Nanostructured materials play a vital role in almost all aspects of science and technology in the 21st century. The materials include nanoparticles, nanofilms, biological membranes etc. whose physicochemical properties are size-dependent. Thin films have wide range of applications in various branches of science. One of the efficient methods to form miniaturized structures for device applications is to fabricate nanostructured films on different substrates. Surfactant assembly on metallic and non-metallic surfaces based on self assembly and Langmuir-Blodgett technique offers a unique way to form thin films at molecular levels. The process of formation of unimolecular assemblies gives the flexibility of tuning the properties of underlying substrates for various applications including wetting characteristics, lubrication, passivation, mimicking biological phenomena etc. Towards this direction, self assembled monolayers (SAMs) of alkanethiols on gold and silver surfaces have been studied comprehensively for the past two decades. The reported literature on short chain length thiol-based monolayers is however, limited since the formation using conventional methods yield poor quality monolayers. The short chain length monolayers are useful in various applications like tribology, layer-by-layer assemblies, biosensors etc. Hence, it is essential to reproducibly form SAMs of various chain lengths and understand their properties. The present study is related to the formation of SAMs of alkanethiols and diselenides on gold and silver surfaces to form ordered and well-oriented monolayers. Monolayers of varying chain lengths (CH3(CH2)nSH where n = 3, 5, 7, 9, 11, 15) have been formed on gold and silver surfaces using different methods, (1) adsorption from neat thiols; (2) adsorption under electrochemical control and (3) adsorption from alcoholic solutions of the thiols. The characteristics features of the SAMs have been followed based on three different aspects, (i) structure and stability of the methylene groups (ii) interfacial characteristics involving the end group and the solvent and (iii) metal-head group interactions. The structure and stability of the monolayers have been followed based on vibrational spectroscopy and electrochemistry under different environment including thermal perturbations. The stability of the SAMs at different temperatures and subsequent changes associated with the orientation / packing has been monitored both in the dry state using reflection absorption infrared spectroscopy (RAIRS) and under electrochemical conditions using cyclic voltammetry and impedance analysis. Monolayers adsorbed from neat thiols show superior quality in terms of stability and structural arrangement. Short chain thiols with n = 3, 5, 7 show substantial stability when the adsorption is carried out from neat thiols. Figure 1 shows the RAIR spectra of hexanethiol SAM on gold adsorbed by three different procedures. Monolayers adsorbed under potential control behave very similar to the monolayers adsorbed from neat thiol as for as stability and structural orientation are concerned. Monolayers prepared using conventional methods of adsorption from alcoholic solutions are of inferior quality in terms of stability and arrangement especially for the short chain lengths. This is likely to be due to the fact that monolayers prepared using conventional methods may have intercalated solvent molecules within the monolayer assembly that degrade the integrity of the SAM leading to poor quality. The blocking characteristics of the monolayers for diffusing redox couple have been followed by determining the heterogeneous electron transfer rate constant using electrochemical techniques. The spectroscopic data and the electrochemical data follow similar trend indicating the superior quality of monolayer adsorbed from neat thiol in terms of stability as compared to conventionally prepared monolayers. Figure 1. RAIR spectra of hexanethiol-SAMs on Au(111) surface at 25C. The monolayers are formed by adsorption (A) from neat thiol (B) under potential control and (C) from alcoholic solution of the thiol. Wavenumber (cm-1) The interfacial characteristics of the monolayers (effect of end group functionality on the solvent properties) have been monitored on the basis of capacitance, contact angle and atomic force microscopy- measurements. Well-organized monolayers behave like good capacitors with relatively low values of double layer capacitance in presence of a liquid electrolyte as compared to the expected values based on known thickness and dielectric constant of the SAMs. This behavior can be explained by invoking the depletion of water density at the methyl terminated SAM-water interface where the solvent properties are different from that of bulk. Variation of one such property, dielectric constant, has been