The work presented on this thesis is focused on studies of the kinetics of electron transfer in bilayer lipid membranes (BLMs). Three different types of BLM were studied: i) tethered, ii) pore suspended (commonly known as ‘black’) and iii) based on the avidin – biotin interaction (these are part of the wider group of polymer cushioned BLMs). In order to produce tethered BLMs (tBLMs) of the best quality possible, self – assembled monolayers (SAMs) of a thiolipid (1,2 dipalmitoyl-sn-glycero-phosphothioethanol (DPPTE)) and of the same thiolipid mixed with L α phosphatidylcholine (EggPC) were characterised and their behaviour compared to that of SAMs of two alkanethiols (1 – heptanethiol and 1 – dodecanethiol). The SAMs that were formed by a mixture of lipids (DPPTE+EggPC) presented better kinetic parameters and were the chosen to produce tBLMs. Tethered BLMs were made by using the SAM described above as the lower leaflet; the second leaflet was deposited by vesicle fusion, the vesicles were made of EggPC. tBLMs are commonly used as model membranes, however in biophysical studies free-standing membranes or ‘black’ lipid membranes are more realistic models of cellular processes. The rates of electron transfer in both types of bilayer lipid membranes are compared. These BLMs were modified using two very important mitochondrial membrane associated molecules – ubiquinone-10 (UQ10) and α-tocopherol (VitE). The studies involved the use three redox couples, Fe(CN)_6^(3-/4-), Ru(NH_3 )_6^(3+/2+) and NAD+/NADH using cyclic voltammetry and electrochemical impedance spectroscopy. The NAD+/NADH couple is of particular interest as it is the key to several important biochemical processes. The last type of BLM that was studied was the BLMs based on the avidin – biotin interaction. Avidin was deposited on a platinum surface by electrodeposition and then vesicles composed of EggPC and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-(biotinyl) (sodium salt) (DOPE(B)) are burst by applying +0.7V (vs. Ag/AgCl, KCl 3.5M), leading to the formation of a supported BLM. The vesicles used had methylene blue (MB) inside; its release, when the vesicles burst, was monitored by cyclic voltammetry and UV-Vis. The kinetic parameters were determined based on the EIS measurements using Fe(CN)_6^(3-/4-) and Ru(NH_3 )_6^(3+/2+) as redox couples.

Le sujet de cette thèse concerne la spintronique moléculaire. Des jonctions tunnel magnétiques formées par une barrière tunnel moléculaire (monocouche auto-assemblée) insérée entre deux électrodes métalliques ferromagnétiques ont été étudiées. Afin de fabriquer les dispositifs, un procédé de greffage des molécules sur des substrats ferromagnétiques a été mis en place et une technique de lithographie a été développée pour définir des jonctions de taille submicronique. L’ensemble de ce travail expérimental a permis l’obtention de jonctions non court-circuitées et mesurables, où le transport électronique est bien du transport par effet tunnel.Les mesures de magnétotransport de ces échantillons ont amené des résultats intéressants et nouveaux : les jonctions, dont la barrière est formée par des alcanes-thiols, présentent de la magnétorésistance à température ambiante, allant jusqu’à 12%. Une partie de la thèse s’attelle à la compréhension des différents comportements magnétorésistifs observés : un modèle de barrière tunnel à deux niveaux est proposé pour les décrire.La dernière partie du travail présente des résultats préliminaires obtenus lorsque la barrière moléculaire est formée par des molécules aromatiques ou commutables et met en évidence des phénomènes nouveaux par rapport au cas précédent.L’ensemble des résultats prouve le fonctionnement de jonctions tunnel magnétiques à base de monocouches moléculaires à température ambiante et ouvre la voie à l’utilisation de molécules plus complexes pour une électronique de spin moléculaire multifonctionnelle. / This thesis work enters within the molecular spintronic fields. Magnetic tunnel junctions based on molecular self assembled monolayers have been investigated. The devices structure is a molecular monolayer inserted between two ferromagnetic electrodes.A process to graft molecules on a ferromagnet’s surface and a lithography technique have been developed to define the junctions. This experimental work has led to non short-circuited and measurable junctions, in which an electronic tunnel transport has been demonstrated.Interesting and new results have been found out from magnetoresistance measurement of the samples: junctions made with alkanes-thiols barrier have shown magnetoresistance signal at room temperature (up to 12%). In order to explain the magnetoresistive behaviour, a simple model where the barrier is discribed by two levels has been proposed.The last part of the thesis reports preliminary results obtained when the barrier is made of aromatic molecules or switchable molecules and it points out new phenomenons compared to the alkanes case.The overall work proves that devices made from magnetic tunnel junctions with self-assembled monolayers work at room temperature. It is then possible to consider switchable molecules to build multifunctional molecular spintronics devices.

No description available.

