My research is focused on two main objectives, the study of catalytic efficiency and mechanism of palladium nanoparticles stabilized by poly(vinylpyrrolidone) (PVP) for carbon-carbon coupling reactions, and to rationally synthesize metal nanoparticles stabilized by metal-carbon bonds and apply them to catalyze carbon-carbon coupling reactions.<p> In the first project, Pd nanoparticles stabilized by PVP were used to catalyze carbon-coupling reactions, specifically the Stille and Suzuki reactions. The mechanism of carbon-carbon coupling reactions was studied. The uncertainty of whether nanoparticles or Pd salts are the catalyst was also examined using the same experimental procedure with Pd salts to examine their catalytic activity in carbon-carbon coupling reactions. Results show that the presence of O2 is crucial to the Stille reaction with the Pd nanoparticles, which are nearly completely inert under N2, while the K2PdCl4 precursor is itself quite active for the Stille reaction. However, the Pd nanoparticles were found to be active for the Suzuki reaction with high yields in the absence of O2. The yields for 4-chlorobenzoic acid are higher than 4-bromobenzoic acid and occur for un-catalyzed reactions, for reasons that are still unknown. Finally Au nanoparticles have been tested by the same experimental procedure and have no catalytic activity for these two reactions.<p> In the second project, the synthesis of Au and Pd monolayer protected clusters (MPCs) with metal carbon covalent linkages was examined, and the stability of the resulting MPCs was tested. UV-Vis spectra and TEM images show the formation of Au and Pd nanoparticles and 1H NMR was used to characterize the ligands attached to the surface of the nanoparticles. The decylphenyl-stabilized Pd MPCs were synthesized successfully and quite stable in air, while decylphenyl-stabilized Au MPCs prepared with the same protocol have less stability and are easily decomposed. XPS spectra indicate the composition of decylphenyl-stabilized Pd MPCs is a combination of Pd0 and Pd2+ species with the Pd2+ species in excess. In addition, alkylphenyl-stabilized Pd nanoparticles were shown to be effective catalysts for carbon-carbon coupling reactions such as Suzuki and Stille reactions as well as hydrogenation reactions. Finally, it was noted that Pd-C bonds could be easily reduced by H2 when performing hydrogenation reactions resulting in nanoparticle aggregation and precipitation under hydrogenation conditions.

My research is focused on two main objectives, the study of catalytic efficiency and mechanism of palladium nanoparticles stabilized by poly(vinylpyrrolidone) (PVP) for carbon-carbon coupling reactions, and to rationally synthesize metal nanoparticles stabilized by metal-carbon bonds and apply them to catalyze carbon-carbon coupling reactions.<p> In the first project, Pd nanoparticles stabilized by PVP were used to catalyze carbon-coupling reactions, specifically the Stille and Suzuki reactions. The mechanism of carbon-carbon coupling reactions was studied. The uncertainty of whether nanoparticles or Pd salts are the catalyst was also examined using the same experimental procedure with Pd salts to examine their catalytic activity in carbon-carbon coupling reactions. Results show that the presence of O2 is crucial to the Stille reaction with the Pd nanoparticles, which are nearly completely inert under N2, while the K2PdCl4 precursor is itself quite active for the Stille reaction. However, the Pd nanoparticles were found to be active for the Suzuki reaction with high yields in the absence of O2. The yields for 4-chlorobenzoic acid are higher than 4-bromobenzoic acid and occur for un-catalyzed reactions, for reasons that are still unknown. Finally Au nanoparticles have been tested by the same experimental procedure and have no catalytic activity for these two reactions.<p> In the second project, the synthesis of Au and Pd monolayer protected clusters (MPCs) with metal carbon covalent linkages was examined, and the stability of the resulting MPCs was tested. UV-Vis spectra and TEM images show the formation of Au and Pd nanoparticles and 1H NMR was used to characterize the ligands attached to the surface of the nanoparticles. The decylphenyl-stabilized Pd MPCs were synthesized successfully and quite stable in air, while decylphenyl-stabilized Au MPCs prepared with the same protocol have less stability and are easily decomposed. XPS spectra indicate the composition of decylphenyl-stabilized Pd MPCs is a combination of Pd0 and Pd2+ species with the Pd2+ species in excess. In addition, alkylphenyl-stabilized Pd nanoparticles were shown to be effective catalysts for carbon-carbon coupling reactions such as Suzuki and Stille reactions as well as hydrogenation reactions. Finally, it was noted that Pd-C bonds could be easily reduced by H2 when performing hydrogenation reactions resulting in nanoparticle aggregation and precipitation under hydrogenation conditions.