mapped using force measurement based on AFM. Dielectric constant of water changes from the bulk value of 78 to a low value as given in figure 2. This cross-over occurs within a span of 1-3 nm depending on the chain length of the thiol. Of the three procedures used, the ones based on the use of neat thiol and electrochemical adsorption result in well-oriented alkyl chains followed by highly oriented methyl terminal groups. This is responsible for the high hydrophobic nature of the interface and the subsequent observation of interfacial water properties. The SAMs prepared from ethanol fail to show the hydrophobic effects. Hydrophilic monolayers (NH2 terminated monolayers) fail to show depletion of water density at the interface indicating the importance of end group functionality in altering the interfacial characteristics of the monolayer. Figure 2. Spatial variation of dielectric permittivity of water at the hexanethiol SAM - water interface. The SAM is formed on gold (111) surface; (a) from ethanolic solution of the thiol (b) under electrochemical control (c) from neat thiol. The origin on the x-axis is the position of the methyl groups of SAM and the direction towards right side is in to the bulk water. The well-oriented SAMs have been used to follow the adsorption of a biopolymer. Zein protein is a prolamine of maize and is projected to be a biocompatible coating for food products and food containers. Hence, it is essential to prepare impermeable coatings of zein with different surface wetting properties. The adsorption of zein on highly ordered SAMs with hydrophobic or hydrophilic end group functionality has been studied and the orientation of the protein followed using spectroscopy, microscopy and electrochemistry. It is observed that zein shows higher affinity towards hydrophilic than hydrophobic surfaces with small foot print size on the Figure 3. Orientation of zein protein on hydrophilic and hydrophobic SAM as deciphered from the experimental data. hydrophilic surface resulting in large surface coverage. Figure 3 shows the schematics of zein deposits on hydrophilic and hydrophobic SAM surfaces determined based on spectroscopy, quartz crystal microbalance and electrochemical studies. The AFM shows cylindrical, rod-like and disc-like features of zein on hydrophilic surfaces that form the base units for the growth of cylindrical structures of zein. The published literature on the studies on SAMs on silver surfaces reveals that there is no consensus on the structure of the monolayers on silver. This may be due to the difficulty in getting pristine oxide-free surfaces in the case of silver and this is likely to affect the monolayer quality. Hence, it is decided to prepare SAMs of alkanethiols on silver and study their characteristics. Subtle differences between the monolayers adsorbed from neat thiol and from alcoholic solutions of thiols have been observed in terms of stability and permeability. Atomic force microscopic studies illustrate the presence of depletion of water at the SAM-aqueous interface. Diselenide-based monolayers have been formed on gold to understand the head group-substrate interactions on the monolayer properties. The disorder observed on short chain diselenide-based monolayers formed from alcoholic solutions can be eliminated by adsorption from neat compounds as described for the thiols. A preliminary account on the stability of SAMs under hydrodynamic conditions has been given based on rotating disc electrode voltammetry. It is observed that the SAMs get well-ordered when the electrode is rotated at a fast rate leading to the hypothesis that the monolayer assembly gets annealed as a function of the rotation rate. The thesis is planned as follows: Chapter 1 gives general introduction about organic thin films with particular emphasis on self-assembled monolayers on gold and silver, their characteristics in terms of stability, interfacial properties and adsorption behaviour. Chapter 2 deals with the experimental methodologies and schematics used for the preparation and characterization of the monolayers. Chapter 3 is on the contribution of alkyl spacer to the stability of the monolayers studied using spectroscopy and electrochemistry. Chapter 4 deals with the interfacial properties of the SAMs in presence of aqueous medium. In order to emphasize the importance of the terminal functional groups, adsorption of zein has been demonstrated on surfaces of controlled wettablity. Chapter 5 explains the formation and stability of monolayers of short and long chain alkyl diselenides on gold surfaces. Chapter 6 gives the structural and interfacial characteristics of alkanethiol monolayers on silver surfaces. The stability and subsequent changes of alkanethiol monolayers under hydrodynamic conditions has been discussed in the appendix section.(For fig pl refer pdf file.)