Cell adhesion is the first step of cell response to materials and the extracellular matrix (ECM), and is essential to all cell behaviours such as cell proliferation, differentiation, migration and apoptosis for anchor-dependent cells. Therefore, studies of cell attachment have important implications to control and study cell behaviours. During many developed techniques for cell attachment, the manipulation of surface chemistry is a very important method to control initial cell attachment. To control cell adhesion on a two-dimensional surface is a simple model to study cell behaviours, and is a fundamental topic for cell biology, tissue engineering, and the development of biosensors. From the engineering point of view, the preparation of a material with controllable surface chemistry can help studies of cell behaviours and help scientists understand how surface features and chemistry influence cell behaviours. During the fabrication, the challenge is to create a surface with heterogeneous surface properties in the micro scale and subsequently to guide cell initial adhesion. In order to control cell adhesion in a spatial and temporal manner, a photochemical method to control surface chemistry was employed to control the surface property for cell adhesion in this project. Two photocleavable derivatives of the nitrobenzyl group were tried on two types of surfaces: a model self-assembled monolayer (SAM) with alkanethiol-gold surface and biodegradable chitosan. Reactive functional groups on two different surfaces can be inactivated by covalent binding with these photocleavable molecules, and light can be further introduced into the system as a stimulus to recover their reactivity. By simply applying a photomask with diffe

Microarrays on gold have been used to develop new methodologies for biocatalysis and proteomic applications. The technology applies the logic of solid phase supported chemistry using self-assembled monolayers (SAMs) on a gold chip. The advantages of this technology are: i) an easy to handle platform, ii) parallel screening (64 reactions at once), iii) microliter scale reactions (1µL per sample), iv the use of mild conditions (buffers and t=37 °C), v) the absence of purification steps (only chip washing is required), vi) quick and accurate analysis by MALDI ToF MS.The metallopeptidase thermolysin was studied in peptide-coupling reactions to profile reactivity and specificity (Chapter 2). Reactivity was further investigated in transpeptidation reactions. Comparing the serine peptidase chymotrypsin with the zinc dependent thermolysin, it was found that transpeptidations proceed via N-transacylation reactions independent of a specific enzymatic catalytic mechanism (Chapter 3). These transacylations may be exploited for modifications of biocompatible and selective surfaces in ‘bottom-up’ bionanofabrication technologies. Selected peptidases with different catalytic mechanism were also arrayed to investigate polymerisation ability of dipeptides (Chapter 4). It was shown that oligomerisation can be obtained under mild conditions and a set of peptides was synthesised. Chapter 5 describes a new chemical methodology by which crude tryptic peptide digests can be trapped on chip and analysed by MALDI ToF MS without further purification steps. This dramatically improves time and cost efficiency.Finally, a new stepwise native chemical ligation methodology is proposed for amino acids, and peptides containing N-terminal cysteine residues (Chapter 6).

L’objectif de cette thèse de doctorat vise à développer des monocouches organiques auto-assemblées (SAMs) destinées à mieux comprendre la transposition depropriétés macroscopiques observées en solution vers le milieu confiné. Dans le cadre de notre étude, nous avons synthétisé des précurseurs électroactifs (i.e. dérivés du thiophène, du pérylènediimide et du tétrathiafulvalène) comportant des mécanismes électrochimiques (i.e. schéma carré, EDimE) et des propriétés optiques (absorption et/ou émission de fluorescence) spécifiques. L’immobilisation des précurseurs sur substrats d’or à l’aide de fonctions disulfures a permis d’élaborer des SAMs. L’étude des électrodes modifiées par des méthodes électrochimiques (voltammétrie cyclique) et spectroélectrochimiques a permis d’établir des relations de type structure/propriétés et structure/réactivité. / This thesis is devoted to the elaboration of new organic self-assembled monolayers (SAMs) for a better understanding of the transposition of macroscopic properties that are well-known in solution onto metallic surface. In our study we have synthesised electroactive precursors (i.e. thiophene, perylene diimide and tetrathiafulvalene derivatives) with electrochemical mechanisms (i.e. squared scheme, EDimE) and specific optical properties (absorption and/or emission of fluorescence). The immobilization of the precursors on gold substrates was achieved using disulphide moieties to form SAMs. The study of the modified electrodes by electrochemical techniques (cyclic voltammetry) and spectroelectrochemistry helped to establish detailed structure-properties and structure-reactivity relationships, especially on mixed SAMs.

