Lithium iron phosphate (LiFePO4) is one of the most promising cathode materials for lithium ion rechargeable batteries. It has a high theoretical specific capacity (170 mAh/g) and operating potential (3.45 V vs. Li+/Li). Additionally, the material is extremely stable thermally and electrochemically at ambient conditions, which is very suitable to be used in electric vehicles. However, the electronic and ionic conductivities of the material are quite low, which limits the power performance of the batteries. In the last decade, extensive work was reported on various methods to improve the electronic conductivity extrinsically, for example carbon coating, metallic additives and molecular wiring. Nevertheless, energy density of the cells will be reduced because of non-electrochemically active nature of the additives. In principle, electronic and ionic conductivities can be boosted intrinsically. One of the methods is to increase the number of charge carriers in the material, for instance in two-phase solid solution system LiαFePO4/Li1-βFePO4 or single solid solution phase LixFePO4. Since the formation of solid solution has been reported to be size dependent, it is highly desired to know how to synthesize LiFePO4 particles with different sizes. In this study, we have used hydrothermal synthesis and polyol process to control the size of LiMPO4 (M: Fe, Mn, and Co) particles. We will present how we prepare particles with different sizes. Moreover, the solid solution properties of various sizes of LiMPO4 (M: Mn and Fe) were studied. The result will be presented. Part of the preliminary findings have been published in the peer-reviewed journals or conference presentations: 1) Journal of Materials Chemistry [Ellis B.; Kan W. H.; Makahnouk W. R. M.; Nazar L. F. J. Mater. Chem. 2007, 17 (30) 3248., 2) Journal of the American iv Chemical Society [Lee K. T.; Kan W. H.; Nazar L. F. J. Am. Chem. Soc. (submitted)], 3) Material Research Society Meeting [Kan W. H.; Maunders C.; Badi S.; Ellis B.; Botton G.; Nazar L. F. MRS Fall Meeting 2008 in Boston]

The pendant drop technique was used to characterize the adsorption behavior of n-dodecane-1-thiol and n-hexane-1-thiol capped gold nanoparticles at the hexane-water interface. The adsorption process was studied by analyzing the dynamic interfacial tension versus nanoparticle concentration, both at early times and at later stages (i.e., immediately after the interface between the fluids is made and once equilibrium has been established). Following free diffusion of nanoparticles from the bulk hexane phase, adsorption leads to ordering and rearrangement of the nanoparticles at the interface and formation of a dense layer. With increasing interfacial coverage, the diffusion-controlled adsorption for the nanoparticles at the interface was found to change to an interaction-controlled assembly and the presence of an adsorption barrier was experimentally verified. At the same bulk concentration, different sizes of n-dodecane-1-thiol nanoparticles showed different absorption behavior at the interface, in agreement with the findings of Kutuzov et al. [1]. The experiments additionally demonstrated the important role played by the capping agent. At the same concentration, gold nanoparticles stabilized by n-hexane-1-thiol exhibited greater surface activity than gold nanoparticles of the same size stabilized by n-dodecane-1-thiol. 1.6 nm, 2.8 nm, and 4.4 nm nanoparticles capped with n-dodecane-1-thiol, and 2.9 nm, and 4.3 nm particles capped with n-hexane-1-thiol were used in this study. The physical size of the gold nanoparticles was determined by TEM image analysis. The pendant drop technique was also used to study the adsorption properties of mixtures of gold nanoparticles at the hexane-water interface; and also investigate the effects of different factors (i.e., temperature, pH or ionic strength) on interfacial tension (IFT). The interfacial properties of mixtures of these nanoparticles, having different sizes and capping agents, were then studied. No interaction was found between the unmixed studied nanoparticles. Using the theory of non-ideal interactions for binary mixtures, the interaction parameters for mixtures of nanoparticles at the interface were determined. The results indicate that nanoparticle concentration of the mixtures has a profound effect on the interfacial nanoparticle composition. A repulsive interaction between nanoparticles of different size and cap was found in the mixtures at the interface layer. The interfacial tension for mixtures was found to be higher than the interfacial tension for non-mixed nanoparticle suspensions. The nanoparticle composition at the interface was found to differ from the composition of nanoparticles in the bulk liquid phase. The activity of unmixed nanoparticles proved to be a poor predictor of the activity of mixtures. It was observed that the most active nanoparticles concentrated at the interface. The effects of temperature, pH and ionic strength concentration on the equilibrium and dynamic IFT of 4.4 nm gold nanoparticles capped with n-dodecane-1-thiol at the hydrocarbon-water interface was studied. The pendant drop technique was also used to study the adsorption properties of these nanoparticles at the hexane-water and nonane-water interface. The addition of NaCl was found to cause a decrease of the equilibrium and dynamic IFT greater than that, which accompanies the adsorption of nanoparticles at the interface in the absence of NaCl. Although IFT values for acidic and neutral conditions were found to be similar, a noticeable decrease in the IFT was found for more basic conditions. Increasing the temperature of the system was found to cause an increase in both dynamic and equilibrium IFT values. The adsorption of functionalized gold nanoparticles at liquid-liquid interfaces is a promising method for self-assembly and the creation of useful nanostructures. These findings contribute to the design of useful supra-colloidal structures by the self-assembly of alkane-thiol capped gold nanoparticles at liquid-liquid interfaces.