Les microcantileviers fonctionnalisés offrent une plateforme idéale pour la nano- et micro-mécanique et pour le développement de (bio-) capteurs tres sensible. Le principe d’opération consiste dans des évènements physicochimiques qui se passent du côté fonctionnalisé du microcantilevier induisant une différence de stress de surface entre les deux côtés du cantilevier qui cause une déflexion verticale du levier. Par contre, les facteurs et les phénomènes interfacials qui régissent la nature et l'intensité du stress de surface sont encore méconnus. Pour éclaircir ce phénomène, la première partie de cette thèse porte sur l'étude des réactions de microcantileviers qui sont recouverts d'or et fonctionnalisés par une monocouche auto-assemblée (MAA) électroactive. La formation d'une MAA de ferrocènylundécanethiol (FcC11SH) à la surface d'or d'un microcantilevier est le modèle utilisé pour mieux comprendre le stress de surface induit par l’électrochimie. Les résultats obtenus démontrent qu'une transformation rédox de la MAA de FcC11SH crée un stress de surface qui résulte dans une déflexion verticale du microcantilevier. Dépendamment de la flexibilité du microcantilevier, cette déflexion peut varier de quelques nanomètres à quelques micromètres. L’oxydation de cette MAA de FcC11SH dans un environnement d'ions perchlorate génère un changement de stress de surface compressive. Les résultats indiquent que la déflexion du microcantilevier est due à une tension latérale provenant d'une réorientation et d'une expansion moléculaire lors du transfért de charge et de pairage d’anions. Pour vérifier cette hypothèse, les mêmes expériences ont été répéteés avec des microcantileviers qui ont été couverts d'une MAA mixte, où les groupements électroactifs de ferrocène sont isolés par des alkylthiols inactifs. Lorsqu’un potentiel est appliqué, un courant est détecté mais le microcantilevier ne signale aucune déflexion. Ces résultats confirment que la déflexion du microcantilevier est due à une pression latérale provenant du ferrocènium qui se réorganise et qui crée une pression sur ses pairs avoisinants plutôt que du couplage d’anions. L’amplitude de la déflexion verticale du microcantilevier dépend de la structure moléculaire de la MAA et du le type d’anion utilisés lors de la réaction électrochimique. Dans la prochaine partie de la thèse, l’électrochimie et la spectroscopie de résonance de plasmon en surface ont été combinées pour arriver à une description de l’adsorption et de l’agrégation des n-alkyl sulfates à l’interface FcC11SAu/électrolyte. À toutes les concentrations de solution, les molécules d'agent tensio-actif sont empilées perpendiculairement à la surface d'électrode sous forme de monocouche condensé entrecroisé. Cependant, la densité du film spécifiquement adsorbé s'est avérée être affectée par l'état d'organisation des agents tensio-actifs en solution. À faible concentration, où les molécules d'agent tensio-actif sont présentes en tant que monomères solvatés, les monomères peuvent facilement s'adapter à l’évolution de la concentration en surface du ferrocènium lors du balayage du potential. Cependant, lorsque les molécules sont présentes en solution en tant que micelles une densité plus faible d'agent tensio-actif a été trouvée en raison de l'incapacité de répondre effectivement à la surface de ferrocenium générée dynamiquement. / Surface-functionalized microcantilevers provide an ideal platform for nano- and micro-mechanical actuation and highly sensitive sensing technologies. The basic principle of operation is that a chemical or physical event occurring at the functionalized surface of one side of the cantilever generates a surface stress difference (between the active functionalized and passive non-functionalized sides) that causes the cantilever to bend away from its resting position. However, the factors and phenomena contributing to both the nature and magnitude of the surface stress are not well understood. To this end, the first part of this thesis focused on investigating the potential-controlled actuation and surface stress properties of free-standing gold-coated microcantilevers functionalized with a redox-active self-assembled monolayer (SAM). A ferrocenylundecanethiolate (FcC11SAu) SAM on a gold-coated cantilever was used as a model system to investigate the surface stress generated by faradaic chemistry. The data obtained clearly demonstrates that the electrochemical transformation of a ferrocene moiety in a monomolecular organic film can generate a surface stress change of sufficient magnitude to deflect a microcantilever. In fact, depending on the flexibility of the microcantilever, the mechanical deflection resulting from the redox transformation of the surface-tethered ferrocene can range on the order of nanometers to micrometers. The oxidation of the FcC11SAu SAM in perchlorate electrolyte generates a compressive surface stress change. The microcantilever deflection is driven by the lateral tension resulting from molecular reorientation/volume expansion accompanying the charge-transfer and ion-pairing events. To verify this hypothesis, mixed SAM-modified microcantilevers, in which the electroactive ferrocenes are isolated from one another by an inert n-alkylthiolate matrix, were investigated. Under an applied potential, a Faradaic current was measured, but no microcantilever beam deflection was observed. This finding