Dissertations / Theses on the topic 'Langmuir-Blodgett Techniques'

Interest in the Langmuir-Blodgett (LB) technique has led to a number of investigations into different types of materials that can be deposited in the form of monolayers. For example, as well as the classic long Cham fatty acids and alcohols, materials such as polymerisable molecules, aromatic hydrocarbons and dye substances can now all be produced in monomolecular form. Unfortunately, few of these materials yet fulfil the requirements of mechanical and thermal stability that will be necessary if LB films are to be used commercially. This work has dealt with the use of phthalocyanine, a substance well known for its thermal and chemical stability, in the production of LB films. Initially two compounds were investigated, dilithlum phthalocyanine and tetra-tert-butyl phthalocyanine. Although it was found that both materials produced layers of reproducible quality which adhered tenaciously to various substrates and to each other, single monolayers were not obtained. More success has been achieved using an asymmetrically substituted phthalocyanine molecule. Electron microscopy studies have shown that the majority of films are polycrystalline. However, a substitute CuPc proved to be a valuable exception. Multilayer films of this molecule were found to have domains of the order of 3 mm in size showing a preferred orientation. Even so, it has to be accepted that the phthalocyanine films produced to date are not as structurally perfect as for example, multilayers of lo-tricosenoic acid. Our ability to produce monomolecular layers of phthalocyanine now extends the range of possible applications for this material. For instance it is known that the fine control of insulator thickness is crucial in the optimisation of photovoltaic and electroluminescent metal-lnsulator-semlconductor devices. Examples of both types of device have been demonstrated using our phthalocyaine films. For the bistable switch, a gallium arsenide substrate was used; both gallium phosphide and zinc selenlde have been utilized in the electroluminescent structures. Moreover, In the case of phthalocyanine another possibility presents Itself. It has long been known that the conductivities of this material and its derivatives are very sensitive to the presence of certain gases, particularly the oxides of nitrogen. The increased conductivity of such materials has been demonstrated to be confined to the surface of the crystal. Hence many phthalocyanine gas detector systems have been based on thin films. Unfortunately because phthalocyanine exhibits polymorphism, the exact structure of such films can be complicated. making interpretation of results and subsequent device optimisation difficult. Also the response and recovery times of these thin film devices can also be excessively long. It is possible that monomolecular LB films of phthalocyanine could well overcome some or all of these problems. Our experiments have concentrated on asymmetrically substituted copper phthalocyanine and its usefulness to detect nitrogen dioxide. Preliminary results show the response and recovery times for the simple gas structures to be faster than those previously reported for other thin film phthalocyanine devices. It is suggested that this is due to the more ordered structure of the LB film, which enables the gas to adsorb on, or desorb from the molecular sites more readily.

Cette étude porte sur l'organisation en films ultraminces de protéines fortement tensioactives et sur leurs interactions avec des lipides. Elle a été réalisée principalement par microspectroscopie Raman confocale associée à d'autres méthodes complémentaires telles que des mesures de tension superficielle, la microscopie à l'angle de Brewster et la spectroscopie infrarouge PM-IRRAS. Le signal Raman de tels systèmes étant très faible, la première étage de ce travail a consisté à mener des tests comparatifs entre différents types de caméra CCD de technologies récentes afin d'optimiser la détection du montage. L'optimisation de notre instrumentation a permis l'étude de différents films protéiques. D'une part, des films de Langmuir constitués de protéines du surfactant pulmonaire SP-B ou SP-C ont été étudiés, les protéines étant pures ou en interaction avec deux phospholipides, le DPPC et le DPPG, présents majoritairement dans le système in-vivo. Ensuite, la puroindoline-a, protéine végétale dont les fortes propriétés tensioactives permettent la réalisation et la caractérisation de films noirs protéiques, a aussi été étudiée. Nous avons en particulier montré que cette protéine subit des changements importants de structure secondaire selon la nature du système étudié (poudre, solution aqueuse ou film noir). Des changements ont également été constatés en présence du lyso-palmitoylphosphatidylcholine (LPC), phospholipide à une seule chaîne aliphatique.

DE LA TESIS EN CASTELLANO

Antecedentes

Un avance importante en el campo de química analítica se hizo por Clark y Lyons en los años setenta. Ellos propusieron acoplar la especificidad de la enzima glucosa oxidasa con la transducción electroquímica de la señal en "biosensores". En general, los biosensores son artefactos integrados autocontenidos, capazes de proporcionar información analítica, cuantitativa utilizando un elemento biológico de reconocimiento (receptor bioquímico) que se retiene en contacto espacial directo con un elemento de transducción. Posteriormente, los primeros biosensores de glucosa, basados en la detección amperométrica de peróxido de hidrógeno generado por glucosa oxidasa en la presencia de oxígeno fueron introducidos en el mercado por la empresa estadounidense Yellow Spring Instrument Co. (Ohio, EE. UU.) en 1975.
La respuesta de biosensores electroquímicos basados en el uso de oxígeno como cosustrato para oxidasas se ve desviada por la presencia de interferencias que pueden contribuir a la corriente. Por lo tanto la superficie de electrodo debe estar protegida por una membrana no permeable por sustancias que pueden interferir con la señal. Para evitar corrientes que perjudican la selectividad de los biosensores, el potencial aplicado puede ser aminorado usando electrocatalizadores difusionales ("mediadores") en lugar de oxígeno, con un potencial redox controlable. Pero la respuesta de estos sensores también depende de la concentración de oxígeno porque este compite con los mediadores, para la reoxidación de las oxidasas. Un inconveniente adicional del uso de mediadores diffusionales artificiales en biosensores es la baja estabilidad de los mismos debida al escape de mediadores desde la superficie del electrodo cuando esto se usa en linea. Se puede aliviar este problema creando enlaces covalentes entre los mediadores y la superficie del electrodo o usando polímeros redox que se adsorben fućrtemente en la superficie del electrodo.
Una de las posibles maneras para disminuir la influencia del oxígeno a la corriente de la respuesta de biosensores es el uso de las deshidrogenasas dependientes de la pareja redox NAD+/NADH. El potencial estándar redox de esta pareja es -0.56 V vs. SCE pero para conseguir la oxidación de NADH en la superficie de electrodos de carbono un sobrepotencial de +0.5 V vs. SCE debe aplicarse. Bajo estas condiciones los electrodos tienen tiempo de vida corto debido a la adsorción de los productos de oxidación en su superficie ya que la oxidación de NADH no es reversible químicamente. Por otro lado estos electrodos sufren por la oxidación no especifica de interferencias a estos potenciales de operación. Los electrodos modificados químicamente por mediadores pueden oxidar NADH a potenciales más bajos. Sin embargo, muchos de los mediadores mencionados en la bibliografía no son estables o/y no forman NAD+ enzimaticamente activo. Un problema adicional de los sistemas analíticos basados en deshidrogenasas dependientes de NAD+ es la necesidad de añadir este cofactór, que tiene alto coste y es inestable, en las muestras. Se puede inmovilizar NAD+ en la superficie de electrodos para producir biosensores capaces de funcionar en muestras que no contienen NAD+, biosensores reagentless (sin necesidad de adición de reactivos). Los métodos descritos en la bibliografía para la fabricación de biosensores reagentless se basan en cinco estrategias: (1) la inmovilización en hidrogeles formados in situ; (2) la inmovilización por una membrana; (3) la inmovilización en películas preparadas por electropolimerización; (4) la inmovilización en una pasta de carbono; (5) la inmovilización en monocapas auto ensambladas. Sólo los electrodos preparados con la estrategia (4) son biosensores reagentless con estabilidad operacional relativamente alta. Las demás estrategias no resultan en biosensores con suficiente estabilidad operacional por culpa de la perdida del mediador, de NAD+ o de la deshidrogenasa. Sin embargo la estrategia basada en electrodos de pasta de carbono no permite su aplicación a la producción de microsensores (electrodos con diámetro de menos de 10 m) para su uso in vivo.