Research on self-assembling gemini surfactants and other amphiphiles for potential gene delivery applications in research as well as in clinical practice, and as alternatives to viral gene delivery vectors, is beginning to focus more on structureactivity relationships to address the current low gene delivery efficiencies of amphiphiles. Some underlying structureactivity relations are beginning to emerge. But, as a better understanding of the factors that govern the transfection abilities of amphiphile molecules emerges, development of improved non-viral vectors with clinical potential may also emerge.<p> The research conducted for this thesis was aimed at the design, synthesis and in vitro investigation of gemini surfactants as one of a family of novel amphiphiles being investigated for gene therapeutic applications. The properties of these compounds can be controlled as well as allowed to vary naturally. Gemini surfactant-based gene delivery systems were prepared and characterized for transfer of Luciferase plasmid (pMASIA.Luc) to both COS-7 and PAM 212 cells. Characterization was accomplished using microscopy, dynamic light scattering (DLS) and zeta (ζ) potential analysis. In vitro gene expression and toxicities were evaluated in COS-7 cell and PAM 212 keratinocyte cultures.<p> The level of in vitro transfection in general was found to correlate strongly with the structure of the gemini surfactants. Among the 12-spacer-12 surfactants, incorporation of a pH-sensitive aza (N-CH3) group, which is also steric hindrance-imposing, in the spacer chain yielded increased transfection, particularly for the 12-7N-12 surfactant. In comparison, the incorporation of the more pH-sensitive imino (N-H) group in the 12-7NH-12 surfactant yielded the highest increase in transfection among the 12-spacer-12 surfactants. The deleterious effect of steric hindrance due to the aza group is more evident when comparing the transfection efficiency of 12-5N-12 (1 × aza, higher) vs. 12-8N-12 (2 × aza, lower transfection). Another highlighted structural feature is provided by the fact that both the 12-7NH-12 and 12-7N-12 surfactants had higher transfection efficiencies than 12-5N-12 and 12-8N-12 surfactants; the first pair has trimethylene spacing, which constitutes an optimal separation between nitrogen centres, while the second pair has shorter dimethylene spacings.<p> After expanding the structure of surfactants, transfection efficiencies were found to increase in response to increase in hydrocarbon tail length, but were much lower for surfactants with no amino functional groups, those that lacked the optimal trimethylene spacing, or those having both of these limitations in the gemini surfactant spacer. The 18-7NH-18 surfactant had the highest overall transfection in both COS-7 and PAM 212 cells. Gemini surfactant-based gene delivery systems capable of adopting both polymorphic structural phases and which could undergo pH-induced structural transition demonstrated high transfection efficiencies. Gemini surfactants with both characteristics (e.g., 12-7NH-12-based complexes are both polymorphic and pH-sensitive) had higher transfection than gemini surfactants with only one (e.g., 12-3-12-based complexes are only polymorphic).<p> Overall, the m-7NH-m surfactants, the most efficient surfactants studied, had transfection efficiencies similar to that of the commercial Lipofectamine Plus reagent and imposed no higher toxicity on cells relative to the less efficient surfactants. Thus, the design of the m-7NH-m surfactants to enhance their transfection abilities also ensured that their toxicity to cells were kept minimal. Overall, the design, synthesis and in vitro transfection screening of gemini surfactant candidates has revealed that the m-7NH-m surfactants have the highest transfection efficiencies; they have emerged as suitable candidates for non-viral gene delivery in vivo or at higher levels. Gene delivery investigations for six of the gemini surfactant candidates are being reported for the first time.