confirms that the cantilever responds to the lateral pressure exerted by an ensemble of re-orienting ferrocenium-bearing alkylthiolates upon each other rather than to individual anion pairing events. Changes in molecular structure and anion type can also be used to modulate the extent of micromechanical motion. In the next part of the dissertation, electrochemical measurements and surface plasmon resonance spectroscopy were combined to present a description of the adsorption and aggregation of n-alkyl sulfates at the FcC11SAu/electrolyte interface. At all bulk solution concentrations, the surfactant moieties packed perpendicular to the electrode surface in the form of an interdigitated condensed film. However, the density of the specifically adsorbed film was found to be affected by the organizational state of the surfactants in solution. At low concentrations, where the surfactant molecules are present as solvated monomers, the monomers can readily adapt to the changing ferrocenium concentration with the potential potential scan. However, when the molecules are present as micellar structures in solution, a lower surfactant packing density was found because of the inability to respond effectively to the dynamically generated surface ferroceniums. This research demonstrates the potential utility of charge-transfer interactions for organizing materials at solid interfaces and effecting micromechanical actuation using an electrifical stimulus.

Functionalized nanoparticles provide a wide range of potential applications for Biological Mass Spectrometry (MS). Particularly, we have studied the effects of chromophore activity on the performance of gold nanoparticles (AuNPs) capped with substituted azo (-N=N-) dyes for analyte ion production in Laser Desorption Ionization Mass Spectrometry (LDI-MS) conditions. A series of aromatic thiol compounds were used as Self-Assembled Monolayers (SAM) to functionalize the surface of the AuNPs. Results indicate that AuNPs functionalized with molecules having an active azo chromophore provide enhanced analyte ion yields than the nanoparticles capped with the hydrazino analogs or simple substituted aromatic thiols. We have also conducted experiments using the azo SAM molecules on 2, 5, 20, 30, and 50 nm AuNPs exploring the changes of Relative Ion Yield (RIY) with increased AuNP diameters. Our results indicate that the role of the SAM to drive energy deposition decreases as the size of the AuNP increases. It was determined that 5 nm is the optimum size to exploit the benefits of the SAM on the ionization and selectivity of the AuNPs.

Kyoto University (京都大学) / 0048 / 新制・論文博士 / 博士(工学) / 乙第12460号 / 論工博第4042号 / 新制||工||1497(附属図書館) / 28070 / (主査)教授 岩田 博夫, 教授 伊藤 紳三郎, 教授 辻井 敬亘 / 学位規則第4条第2項該当

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第16851号 / 工博第3572号 / 新制||工||1540(附属図書館) / 29526 / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 杉村 博之, 教授 酒井 明, 准教授 鈴木 基史 / 学位規則第4条第1項該当

<div>Surface level molecules act as an interface that mediates between the surface and the environment. In this way, interfacial molecules are responsible for conferring characteristics of relevance to many modern material science problems, such as electrical conductivity and wettability. For many applications, such as organic photovoltaics and nanoelectronics, macroscopic placement of chemical patterns at the sub-10 nm must be achieved to advance next generation device applications.</div><div><br></div><div>In the work presented here, we show that sub-10 nm orthogonal features can be prepared by translating the building principles of the lipid bilayer into striped phase lipids on 2D materials (e.g. highly ordered pyrolytic graphite (HOPG), MoS2). Macroscopic patterning of these nanoscopic elements is achieved via Langmuir Schafer deposition of polymerizable diyne amphiphiles. On the Langmuir trough, amphiphiles at the air water interface are ordered into features that can be observed on the macroscale using Brewster angle microscopy. Upon contact of the 2D material with the air-water interface the macroscopic pattern on the trough is transferred to the 2D material creating a macroscopic pattern consisting of sub-10 nm orthogonal chemistries. We also show here how hierarchical ordering can be accomplished via noncovalent microcontact printing of amphiphiles onto 2D materials. Microcontact printing allows a greater measure of control over the placement and clustering of interfacial molecules.</div><div><br></div><div>The alkyl chain/surface enthalpy has a great deal of influence over the ordering of amphiphiles at the sub-nm scale. Here, we examine this influence by depositing diyne amphiphiles onto MoS2 which has a weaker alkyl adsorption enthalpy compared to HOPG. We found that dual-chain amphiphiles deposited on MoS2 adopt a geometry that maximized the molecule-molecule interaction compared to the geometry adopted on HOPG.</div><div><br></div><div>Finally, we show how the hierarchical pattern of diyne amphiphiles can be transferred off of the 2D material onto an amorphous material. This is done by reacting the amorphous material with the conjugated backbone of the diyne moiety through a hydrosilylation reaction to exfoliate the film from the 2D crystalline material. The resulting polymer ‘skin’ has many applications were controlling interfacial properties of an amorphous material is important.</div>

No description available.