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¡@Silver nanowires prepared by the the reduction of AgNO3 at low temperature with thermocatalystic biphase (anatase and brookite phases) TiO2 nanoparticles are described. Furthermore, the possible mechanism to grow silver nanowires without the help of the Ag seed and capping reagent is proposed. ¡@Firstly, the amorphous TiO2 nanoparticles prepared by sol-gel method were spin-coated on the silicon wafer to form amorphous TiO2 matrix. Then an aqueous AgNO3 (1 &#x00B5;L 0.7 M) solution was dropped on the amorphous TiO2 matrix. Following the heat treatment at 200 ¢XC for 8 h, the silver nanowires (length~10 &#x00B5;m, line width~100 nm) were grown on the silicon wafer. We found that amorphous phase of TiO2 was changed to the anatase and brookite phases during the thermal reduction of the aqueous solution of AgNO3. ¡@Silver nanowires were characterized as f.c.c. structure by XRD. The TiO2 particles play an important role in providing electrons and holes for redox reaction and nucleation. With the controlling of the heating temperature and the amount of AgNO3, the silver nanowires were selectively grown in one dimension with large energetic surface. A combination of HR-TEM imaging and selected area electron diffraction reveals that the growing direction for the Ag wires is <011>.

The simultaneous separation of anionic and cationic proteins has been achieved by addition of high concentration of poly(diallyldimethylammonium chloride) (PDDAC) in capillary electrophoresis. A capillary was filled with PDDAC so that it would act as ion-pair reagents in the separation of anionic proteins. On the other hand, the PDDAC can also be used as coating additives for the analysis of cationic proteins. Increasing the concentration of PDDAC in the separation buffer had the ability to improve the separation efficiency, change the electrophoretic mobility, and alter the separation selectivity; however, this was not true in the case of analyzing proteins by using the PDDAC larger than 1.6%. By both using a buffer containing 1.6% PDDAC and applying pH-stepwise techniques, 13 proteins with a wide range of pI (4.7¡V11.1) and molecular masses (6.5¡V198.0 kDa) could be separated within 30 min in a single run. In addition to this separation, we observed notonly more peaks from alph-chymotrypsinogen A and aprotinin but also the bovine serum albumin (BSA) dimer and trimer. The second part describes a method for enrichment and separation of acidic and basic proteins using the centrifugal ultrafiltration followed by polyelectrolyte-filled capillary electrophoresis. In order to improve stacking and separation efficiencies of proteins, the separation buffer containing 1.6% poly(diallyldimethylammonium chloride) was added with gold nanoparticles (AuNPs), poly(ethylene oxide), cetyltrimethyl ammonium bromide, and poly(vinyl alcohol). As a result, the use of AuNPs as additives exhibited better efficiency in separation, stacking and analysis time. Even for large-volume samples (110 nL), the separation efficiencies of acidic and basic proteins remained greater than 104 and 105 plates/m, respectively. To further enhance detection sensitivity, protein samples were enriched using the centrifugal ultrafiltration, followed by our proposed stacking method. As a result, the detection sensitivity was improved up to 314-fold as compared with normal hydrodynamic injection. Additionally, the limits of detection at a signal-to-noise of 3 for most proteins are down to nanomolar range. We have validated the application of our method by means of analyses of 50 nM lysozyme in saliva samples. The proposed method was also successfully applied to the analyses of egg-white proteins, which have large differences in molecular weight and pI.

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Spintronics is an emerging technology that arises from the interplay between spin of the charge carrier and the magnetic property of the materials. The miniaturization of spintronic devices requires a deep understanding of ferromagnetic materials at the nanometer scale. This thesis studies the properties of ferromagnetic particles (2-5nm in diameter) using electron transport measurements. A technique to fabricate nanoparticle devices and incorporate microwave in the electron tunneling measurement of the particles is presented. Repeated microwave pulses can directly excite the magnetization of the particles without heating the electrons. Results of the transport measurements on Co particles will be discussed, which demonstrate that electron tunneling through a ferromagnetic particle can induce magnetization excitations in that particle. A physical model regarding the mesoscopic fluctuations is presented to address the current driven magnetization noise. Numerical simulations based on that model are performed to explain the experimental data and validate the model. Electron transport measurements on Ni, Fe, and Ni??Fe?? are conducted. The hysteretic behaviors of the particles in presence of electron tunneling have strong material dependence, which is mainly due to the magnetic shape anisotropy. Electron tunneling is a main source of magnetization noise, while other sources still need to be identified. Some data we collected from literature will be included in this thesis as an appendix.