Polymeric nanoparticles are potential candidates as carriers for pharmaceutical agents. Development of such nanoparticles generally requires molecules immobilized on the particle surfaces to ensure biocompatibility and/or targeting abilities. Following particle preparation and surface modification, excess reagents must be removed. Ultracentrifugation, which is the most widely used purification technique as per today, is not feasible in industrial applications. In this diploma work, tangential flow filtration is studied as an alternative purification method which is better suited for implementation in a large-scale process. Comparison of ultracentrifugation and tangential flow filtration in diafiltration mode for purification of nanoparticles, indicate that they are comparable with respect to particle stability and the removal of the surfactant SDS from methacrylic anhydride nanoparticles. The purification efficiency of tangential flow filtration is superior to that of ultracentrifugation. Conductivity measurements of filtrates and supernatant liquids show that a stable conductivity value can be reached 6 times faster in filtration than in centrifugation with equipment and settings used. This conductivity arises from several types of molecules, and the contribution from surfactant molecules alone is not known. However, protein adsorption on the particles indicates successful removal of surfactant. Conductivity and tensiometry were evaluated as potential methods to quantify surfactant in solutions, but both proved unsatisfactory. Using bovine serum albumin as a model protein, the extent of immobilization to nanoparticles is evaluated at different pH. A maximum amount of 6,8 mg/m2 is immobilized, whereof an unknown part is covalently bound. This coverage is achieved at pH 4,0 and is probably partly due to low electrostatic repulsion between particle and protein. An estimation of 2,0 µmol covalently bound BSA per gram of nanoparticles corresponds to 5,3 mg/m2 and a surface coverage of 76%. Removal of excess reagents after surface modification is done with ultracentrifugation instead of filtration, as particle aggregates present after the immobilization reaction might foul the membrane.

<p>Although various proof-of-concept studies have demonstrated the eventual potential of a multifunctional SERS-active metallic nanostructures for biological applications such as single cell analysis/measurement and drug delivery, the actual development and testing of such a system in vitro has remained challenging. One key point at which many potentially useful biomethods encounter difficulty lies in the translation of early proof-of-concept experiments in a clean, aqueous solution to complex, crowded, biologically-active environments such as the interior of living cells. The research hypotheses for this work state that multifunctional nanoconstructs can be fabricated and used effectively in conjunction with surface-enhanced Raman scattering (SERS) spectroscopy and other photonics-based methods to make intracellular measurements in and deliver treatment to single cells. The results of experimental work address the specific research aims, to 1) establish temporal and spatial parameters of nanoprobe uptake and modulation, 2) demonstrate targeting of functionalized nanoparticles to the cytoplasm and nucleus of single cells, 3) deliver to and activate drug treatment in cells using a multifunctional nanosystem, and 4) make intracellular measurements in normal and disease cells using external nanoprobes,</p><p>Raman spectroscopy and two-dimensional Raman imaging were used to identify and locate labeled silver nanoparticles in single cells using SERS detection. To study the efficiency of cellular uptake, silver nanoparticles were functionalized with three differently charged SERS/Raman labels and co-incubated with J774 mouse macrophage cell cultures for internalization via normal cellular processes. The surface charge on the nanoparticles was observed to modulate uptake efficiency, demonstrating a dual function of the surface modifications as tracking labels and as modulators of cell uptake. </p><p>To demonstrate delivery of functionalized nanoparticles to specific locations within the cell, silver nanoparticles were co-functionalized with the HIV-1 TAT (49-57) peptide for cell-penetrating and nuclear-targeting ability and p-mercaptobenzoic acid (pMBA) molecules as a surface-enhanced Raman scattering (SERS) label for tracking and imaging. Two-dimensional SERS mapping was used to track the spatial and temporal progress of nanoparticle uptake in PC-3 human prostate cells and to characterize localization at various time points, demonstrating the potential for an intracellularly-targeted multiplexed nanosystem. Silver nanoparticles co-functionalized with the TAT peptide showed greatly enhanced cellular uptake and nuclear localization as compared with the control nanoparticles lacking the targeting moiety. </p><p>The efficacy of targeted nanoparticles as a drug delivery vehicle was demonstrated with development and testing of an anti-cancer treatment in which novel scintillating nanoparticles functionalized with HIV-1 TAT (49-57) for cell-penetrating and nuclear-targeting ability were loaded with tethered psoralen molecules as cargo. The experiments were designed to investigate a nanodrug system consisting of psoralen tethered to a nuclear targeting peptide anchored to UVA-emitting, X-ray luminescent yttrium oxide nanoparticles. Absorption of the emitted UVA photons by nanoparticle-tethered psoralen has the potential to cross-link adenine and thymine residues in DNA located in the nucleus. Such cross-linking by free psoralen following activation with UVA light has previously been shown to cause apoptosis in vitro and an immunogenic response in vivo. Experimental results using the PC-3 human prostate cancer cell line demonstrate that X-ray excitation of these psoralen-functionalized Y2O3 nanoscintillators yields concentration-dependent reductions in cell number density when compared to control cultures containing psoralen-free Y2O3 nanoscintillators. </p><p>The development and demonstration of a small molecule-sensitive SERS-active fiber-optic nanoprobe suitable for intracellular bioanalysis was demonstrated using pH measurements in single living human cells. The proof-of-concept for the SERS-based fiber-optic nanoprobes was illustrated by measurements of intracellular pH in MCF-7 human breast cancer, HMEC-15/hTERT immortalized normal human mammary epithelial, and PC-3 human prostate cancer cells. Clinical relevance was demonstrated by pH measurements in patient biopsy cell samples. The results indicated that that fiber-optic nanoprobe insertion and interrogation provide a sensitive and selective means to monitor biologically relevant small molecules at the single cell level.</p> / Dissertation