This thesis presents rubidium packaging methods for integration using anti-resonant reflecting optical waveguides (ARROWs) on a planar chip. The atomic vapor ARROW confines light through rubidium vapor, increases the light-vapor interaction length, decreases the size of the atomic cell to chip scales, and opens up possibilities for waveguide systems on chips for additional optoelectronic devices. Rubidium vapor packaging for long-life times are essential for realizing feasibly useful devices. Considerations of outgassing, leaking and chemical compatibilities of materials in rubidium vapor cells lead to an all-metal design. The effect of these characteristics on the rubidium D2 line spectra is considered.

Les travaux de la thèse portent sur l’impact de la structure des électrolytes hautement concentrés (ÉHC) à base de Lithium Bis[trifluorométhane(sulfonyl)]imide (LITFSI) et d’acétonitrile (ACN) dans les réactions de transfert d’électron et les interactions présentes avec les différentes espèces en jeu. Ces électrolytes sont étudiés comme électrolyte dans les dispositifs de stockage d’énergie (batteries, supercapaciteurs), mais la recherche sur les transferts d’électron dans ces ÉHC est presque inexistante. Les travaux sont présentés en deux volets; dans le premier, nous nous sommes concentrés à assurer de la qualité des ÉHC. Nous avons identifié les principales sources d’eau dans ces électrolytes : la présence d’eau varie selon le fournisseur de sel et le taux d’adsorption d’eau de l’électrolyte. Nous avons aussi analysé les impacts de la quantité d’eau sur les propriétés physicochimiques et la fenêtre de stabilité électrochimique. Une teneur d’eau dans les ÉHC sous 1000 ppm n’affecte pas les propriétés physicochimiques. Cependant, la fenêtre de stabilité électrochimique est affectée par une faible présence d’eau (>200 ppm), particulièrement la stabilité en réduction. Le second volet porte sur l’étude du transfert d’électron du couple Fc+/Fc dissout et adsorbé à l’électrode dans les ÉHC LiTFSI : ACN. Nous avons montré que la cinétique du transfert d’électron varie avec la concentration (dilué vs. hautement concentré) et avec l’état d’oxydation du couple rédox (Fc+ vs Fc). La constante de transfert d’électron est plus élevée avec le Fc+ que le Fc dans les milieux dilués, mais la situation est inversée dans les ÉHC. En complément à l’électrochimie, les études Raman couplées à l’électrochimie ont révélé que cette différence provient de l’environnement chimique qui diffère entre les deux espèces, dues à la charge des deux espèces (Fc+ vs. Fc) aux différentes concentrations de sel. Les travaux de cette thèse sont les premiers à montrer l’électrochimie d’une molécule électroactive couplée avec l’utilisation de méthode spectroscopique pour le couple Fc+/Fc dans les ÉHC. Cette recherche ouvre la porte à l’utilisation de ces méthodes d’analyse pour les ÉHC et montre un grand potentiel pour des applications autre que le stockage d’énergie. Les résultats obtenus sont un premier pas vers la formulation d’ÉHC adaptés aux applications d’électrocatalyse : l’utilisation des interactions électrostatiques présentes à haute concentration pourraient ralentir les réaction secondaires formant des cations ou ralentir la diffusion de cations impliqués dans les réactions de transfert d’électron couplées. / The work of this thesis focuses on the impact of the structure of highly concentrated electrolytes (HCE) based on Lithium Bis[trifluoromethane(sulfonyl)]imide (LITFSI) and acetonitrile (ACN) on the electron transfer reactions and the interactions present with the different species involved. These electrolytes are studied as electrolytes in energy storage devices (batteries, supercapacitors), but research on electron transfers in these HCE is almost non-existent. The work is presented in two parts; in the first