Metodología

El objetivo principal de esta tesis es el desarrollo de nuevas estrategias para la fabricación de biosensores reagentless basados en deshidrogenasas dependientes de NAD+ con características mejoradas respecto a la densidad de la corriente, de la estabilidad operacional y de almacenamiento.
Para cumplir el objetivo se han sintetizado dos nuevos mediadores para la oxidación de NADH: un polímero insoluble en agua [Os(1,10-fenantrolina-5,6-diona)2(PVP)4Cl]Cl, (Os-fendiona-PVP) y un complejo amfifílico [Os(1,10-fenantrolina-5,6-diona)24,4'-(n-C18H37NHCO)2bpi)](PF6)2 (Os-fendiona-surfactante). El polímero Os-fendiona-PVP fue producido vía la derivatización de poli(vinilpiridina) (peso molecular 50000) con [Os(1,10-fenantrolina-5,6-diona)2Cl2]. El estudio electroquímico de este polímero redox adsorbido en electrodos de grafito se realizó por voltametría cíclica a distintas velocidades de barrido para evaluar el número de protones y electrones que participan en la reacción redox, la influencia del pH a su potencial estándar formal, y la constante de la transferencia heterogénea del electrónes kS. Bajo bien definidas condiciones hidrodinámicas se realizaron estudios para encontrar la constante de la interacción con NADH k[NADH]=0. Os-fendiona-surfactante fue producido por la complejacion de [Os(1,10-fenantrolina-5,6-diona)2]Cl2 con el ligando hidrófobo octadodecilamida del acido 2,2'-Bipiridina-4,4'-dicarboxilico. Las monocapas de Langmuir-Blorgett de Os-fendiona-surfactante y las de su análogo [Os(bpi)24,4'-(n-C18H37NHCO)2bpi)](PF6)2 fueron estudiados en un equipo de Langmuir-Blodgett.
Os-fendiona-surfactante fue aplicado a la construcción de biosensores reagentless del glutamato vía la inmovilización de glucosa deshidrogenasa y de NAD+ entre las bicapas en la fase lamelar formada por Os-fendiona-surfactante y el lípido 1,2-dioleoilo-sn-glicero-3-fosfatidilcolina. Dos métodos adicionales para la fabricación de los biosensores reagentless de glutamato y glucosa basados en deshidrogenasas fueron desarrollados. Los electrodos del grafito fueron modificados con Os-fendiona-PVP y utilizados para (a) la inmovilización de deshidrogenasa y de NAD+ en un hidrogel formado por entercruzamiento de poli(vinilpiridina) modificado por grupos amino con el éter diglicidil de poli(etilenglicol); (b) la inmovilización por adsorción de la deshidrogenasa y del ácido algínico modificado por NAD+. Se ha hecho un estudio de los biosensores reagentless para calcular sus constantes de Michaelis, el efecto del pH y de la temperatura en su respuesta y su estabilidad operacional. Además se ha comparado la estabilidad operacional a temperaturas elevadas de biosensores de la configuración (a) usando glutamato, glucosa y glucosa-6-fosfato deshidrogenasas termófilas y mesófilas. Por otro lado se han estudiado métodos nuevos para mejorar le estabilidad durante el almacenamiento de sensores de glutamato. Con este fin, se han preparado electrodos utilizando glutamato deshidrogenasa mesófila y termófila con varios estabilizadores.

Conclusiones

1. El polímero [Os(1,10-fenantrolina-5,6-diona)2(PVP)4Cl]Cl, (Os-fendiona-PVP) para la oxidación de NADH se puede sintetizar por la complejación de [Os(1,10-fenantrolina-5,6-diona)2Cl2] con poli(vinilpiridina). La adsorción física de este polímero sobre los electrodos de grafito desde su solución en etilenglicol resulta en la formación de una monocapa de este polimero redox en la superficie del electrodo.

2. El proceso redox de este mediador es casi-reversible e implica 4 electrones y 4 protones dentro del rango del pH de 3-6.5. El mediador pierde su estabilidad química en valores de pH más altos que 6.5. Tres ramas lineales en el diagrama de E0' frente a pH con diversas pendientes se observan.

3. La constante heterogénea de la velocidad de transferencia de electrones (kS) de Os-fendiona-PVP es del mismo orden de magnitud que la de otros mediadores capaces de oxidar NADH mencionados en la bibliografía (kS= 18±2 s-1) .

4. Os-fendiona-PVP es un electrocatalizador eficiente para la oxidación del NADH. La modificación de los electrodos del grafito con Os-fendiona-PVP conduce a la disminución del sobrepotential para la oxidación electroquímica del NADH desde +0.33 V vs. Ag/AgCl/KClsat para los electrodos no modificados hasta +0.11 V vs. Ag/AgCl/KClsat. La constante cinética para la interacción del polímero redox con el NADH (k1,[NADH]=0 = (1.9±0.2)x103 s-1 M-1) coincide prácticamente con la de Os-fendiona que sugiere que el número de los ligandos de fendiona en los complejos del osmio es proporcional a la corriente de la respuesta al NADH pero no afecta a las constantes cinéticas electroquímicas.
The objective of this work was the development of new configurations of reagentless biosensors based on NAD+ dependent dehydrogenases. These configurations are based on the immobilisation of enzyme, cofactor and the electrochemical catalyst used for its regeneration. In addition to being reagentless these configurations yielded biosensors with improved current density and operational stability compared to the state of the art.
To achieve the objective two new NADH oxidising mediators were synthesised: a water insoluble polymer [Os(1,10-phenanthroline-5,6-dione)2(PVP)4Cl]Cl (Os-phendione-PVP) and an amphiphilic complex [Os(1,10-phenanthroline-5,6-dione)24,4'-(n-C18H37NHCO)2bpy)](PF6)2 (Os-phendione-surfactant). The electrochemical study of Os-phendione-PVP has revealed a rate constant for the heterogeneous electron transfer of the phendione redox couple ks = 252 s-1, and a second order rate constant for NADH oxidation k[NADH]=0=(1.10.1)x103 M-1 s-1. These constants are higher or of the same order of magnitude as those of previously described NADH oxidising mediators. The tensoactive mediators Os-phendione-surfactant and its analogue [Os(bpy)24,4'-(n-C18H37NHCO)2bpy)](PF6)2 (Os-bpy-surfactant) form very stable monolayers at the air-water interface collapsing at the surface pressure 60-65 mN m-1.
The Os-phendione-surfactant was used for the construction of reagentless glutamate biosensors via the immobilisation of dehydrogenase and NAD+ between bilayers in lamellar phase formed by Os-phendione-surfactant and the lipid 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine. The resulting glutamate biosensors demonstrated maximum current density of 3.5 A cm-2 (RSD=25%), apparent Michaelis constant of 47 mM, and operational half life of 0.5 h. In addition graphite electrodes were modified by Os-phendione-PVP and utilised for (a) immobilisation of dehydrogenase and NAD+ in a hydrogel formed by crosslinking of poly(vinylpyridine) carrying amino groups with polyethylene glycol diglycidyl ether and (b) immobilisation of dehydrogenase and an NAD+-alginic acid derivative by adsorption. The configuration (a) yielded glutamate sensors with maximum current density of 8.7 A cm-2 (RSD=5%), apparent Michaelis constant of 9.1 mM, operational half life of 12 h and glucose sensors with maximum current density of 37 A cm-2 (RSD=14%), apparent Michaelis constant of 4.2 mM, the operational half life of 1 h. The glutamate sensors based on the configuration (b) showed maximum current density of 15.8 A/cm2 (RSD=21%), apparent Michaelis constant of 17.6 mM and operational half life of 1.5 h.
Glucose, glucose-6-phosphate, and glutamate biosensors were prepared and characterised. The employment of the thermophilic enzymes helps to dramatically increase the operational stability of biosensors at elevated temperatures higher than 60oC. The shelf life of glutamate electrodes built with the use of thermophilic dehydrogenase was eleven times longer than this of electrodes modified with the mesophilic enzyme. The addition of the copolymer of vinyl-pyrrolidone and dimethylamino ethyl methacrylate termed as Gafquat HS100 to the enzyme also significantly improved shelf life

In the work 9,10-diphenyl anthracene and rubrene were used to decorate an amphiphilic polymer matrix polymethylmethacrylate (PMMA) lm. ITO electrodes equipped with LB lm were used in ECL experiment with tripropylamine co-reactant. Obtained ECL response satis es expectation in looking for a new technology for ECL sensor fabrication.

In this project, the formation and characterisation of CdS nanoparticles embedded within Langmuir-Blodgett (LB) films have been studied systematically. CdS nanoparticles were formed within calix[8]arene (CA) and stearic acid (SA) Cd-salt LB films by exposure to H[2]S gas at room temperature. The AFM images of the treated SA and CA bilayers show CdS clusters with lateral dimensions in the range of 20-30 nm and 10-15 nm, respectively. These particles are pseudo two-dimensional and have a shape of hexagonal platelets which is most likely consequence of their wurtzite structure. Calculations of the cluster thickness Lz yield the value of 2 nm (Photoluminescence excitation-PLE) and 1.9 nm (UV-visible) for CdS clusters in SA matrix and two values of 1.2 nm and 1.6 nm (PLE) and 1.08 nm and 1.42 nm (UV-visible) for CA LB films. The PL spectra demonstrate a large Stokes shift, indicating the formation of "dark excitons" in the platelet CdS clusters. The transformations of the absorption spectra caused by ageing yield a monotonic increase in CdS cluster size with the tendency of saturation. This behaviour can be explained by the model of two dimensional (2D) diffusion. According to this model, CdS molecules in the SA films, initially evenly distributed within each LB bilayer, aggregate and form "large" particles with an average size of 1.9 nm and smaller particles with their size distributed over a wide range down to single molecules. The Surface Plasmon Resonance (SPR) and ellipsometry measurements confirmed that the H2S treatment to the LB films results both in the increase in thickness and refractive index of the LB films due to formation of CdS nanoparticles inside. SPR kinetics measurements during H[2]S treatment show that the formation of CdS clusters happened very fast and almost reached the saturation in about 30 minutes. The I-V characteristics of the sandwich structures of Aluminium/LB films/ Aluminium show exponential behaviour and weak temperature dependence, indicating a combination of electron-tunnelling and hopping mechanism. The formation of CdS clusters in the film matrix did not result in either an enhancement of the electron transfer or an additional polarisation at a small (50 mV) AC signal. Most likely, the observed changes in DC conductivity and AC impedance are caused by the film disorder introduced by CdS nanoparticles.