<p>The electromagnetic properties of various plasmonic nanostructures are investigated. These nanostructures, which include random clusters, controlled clusters and particle-film hybrids are applied to surface-enhanced Raman scattering (SERS). A variety of techniques are utilized to fabricate, characterize, and model these SERS-active structures, including nanoparticle functionalization, thin film deposition, extinction spectroscopy, elastic scattering spectroscopy, Raman scattering spectroscopy, single-assembly scattering spectroscopy, transmission electron microscopy, generalized Mie theory, and finite element method. </p><p>Initially, the generalized Mie theory is applied to calculate the near-field of the small random clusters to explain their SERS signal distribution. The nonlinear trend of SERS intensity versus size of clusters is demonstrated in experiments and near-field simulations. </p><p>Subsequently, controlled nanoparticle clusters are fabricated for quantitative SERS. A 50 nm gold nanoparticle and 20nm gold nanoparticles are tethered to form several hot spots between them. The SERS signal from this assembly is compared with SERS signals from single particles and the relative intensities are found to be consistent with intensity ratios predicted by near-field calculation.</p><p>Finally, the nanoparticle/film hybrid structure is studied. The scattering properties and SERS activity are observed from gold nanoparticles on different substrates. The gold nanoparticle on gold film demonstrates high field enhancement. Raman blinking is observed and implies a single molecule signal. Furthermore, the doughnut shape of Raman images indicates that this hybrid structure serves as nano-antenna and modifies the direction of molecular emission. </p><p>In additional to the primary gap dipole utilized for SERS, high order modes supported by the nanoparticle/film hybrid also are investigated. In experiments, the HO mode show less symmetry compared to the gap dipole mode. The simulation indicates that the HO modes observed may be comprised of two gap modes. One is quadrupole-like and the other is dipole-like in terms of near-field profile. The analytical treatment of the coupled dipole is performed to mimic the imaging of the quadrupole radiation.</p> / Dissertation

From catalytic studies in surface science, it has been shown that the catalytic activity is dependent on the type of metal facet used. Nanocrystals of different shapes have different facets. This raises the possibility that the use of metal nanoparticles of different shapes could catalyze different reactions with different efficiencies. The catalytic activity is found to correlate with the fraction of surface atoms located on the corners and edges of the tetrahedral, cubic, and spherical platinum nanoparticles. It is observed that for nanoparticles of comparable size, the tetrahedral nanoparticles have the highest fraction of surface atoms located on the corners and edges and also have the lowest activation energy, making them the most catalytically active. Nanoparticles have a high surface-to-volume ratio, which makes them attractive to use compared to bulk catalytic materials. However, their surface atoms are also very active due to their high surface energy. As a result, it is possible that the surface atoms are so active that their size and shape could change during the course of their catalytic function. It is found that dissolution of corner and edge atoms occurs for both the tetrahedral and cubic platinum nanoparticles during the full course of the mild electron transfer reaction and that there is a corresponding change in the activation energy in which both kinds of nanoparticles strive to behave like spherical nanoparticles. When spherical palladium nanoparticles are used as catalysts for the Suzuki reaction, it is found that the nanoparticles grow larger after the first cycle of the reaction due to the Ostwald ripening process since it is a relatively harsh reaction due to the need to reflux the reaction mixture for 12 hours at 100 oC. When the tetrahedral Pt nanoparticles are used to catalyze this reaction, the tetrahedral nanoparticles transform to spherical ones, which grow larger during the second cycle. In addition, studies on the effect of the individual reactant have also provided clues to the surface catalytic process that is taking place. In the case of the electron transfer reaction, the surface catalytic process involves the thiosulfate ions binding to the nanoparticle surface and reacting with the hexacyanoferrate (III) ions in solution. In the case of the Suzuki reaction, the surface catalytic mechanism of the Suzuki reaction involves the phenylboronic acid binding to the nanoparticle surface and reacting with iodobenzene via collisional processes.

