Two different strategies for producing hierarchical polymer/nanoparticle (NP) patterned structures are presented in this work. The first strategy combines self-assembly of amphiphilic block copolymers at the air-water interface with microscale template assembly of the resulting aggregates on chemically-patterned substrates. Aggregates are formed via interfacial self-assembly of 141k polystyrene-block-poly (ethylene oxide) (PS-b-PEO, Mw=141 k) or a blend of PS-b-PEO (Mw=185 k) and PS-coated CdS (PS-CdS) quantum dots (QDs), to form aggregates of copolymer or copolymer/NP. Using Langmuir-Blodgett (LB) technique, the formed aggregates are then transferred to patterned substrates with alternating hydrophilic/hydrophobic stripes, obtained by microcontact printing (µCP) octadecyltrichlorosilane (OTS) on glass. The effect of different parameters including surface pressure, orientation of the patterned substrate respect to the air-water interface, and withdrawal speed was studied. Successful aggregate transfer to the hydrophilic domains of the patterned hydrophilic/hydrophobic substrate is achieved when patterned stripes are oriented perpendicular to the water surface during LB transfer and when substrates are withdrawn at low speed and low compression pressure. The second strategy combines the phase-separation of immiscible polymer blends during spin-coating with µCP. We show the surface-directed patterning of a phase-separating polymer blend on optically-transparent (OTS)-patterned glass substrate obtained via µCP. First, morphologies and pattern registration of thin spin-coated films of PS (Mw=131 k)/ poly(methyl methacrylate) (PMMA, Mw= 120 k) blends on patterned glass with alternating hydrophilic/hydrophobic stripes is studied for a range of experimental conditions including polymer concentration, blend composition, solvent, and spin rate. Good registration of polar PMMA to hydrophilic glass surface and non-polar PS to hydrophobic OTS lines is found under conditions, where polymer domain sizes are commensurate with the pattern periodicity. Next, we apply this method to pattern NPs using blends of PMMA and PS-CdS QDs via spin-coating onto OTS-patterned glass. Ultimately the method was extended to simultaneously pattern multi-NP functional assemblies using PS-CdS and a sample of PMMA-coated silver NP (PMMA-Ag). The specific interest in patterns of Ag NPs and CdS QDs is to provide a suitable proof-of-concept system for simultaneous multi-NP patterning. However, this system also has some interesting optical behaviour as a result of QD-surface plasmon interactions that is investigated in details. The challenge in PS-CdS/PMMA-Ag NPs patterning is the gelation as the solvent evaporates during spin-coating that restricts the NPs mobility and constraints their phase-separation. We show that adding homopolymers to the NPs blends prevents the overlap of approaching NP brushes and prevents the resulting gelation. Feature sizes were then fine-tuned by changing solution concentration and spin rate, in order to obtain NPs domains which can be surface-directed on OTS-patterned glass substrates. / Graduate

We plan to form and characterize surface-attached catenane gold nanoparticles. The proposed catenane self-assembles when a pi-electron-rich bis(thiol)hydroquinone derivative (hereby referred to as the dithiol) threads through a pi-electron-deficient inorganic molecular square forming a charge-transfer complex in solution and then attaches itself to a particle via two gold-sulfur covalent bonds.In preparation of this goal, an inorganic molecular square had to be synthesized. We synthesized, recrystallized, and characterized a cationic, tetranuclear, Pd(II)-based macrocyclic square according to the procedures published by Stang2.Then various methods of synthesis and derivatization of gold nanoparticles were investigated. Using a two-phase method published in the literature, dodecanethiolderivatized nanoparticles were synthesized,8 and attachment of the dodecanethiol was confirmed by NMR, IR, and UV/Vis spectroscopy. After the confirmation of the model compound, the reaction scheme was scaled-down for the derivatization of the nanoparticle with the dithiol alone which will be one of the components that will form the proposed catenane.Upon the derivatization of the nanoparticle with the dithiol, there was great difficulty in dissolving the nanoparticles in any polar or non-polar solvent. This led us to believe that nanoparticles are cross-linking with each other and therefore not dissolving. However, the attachment of the dithiol to the nanoparticle was confirmed by infrared spectroscopy. To solve the cross-linking problem an exchange reaction was conducted between the dodecanethiol-derivatized gold nanoparticles and the dithiol in a modified procedure from the literature.18 Although a successful exchange was confirmed by infrared spectroscopy, the dithiol-derivatized gold nanoparticles were still not soluble in any suitable solvent. / Department of Chemistry

Styrene-butadiene rubber (SBR) copolymer nanosized latex particles were synthesized via differential microemulsion polymerization (DMP) in a 300ml bench-scale semi-batch reactor, equipped with a thermocouple and a magnetic four-blade stirrer. This approach employed a continuous and slow addition of styrene and butadiene monomers drop-wise into a continuous aqueous phase comprising DI water, an initiator, a surfactant and a chain transfer agent. It was found that this approach offered an efficient heterogeneous phase path to synthesize styrene-butadiene copolymer latices with a high-butadiene-level of the resulting latex particles. The latex nanoparticles were formed as the SBR copolymer monomers undergo a self-assembly process in the continuous phase and were stabilized by their surrounding surfactant particles. The size of the latex particles could be easily adjusted by alternating the monomer addition speed, the reaction temperature, the amount of chain transfer agent applied and the type and the amount of surfactant introduced in the process. Not surprisingly, a small amount of chain transfer agent introduced into the DMP system might facilitate micellar nucleation and reduction of gel content in the polymer dramatically and may also aid increasing the size of the SBR latex particles. Owing to the small size of SBR latices prepared by the DMP method, the glass transition temperature (Tg) of the latices is much lower than the SBR latices generated by conventional technique. Furthermore, the increase of Tg was observed with an increase of the SBR particle size.

Studies of liquid crystal (LC) /Au nanoparticle (NP) composites have been pursued in columnar and in nematic phases of thermotropic LCs. Using LCs forming a columnar phase, we found that different functionalities on the corona of the Au NPs (hydrophobic vs. hydrophilic) display unique effects on the stability and ordering of the columnar LC phase. Doping nematic LCs with non-chiral or chiral Au NPs causes the formation of textures commonly observed for chiral nematic LCs, i.e., the formation of somewhat uniform stripe textures or patterns separated by areas of homeotropic alignment of LC molecules. Two scenarios are proposed. In the first scenario, the Au NPs form topological chain-like defects and the remaining Au NPs reside at the interface inducing vertical alignment of the LC molecules. In the second scenario, chiral Au NPs transfer chirality to the nematic LC host. Further, induced circular dichroism studies proved the second scenario. Using the same chiral Au NP systems, the origin of chirality of Au NPs has also been studied, and a powerful methodology has been proposed to unravel the puzzle of chirality of chiral ligand-protected Au NPs. Further investigations of these texture phenomena led to the discovery of using metal NPs to control the orientation and alignment of LCs. In due course, a dual alignment and electro-optical switching behaviour was found using alkylthiol-capped Au NPs doped into a nematic LC with positive dielectric anisotropy in planar namatic LC cells. This study was also expanded to Ag and CdTe NPs, which showed the same phenomenon, and all investigated NPs significantly reduced the voltage needed to re-orient the LCs in an electric field (threshold voltage). Starting from basic and moving on to more application-oriented research, we finally also initiated structure-property relationship studies of LC/NP composites.

This thesis describes some experiments developed to probe the fundamental aspects of the interfacial behaviour of proteins. The contents of this thesis can be broadly divided into two parts. In the first part, we studied how the size of the nanoparticles and other variables such as pH and bulk protein concentration affect the structure of the adsorbed protein layers. We also probed how these factors can influence the binding activity of adsorbed proteins. Study on the adsorption of IgG, Protein A and streptavidin on gold nanoparticles reveals that not all proteins are similarly affected by the size of the adsorbing surface. We found that though the optical properties of all the proteins vary with the size of the nanoparticle, their functionalities are not similarly affected by nanoparticle curvature. Protein A and streptavidin retain their binding capacity to IgG and biotin, respectively, irrespective of the size of the gold nanoparticle that they are attached to. On the other hand, a reduction/ loss in binding of adsorbed IgG to Protein A molecules is observed. The reduction in biological activity further depends on the radius of curvature of the adsorbing surface. The second part of the thesis describes how nanoparticles can used as a probe to study the complex interfacial behaviour of proteins. We have utilized the extreme sensitivity of localized surface plasmon resonance (LSPR) of gold nanoparticles to local refractive index to determine the optical properties of BSA adsorbed on various polymer surfaces. The dielectric properties of the adsorbed protein depend on the nature of the substrate. Further, we have developed a model to determine the refractive index profile of adsorbed protein as a function of the distance from the substrate.