There have been significant advances in the research of nanoparticle technologies for formation evaluation and reservoir engineering operations. The target applications require a variety of different retention characteristics ranging from nanoparticles that adsorb near the wellbore to nanoparticles that can travel significant distances within the porous medium with little or no retention on the grain substrate. A detailed understanding of the underlying mechanisms that cause nanoparticle retention is necessary to design these applications. In this thesis, experiments were conducted to quantify nanoparticle retention in unconsolidated columns packed with crushed Boise sandstone and kaolinite clay. Experimental parameters such as flow rate, injected concentration and sandpack composition were varied in a controlled fashion to test hypotheses concerning retention mechanisms and enable development and validation of a mathematical model of nanoparticle transport. Results indicate nanoparticle retention, defined as the concentration of nanoparticles remaining attached to grains in the porous medium after a volume of nanoparticle dispersion is injected through the medium and then displaced with brine, is a function of injected fluid velocity with higher injected velocities leading to lower retention. In many cases nanoparticle retention increased nonlinearly with increasing concentration of nanoparticles in the injected dispersion. Nanoparticle retention concentration was found to exhibit an upper bound beyond which no further adsorption from the nanoparticle dispersion to the grain substrate occurred. Kaolinite clay was shown to exhibit lower retention concentration [mg/m2] than Boise sandstone suggesting DLVO interactions do not significantly influence nanoparticle retention in high salinity dynamic flow environments. / text

The small size regime and bulky hydrocarbon exterior of dendrimer encapsulated nanoparticles (DENs) often make characterization of these materials a unique challenge. Here, I report on three studies utilizing the techniques of extended X-ray absorption fine structure (EXAFS) and electrochemistry to probe the properties and behavior of these materials. First, the synthesis and characterization of PdCu bimetallic nanoparticles, and Pd and Cu monometallic nanoparticles, consisting of an average of ~64 atoms is described. The bimetallic nanoparticles were prepared by co-complexation of Pd²⁺ and Cu²⁺ salts to interior functional groups of a dendrimer template followed by chemical reduction to yield DENs. EXAFS spectroscopy indicates that these particles have an alloy structure. This is a rare example of a stable nanoparticle in this size range that consists of one reactive metal and one substantially more noble metal. Second, in-situ electrochemical EXAFS is used to evaluate the structure of Pt DENs during the oxygen reduction reaction (ORR). The DENs contained an average of just 225 atoms each. The results indicate that the Pt coordination number (CN) decreases when the electrode potential is moved to positive values. The results are interpreted in terms of an ordered core, disordered shell model. The structure of the DENs is not significantly impacted by the presence of dioxygen, but other electrogenerated species may have a significant impact on nanoparticle structure. Third, the electrochemical dissolution of Cu DENs is investigated using anodic stripping voltammetry (ASV). The effect of the scan rate and Cu loading on the electrode to the stripping wave is performed. The results indicate a large, positive shift of the stripping potential for the dendrimer-metal composites, but no size-dependent changes to peak position. / text

Foamed cement is widely used in the oil and gas industry to provide zonal isolation. Foamed cement provides various advantages vs. pure cement. The primary purpose of foamed cement is to reduce the density of the cement mixture. Consequently, foamed cement can be used in weak formations were reduced exerted hydrostatic pressure is needed to prevent/control cement circulation loss into the formation. However, Due to gas compressibility, foamed cement’s gas injection rate has to be constantly adjusted in order to create a constant density slurry through the height of the cement column. Furthermore, foamed cement’s properties include higher ductility, constant pressure exertion to the formation during cement transition time (gelling) and lower thermal conductivity. The ability of solid silica nanoparticles to generate stable gas/water foams was researched for foamed cement applications. Solid nanoparticles have been shown to permanently stabilize foams by assembling into layers at the gas/water interface. A potential decrease in compressibility of the gas phase by the presence of these armoring bubble layers was investigated. Enhancement of cement’s splitting tensile strength and compressive strength by silica nanoparticles was also investigated. The addition of uncoated silica nanoparticles at various concentrations did not appear to enhance neither cement’s splitting tensile or compressive strength. In most tests with varying silica nanoparticles concentrations, the samples with nanoparticles exhibited a slightly reduced splitting tensile and compressive strength. The exception being the compressive strength of the samples mixed with the highest nanoparticle concentration tested. However, the strength improvement was small vs. its pure cement counterpart. An apparatus to test the compressibility of nanoparticle stabilized foams was built for this research. The functionality of the apparatus was validated using various test fluids. The validation process allowed for the establishment of a compressibility benchmark to compare the compressibility of nanoparticle stabilized foams. A vital conclusion of this process was that generating the particle stabilized foams under pressure would allow for greater discernment between the existence of the armored bubble effect and gas dissolution into the water phase. A type of nanoparticle was identified as having the capacity to generate long term stable foams without the need of surfactant. Partially hydrophobic surface treated silica nanoparticles were utilized to generate gas/water foams under pressure and subsequently their compressibility was measured. The compressibility of these foams did not appear to show the armored bubble effect behaving as an equivalent ideal gas + water mixture. An additional surfactant and particle stabilized foam recipe was tested and displayed the same results. It was concluded that either the particle layers were not fully forming in the foam or in the case they were forming; either foam geometry was not conductive to the distribution of forces or they likely had limited rigidity and buckled when compressed. If the latter was true, the apparatus was not sensible enough to measure the limited rigidity. / text