Nous presentons ici le developpement d'un biocapteur de glucose base sur la technique de langmuir-blodgett. Cette approche consiste en l'elaboration de structures organisees dans lesquelles est immobilisee une enzyme (la glucose oxydase). Une couche monomoleculaire mixte acide gras/enzyme formee a la surface d'une solution aqueuse dans une cuve de langmuir est transferee sur un support solide recouvert d'or. Nous nous sommes attaches a definir les proprietes physico-chimiques des films deposes. Par spectroscopies (ir et uv) nous avons pu correler la quantite d'acide behenique et de glucose oxydase en fonction du nombre de couches deposees. Par microscopie a force atomique et microscopie electronique a balayage, nous avons observe des structures dont les dimensions sont en accord avec les donnees de la litterature. La technique de langmuir-blodgett est adaptee a l'immobilisation d'enzyme et permet d'elaborer des echantillons pouvant servir d'electrode specifique du glucose. Cette electrode permet de detecter le courant d'oxydation de l'eau oxygenee, produit issu de la reaction enzymatique. Par chronoamperometrie, on mesure le courant d'oxydation a potentiel constant; la reponse du biocapteur est rapide (quelques secondes) et le signal obtenu presente une quasi-linearite en fonction de la concentration en glucose. Neanmoins, la faible reproductibilite des resultats nous a conduits a l'emploi d'un mediateur electrochimique qui permet d'abaisser le potentiel de travail

The piezoelectric and pyroelectric properties of oriented films possessing dipole moments are increasingly being used in pressure, acoustic, thermal and optical devices. The performance of these devices in many applications may be enhanced by thin-film technology.The developing Langmuir-Blodgett thin-film deposition technique offers the opportunity to obtain highly oriented and uniform organic-based films in the 10–5000 nm thickness range. Special techniques must be used, however, to assemble these molecules in such a way as to result in polar multilayer films. Several possible deposition techniques are investigated, with one resulting in a polar and pyroelectric film about 50 nm thick.

Various technologies depend on interfacial events that are influenced by various molecular interactions at a solid-liquid interface. The functionality of a surface plays an important role in many applications such as catalysis, sensing, and bio-compatibility, which can benefit from distinctive chemical and physical surface properties. To create tailor-made functional surfaces, surface host-guest assemblies based on Langmuir-Blodgett and self-assembly technique have been employed as a model system as they may offer the potential ability to regenerate surface properties via intercalation of various functional guest molecules. This thesis ranges over the development and characterization of host-guest assemblies and their feasibilities for the regeneration of surface properties via intercalation of functional guests. In our work, 3-dimensional host structures with cavities are constructed on a targeted solid substrate using Langmuir-Blodgett and self-assembly techniques. In particular, by adopting the fundamental concept of host-guest interaction in supramolecular chemistry, we expect that structurally homologous guest molecules where functional groups are anchored can be intercalated into the cavities between hydrophobe arrays at the liquid-solid interface from solution under well-controlled conditions. This approach offers the potential of separating the functional of the monolayer from the inherent structure of the host. The first part of this thesis details two-dimensional host-guest assemblies consisting of guanidinium (G), octadecylsulfonate (S) and various functional alkane guests at the air-aqueous interface and following deposition onto solid substrates via the Langmuir-Blodgett technique. In particular, we evaluated the stability of the host-guest assemblies and the feasibility of exchanging molecular guests under exposure to various organic solvent environments. Analysis of X-ray reflectivity measurements of the thin films showed that good stability of the host-guest assembly could not be achieved due to weak interactions between the host monoalyer and the solid surface. In addition, no evidence of intercalation of guest molecules into guest-free host-cavities was observed. The second part of this thesis discusses the effective methodologies to prepare low-density self-assembled monolayers (LDSAMs) with cavities on silicon substrates. We employed a step-wise reaction based on hydrolytic or silane chemistry: integral spacer molecules such as anthracene-derivatives were anchored to the Si substrate and then long alkane chains were appended to the spacer molecules. The results showed that LDSAMs using an anthryl spacer are attached at the SAM/Si interface via a Si-O-C linkage, and the films do not exhibit a densely packed monolayer quality as would be expected for a non-sterically hindered alkyltrichlorosilane on Si. Thus, the resulting LDSAMs (with cavities) may be capable of accommodating other guest molecules with hydrocarbon chains through intercalation in order to form host-guest assemblies. The third part of this thesis demonstrates the ability of LDSAMs to produce functional surfaces via the intercalation of various functional guest molecules. Self-assembled monolayers of (10-octadecyl)-9-anthracenethiol (host-SAMs) on Au substrates were prepared. Quartz crystal microbalance with dissipation (QCM-D) measurements was used to demonstrate the capacity of LDSAMs to confine guest molecules in the cavities and to probe the structural changes of the host-guest assembly during guest intercalation from ethanol solution. X-ray photoelectron spectroscopy (XPS) measurements were then used to probe host-guest monolayers formed by immersing the host monolayer in solutions in a variety of other solvents. A combined study of QCM-D and XPS showed that guest molecules were intercalated into host-cavities. The reversibility of the intercalation process allows a guest already situated in a host-cavity to be replaced with second guest under well-regulated solvent conditions.
Ph. D.

Le present travail concerne la realisation d'edifices supramoleculaires organises en film langmuir-blodgett (lb). Les molecules utilisees appartiennent a la famille des porphyrines. Elles sont tetrafonctionnalisees et peuvent etre transferees suivant une methode semi-amphiphile. La premiere voie abordee concerne la realisation de divers edifices moleculaires par la methode amphiphile. Elle est basee sur une reconnaissance moleculaire a l'interface air-eau, faisant appel aux forces de coulomb, entre deux macrocycles differemment tetrafonctionnalises. Le simple melange equimolaire d'un macrocycle a caractere basique conduit a la formation d'heterodimeres en film b. La caracterisation precise des heterodimeres porphyrine-porphyrine et porphyrine-phtalocyanine a ete mise en evidence par diverses techniques convergentes (isothermes de compression, spectroscopie ir, rpe et uv-visible). L'utilisation de macrocycles axialement encombres (ferriporphyrines dimerisees par un lien oxo, porphyrines de cobalt axialement complexees par un derive amphiphile de l'imidazole) permet l'elaboration, suivant le meme principe, d'un reseau ionique en film lb. La seconde voie abordee utilise une methode semi-amphiphile et concerne l'etablissement de liaisons covalentes entre macrocycles identiques et tetrafonctionnalises. La formation d'un polymere bidimensionnel par une reaction de polycondensation a l'interieur des films lb ou a l'interface air-eau est mise en evidence. Les macrocycles porphyriniques utilises dans cette etude sont substitues par quatre fonctions alcynes vraies. Ils sont relies les uns-aux-autres par couplage oxydant des triples liaisons. Le polymere obtenu est hautement insoluble et peut former des membranes autosustentees

Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第13865号
農博第1680号
新制||農||952(附属図書館)
学位論文||H20||N4332(農学部図書室)
UT51-2008-C781
京都大学大学院農学研究科森林科学専攻
(主査)教授 中坪 文明, 教授 西尾 嘉之, 教授 木村 恒久
学位規則第4条第1項該当