This dissertation evaluates how gold nanoparticle structure and local environment influence resulting sensor function when using these nanomaterials for complex sample analysis. Molecular imprinted polymers (MIPs), a class of plastic antibodies, are engineered and incorporated into these nanosensors thereby facilitating the quantitative detection of a variety of small molecules when Raman spectroscopy and surface enhanced Raman scattering (SERS) are used for detection. First, homogeneous seeded growth gold nanosphere synthesis is evaluated as a function of ionic double layer composition and thickness. Systematically increasing the citrate concentration during synthesis improves nanomaterial shape homogeneity; however, further elevations of citrate concentration increase the number of internal and/or external atomic defects in the nanomaterials which leads to decreasing solution-phase stability. Next, spherical gold nanoparticles are modified with self-assembled monolayer (SAM), modeled using interfacial energy calculations, and experimental characterized using transmission electron microscopy, NMR, extinction spectroscopy, zeta potential, X-ray photoelectron spectroscopy, and flocculation studies to assess the morphology, surface chemistry, optical properties, surface charge, SAM packing density, and nanoparticle stability, respectively. The number of molecules on the nanostructures increases with increasing ionic strength (by decreasing the electrostatic interfacial energy between assembled molecules) which subsequently promotes nanoparticle stability. Third, plastic antibodies that recognize three drugs commonly used to treat migraines are engineered. These methacrylate-based MIPs are synthesized, extracted, characterized, and used to quantitatively and directly detect over-the-counter drugs in complex samples using Raman microscopy. These results along with numerical approximation methods to estimate drug binding site densities and dissociation constants with the MIPs serve as a foundation for understanding how modest recognition selectivity of MIPs coupled with shifts in the vibrational energy modes from the drugs upon hydrogen binding to the polymer backbone promote sensitive and selective drug detection in complex samples. Finally, nanomaterial incorporation into MIPs for applications in SERS-based biosensors is evaluated. Importantly, gold nanorod concentration increases the detectability of the same drugs using MIPs as pre-concentration and recognition elements. This combination of materials, theory, and applications forms a solid foundation which should aid in the design and development of MIP nanobiosensors for specific and sensitive detection of small molecules in complex matrices.

Organic photovoltaics (OPVs) have received tremendous attention in recent years due to their numerous attractive attributes such as, the potential for high power conversion efficiency (PCE), mechanical flexibility, and the potential for large-scale manufacturing via low-cost techniques. To date, the record PCE values for bulk-heterojunction (BHJ) OPVs exceed 18% for single-junction cells thanks to the rapid development of donors and acceptors materials for active layer. However, the progress of hole-transporting layer (HTL) systems, which is a key device component to reduce the additional performance losses of OPVs, has been limited with only a handful of materials available like PEDOT:PSS and MoOX. In this thesis, I introduce serval materials to unitize as hole-selective contact in high-performance OPVs. Firstly, the application of liquid-exfoliated two-dimensional transition metal disulfides (TMDs) is demonstrated as the HTLs in OPVs. The solution processing of few-layer WS2 suspensions was directly spun onto transparent indium-tin-oxide (ITO) electrodes yield solar cells with superior power conversion efficiency (PCE), improved fill-factor (FF), enhanced short-circuit current (JSC), and lower series resistance than devices based on PEDOT:PSS. Based on PM6:Y6:PC71BM BHJ layer, the cells with WS2 HTL exhibit the highest PCE of 17% thanks to the favorable photonic structure and reduced bimolecular recombination losses in WS2-based cells. Next, the self-assembled monolayer (SAM) namely 2PACz is utilized as hole-selective contact directly onto the ITO anode. The 2PACz modifies the work function of ITO while simultaneously affecting the BHJ layer’s morphology deposited atop. This ITO-2PACz anode is utilized in OPV with PM6:BTP-eC9:PC71BM, showing a remarkable PCE of 18.0%. The enhanced performance is attributed to reduced contact-resistance, lower bimolecular recombination losses, and improved charge transport within the BHJ layer. Lastly, the previously 2PACz SAM was functionalized with bromide functional groups, namely Br-2PACz, which is investigated as hole-extracting interlayers in OPVs. The highest occupied molecular orbital (HOMO) energy of Br-2PACz was measured at -6.01 eV, and significant changes the work function of ITO electrodes upon chemical functionalization. OPV cells based on PM6:BTP-eC9:PC71BM using ITO/Br-2PACz anodes exhibit a maximum PCE of 18.4%, outperforming devices with ITO/PEDOT:PSS (17.5%), resulting from lower interface resistance, improved hole transport, and longer carrier lifetimes.

In this paper, a nanometer-sized gold electrode with an effective radius around several tens of nanometers has been modified with a monolayer of alkanethiols. There are pinholes in the monolayer, and the pinholes can be used as very small electrode. Our evaluation shows that it is possible to have only one pinhole on the monolayer covered electrode. The single pinhole electrode has been used to study the electrochemical behaviors of fast and slow electrochemical reactions. Our results show that the electrochemical response of a slow electrochemical reaction is not a Butler-Volmer response if the electrode is small enough.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20702号 / 工博第4399号 / 新制||工||1683(附属図書館) / 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 河合 潤, 教授 邑瀬 邦明 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM