L’aparició de noves propietats químiques i físiques dins l’escala nanomètrica és un dels motius principals que fa necessari l’estudi de nanopartícules de diferents metalls, del seus òxids i dels seus aliatges, pel disseny de les seves futures aplicabilitats. Aquesta tesi estudia dos blocs temàtics: i) la síntesi i ii) l’autoensamblatge de nanopartícules metàl·liques. En el primer bloc, s’estudien els aspectes més rellevants de la preparació de nanopartícules metàl·liques (constituïdes per un o dos metalls diferents) de mida i forma controlada. Es desenvolupa les síntesis de diferents partícules magnètiques, i s’obtenen dispersions col·loïdals de nanopartícules de cobalt (Co) i alguns del seus òxids, així com d’ or (Au), platí (Pt) i alguns dels seus aliatges. Les nanopartícules de Co estan rebent un interès creixent degut a les propietats magnètiques que presenta el material, la qual cosa les fa molt interessants per a un nombre elevat d’aplicacions tecnològiques. Però la sensibilitat del material en front l’oxidació (la qual produeix canvis en les seves propietats magnètiques) requereix que es faci un estudi profund d’aquests processos. En aquest treball, s’han sintetitzat nanopartícules de Co de diferents mides i s’han estudiat els paràmetres que afecten les seves propietats magnètiques. A més, s’han estudiat els processos d’oxidació de les nanopartícules de Co, que han generat tant nanopartícules core/shell (nucli/recobriment) Co/CoO com nanopartícules “hollow” (buides) d’òxid de Co. Les nanopartícules de Pt també són de gran interès degut a que presenten propietats òptiques i catalítiques úniques. Les seves propietats catalítiques depenen fortament dels seus àtoms superficials i, per tant, de la mida i de la forma de les nanopartícules. En aquesta tesi s’ha dut a terme la síntesi de nanopartícules de Pt de diferent mida i forma mitjançant el control de diferents paràmetres durant el procés sintètic (com la temperatura, els lligands i els temps de reacció). En particular, s’ha determinat la incorporació de traces metàl·liques durant la síntesis i el seu efecte en el control de la forma final de la nanopartícula. Finalment, l’or es un dels materials més estudiats en l’escala nanomètrica degut a les seves propietats òptiques i el seu caràcter inert, que fa que sigui un dels materials més utilitzats en aplicacions biològiques. Les propietats òptiques són especialment importants en materials amb “aspect ratios” (relació longitud/amplada). En aquesta tesi s’han sintetitzat Au “rods” (barres) de gran llargada utilitzant nanopartícules de Pt com a catalitzador de la reacció, i se n’ha explorat la llargada que poden aconseguir, relacionades amb les seves possibles aplicacions. En el segon bloc, s’estudia l’ús de les nanopartícules en la preparació de materials nanoestructurats mitjançant autoensamblatge. S’ha observat com depenent de la naturalesa i la forma de les nanopartícules, es creen diferents patrons. En particular, aquesta part es centra principalment en la utilització de nanopartícules de Co com a unitats de construcció de estructures autoensamblades, degut a les seves propietats magnètiques. S’ha estudiat l’autoensamblatge de nanopartícules de Co a sobre de diferents substrats d’interès tecnològic i les forces que intervenen en el procés. En particular, en destaquem: l’estudi de l’autoensamblatge de les partícules de Co sobre grafit i sobre substrats de silici. Finalment, s’ha estudiat la influència de les propietats en el procés d’autoensamblatge de nanopartícules de Co, així com l’estructura magnètica dels assemblats, mitjançant holografia electrònica i microscopia Lorentz. S’ha estudiat la variació de l’estructura magnètica dels diferents assemblats en funció de la seva mida total, i també en funció de la temperatura. L’estudi de les propietats individuals de les nanopartícules de Co dins l’assemblat és possible mitjançant les dues tècniques mencionades prèviament, i s’han observat els efectes col·lectius entre totes les partícules integrants de les estructures. Els resultats obtinguts indiquen que l’ordenació ferromagnètica dipolar és molt persistent en les estructures, fins i tot amb un elevat grau de desordre a la xarxa de partícules. / The emergence of new chemical and physical properties at the nanoscale is one of the main reasons that make necessary the study of nanoparticles of different metals, their oxides and alloys for different applications. In this thesis, two thematic blocks are studied: i) the synthesis and ii) the self- assembly of metallic nanoparticles. In the first block, the more relevant aspects in the preparation of metallic and bimetallic nanoparticles of controlled size and shape are studied. The syntheses of different metal nanoparticles are developed, and monodisperse colloidal suspensions of Co metal particles and some of their oxides, as well as Au, Pt and some alloy nanoparticles are obtained. Co particles are receiving much interest due to their magnetic properties of the material, which turn them interesting for a number of technological applications. On the other hand, the sensitivity of the material to oxidation (with a consequent change in its properties) makes necessary a deeper study of these processes. In this work, Co magnetic nanoparticles of different sizes have been synthesized and the parameters that affect the variation of their magnetic properties have been studied. Moreover, the oxidation processes of the Co nanoparticles have been also studied, generating both Co/CoO core/shell and CoO hollow nanoparticles. Pt nanoparticles are also a subject of interest due to their unique optical and catalytic properties. Their catalytic properties strongly depends on their surface atoms and, therefore, on the size and shape of the particles. During this thesis, different size and shape Pt nanoparticles have been synthesized by controlling different parameters during the synthetic process (i.e. temperature, surfactants, and reaction times). In particular, the incorporation of metal “traces” during the synthesis process, and their effect on the control of the shape are determined. Finally, Au is one of the most studied materials at the nanometer scale due to its optical properties and its inertness, making it one of the most used materials in biological applications. The optical properties are particularly important in materials with aspect ratios (length/width). In this thesis, the synthesis of extra long Au rods (bars) using Pt nanoparticles as the reaction catalyst have been synthesized, and the length that they can reach have been also explored for its potential applications (e.g. as connections between electrodes). In the second block, the use of nanoparticles for the preparation of nanostructured materials via self-assembly processes is studied. It is observed how, depending of both the nature and the shape of the nanoparticle, different patterns are created. In particular, this part focuses mainly on the use of Co nanoparticles as building block units for construction of self-assembled structures, due to their magnetic properties. The self-assembly of Co nanoparticles onto different substrates with technological interest and the forces involved in the process have been studied. Particularly, the works to be highlighted are the study of the self-assembly of Co on graphite and on silicon substrates due to dipolar interactions. Finally, the influence of the magnetic properties in the self-assembly process of Co nanoparticles, and the magnetic structure of the formed assemblies, are studied by electron holography and Lorentz microscopy. The variation of the magnetic structure of the different self-assembled structures has been studied as a function of both the assembly total size and the temperature. The study of the individual and collective behavior of the Co nanoparticles on the assembly is possible with these techniques, and collective effects among the whole NPs forming the structures have been observed. The obtained results showed that dipolar ferromagnetism order is extremely persistent even under a high degree of lattice disorder.

The self-assembly of several pyrene-labelled amphiphilic macromolecules in water was characterized by fluorescence. Information on their self-assembly was obtained by monitoring the level of pyrene aggregation in solution. A measure of the level of association was obtained by determining the fraction of aggregated pyrene of the labelled macromolecules from the global analysis of their monomer and excimer fluorescence decays. Global analysis limits the degrees of freedom of the analysis thus reducing the error on the parameters retrieved from the analysis. Extensive developments in the global analysis of the pyrene monomer and excimer decays enabled the first characterization of the molar absorbance coefficient of the pyrene aggregates formed by aqueous solutions of pyrene-labelled poly(N,N-dimethylacrylamide) (PyPDMA) and poly(ethylene oxide) (PyPEO). The molar absorbance coefficients of the pyrene aggregates determined for PyPDMA and PyPEO were both found to be broader and red-shifted compared to that of unaggregated pyrene. These results agree with observations found in the scientific literature made by using absorption and excitation fluorescence measurements. Attempts to determine the molar absorbance coefficient of pyrene-labelled hydrophobically-modified alkali-swellable emulsion (PyHASE) polymers were unsuccessful. The inability to characterize the pyrene aggregates of PyHASE was attributed to the greater complexity of the PyHASE polymer compared to PyPDMA and PyPEO. For these simpler pyrene-labelled polymers, a protocol has been established which uses the global analysis of the pyrene monomer and excimer decays to determine quantitatively the level of association of pyrene-labelled polymers as well as the molar absorbance coefficient of their aggregates. Changes in the level of aggregation of pyrene-labelled lipids (PLLs) having head groups bearing an alcohol (PSOH) or imido diacetic acid (PSIDA) embedded in 1-palmitoyl-2-oleyl-3-sn-phosphatidylcholines (POPC) or distearylphosphatidylcholine (DSPC) liposomes were probed by fluorescence. Distribution of the PLLs in the fluid POPC membrane was found to be homogeneous while the PLLs phase-separated into amorphous channels created in the DSPC membranes. Multivalent cations Cu2+ and La3+ were found to bind to PSIDA, hindering diffusional encounters between unaggregated PSIDA but leaving the PLL aggregates intact. Using the fluorescence quenching ability of Cu2+, the viscosity of the amorphous channels of the DSPC membrane was determined to be about six times greater than that of the more fluid POPC membrane. Simultaneous rheological and fluorescence measurements were achieved by interfacing a rheometer with time-resolved and steady-state fluorometers using fiber-optic cables. This joint set up enabled the simultaneous rheological and fluorescence measurements of PyHASE solutions having concentrations ranging from 0.5 w/w% to 5 w/w%. The level of association of the PyHASE solutions was tracked using fluorescence at shear rates of 0, 0.1 and 100 s–1. Despite the presence of shear thinning leading to viscosity drops of up to four orders of magnitude, no change in the fluorescence and hence the level of association was observed. The lack of change in level of association implied that the mechanism of shear thinning is due to a switching from inter- to intramolecular association rather than a drop in the level of association. This information will prove useful for future models attempting to predict the rheological behaviour of sheared associative polymers.

<p>The control of matter and phenomena at the nanoscale is fast becoming one of the most important challenges of the 21st century with wide-ranging applications from energy and health care to computing and material science. Conventional top-down approaches to nanotechnology, having served us well for long, are reaching their inherent limitations. Meanwhile, bottom-up methods such as self-assembly are emerging as viable alternatives for nanoscale fabrication and manipulation.</p><p>A particularly successful bottom up technique is DNA self-assembly where a set of carefully designed DNA strands form a nanoscale object as a consequence of specific, local interactions among the different components, without external direction. The final product of the self-assembly process might be a static nanostructure or a dynamic nanodevice that performs a specific function. Over the past two decades, DNA self-assembly has produced stunning nanoscale objects such as 2D and 3D lattices, polyhedra and addressable arbitrary shaped substrates, and a myriad of nanoscale devices such as molecular tweezers, computational circuits, biosensors and molecular assembly lines. In this dissertation we study multiple problems in the theory, simulations and experiments of DNA self-assembly. </p><p>We extend the Turing-universal mathematical framework of self-assembly known as the Tile Assembly Model by incorporating randomization during the assembly process. This allows us to reduce the tile complexity of linear assemblies. We develop multiple techniques to build linear assemblies of expected length N using far fewer tile types than previously possible.</p><p>We abstract the fundamental properties of DNA and develop a biochemical system, which we call meta-DNA, based entirely on strands of DNA as the only component molecule. We further develop various enzyme-free protocols to manipulate meta-DNA systems and provide strand level details along with abstract notations for these mechanisms. </p><p>We simulate DNA circuits by providing detailed designs for local molecular computations that involve spatially contiguous molecules arranged on addressable substrates via enzyme-free DNA hybridization reaction cascades. We use the Visual DSD simulation software in conjunction with localized reaction rates obtained from biophysical modeling to create chemical reaction networks of localized hybridization circuits that are then model checked using the PRISM model checking software.</p><p>We develop a DNA detection system employing the triggered self-assembly of a novel DNA dendritic nanostructure. Detection begins when a specific, single-stranded target DNA strand triggers a hybridization chain reaction between two distinct DNA hairpins. Each hairpin opens and hybridizes up to two copies of the other, and hence each layer of the growing dendritic nanostructure can in principle accommodate an exponentially increasing number of cognate molecules, generating a nanostructure with high molecular weight. </p><p>We build linear activatable assemblies employing a novel protection/deprotection strategy to strictly enforce the direction of tiling assembly growth to ensure the robustness of the assembly process. Our system consists of two tiles that can form a linear co-polymer. These tiles, which are initially protected such that they do not react with each other, can be activated to form linear co-polymers via the use of a strand displacing enzyme.</p> / Dissertation

Current microfabrication materials include silicon, a wide variety of metals, dielectrics, and some polymers. Because of the low cost and high processing flexibility that polymers generally have, expanding the use of polymers in microfabrication would benefit the microfabrication community, enabling new routes towards goals such as low-cost 3D microfabrication. This work describes two main unconventional uses of polymers in microfabrication. The first unconventional use is as a carrier material in the self-assembly (SA) of millimeter-scale parts in which functional electronic components and electrical interconnects were cast into 5 mm cubes of Polymethylmethacrylate (PMMA). The second unconventional use is as a non-flat micromold for an alumina ceramic and as transfer material for multiple layers of micropatterned carbon nanotubes (CNTs). Both of these uses demonstrate 3D low-cost microfabrication routes. In the SA chapter, surface forces induced both gross and fine alignment of the PMMA cubes. The cubes were bonded using low-melting temperature solder, resulting in a self-assembled 3D circuit of LEDs and capacitors. The PMMA-encasulated parts were immersed in methyl methacrylate (MMA) to dissolve the PMMA, showing the possibility of using MEMS devices with moving parts such as mechanical actuators or resonators. This technique could be expanded for assembly of systems having more than 104 components. The ultimate goal is to combine a large number of diverse active components to allow the manufacture of systems having dense integrated functionality. The ceramic micromolding chapter explores micromolding fabrication of alumina ceramic microstructures on flat and curved surfaces, transfer of carbon nanotube (CNT) micropatterns into the ceramic, and oxidation inhibition of these CNTs through ceramic encapsulation. Microstructured master mold templates were fabricated from etched silicon, embossed thermally sacrificial polymer, and flexible polydimethylsiloxane (PDMS). The polymer templates were themselves made from silicon masters. Thus, once the master is produced, no further access to a microfabrication facility is required. Using the flexible PDMS molds, ceramic structures with mm-scale curvature were fabricated having microstructures on either the inside or outside of the curved macrostructure. It was possible to embed CNTs into the ceramic microstructures. To do this, micropatterned CNTs on silicon were transferred to ceramic via vacuum molding. Multilayered micropatterned CNT-ceramic devices were fabricated, and CNT electrical traces were encapsulated with ceramic to inhibit oxidation. During oxidation trials, encapsulated CNT traces showed an increase in resistance that was 62% less than those that were not encapsulated.

In this thesis we synthesize discotic liquid crystal materials. After demonstrating the molecular structures by 1H-NMR of Acid-6, we measure the properties of this material. We use discotic liquid crystal Acid-6 and measure its¡¦ properties. It shows the properties of Acid-6 which is having the ability of absorbing visible light. By UV-Vis spectrum, we can realize the absorption band is located at 400 nm and confirm that it is able to be a photo-sensitized dye. Besides, the property of discotic liquid crystal is the self-assembly ability, the molecular can assemble into hexagonal columnar structure by themselves, which enable discotic liquid crystal to have better mobility. The DSSCs have good power conversion efficiency with using discotic liquid crystals Acid-6. We can measure its¡¦ mobility to know the component with which the most appropriate.

A series of immiscible crystalline-crystalline diblock copolymers, poly(ethylene oxide)-b-(£`-caprolactone) (PEO-b-PCL), were blended with (3-phenyl-3,4-dihydro-2H-1,3-benzoxazin-6-yl) methanol (Pa-OH). FT-IR analyses provide that the ether group of PEO is a stronger hydrogen bond acceptor than the carbonyl group of PCL with the hydroxyl group of Pa-OH. Pa-OH after curing results in the excluded and confined PCL phase based on differential scanning calorimeter (DSC) analyses. In addition, the mesoporous structure was proved with the increasing the ratio of PCL to PEO in block copolymers by small angle X-ray scattering (SAXS), transmission electron microscopy (TEM) analyses and N2 adsorption-desorption isotherms (BET) The poly(styrene-b-4-vinyl pyridine) diblock copolymer was blended with Pa-OH monomer. FT-IR analyses demonstrate the intermolecular hydrogen bonding interaction between the pyridine group of P4VP and the hydroxyl group of Pa-OH. After curing, the block copolymers were incorporated into polybenzoxazine resin to access the nanostructure through the reaction induced microphase separation mechanism by TEM and SAXS analyses.

The fabrication of one-dimensional (1-D) polymeric photonic crystals from the self-assembly of ultra-high-Mw polystyrene-b-polyisoprene (PS-PI) block copolymers (BCPs) were conducted in this study. Well-ordered microphase-separated lamellar structures can be observed in the ultra-high-Mw PS-PI BCPs in the bulk by transmission electron microscopy (TEM) and ultra-small angle X-ray scattering (USAXS). To fabricate large-area and well-oriented lamellar microstructures with parallel orientation to the substrate, substrate-induced microstructural orientation with the accompanying solvent annealing method (i.e., solvent-induced orientation) was carried out in the PS-PI film. By grazing-incidence ultra-small angle X-ray scattering (GIUSAXS), scanning probe microscope (SPM) and cross-sectional TEM morphological observation, identification of the microstructural orientation in the PS-PI film can be achieved. A disordered wormlike morphology is observed in the as-spun PS-PI thin film from toluene on the PS-grafting substrate and on neat glass or wafer. This is attributed to the fast solidification of the disordered microstructure due to fast evaporation rate of the toluene solvent. After solvent annealing by the PS-selective or PI-selective solvents such as divinylbenzene (DVB) (neutral but highly PS-selective), benzene (PS-selective) and cyclohexane (PI-selective), parallel lamellar microstructures can be obtained in the PS-PI films on the PS-grafting substrate. By contrast, the coexistence of parallel and perpendicular lamellar microstructures is obtained in the PS-PI film from toluene after solvent annealing by neutral toluene on the PS-grafting substrate or by PS-selective benzene on the neat glass or wafer. This indicates that the formation of the parallel lamellar microstructures is mainly determined by both solvent-induced and substrate-induced orientation. In contrast to the as-spun disordered morphology from toluene, well-ordered parallel lamellar microstructures with few defects was found in the as-spun PS-PI film from DVB on the PS-grafting substrate, whereas parallel lamellar microstructures with many defects was observed in the as-spun PS-PI film from DVB on the neat glass or wafer. This further demonstrates that the PS-grafting substrate indeed plays an important role on the fabrication of well-ordered parallel lamellar microstructures. Interestingly, once the initial morphology of the PS-PI BCP reaches a relative stable state (i.e., parallel lamellar microstructures versus disordered wormlike morphology), it is hardly to trigger the microstructural reorientation by the subsequent solvent annealing. We suggest that the stable initial morphology in the PS-PI film may create high energy barrier for microstructural reorientation. With the controllable microstructural orientation, a PS-PI thick film having large-area and well-oriented parallel lamellar microstructures can be successfully carried out. Therefore, 1-D polymeric photonic crystals from the self-assembly of the lamella-forming PS-PI BCPs can be achieved. The in-situ UV reflectance spectra show that the reflective band shifts from ultraviolet wavelength to visible wavelength was observed in the lamella-forming PS-PI thick film with elapse of time by solvent annealing. Notably, the band gap can be recovered to the initial state once the solvent is removed, indicating the reversible process. As the results, the solvatochromic BCP photonic crystals can be successfully carried out by the manipulation of the solvent swelling in the large-area and well-oriented lamella-forming PS-PI BCP film.