part, we focused on ensuring the quality of HCE. We identified the main sources of water in these electrolytes: the presence of water varies depending on the salt supplier and the water adsorption rate of the electrolyte. We also analyzed the impacts of the amount of water on the physicochemical properties and the electrochemical stability window. A water content in HCE below 1000 ppm does not affect the physicochemical properties. However, the electrochemical stability window is affected by low water content (>200 ppm), especially the reduction stability. The second part deals with the study of the electron transfer of the dissolved and adsorbed Fc+/Fc couple at the electrode in LiTFSI: ACN HCE. We have shown that the electron transfer kinetics varies with concentration (dilute vs. highly concentrated) and with the oxidation state of the redox couple (Fc+ vs. Fc). The electron transfer constant is higher with Fc+ than Fc in dilute media, but the situation is reversed in HCE. In addition to electrochemistry, Raman studies coupled with electrochemistry revealed that this difference in electron transfer comes from the chemical environment which differs between the two species, due to the charge of the two species (Fc+ vs. Fc) at different salt concentrations. The work of this thesis is the first to show the electrochemistry of an electroactive molecule coupled with the use of spectroscopic methods for the Fc+/Fc couple in HCE. This research opens the door to the use of these analytical methods for HCE and shows a great potential for applications other than energy storage. The results obtained are a first step towards the formulation of HCE adapted to electrocatalysis applications: the use of electrostatic interactions present at high concentration could slow down the secondary reactions forming cations or slow down the diffusion of cations involved in coupled electron transfer reactions.

Die vorliegende Dissertation beschreibt die Erarbeitung anwendbarer Methoden zum Aufbau Oberflächenplasmonenresonanz (SPR)-basierter DNA-Mikroarrays. Es werden die Beziehungen zwischen allen Teilschritten der Entwicklung eines DNA-Biosensors aufgezeigt. Die Sondendichte auf der Sensoroberfläche ist entscheidend für die Leistungsfähigkeit eines DNA-Chips. In dieser Arbeit werden thiolmodifizierte Sonden und solche mit Phosphorothioatgruppen verwendet und verglichen. Der Aufbau selbstorganisierender Monoschichten, bestehend aus Mercaptoalkoholen und thiolmodifizierten DNA-Einzelsträngen, wird mittels Röntgenphotoelektronenspektroskopie untersucht. Es werden bis zu 180 Spots auf einem SPR-Chip aufgetragen. Eine weitere Erhöhung der Anzahl an Sondenorten pro Chip wird mit einer hydrophil/hydrophoben Strukturierung der Arrayoberfläche erreicht. Dies erfolgt durch das Mikrokontaktdrucken mit Alkanthiolen. Die selektiven Hybridisierungen der Produkte der Polymerase-Kettenreaktion (PCR) werden bei SPR-Messungen auf DNA-Mikroarrays detektiert. Eine schnelle markierungsfreie Echtzeitanalyse wird bei Hybridisierungen im mikrofluidischen Kanal innerhalb weniger Minuten erzielt. Die Anwendbarkeit dieser Methoden wurde anhand der Mutationsanalyse der Fusionsgene AML1-ETO und CBFB-MYH11 bei der akuten myeloischen Leukämie bestätigt. Die Hybridisierungseffizienz auf DNA-Mikroarrays hängt stark von der Sodensequenz ab. SPR-Experimente zeigen, dass die Ausbildung der Haarnadelstrukturen die Ursache dafür ist. Ein Computerprogramm (EGNAS) auf Grundlage eines neu entwickelten Nucleobasen-Sequenzentwurf-Algorithmus, ermöglicht die Generierung vollständiger Sequenzsätze. Die Intra- und Interstrangeigenschaften dieser Sequenzen können kontrolliert werden, um Haarnadelstrukturen und Kreuzhybridisierungen zu vermeiden. Dadurch können optimierte Sequenzen für Anwendungen auf DNA-Chips oder in der DNA-Nanobiotechnologie entworfen werden.