Nanoparticle self-assembly is a versatile and coherent strategy for the development of functional nanostructured materials, offering low-cost and scalable methods that can be fine-tuned for many different specific application. Functionalized nanoparticles could be spread at the interface of liquid/gas by means of self-assembly. In this work, we demonstrate a pathway for the fabrication of tailorable quasi two-dimensional lattices of gold nanoparticles with several core sizes and shapes (5, 10, 20, 30, 40 nm and nano-urchin) to be used in surface enhanced Raman scattering (SERS) detection of biomolecules. Upon spreading gold nanoparticles at the water/air interface in this research, we used the Langmuir-Blodgett technique as a way of making supra-molecular and nano-structure assembly in ultrathin films with a controlled layered and spatial structure, which have many envisioned technological applications for several branches of science as well as to develop SERS substrates. Monolayers of gold particles were transferred at a target lateral density using the Langmuir–Blodgett technique. Once gold nanoparticles were firmly adhered to the substrate, we used electroless plating to let the nanoparticle grow, thus tuning the plasmonic response and leading to SERS enhancement. Compared to direct deposition, chemical deposition or lithographic methods, our protocol enables to obtain consistent results and much higher coverages of Au nanoparticles thanks to the active control of the surface pressure of the spread monolayers. Prepared substrates were analyzed with different techniques such as UV/VIS spectroscopy, SEM and TEM microscopy. We have demonstrated that, for a given particle size, the enhancement for SERS detection of a referent analyte, 4-MBA, can be tuned by controlling the packing density of the nanoparticles at the water/air interface by adjusting the surface pressure using the Langmuir film balance setup. The other factor which affects the SERS signals is the thickness of a subsequent gold layer, deposited and tuned by using electroless plating. After finding the optimum conditions of surface pressure and electroplating time for 10 nm gold nanoparticles, we entered the second phase of the experiments to unveil the effect of gold nanoparticle size on our study. SERS data of different- sized nanoparticles did not prove that bigger particles result in better SERS signals. However, urchin-shaped gold nanoparticles have shown more intense signals in comparison with spherical nanoparticles. For the same conditions of preparation, we achieved better result by using urchin-shaped nanoparticles. In order to test our substrate efficiency to detect more substances, in the final step of this research, we investigated and performed tests on Thiram and Carbaryl as water-polluting molecules that are widely using as pesticide compounds. We performed several SERS measurements with different substrates and studied the effect of gold nanoparticles shape, contact time between substrate and pollutant solution, substrate functionalization with thiol groups, and effect of pollutant solution concentration on SERS signals. Finally, we report the limit of pollutant detection with our prepared substrates.
El procés d’autoassemblatge de nanopartícules és una estratègia versàtil i coherent per al desenvolupament de materials nanoestructurats funcionals, que ofereix mètodes de baix cost i escalables que es poden ajustar per a diferents aplicacions específiques. Les nanopartícules funcionalitzades es podrien estendre a la interfície de líquid / gas mitjançant un fenomen d’autoassemblatge. En aquest treball, demostrem una via per a la fabricació de xarxes quasi bidimensionals adaptables de nanopartícules d’or amb diverses mides i formes de nucli (5, 10, 20, 30, 40 nm i nano-eriçó) que s’utilitzaran per a la detecció de biomolècules en dispersió Raman de superfície millorada (SERS). En estendre nanopartícules d’or a la interfície aigua / aire en aquesta investigació, hem utilitzat la tècnica Langmuir-Blodgett com una manera de fer un assemblatge de nanoestructures en pel·lícules ultrafines amb una estructura espacial i de capes controlades, que tenen moltes aplicacions tecnològiques potencials en diverses branques de la ciència, com ara substrats SERS. Les monocapes de partícules d'or es transfereixen, a una densitat lateral determinada, sobre substrats de vidre o sílice mitjançant la tècnica LB. Una vegada que les nanopartícules d'or s’han adherit fermament al substrat, vam utilitzar un mètode d’electrodeposició d’or sense electròlisi per fer créixer le nanopartícules, ajustant així la resposta plasmònica i la millora del SERS. En comparació amb la deposició directa, la deposició química o els mètodes litogràfics, el nostre protocol permet obtenir resultats consistents i una cobertura molt més gran de nanopartícules d’or gràcies al control actiu de la pressió superficial de la monocapa estesa sobre la interfície aigua/aire. Els substrats preparats es van analitzar amb diferents tècniques com l'espectroscòpia UV / VIS, microscòpia SEM i TEM. Hem demostrat que, per a una mida de partícula determinada, la millora per a la detecció SERS d’un analit referent, 4-MBA, es pot ajustar controlant la densitat d’empaquetament de les nanopartícules a la interfície aigua / aire ajustant la pressió superficial mitjançant la balança de pel·lícules de Langmuir. L’altre factor que afecta els senyals SERS és el gruix de la capa d’or dipositada posteriorment mitjançant una tècnica no-electrolítica. Després de trobar els paràmetres òptims de pressió superficial i temps d’electrodeposició per a nanopartícules d’or de 10 nm, vam entrar a la segona fase de l’estudi per descobrir l’efecte de la mida de les nanopartícules d’or en el nostre sistema. Tot i que les dades SERS de nanopartícules de diferent mida no van indicar que les partícules més grans donessin millors senyals SERS, les nanopartícules d'or en forma d’eriçó han mostrat senyals més intensos en comparació amb les nanopartícules esfèriques. En les mateixes condicions de preparació, vam obtenir un millor resultat mitjançant l’ús de nanopartícules de forma d’eriçó. Per tal de provar l’eficiència del nostre substrat per detectar més substàncies, en el darrer pas d’aquesta investigació vam investigar i realitzar proves emprant Thiram i Carbaryl com a molècules contaminants de l’aigua que s’utilitzen àmpliament com a compostos pesticides. Hem realitzat diverses mesures de SERS amb substrats diferents i hem estudiat l’efecte de a) la forma de les nanopartícules d’or, b) el temps de contacte entre el substrat i la solució contaminant, c) la funcionalització del substrat amb grups tiol i d) l’efecte de la concentració de solució contaminant en els senyals SERS. Finalment, informem del límit de detecció d’aquests contaminants amb els nostres substrats nanoestructurats.

Le but de ce travail a été de caractériser des films mixtes acide gras/enzyme élaborés par la technique de Langmuir-Blodgett. L'acide gras utilisé est l'acide béhénique (AB) et l'enzyme est la glucose oxydase (GOx). Les études sur le film à l'interface eau/air (isothermes de compression, stabilité, hystérésis, microscopie à l'angle de Brewster) ont montré que l'enzyme s'adsorbait entre les molécules d'acide béhénique et sous le film, ce qui a pour effet de stabiliser le film. Ces études ont aussi permis de mettre au point un protocole d'élaboration du film mixte à l'interface. Les spectroscopies IR et UV-Vis ont permis de quantifier les deux espèces. La quantité d'enzyme déterminée indique que l'enzyme présente dans le film LB provient principalement de l'enzyme présente à l'interface, ce qui montre que les interactions AB/GOx sont faibles. La microscopie à force atomique montre qu'à l'échelle micrométrique, les échantillons préparés par les techniques de transferts vertical et horizontal sont hétérogènes. Les échantillons préparés sur graphite laissent apparaître des agrégats enzymatiques. A l'échelle nanométrique, nous avons observé l'arrangement des molécules de GOx présentant une organisation en quasi cristaux 2D et mis en évidence l'arrangement des molécules d'acide béhénique sur les molécules de GOx. Les échantillons préparés sur mica se caractérisent par la présence d'une monocouche d'acide béhénique et d'agrégats enzymatiques non recouverts par l'acide béhénique. Il apparaît que la structure des échantillons préparés sur mica est plus proche de la structure du film à l'interface eau/air que celle des échantillons préparés sur graphite

Ce memoire traite de la caracterisation physico-chimique et structurale d'un polymere bidimensionnel (2d) constitue de macrocycles polymerisables et preorganises dans le plan par la technique de langmuir-blodgett (lb). Les macrocycles sont des porphyrines portant 4 fonctions acetyleniques vraies peripheriques qui, par couplage oxydant, se lient dans les deux directions du plan par formation de liens covalents diacetyleniques. Ces porphyrines, solubles dans l'eau, sont absorbees sous une monocouche d'acide dihexadecylphosphorique, pour constituer le film semi-amphiphile monomere. Le film de langmuir est caracterise avant transfert par l'etude des isothermes de compression et par microscopie a angle de brewster, mettant ainsi en evidence l'interaction du phosphate a chaines et de la porphyrine tetracationique. Puis, les techniques de spectroscopie uv-visible, infra-rouge ainsi que la spectroscopie raman exaltee par effet de surface sont largement utilisees pour mettre en evidence la polymerisation en film lb. Notamment, la spectroscopie de photoelectrons x et la spectrometrie de masse d'ions secondaires apportent des elements de reponse quant au mecanisme. L'etude de la structure comporte deux champs d'investigation: nous etudions l'orientation des macrocycles avant et apres polymerisation par dichroisme lineaire, resonance paramagnetique electronique et diffraction de rayons x en reflexion puis la structure des films lb dans le plan du substrat est etudiee par les techniques de diffraction de rayons x en transmission, de microscopie a force atomique en correlation avec la modelisation moleculaire. Enfin, nous mettons en evidence le caractere bidimensionnel du polymere forme a la surface de l'eau par sa rigidite et sa stabilite mecanique. Les techniques de microscopie optique et electronique permettent de visualiser cette membrane, de la caracteriser par edxs et diffraction electronique

Ce travail de thèse consiste à utiliser une technique d'ingénierie moléculaire, la technique de Langmuir Blodgett, pour la réalisation d'une membrane permettant la fonctionnalisation de micro-capteurs biochimiques usinés collectivement sur substrat silicium selon les techniques de fabrication des MEMS (Micro Electro Mechanical System). L'objectif de cette fonctionnalisation est la détection conductimétrique du glucose en milieu liquide. Le document présente un état de l'art des micro-biocapteurs avant de présenter la technique de Langmuir Blodgett, principale technique expérimentale utilisée au cours de l'étude. Les conditions de formation de la membrane de Langmuir Blodgett et l'optimisation de son transfert sur support silicium sont ensuite décrits. La microscopie de force atomique et la spectroscopie infra-rouge à transformer de Fourier ont permis de caractériser la membrane de Langmuir Blodgett et de proposer un modèle de comportement dynamique de la membrane mixte comprenant une protéine et un acide gras, la glucose oxydase et l'acide béhénique. Ce modèle propose une structure à l'échelle nanométrique pour la couche mixte et une explication de son évolution en fonction du temps ou de la pression. Enfin, l'application de cette technique à la fonctionnalisation de micro-capteurs silicium est évaluée en la comparant à la technique de co-réticulation par la glutaraldéhyde, prise comme technique de référence. La technique de Langmuir Blodgett, bien que permettant d'obtenir de bonnes caractéristiques en terme de domaine de linéarité, ne permet pas d'obtenir des caractéristiques satisfaisantes en terme de reproductibilité de fabrication et de durée de vie. Le domaine de linéarité de réponse du micro-capteur est compatible avec une application de monitoring du diabète. Une solution technique est proposée pour améliorer les performances des capteurs fonctionnalisés selon la technique de Langmuir Blodgett et sera evaluée lors de prochains travaux

Au cours de ce travail, nous nous sommes intéressés à l’élaboration de cristaux photoniques colloïdaux d’architecture contrôlée afin d’étudier leur effet sur les spectres de photoluminescence de luminophores. Notre stratégie a été d’incorporer les émetteurs au sein des particules de silice composant les cristaux colloïdaux de façon à les répartir de manière homogène dans l’ensemble des matériaux. Nous présentons la synthèse des précurseurs minéraux et l’élaboration de cristaux colloïdaux d’épaisseur contrôlée à la couche près grâce à la technique de Langmuir-Blodgett. Ces structures sont caractérisées par une bande interdite qui affecte la propagation de la lumière. L’insertion d’une couche de particules de diamètre différent dans un cristal colloïdal induit l’apparition d’une bande passante au sein de la bande interdite. Nous avons ainsi étudié l’influence de la structure de cristaux avec et sans défaut(s) sur les spectres d’émission de différents luminophores. Nous avons observé une inhibition et une exaltation locale de la lumière émise dans les zones spectrales correspondant respectivement aux bandes stoppante et passante. Nous avons également observé des modifications réversibles des spectres de photoluminescence des émetteurs, lorsque ceux-ci sont incorporés au sein de cristaux colloïdaux dont les propriétés optiques peuvent être modulées via l’application d’un stimulus extérieur
During this work, we were interested in the elaboration of colloidal photonic crystals with a controlled architecture to study their effect on the photoluminescence spectra of emitters. Our strategy was to incorporate the emitters within the silica particles composing the colloidal crystals in order to distribute them homogeneously in the samples. We present the synthesis of the mineral precursors and the elaboration of colloidal crystals whose thickness is controlled at the layer level thanks to the Langmuir-Blodgett technique. These structures are characterized by a band gap which affects the light propagation. Insertion of a monolayer of particles with a different size as a planar defect within a colloidal crystal leads to the formation of a pass band in the band gap. We thus studied the effect of the structure of crystals with or without planar defect(s) on the emission spectra of different emitters. We observed local inhibition and exaltation of the emission in the spectral region corresponding to the stop band and the pass band, respectively. We have also observed reversible modulations of the photoluminescence spectra of the emitters when these ones were incorporated in colloidal crystals whose optical properties can be tuned by an external stimulus

Ce projet de thèse explore les paramètres régissant l’incorporation de nanoparticules métalliques à l’intérieur d’une couche ultramince de copolymère à bloc. Les composites sont mis en forme à l’interface air/eau à l’aide d’une cuve de Langmuir, puis transférés sur substrat solide à l’aide de la technique de Langmuir-Blodgett. Cette méthode permet d’obtenir une couche pseudo-monomoléculaire nano-structurée. Le comportement du copolymère seul à l’interface air-eau est d’abord étudié en fonction de différents paramètres tels que la température de la sous-phase, la masse molaire du copolymère, la vitesse de compression de la couche, etc… Deux types de nanoparticules métalliques sont utilisés afin de former les composites : celles étant décorées de polystyrène comportant un groupement thiol en bout de chaîne et celles étant décorées de courts thioalcanes. Pour chacun des deux cas la morphologie du nanocomposite est systématiquement étudiée en fonction de la taille des cœurs d’or et de la longueur des ligands organiques greffés à leur surface. Il est démontré que ces paramètres affectent la morphologie de la matrice ainsi que la distribution des nanoparticules. Quatre morphologies principales sont observées : particules disposées de manière disparate et brisant la morphologie de la matrice, particules agrégées sous forme d’îlots sans égards à la structure de la matrice, particules dispersées l’intérieur des domaines hydrophobes du copolymère et particules ségrégées à l’interface triple entre les deux blocs et l’air formant des anneaux de nanoparticules. Diverses expériences permettant de mieux caractériser ces systèmes ainsi que des preuves de concept permettant de valider les modèles débattus dans la thèse sont aussi présentées. Les systèmes sont principalement caractérisés par microscopie électronique en transmission et microscopie à force atomique.

The paper presents the grazing-incidence small-angle X-ray scattering technique and its application to the studies of self-assembly and re-assembly effects of colloidal nanoparticles. Two basic cases are exemplified - solvent evaporation driven self-assembly and self-assembly driven by barrier movement in the Langmuir-Blodgett trough. Studies of the nanoparticle re-assembly effects due to the surfactant removal complete the overview. These examples document strength of GISAXS for an in situ tracking of processes at nanoscale. The results have direct implications for tailored preparation of the self -assembled nanoparticle templates for sensing, plasmonics and other applications.

Ce manuscrit décrit l'élaboration de cristaux photoniques d'architecture contrôlée par l'assemblage de particules colloïdales. Nous avons présenté tout d'abord les voies de synthèse des particules colloïdales monodisperses minérales et organiques ainsi que les méthodes d'élaboration de cristaux photoniques colloïdaux d'épaisseur homogène. La qualité cristalline des édifices a été caractérisée par microscopie électronique à balayage et leurs propriétés optiques enregistrées par spectroscopie proche infrarouge. Dans le but de moduler l'architecture des matériaux, nous avons aussi fabriqué des hétérostructures en superposant deux cristaux colloïdaux de particules de diamètres différents, ou inséré de façon parfaitement contrôlée au sein des édifices des défauts planaires, matérialisés par des monocouches de particules de diamètres ou de natures différentes. Une étude de la relation structure - réponses optiques des différents matériaux a été systématiquement menée et met en évidence la diversité des propriétés optiques qui peuvent être obtenues en modulant précisément l'architecture des cristaux photoniques élaborés.

Au cours de ce travail, nous nous sommes intéressés à l'élaboration de cristaux photoniques colloïdaux d'architecture contrôlée afin d'étudier leur effet sur les spectres de photoluminescence de luminophores. Notre stratégie a été d'incorporer les émetteurs au sein des particules de silice composant les cristaux colloïdaux de façon à les répartir de manière homogène dans l'ensemble des matériaux. Nous présentons la synthèse des précurseurs minéraux et l'élaboration de cristaux colloïdaux d'épaisseur contrôlée à la couche près grâce à la technique de Langmuir-Blodgett. Ces structures sont caractérisées par une bande interdite qui affecte la propagation de la lumière. L'insertion d'une couche de particules de diamètre différent dans un cristal colloïdal induit l'apparition d'une bande passante au sein de la bande interdite. Nous avons ainsi étudié l'influence de la structure de cristaux avec et sans défaut(s) sur les spectres d'émission de différents luminophores. Nous avons observé une inhibition et une exaltation locale de la lumière émise dans les zones spectrales correspondant respectivement aux bandes stoppante et passante. Nous avons également observé des modifications réversibles des spectres de photoluminescence des émetteurs, lorsque ceux-ci sont incorporés au sein de cristaux colloïdaux dont les propriétés optiques peuvent être modulées via l'application d'un stimulus extérieur.

Ce manuscrit décrit l'utilisation de particules de silice colloïdale de taille et de fonctionnalité définies pour élaborer des matériaux aux propriétés spécifiques. Dans un premier temps, nous avons comparé différentes méthodes de synthèse de particules de silice à partir d'un précurseur moléculaire selon un procédé sol-gel. Celles-ci nous ont permis de fabriquer des objets sphériques de fonction de surface contrôlée et avec une taille moyenne régulière comprise entre 50 nm et 2 microns. Une fois ces particules synthétisées, nous avons étudié leur comportement à l'interface air-eau grâce à la technique de Langmuir puis fabriqué des cristaux colloïdaux d'épaisseur contrôlée par dépositions successives de monocouches de particules sur des substrats hydrophiles selon le principe de la technique de Langmuir-Blodgett. Ce contrôle nous a permis d'étudier l'influence de l'épaisseur des cristaux sur leurs propriétés spectroscopiques. Le second axe de notre recherche concernait l'élaboration de particules à morphologie originale et en particulier d'objets dissymétriques. L'utilisation de différentes techniques impliquant des phénomènes interfaciaux a d'abord été envisagée (interfaces planes puis courbes à l'échelle macroscopique). Nous avons également élaboré de particules organiques-inorganiques grâce à un procédé de polymérisation en émulsion de styrène en présence de particules de silice modifiées en surface. La maîtrise des différents paramètres expérimentaux nous a ainsi permis d'obtenir des objets hybrides aux morphologies originales mais prédictibles et variées, qu'elles soient dissymétriques (± haltère a, ± bonhomme de neige a, ± cœur-écorce décentré a) ou non (± marguerite a, ± multipode a ou ± framboise a). Ces nouveaux types de particules colloïdales pourraient présenter des propriétés innovantes dans de nombreux domaines tels que la catalyse, l'affichage électronique ou la stabilisation de milieux complexes

Surface-assisted directed assembly allows ultrasoft and replusive functional polymeric “colloids” to assemble into the organized supramolecular ultrathin films on a monomolecular level. This study aims at achieving a fundamental understanding of molecular morphology and responsive behavior of major classes of branched star-shaped polymers (star amphiphilic block copolymers and star polyelectrolytes) and their aggregation into precisely engineered functional ultrathin nanofilms. Thus, we focus on elucidating the role of molecular architecture, chemical composition, and intra/intermolecular interactions on the assembly behavior of highly-branched entities under variable environmental and confined interfacial conditions. The inherent molecular complexity of branched architectures facilitates rich molecular conformations and phase states from the combination of responsive dynamics of flexible polymer chains (amphiphilic, ionizable arms, multiple segments, and free chain ends) and extened molecular design parameters (number of arms, arm length, and segment composition/sequence). These marcromolecular building components can be affected by external conditions (pH, salinity, solvent polarity, concentration, surface pressure, and substrate nature) and transformed into a variety of complex nanostructures, such as two-dimensional circular micelles, core/shell unimicelles, nanogel particles, pancake & brush micelles, Janus-like nanoparticles, and highly nanoporous fractal networks. The fine balance between repulsive mulitarm interactions and surface energetic effects in the various confined surfaces and interfaces enables the ability to fabricate and tailor well-organized ultrathin nanofilms. The most critical findings in this study include: (1) densely packed circular unimicelle monolayers from amphiphilic and amphoteric multiblock stars controlled by arm number, end blocks, and pH/pressure induced aggregation, (2) monolayer polymer-metal nanocomposites by in-situ nanoparticle growth at confined interfaces, (3) on-demand control of exponentially or linearly grown heterogeneous stratified multilayers from self-diffusive pH-sensitive star polyelectrolyte nanogels, (4) core/shell umimicelle based microcapsules with a fractal nanoporous multidomain shell morphology, and (5) preferential binding and ordering of Janus-like unimicelles on chemically heterogeneous graphene oxide surfaces for biphasic hybrid assembly. The advanced branched molecular design coupled with stimuli responsive conformational and compositional behavior presents an opportunity to control the lateral diffusion and phase segregation of branched compact supermolecules on the surface resulting in the generation of well-controllable monolayers with tunable ordering and complex morphology, as well as to tailor their stratified layered nanostructures with switchable morphological heterogeneity and multicompartmental architectures. These surface-driven star polymer supramolecular assemblies and interfaces will enable the design of multifunctional nanofilms as hierarchical responsive polymer materials.

博士
國立成功大學
化學工程學系碩博士班
97
Nanoparticulate monolayers were prepared by using Langmuir-Blodgett and self-assembly techniques and used for superhydrophobic surface application. Langmuir monolayers of octadecylamine (ODA), octadecylthiol (ODT), and mixed ODA/ODT at air/liquid interface were used as template layers to adsorb gold nanoparticles (AuNPs) dispersed in the subphase. Furthermore, the adsorption of AuNPs was also enhanced by the destabilization effect of ethanol introduced into the colloidal solution. The monolayer not only acts as a template layer to incorporate AuNPs but also as a capping agent to in-situ modify the adsorbed NPs, providing van der Waals interaction among NPs for self-organization into ordered domains. The behaviors of the monolayers were studied using the pressure-area (π-A) isotherms, hysteresis and relaxation curves, and the observations of transmission electron microscopy (TEM) and Brewster angle microscope (BAM). For the ODA/AuNPs and ODT/AuNPs systems, the results indicated that ODA monolayer has a much higher ability, than the ODT monolayer, in incorporation AuNPs, attributed to the electrostatic interaction between ODA and AuNPs. By using ODA monolayer with appropriate molecular density, as well as the adjusting of the ethanol concentration, a close-packed particulate film of AuNPs can be prepared through the monolayer compression. The results also show that over loading of the ODA molecules increases the fractional ratio of free ODA molecules at the interface which obstructs the coalescence of particulate domains and, therefore, a close-packed particulate monolayer cannot be approached. The presence of ethanol in the subphase not only enhances the particle adsorption to the interface but also triggers a more expanded ODA monolayer, which plays a key role in preparing a close-packed particulate monolayer. For the mixed ODA/ODT systems, the incorporation of AuNPs was mainly performed by ODA molecules through the electrostatic interaction, while the specific affinity of ODT molecules to the AuNPs plays a role to increase the density of capping agents on an AuNPs, leading to a higher van der Waal interaction among NPs for self-organization into ordered domains. The experimental results showed that the utilization of the mixed ODA/ODT monolayer can improve the stability of AuNPs incorporated at the air/liquid interface and is helpful to the formation of an AuNPs particulate film with close-packed and ordered structure. For the application of particulate thin films on surperhydrophobic surface, a micro/nano dual-scale particulate film with raspberry-like morphology was prepared by using LB deposition and electrostatic layer-by-layer (ELBL) technique. Micro-size silica particles were used to prepare a surface with microscale roughness. Nano-size silica particles were then assembled on the particulate film to construct a finer structure on top of the coarse one. The as-deposited particulate films were surface-modified with alkylsilane to render a surface with surperhydropboic property. The advancing and receding contact angles of water on the dual-size structured surface were 169o and 165o, respectively. The scale ratio of the micro/nano surface structure and the regularity of the particulate films on the superhydrophobic surface performance are discussed.

碩士
中原大學
應用物理研究所
94
In this thesis, we introduce the principle and application of the Langmuir-Blodgett technique. By this method, we fabricate the ordered Polystyrene 2D structure, and discuss the relation between the surface pressure and the area of the LB-film in the process of forming the 2D structure. The surface pressure increases as compressing the bipolar molecules on the air/water interface continuously. As the separation distance between molecules decreasing, the surface pressure goes through two phase transitions (2D-gas to 2D-liquid and 2D-liquid to 2D-solid). If PS micro-balls have the similar behavior on the air/water interface, such two phase transitions should be observed. In the case of 1�慆 in diameter, we observe two phase transitions successfully. In the 150nm and 250nm cases, we only discover one phase transition (2D-gas to2D-liquid). As the phase transition occurs, the ratio of separation distance to micro-ball diameter (D/R value) is less than unity. This phenomenon is possibly due to the non-uniformity caused by the thermal fluctuation. More over, we try to disperse silver nano-powder into HPLC grade chloroform to get the suspension with ultrasonic cleaner. However, the concentration of the suspension is far thinner than 1mg/ml, so it is difficult to apply in this LB technique.

