influence of mercaptopyridines SAMs on the copper monolayer electrodeposited
on the gold surface. The copper adlayer was found to be partially displaced by 2MP
and 4MP monolayers.
The rate of electron transfer for the Fe3+/2+ redox system on the gold electrode
has been probed in the absence and presence of 2MP and 4MP monolayers by cyclic
voltammetry and electrochemical impedance measurements (EIM). The charge transfer
process was suggested to occur through the defects (pinholes) in the monolayer. In
case of aqueous solvent 4MP decreases the electron transfer reaction stronger than
2MP. Since the packing density for 4MP is higher than that of 2MP the number of
pinholes might be lower in 4MP monolayer. In acidic solvent the N-atoms of the mercaptopyridines
will be protonated. It is proposed that two effects, which exist at the
same time, are responsible for the electron transfer process in acidic solution. First,
there will be a repulsive interaction between the positively charged monolayer and the
positively charged redox probe. Second, there is a repulsion among the positively
charged monolayer molecules that results in a less compact monolayer. The charge
transfer is dominated due to the latter effect. With the EIM the rate of electron transfer
and the surface coverage were determined.
2MP and 4MP were examined as steel corrosion inhibitors in 3.5% aqueous
NaCl solution using EIM. 2MP shows higher inhibition efficiency than 4MP.
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Development of Epidermal Growth Factor Receptor (EGFR) Specific Nanoprobes for Surface Enhanced Raman Spectroscopy (SERS)Lucas, Leanne Jennifer 29 July 2013 (has links)
Novel biocompatible nanoprobes for optical imaging of Epidermal Growth Factor receptor (EGFR) were created. 5 and 18 nm gold nanoparticles (AuNPs) and 5 and 45 nm diameter silver nanoparticles (AgNPs) were conjugated to EGF protein via ?-lipoic acid. AgNPs were not previously attached to EGF. TOF-MS confirms EGF-linker formation. ELISA verifies the linked-EGF activity alone and with EGF-NPs. Core-shell silver-gold nanoparticles (AgAuNPs) gave similar results. TEM staining with uranyl acetate exhibits a bright ring, smaller than EGF, around nanoparticles. Dark field microscopy shows localized, intense cytoplasmic scattering, possibly lipid droplets, in cancer cells incubated with or without nanoprobes. Following injection, mice organs were harvested for EGF-NP immune response determination. Sterilization likely inactivated EGF before ICP-MS. Intense surface enhanced Raman scattering (SERS, 632.8 nm) follows MgSO4 induced EGF-AgNPs aggregation. Pelleted EGF-AgNP tagged cancer cells lack SERS indicative intensity contrast. AgAuNPs could provide increased stability, brighter SERS, and reduced silver biocompatibility concerns.
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Adsorbuotų ant metalo paviršiaus monosluoksnių su piridinio funkcine grupe struktūros ir sąveikos su tirpalo komponentais tyrimas virpesinės spektroskopijos metodais / Vibrational spectroscopic study on the structure and interaction with solution components of monolayers with pyridinium functional group adsorbed on metal surfaceMatulaitienė, Ieva 06 January 2014 (has links)
Savitvarkiai monosluoksniai suteikia metalų paviršiams norimas savybes ir plačiai taikomi elektronų pernašos tyrimuose, konstruojant (bio)jutiklius, biotechnologinius bei fotoelektroninius procesus. Teigiamo krūvio monosluoksniai naudojami kuriant anijonų jutiklius ir (bio)technologinius procesus su adsorbuotomis neigiamo krūvio makromolekulėmis. Darbe buvo susintetinta bifunkcinė molekulė su galinėmis tiolio ir piridinio grupėmis, suformuotas monosluoksnis ir ištirtos jo struktūrinės ir funkcinės savybės. Pagrindiniai darbo tikslai buvo ištirti N-(6-merkapto)heksilpiridinio (MHP) adsorbuoto ant Au ir Ag elektrodų struktūrą ir nustatyti monosluoksnio sąveikos su neorganiniais anijonais, dodecilsulfato anijonu ir grafeno oksidu dėsningumus. Naudojant paviršiaus sustiprintos Ramano spektroskopijos, kvantų chemijos skaičiavimo ir izotopinio pakeitimo metodus nustatyti MHP struktūros ir orientacijos elektrodo atžvilgiu Ramano sklaidos žymenys. Tiriant juostų intensyvumo priklausomybes nuo potencialo ir žadinančios spinduliuotės bangos ilgio parodyta, kad Au/MHP sistemoje pasireiškia krūvio pernešimo Ramano spektrų stiprinimo mechanizmas. Nustatyta, kad adsorbuotų neorganinių anijonų pilnai simetrinio virpesio dažnis sumažėja lyginant su tirpalo spektru ir tas pokytis koreliuoja su Gibso dehidracijos energija. Parodyta, kad MHP pritraukia grafeno oksidą. Nustatyta, kad grafeno oksido C-C ryšio ilgis ir elektroninė struktūra gali būti keičiama, keičiant potencialą. / Self-assembled monolayers provide possibility of changing metal surface properties in controllable manner and are widely used in studies of electron transfer, construction of (bio)sensors, and biotechnological and photoelectronic processes. Positively charged monolayers are valuable in development of sensors for anions and (bio)technological processes with adsorbed negatively charged macromolecules. In this work the structural and functional properties of monolayer formed from synthesized molecule with terminal thiol and pyridinium groups have been studied. The main tasks were to assess the structure of N-(6-mercapto)hexylpyridinium (MHP) on Ag and Au electrodes, and to determine the peculiarities of interaction with inorganic anions, dodecylsulfate, and graphene oxide. Based on surface enhanced Raman spectroscopy (SERS), quantum chemical calculations, and isotopic substitution studies, the Raman marker bands for structure and orientation of MHP have been evaluated. Dependence of SERS intensity on potential and excitation wavelength has revealed the operation of charge transfer Raman enhancement mechanism. It was found that the frequency of symmetric stretching mode of adsorbed ions decreases comparing with solution value and the extent of the shift correlates with the Gibbs dehydration energy. Adsorption of graphene oxide at MHP monolayer has been demonstrated. The electronic structure and length of C-C bonds of graphene oxide was found to be altered by the potential.
