Large and small nanospheres, large and small nanoplates, nanorods and nanostars have been synthesized and fabricated into SERS substrates consisting of sandwiched and aggregated structure. Using 633 nm laser as excitation, individual SERS spectra of each labeling molecules, benzenethiol, 4-nitrobenzenethiol and 4-quinolinethiol, have been successfully obtained and the combination of these three molecules have the least amount of overlapping and can all be identified from the reference multiplexed spectra. Among all the substrates that have analyzed, the substrate made from nanospheres with sandwiched structure is able to produce multiplexed SERS spectra with more details and higher reproducibility. Although multiplexed SERS spectra can also be observed from substrates made from small nanoplates, nanostars and nanorods substrates with sandwiched structures, the unique peaks representing the labeling molecules are less consistent in their intensity. In addition, substrates with micro sized plates in sandwiched configuration are found to exhibit much lower SERS activities and this can be due to the size of the plate being much greater than the light source, restraining the surface plasmon resonance effect. Most of the substrates fabricated with aggregated nanoparticles have very low reproducibilities and saturated signals with 633 nm excitation. The spectra peaks are much easier to identify and are much more reproducible when 785 nm excitation have been adopted. This can be due to the size of the aggregated nanoparticles are much bulkier which a deeper penetrating light source is required to induce more molecules labels to exhibit SERS activities. A novel SERS substrate has been fabricated with nanoparticle-thiol-microplate sandwiched configuration by using a double ended thiol molecules, benzenedithiol, to strongly connect nanospheres and the plates together. However, the measurement of the SERS activity is limited by the overpowering of the light source, which has frequently melted and evaporated the plate samples once they have been exposed to the excitation radiation. In addition, instead of spreading evenly on the microplate surfaces, the nanoparticles have appeared to be aggregated which may have increased the difficulty in obtaining SERS activity.

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Viscoelastic surfactant (VES) fluids are preferred for many applications in the oil industry. Their viscoelastic behavior is due to the overlap and entanglement of very long wormlike micelles. The growth of these wormlike micelles depends on the charge of the head group, salt concentration, temperature, and the presence of other interacting components. The problem with these fluids is that they are expensive and used at temperatures less than 200°F. The viscoelasticity of nanoparticle-networked VES fluid systems were analyzed in an HP/HT viscometer. A series of rheology experiments have been performed by using 2-4 vol% amidoamine oxide surfactant in 13 to 14.2 ppg CaBr2 brines and 10.8 to 11.6 ppg CaCl2 brines at different temperatures up to 275°F and a shear rate of 10 s-1. The nanoparticles evaluated were MgO and ZnO at 6 pptg concentration. In addition, the effect of different nanoparticle concentrations (0.5 to 8 pptg) and micron size particles on the viscosity of VES fluid was investigated. The oscillatory shear rate sweep (100 to 1 s-1) was performed from 100 to 250°F. The effect of fish oil as an internal breaker on the viscosity of VES micelles was examined. This study showed that the addition of nanoparticles improved the thermal stability of VES micellar structures in CaBr2 and CaCl2 brines up to 275°F and showed an improved viscosity yield at different shear rates. Micro- and nanoparticles have potential to improve the viscosity of VES fluids. Lab tests show that for VES micellar systems without nanoparticles, the dominant factor is the storage modulus but when nanoparticles are added to the system at 275°F the loss modulus becomes the dominant factor. These positive effects of nanoparticles on VES fluid characteristics suggest that these particles can reduce treatment cost and will exceed temperature range to 275°F. With this work, we hope to have better understanding of nanoparticle/viscoelastic surfactant interaction.

The goal of this study was to develop a model of the gastrointestinal tract (GIT) to be used for in vitro testing of oral insulin delivery devices. The method and intensity of mixing and effects of gastrointestinal fluids with and without enzymes were evaluated. Comparisons were made between an actively mixed simulator and a passively mixed simulator, where the actively mixed simulator is a magnetically stirred flask while the passively mixed simulator is a flexible container on a rocking stage. Slower mixing times and larger time constants for mixing were seen for the passively mixed simulator during a pH tracer experiment. Release studies were performed with several oral insulin delivery device models to evaluate the effects of different mixing techniques on insulin release. In all cases, the more intense mixing of the actively mixed simulator resulted in more insulin release. When using a nanoparticle model in intestinal fluid for example, 100% insulin release was observed in the actively mixed simulator while only 53% was released in the passively mixed simulator after 1 hour. Trypsin and pepsin were used to determine the ability of a drug delivery device to protect insulin from enzymatic degradation in which trypsin was added to simulated intestinal fluid and pepsin was added to simulated gastric fluid. Premature insulin release and insulin denaturation at body temperature occurred in the intestinal fluid so the protective effects against trypsin were unable to be effectively evaluated. An increase in insulin loss from 70% to 95% was detected in the presence of pepsin compared to gastric fluid without enzymes in the actively mixed simulator, indicating that acid hydrolysis of insulin as well as protease attack by pepsin will impact the behavior of an insulin delivery device. An improvement in insulin retention was observed in the passively mixed simulator. After 1 hour, insulin retained was increased from 4% in the actively mixed simulator to 10% in the passively mixed simulator, and after 2 hours, this increase was 2% to 7%. Premature insulin release from the delivery device, acid hydrolysis, temperature denaturation, and enzymatic degradation are factors limiting the effectiveness of oral insulin. / Thesis (Master, Chemical Engineering) -- Queen's University, 2011-08-19 19:29:52.804

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DNA is a remarkable material that is both an inspiration for polymer nanotechnology and a versatile building block for assembling well-defined nanostructures. To create polymeric materials that would be useful in nanotechnology, we synthesized block copolymers containing thymine and diamidopyridine side chains. These DNA-mimetic polymers self-assembled into spherical aggregates in solution, held together by hydrogen bonding interactions. We have reported the first example of a block copolymer micellar aggregate that is capable of selective recognition of small-molecule guests, with concomitant changes in its aggregation behavior. / In the field of DNA-mediated materials, the ordering of gold nanoparticle (AuNP) arrays can be hindered by the lability of AuNP-DNA linkages. In the search of an indefinitely stable AuNP-DNA linkage, three dendritic thiol-terminated DNA strands were synthesized, and were bound to AuNPs. A preliminary AuNP-DNA linkage lability study showed potential in forming nonlabile AuNP-DNA linkages through the use of dendritic thiol-modified DNA.

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.

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