The Langmuir – Blodgett (LB) technique is about forming insoluble monolayer on the surface of aqueous solution and recently, it has emerged as one of the best method to study floating monolayer at the air – water interface. It has gained popularity after the use of monolayer with chemical complexes as well as biological species, and recently it has been used for the formation of biosensors. Langmuir monolayer arrays the amphiphilic molecules in a fashion where the hydrophobic part points towards the air and the hydrophilic group remains in contact with the aqueous subphase. Due to this property of Langmuir monolayer to orient the molecules at the air – water interface in a particular fashion, it can successfully serve as a template for two – dimensional reactions with restricted freedom. Hence, Langmuir monolayer has been extensively employed to study chemical and biological reactions at the air – water interface. To understand the behavior of Langmuir monolayer, surface pressure – molecular area (P – A) isotherms are studied as these P – A isotherms illustrate general conditions regarding the phase behavior of the two-dimensional Langmuir monolayer. Any change occurring due to the alignment of aliphatic molecules forming the monolayer is reflected by the change in P – A isotherms, which is known as phase transition. The phase transition is the most important element of the P – A isotherms with a characteristic signature of a plateau region in the isotherms. This phase transition point changes with the change of certain external parameters such as temperature, pH, and ionic strength, and as a result gives general information regarding the phase transition behavior. Therefore, with the little change of external parameters, the arrangement of the molecules in the monolayer also changes, which is reflected in the change in the nature of the isotherms. Thus, the system can, in principle, be used to define several physical parameters associated with it. On account of the property of Langmuir monolayer to orient the molecules at the air – water interface with restricted mobility and due to their condensed nature known as solid like phase, it closely mimics the situation inside a biological cell. Hence, we wanted to test whether an artificial nucleus can be generated at LB films. This can be achieved by immobilizing DNA or protein at the air – water interface and then by promoting their biological properties through macromolecular recognition. Here, immobilization of a macromolecule of biological relevance, its interaction with another component of a cell and extracting the thermodynamic parameters utilizing the LB technique will be of significance. This thesis embodies the immobilization of some biologically important proteins then follows their activity as well as DNA recognition properties at the air – water interface. A set of equations are derived here for the two dimensional Langmuir monolayer, which are used to calculate the thermodynamics of the system under study. Chapter 1 outlines the information about Langmuir monolayer and LB films. It sketches the historical background of the Langmuir monolayer and also elucidates the theory behind the same. This chapter cites the technical details of formation of Langmuir monolayer and LB films viś – a – viś other methods available for the fabrication of monomolecular films. It adequately discusses the functional LB films and their utilization for various different purposes. Finally, the role of metal ions in the LB films and in immobilizing biological macromolecules is discussed. Chapter 2 discusses the different techniques employed to perform the experiments described in this thesis. It includes the purification methods for the different proteins and DNA; the details of formation of Langmuir monolayer and fabrication of LB films. This chapter also describes the various techniques used for the characterization of the LB films, i.e Atomic Force Microscopy (AFM) and Fourier Transform Infrared (FTIR) spectroscopy. In Chapter 3, immobilization and imaging of protein molecules and protein DNA complexes on a LB substrate have been explored. Firstly, we describe the preparation of a Ni (II) – arachidate (NiA) monolayer and its characterization through P – A isotherm on a LB trough. Then, recombinant RNA polymerase from Escherichia coli, where the largest subunit was replaced with the same gene having a series of histidine amino acids at the C-terminus end of the protein, was immobilized over the NiA monolayer through a Ni (II) – histidine interaction. A single molecule of RNA polymerase (RNAP) could be seen through intermittent-contact AFM. Under the condition of the formation of the LB monolayer, the enzyme molecules were arrayed and transcriptionally active. Interestingly, they could pick up sequence specific DNA molecules from the subphase in an oriented fashion. In Chapter 4, the interaction between NiA and histidine tagged RNAP (HisRNAP), and RNAP and DNA were studied. LB films of Arachidic acid – NiA, NiA -HisRNAP and NiA – HisRNAP – DNA with different mole fractions were fabricated systematically. P -A isotherms were registered, and the excess Gibbs energy of mixing was calculated. The LB films were then deposited on solid supports for FTIR spectroscopic measurements. The FTIR spectra revealed the change in the amount of incorporated Ni (II) ions into the AA monolayer with the change in pH. The increase in mole fraction of RNAP and DNA in the NiA and NiA – RNAP monolayer, respectively, with their increasing concentration in the subphase are also noticed. The system developed here is robust and can be utilized to follow macromolecular interactions. In chapter 5, the Langmuir monolayer has been utilized to array a protein, Dps, specific for Fe (II) and non-specific for DNA. Dps from Mycobacterium smegmatis is known to have a cage like structure, exists in two oligomeric states, trimer and dodecamer, and can accommodate Fe (II) ions in its internal cavity. In addition, it converts Fe (II) to Fe (III), both in trimeric and dodecameric form, whereas the latter species is specific for non-specific DNA binding. We demonstrate here that, histidine tagged Dps in both oligomeric states can be immobilized on NiA LB films, where both ferroxidation and DNA binding ability remained unaffected in the ordered protein assembly. Interestingly, when Fe (II) – arachidate was used to generate a LB layer instead of NiA, Dps protein not only recognizes Fe (II) ion in the monolayer, it also converts it to Fe (III) ion in a time dependent fashion. However, once Fe (III) – Dps complex is formed and arrayed on LB monolayers, it remains very stable.

The Langmuir – Blodgett (LB) technique is about forming insoluble monolayer on the surface of aqueous solution and recently, it has emerged as one of the best method to study floating monolayer at the air – water interface. It has gained popularity after the use of monolayer with chemical complexes as well as biological species, and recently it has been used for the formation of biosensors. Langmuir monolayer arrays the amphiphilic molecules in a fashion where the hydrophobic part points towards the air and the hydrophilic group remains in contact with the aqueous subphase. Due to this property of Langmuir monolayer to orient the molecules at the air – water interface in a particular fashion, it can successfully serve as a template for two – dimensional reactions with restricted freedom. Hence, Langmuir monolayer has been extensively employed to study chemical and biological reactions at the air – water interface. To understand the behavior of Langmuir monolayer, surface pressure – molecular area (P – A) isotherms are studied as these P – A isotherms illustrate general conditions regarding the phase behavior of the two-dimensional Langmuir monolayer. Any change occurring due to the alignment of aliphatic molecules forming the monolayer is reflected by the change in P – A isotherms, which is known as phase transition. The phase transition is the most important element of the P – A isotherms with a characteristic signature of a plateau region in the isotherms. This phase transition point changes with the change of certain external parameters such as temperature, pH, and ionic strength, and as a result gives general information regarding the phase transition behavior. Therefore, with the little change of external parameters, the arrangement of the molecules in the monolayer also changes, which is reflected in the change in the nature of the isotherms. Thus, the system can, in principle, be used to define several physical parameters associated with it. On account of the property of Langmuir monolayer to orient the molecules at the air – water interface with restricted mobility and due to their condensed nature known as solid like phase, it closely mimics the situation inside a biological cell. Hence, we wanted to test whether an artificial nucleus can be generated at LB films. This can be achieved by immobilizing DNA or protein at the air – water interface and then by promoting their biological properties through macromolecular recognition. Here, immobilization of a macromolecule of biological relevance, its interaction with another component of a cell and extracting the thermodynamic parameters utilizing the LB technique will be of significance. This thesis embodies the immobilization of some biologically important proteins then follows their activity as well as DNA recognition properties at the air – water interface. A set of equations are derived here for the two dimensional Langmuir monolayer, which are used to calculate the thermodynamics of the system under study. Chapter 1 outlines the information about Langmuir monolayer and LB films. It sketches the historical background of the Langmuir monolayer and also elucidates the theory behind the same. This chapter cites the technical details of formation of Langmuir monolayer and LB films viś – a – viś other methods available for the fabrication of monomolecular films. It adequately discusses the functional LB films and their utilization for various different purposes. Finally, the role of metal ions in the LB films and in immobilizing biological macromolecules is discussed. Chapter 2 discusses the different techniques employed to perform the experiments described in this thesis. It includes the purification methods for the different proteins and DNA; the details of formation of Langmuir monolayer and fabrication of LB films. This chapter also describes the various techniques used for the characterization of the LB films, i.e Atomic Force Microscopy (AFM) and Fourier Transform Infrared (FTIR) spectroscopy. In Chapter 3, immobilization and imaging of protein molecules and protein DNA complexes on a LB substrate have been explored. Firstly, we describe the preparation of a Ni (II) – arachidate (NiA) monolayer and its characterization through P – A isotherm on a LB trough. Then, recombinant RNA polymerase from Escherichia coli, where the largest subunit was replaced with the same gene having a series of histidine amino acids at the C-terminus end of the protein, was immobilized over the NiA monolayer through a Ni (II) – histidine interaction. A single molecule of RNA polymerase (RNAP) could be seen through intermittent-contact AFM. Under the condition of the formation of the LB monolayer, the enzyme molecules were arrayed and transcriptionally active. Interestingly, they could pick up sequence specific DNA molecules from the subphase in an oriented fashion. In Chapter 4, the interaction between NiA and histidine tagged RNAP (HisRNAP), and RNAP and DNA were studied. LB films of Arachidic acid – NiA, NiA -HisRNAP and NiA – HisRNAP – DNA with different mole fractions were fabricated systematically. P -A isotherms were registered, and the excess Gibbs energy of mixing was calculated. The LB films were then deposited on solid supports for FTIR spectroscopic measurements. The FTIR spectra revealed the change in the amount of incorporated Ni (II) ions into the AA monolayer with the change in pH. The increase in mole fraction of RNAP and DNA in the NiA and NiA – RNAP monolayer, respectively, with their increasing concentration in the subphase are also noticed. The system developed here is robust and can be utilized to follow macromolecular interactions. In chapter 5, the Langmuir monolayer has been utilized to array a protein, Dps, specific for Fe (II) and non-specific for DNA. Dps from Mycobacterium smegmatis is known to have a cage like structure, exists in two oligomeric states, trimer and dodecamer, and can accommodate Fe (II) ions in its internal cavity. In addition, it converts Fe (II) to Fe (III), both in trimeric and dodecameric form, whereas the latter species is specific for non-specific DNA binding. We demonstrate here that, histidine tagged Dps in both oligomeric states can be immobilized on NiA LB films, where both ferroxidation and DNA binding ability remained unaffected in the ordered protein assembly. Interestingly, when Fe (II) – arachidate was used to generate a LB layer instead of NiA, Dps protein not only recognizes Fe (II) ion in the monolayer, it also converts it to Fe (III) ion in a time dependent fashion. However, once Fe (III) – Dps complex is formed and arrayed on LB monolayers, it remains very stable.