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Vibrational spectroscopic study on the structure and interaction with solution components of monolayers with pyridinium functional group adsorbed on metal surface / Adsorbuotų ant metalo paviršiaus monosluoksnių su piridinio funkcine grupe struktūros ir sąveikos su tirpalo komponentais tyrimas virpesinės spektroskopijos metodaisMatulaitienė, Ieva 06 January 2014 (has links)
Self-assembled monolayers provide possibility of changing metal surface properties in controllable manner and are widely used in studies of electron transfer, construction of (bio)sensors, and biotechnological and photoelectronic processes. Positively charged monolayers are valuable in development of sensors for anions and (bio)technological processes with adsorbed negatively charged macromolecules. In this work the structural and functional properties of monolayer formed from synthesized molecule with terminal thiol and pyridinium groups have been studied. The main tasks were to assess the structure of N-(6-mercapto)hexylpyridinium (MHP) on Ag and Au electrodes, and to determine the peculiarities of interaction with inorganic anions, dodecylsulfate, and graphene oxide. Based on surface enhanced Raman spectroscopy (SERS), quantum chemical calculations, and isotopic substitution studies, the Raman marker bands for structure and orientation of MHP have been evaluated. Dependence of SERS intensity on potential and excitation wavelength has revealed the operation of charge transfer Raman enhancement mechanism. It was found that the frequency of symmetric stretching mode of adsorbed ions decreases comparing with solution value and the extent of the shift correlates with the Gibbs dehydration energy. Adsorption of graphene oxide at MHP monolayer has been demonstrated. The electronic structure and length of C-C bonds of graphene oxide was found to be altered by the potential. / Savitvarkiai monosluoksniai suteikia metalų paviršiams norimas savybes ir plačiai taikomi elektronų pernašos tyrimuose, konstruojant (bio)jutiklius, biotechnologinius bei fotoelektroninius procesus. Teigiamo krūvio monosluoksniai naudojami kuriant anijonų jutiklius ir (bio)technologinius procesus su adsorbuotomis neigiamo krūvio makromolekulėmis. Darbe buvo susintetinta bifunkcinė molekulė su galinėmis tiolio ir piridinio grupėmis, suformuotas monosluoksnis ir ištirtos jo struktūrinės ir funkcinės savybės. Pagrindiniai darbo tikslai buvo ištirti N-(6-merkapto)heksilpiridinio (MHP) adsorbuoto ant Au ir Ag elektrodų struktūrą ir nustatyti monosluoksnio sąveikos su neorganiniais anijonais, dodecilsulfato anijonu ir grafeno oksidu dėsningumus. Naudojant paviršiaus sustiprintos Ramano spektroskopijos, kvantų chemijos skaičiavimo ir izotopinio pakeitimo metodus nustatyti MHP struktūros ir orientacijos elektrodo atžvilgiu Ramano sklaidos žymenys. Tiriant juostų intensyvumo priklausomybes nuo potencialo ir žadinančios spinduliuotės bangos ilgio parodyta, kad Au/MHP sistemoje pasireiškia krūvio pernešimo Ramano spektrų stiprinimo mechanizmas. Nustatyta, kad adsorbuotų neorganinių anijonų pilnai simetrinio virpesio dažnis sumažėja lyginant su tirpalo spektru ir tas pokytis koreliuoja su Gibso dehidracijos energija. Parodyta, kad MHP pritraukia grafeno oksidą. Nustatyta, kad grafeno oksido CC ryšio ilgis ir elektroninė struktūra gali būti keičiama, keičiant potencialą.
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