Superparamagnetic iron oxide nanoparticles (SPIONs), due to their controllable sizes, relatively long in vivo half-life and limited agglomeration are ideal for biomedical applications such as magnetic labeling, hyperthermia cancer treatment, targeted drug delivery and for magnetic resonance imaging (MRI) as contrast enhancement agents. However, very limited studies exist on detecting and characterizing these SPIONs in vitro in physiologically relevant conditions. It would be of interest to localize and characterize individual SPIONs at the nanoscale in physiologically relevant conditions. MFM offers great potential for this purpose. We evaluate the applicability of Magnetic Force Microscopy (MFM) in air as well as in liquid to characterize bare and SiO2 coated SPIONs on mica .The magnetic properties of bare and SiO2 coated SPIONs are compared on the nanoscale using MFM. MFM phase- shift dependence on scan height is investigated using SPION samples that have been coated in hydrophobic polymers, polystyrene (PS) and poly (methyl methacrylate) (PMMA). The polymers are used to spin-coat SPION samples and mimic cell lipid bilayers. Nanoscale MFM images of SPIONs in a liquid environment, covered with these hydrophobic polymers are also presented for the first time. The use of 3-merceptopropyltrimethoxysilane (3-MPTS) to covalently attach SiO2 SPIONs to gold substrates for the potential purpose of MFM imaging in liquid is also briefly addressed. These results will allow us to understand the feasibility of detecting magnetic nanoparticles within cell membranes without any labeling or modifications and present MFM as a potential magnetic analogue for fluorescence microscopy. These results could be applied to cell studies and will lead to a better understanding of how SPIONs interact with cell membranes and have a valuable impact for biomedical applications of all types of magnetic nanoparticles.

The purpose of this project was to formulate, modify and evaluate nanoparticles for targeting asialoglycoprotein receptor found in large numbers exclusively on hepatocyte surfaces. Our goal is to increase the efficacy, reduce the side effects and the cost of the hydrophilic drugs administered to cure diseases like hepatitis C virus. Selective drug delivery into targeted cells using nanoparticles is one effective approach to enhance activity and avoid systemic side effects. Here we describe our effort towards the development of specially engineered poly(D,L-lactic-co-glycolic acid) nanoparticles using double emulsion method and surface coat them with asialofetuin for targeted delivery into hepatocytes. Bovine Serum Albumin-coated nanoparticles were prepared as a negative control. Furthermore, covalently conjugated protein on nanoparticle was labeled with rhodamine and was used for cell-based studies. Results from these studies indicated that asialofetuin conjugated with nanoparticles showed enhanced and selective uptake by hepatocytes compared to nanoparticles conjugated with Bovine Serum Albumin. / Pharmaceutical Sciences

Monolayer protected nanoparticles (MPNs) display fascinating size-dependent electronic, optical and catalytic properties. They are promising candidates to be used as building blocks with which to construct new generation nanoarchitectures and nanodevices for sensing, electronic and optoelectronic applications. The aggregation and dispersion of colloidal nanoparticles is one of the key issues closely related to their potential applications. Our knowledge of the colloid stability of nanoparticle dispersions with small sizes is still in its infancy, however, thymine is one of the bases in DNA, and is a pH sensitive and chromatic molecule. In the present study, thymine-functionalized self-assembled monolayer protected gold nanoparticles were synthesized. Their morphology and surface structure were characterized using TEM, UV-vis, FTIR, DSC-TGA and XPS techniques. The colloid stability of thymine-capped gold nanoparticle dispersions as a function of the type and concentration of monovalent salt, pH and particle size in alkaline aqueous solution were investigated. The manipulation of colloid stability with light was further explored. The results and conclusions are summarized inthis thesis.

Thesis (Ph.D.)--Auburn University, 2007. / List of publication generated from this dissertation research (ℓ. ix) Abstract. Vita. Includes bibliographic references (ℓ. 231-259)

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 95-99). Also available on the World Wide Web.