碩士
國立中正大學
化學所
94
The main theme of my thesis is of the development of a suitable technique in the preparation of a dense film composed of 0D nanoparticles. We have chosen silver nanoparticles synthesized in hexane, with capping (stabilizing) molecules of oleic acid and the average diameters in 5-6 nm, as a model system in our entire studies. The niche of my approach is to combine both conventional Langmuir-Blodgett (LB) technique and the spontaneous self-assembly of hydrophobic nanoparticles at the water-air interface. The method we have been developed called the Constant-Pressure Self-Assembly (CPSA) procedure for fabricating such film. The CPSA comprises of two steps: (i) the conventional LB barrier movement from a dispersed “gas” state to the “transition” state and (ii) self-assembly of nanoparticles at the water/air interface at a constant surface pressure. The second stage of the CPSA process proceeds along with the automatic barriers’ movement to maintain the constant surface pressure. Generally, the reduction of the amount of empty areas on the surface due to the self-assembly leads to the barriers moving towards each other and a decrease of the total surface area. We can then successfully obtain a two-dimensional dense film composed of hydrophobic nanoparticles from such CPSA process, dense monolayer LB film that were pushed by two barriers to compress. The resulting dense monolayer film indicates the interparticle distances are as closed as 2~3 nm which is in accordance with the total length of the capping molecules at the nanoparticle surfaces. I have arranged the content of my thesis in such a way that the readers can get a clear pictures of the CPSA technique in detail, including Chapter 1: the introduction of the LB technique, isotherm, model derivation of surface pressure detection, Chapter 2: the preparation of a suitable silver nanoparticles LB solution and its characterization, Chapter 3: the detail description and discussion of our CPSA technique, and Chapter 4: the conclusion and prospect of this new LB-CPSA technology.

碩士
國立東華大學
化學系
95
[Pd(imC16H33)2Cl2] and [Pd(imC16(2-OH))2Cl2] are both amphiphilic complexes. Molecular ordering of Pd(II)-imidazole complexes upon mechanical compression at the air/water interface is studied by surface pressure-area (π-A) isotherms and Brewster angle microscope (BAM). The repeatability of the isotherms and the stability of the Langmuir films are examined by successive compression–expansion cycles. The monolayers at the air/water interface are transferred onto solid substrate using vertical dipping Langmuir-Blodgett (LB) technique. The LB films are comprised of monolayers or multilayers of Pd(II)-imidazole complexes, which are precisely controlled by the number of deposition cycles and the transfer ratio. It is found that after combustion of the LB films of [Pd(imC16(2-OH))2Cl2] at or below 350°C, fairly uniform and well dispersed Pd nanoparticles are formed on the solid substrate. The relationships between particle size and parameters including combustion temperature, combustion time, and the number of layers of LB films are explored.

碩士
中原大學
物理研究所
98
We study the impact of surface roughness of TiO2 thin films on dye-sensitized solar cells and the characteristic of surface of TiO2 thin films. Langmuir-Blodgett (LB) technology was utilized to prepare TiO2 thin film electrodes of the dye-sensitized solar cells.The result clearly demonstrates that the presence of the LB layer significantly improved the contact between the FTO and the main TiO2 layer by particle size of 20nm deposited TiO2 particle. As a result, the conversion efficiency was improved by 47.0% from 1.7% to 2.5% due to the introduction of the interfacial P25 LB layer. From atomic force microscopy (AFM) images it was found that the particle size of 5nm and 60nm deposited TiO2 particle have high surface roughness and LB film with high surface roughness of TiO2 particles cannot form a good contact, bringing the total decline in their efficiency.

碩士
國立臺灣科技大學
材料科學與工程系
100
The metal nanoparticle film with well arrangement has good applicability in many fields, such like photonics, electronics, biomaterials and sensors. Among all methods for the film preparation, such like vapor deposition, etching and wet chemical method, we use Langmuir-Blodgett technique to prepare the gold nanoparticle film in this research. This method has obvious advantages such like simple process, less time cost, and controllable operating parameters. It can be applied to various nanoparticles with any shape and size, such as spherical, rod, square or triangle type. After the film preparation, we tend to demonstrate the surface enhanced infra-red absorption (SEIRA) technique by using our own films. The film preparation process used in this study can be separated into three steps, including nanoparticle synthesis, surface modification and film forming. In the particle preparation, we use metal salt reduction method to prepare gold nanoparticle colloidal solution, and then apply seed-mediated growth method to synthesis gold nanorod solution. During the surface modification process, we use n-dodecyl mercaptan to modify the surfaces of gold nanoparticles and gold nanorods to make them hydrophobic. In the film forming part, we use LB deposition system to prepare gold nanoparticle and gold nanorod films with different surface pressures. From the experiment results, we find the relationship between gold nanoparticle and gold nanorod films to surface pressure. With surface pressure increase, the coverage and the uniformity get large; also the particle density and arrangement get increased. In SEIRA experiment, we chose Eicosanoic Acid and PAMAM Dendrimer G4.5 as the target molecule to check the SEIRA phenomenon of gold nanoparticle and gold nanorod films. The structures of the films have great relevance to SEIRA effect. The experiment results show that the gold nanoparticle and gold nanorod film with higher coverage and particle density have larger enhancing factors, close to 50-fold.

Głównym przedsięwzięciem niniejszej rozprawy doktorskiej jest opracowanie metod unieruchamiania enzymów na wybranych podłożach, biorąc szczególnie pod uwagę kontrolowanie orientacji przestrzennej cząsteczek enzymów na powierzchni oraz określenie jej wpływu na aktywność bioelektrokatalityczną, strukturę oraz stabilność biokatalizatorów. Tematyka badawcza skupia się na opracowaniu efektywnych powierzchni katalitycznych, które mają kluczowe znaczenie dla rozwoju technologii biopaliwowych i biosensorów trzeciej generacji. Ponadto praca obejmuje charakterystykę fizykochemiczną układów nanostrukturalnych, których oddziaływanie na biomolekuły jest niezwykle ważne z punktu widzenia zastosowań biomedycznych. W pracy wykorzystywane są trzy wybrane enzymy: lakaza, peroksydaza chrzanowa (HRP) oraz katalaza (CAT). Stanowią one główny element otrzymywanych, a następnie badanych układów elektrodowych. Aktywność elektrokatalityczna biokatalizatorów sprawdzana jest na kilku podłożach modyfikowanych chemicznie bądź elektrochemicznie np. tioalkoholami, solami diazoniowymi, lipidami, tlenkiem grafenu (GO), makro- oraz nanostrukturalną polianiliną lub poprzez chropowacenie złota. Realizację poszczególnych zadań badawczych umożliwiła duża różnorodność dostępnych technik pomiarowych np.: woltamperometria cykliczna (CV), chronoamperometria (CA), technika Langmuira - Blodgett (LB), mikroskopia kąta Brewstera (BAM), skaningowa mikroskopia elektronowa (SEM), mikroskopia optyczna i mikroskopia w podczerwieni, spektroskopia UV-Vis, Ramana oraz absorpcyjna spektroskopia odbiciowa w podczerwieni z modulacją polaryzacji światła (PMIRRAS). Na efektywne działanie badanych układów wpływa wiele parametrów. Szczególnie ważne jest odpowiednie zorientowanie się cząsteczek enzymów względem powierzchni elektrody, a także ich oddziaływanie z warstwą pośredniczącą w transporcie elektronów, pamiętając że modyfikacje podłoża powinny charakteryzować się dużym przewodnictwem elektrycznym.
The main goal of this thesis is to develop methods of enzymes immobilization on selected substrates, considering controlling of the spatial orientation of the enzymes molecules and to determine this effect of immobilization on bioelectrocatalytical activity and stability of biocatalysts. Research focuses on developing of efficient catalytic surfaces which are crucial for biofuel technolgies and third-generation biosensors. In addition, the work involves physicochemical characteristics of nanostructured systems, being extremely important for biomedical applications. In this PhD thesis three selected enzymes are used: laccase, horseradish peroxidase (HRP) and catalase. They are the main component of obtained and studied electrode systems. The electrocatalytic activity of biocatalysts is checked on several, chemically or electrochemically modified substrates eg. tioles, diazonium salts, lipids, graphene oxide (GO), macro- and nanostructured polyaniline or on roughened gold. The implementation of individual research tasks enabled the wide variety of available measurement techniques such as: cyclic voltammetry (CV), chronoamperometry (CA), the Langmuir-Blodgett technique (LB), Brewster angle microscopy (BAM), scanning electron microscopy (SEM), optical microscopy and infrared microscopy, UV-Vis spectroscopy, Raman spectroscopy and polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS). Many parameters influence the performance of studied systems. Particularly important is the appropriate orientation of the enzyme molecules with respect to the surface of the electrode and their interaction with the intermediate layer, which influence the electron transport. Apart from the orientation, the electrical conductivity of intermediary layer plays an important role.

Improved fabrication of poly(vinylindenefluoride)-hexafluoropropylene (PVDF-HFP) thin films is of particular interest due to the high electric coercivity found in the beta-phase structure of the thin film. We show that it is possible to obtain high-quality, beta-phase dominant PVDF-HFP thin films using a direct approach to Langmuir-Blodgett deposition without the use of annealing or additives. To improve sample quality, an automated Langmuir-Blodgett thin film deposition system was developed; a custom dipping trough was fabricated, a sample dipping mechanism was designed and constructed, and the system was automated using custom LabVIEW software. Samples were fabricated in the form of ferroelectric capacitors on substrates of glass and silicon, and implement a unique step design with a bottom electrode of copper with an aluminum wetting layer and a top electrode of gold with an aluminum wetting layer. Samples were then characterized using a custom ferroelectric measurement program implemented in LabVIEW with a Keithley picoammeter/voltage supply to confirm electric coercivity properties. Further characterization using scanning electron microscopy and atomic force microscopy confirmed the improvement in thin film fabrication over previous methods.