Layer-by-layer (LbL) assembly based on ionic interactions has proven to be a versatile route for surface modification and construction of ultrathin nanocomposites. Covalent LbL assembly based on facile ‘click’ covalent bond formation is an effective alternative, especially for the applications where a more robust ultrathin films or nanocomposites is desired. The subject of this dissertation focuses on the design of three different covalent LbL assemblies and their applications on conductive thin films, superhydrophobic surfaces, and solute responsive surfaces, respectively. Surface modification of PE substrates using covalent LbL assembly with PEI and Gantrez is a successful route to prepare a surface graft. The procedure is relative easy, fast and reproducible. Grafting multiple layers of PEI/Gantrez to the PE powder surface provided excellent coverage and promoted stable LbL film growth and excellent adhesion. This carbon black (CB) coated powder was compression molded into films, and their conductivity was measured, which revealed a percolation threshold below 0.01 wt % CB for the PEI-grafted system. Electrical conductivity of 0.2 S/cm was achieved with only 6 wt % CB, which is exceptional for a CB-filled PE film. Direct amination of MWNTs with PEI is a convenient and simple method leading to highly functionalized product that contains 6-8 % by weight PEI. Superhydrophobic PE films can be formed either from ionic LbL self-assembly of MWNT-NH-PEIs and poly(acrylic acid) or from covalent LbL self-assembly of MWNTNH- PEIs and Gantrez when the final graft is acrylated with octadecanoic acid. While the ionically assembled nanocomposite graft is labile under acid, the covalently assembled graft is more chemically robust. Responsive surfaces with significant, reversible, reproducible wettability changes can be prepared by covalent LbL grafting using PNIPAM-c-PNASI and aminated silica nanoparticles. A 65º ΔΘ value was observed with water vs. 1.4 M Na2SO4. The prepared film shows a high surface roughness of ~300 nm, which contributes to the large solute responsive ΔΘ values. The surfaces are reconfigurable in different solute conditions and that the changes in water contact angle are likely due to combination of change in surface roughness along with swell and intercalation of the solute ions into the PNIPAM surface.

The article reports the lattice pattern self-assemble formation of polystyrene thin films. According to a simple observing device which using dark-field microscope, we collect a series of dynamitic image that air bubbles form a two-dimensionally or three-dimensionally ordered array in polymer film with Marangoni convection effect. In order to explain the array formation, we also provide two new models to discuss the phenomenon about 2D & 3D structure in this paper.

Here we report the preparation, structure, and spectroscopic properties of an intriguing copper(I) cyclophane-like dimeric complex [Cu2(dppa)2(bpy)2][BF4]2(2)¡B[Cu2(dppa)2(mbpy)2][BF4]2(3)¡B[Cu2(dpbp)2(bpy)2][BF4]2(7)©M[Cu2(dppb)2(bpy)2] [BF4]2(8), containing phenyl phosphine bridge ligands, such as diphenylphosphino acetylene (dppa), 1,4-bis(diphenylphosphino)benzene (dppb) and 4,4'-bis(diphenyl phosphino)biphenyl (dpbp). As a building unit, the complex [Cu2(dpbp)2(NCMe)4] [BF4]2(9) containing labile acetonitrile molecules those can be easily substituted by anionic ligands, is expected to combine with suitable linkers to synthesize supramolecular arrays with shapes of polygons and polyhedra.