In order to optimize the synthesis of metal nanoparticle-polymer systems, there are certain processes which must be understood. Perhaps the most important one is the selective interfacial interaction between the block copolymer and the growing metal nanoparticles. To investigate this interaction, four different approaches were taken. The first approach looked at the strength of interaction between the competing blocks of the copolymer and the metal nanoparticles surface. The second approach looked at the effect of polymer architecture on the metal nanoclusters. The third approach looked at the polymer composition and solvent effects on the phase behavior of the metal nanocluster-block copolymer nanocomposite. Finally, the influence of the metal precursor on the rate of the decomposition was examined. It was found that adsorbed layers of PS on the cobalt nanoparticles are completely displaced by PMMA when the solvent is a common good solvent. An adsorbed layer of only PMMA is also obtained through competitive adsorption from a common good solvent. However, in a selective solvent that is poor for PS, sequential adsorption leads to the formation of mixed layers. In homopolymer solutions, the cluster size reaches a minimum at a finite chain MW. In the case of diblock copolymers, the only parameter (for a fixed copolymer concentration) controlling the cluster size in suspensions of di-block copolymers is the molecular weight of one block, in this case PMMA, and is indifferent to other parameters including the molecular weight of the other block (PS) or the solvent quality. It was also found that the spatial distribution of the metal clusters synthesized in-situ coincided with the morphology dictated by thermodynamically-driven microdomain structure of the block copolymer. Moreover, the overall final morphology of the nanocomposite is locked into place while in solution, and fast solvent evaporation does not cause this morphology to change. Finally, results showed that the rate of nanocomposite synthesis occurred faster in the PS suspensions compared to PMMA, indicating that chemical bonds between PMMA and the cobalt nanoclusters slowed the thermal decomposition of the metal precursor. So the PMMA chains provided sites for nucleation, but did not necessarily aid particle growth.

The structural and electronic properties of small tungsten nanoparticles Wn (n=2-16) were investigated by density functional theory (DFT) calculation. For the W10 nanoparticle, ten lowest-energy structures were first obtained by basin-hopping method (BH) and ten by big-bang method (BB) with the tight-binding many-body potential for bulk tungsten material. These fifty structures were further optimized by the DFT calculation in order to find the better parameters of tight-binding potential adquately for W nanoparticles. With these modified parameters of tight-binding potentials, several lowest-energy W nanoparticles of different sizes can be obtained by BH and BB methods and then further refined by DFT calculation. According to the values of binding energy and second-order energy difference, it reveals that the structure W12 has a relatively higher stability than those of other sizes. The vertical ionization potential (VIP), adiabatic electron affinity (AEA) and HOMO-LUMO Gap are also discussed for W nanoparticles of different sizes.

The fate and transformation of laboratory-prepared nano-ZnO, nano-Ag and nano-CeO2 in three aqueous solutions under different environmental conditions were investigated in this work. Over the past decades nanomaterials have been widely used in different technical fields and consumer goods. As a result, nanomaterials might enter the environmental media via different routes and then posed potential hazards to the environment and human health. Researches in this regard have received much attention worldwide. In this work it was found that the solubility of each nanomaterial was highly influenced by the solution pH, but not by the solution temperature. The maximal solubility for the tested nanomaterials was obtained at pH 3, namely about 100% for nano-ZnO and lower than 2% for both nano-Ag and nano-CeO2. The solution pH and ionic strength were found to affect the stability of nanoparticles in different aquatic environments. For the solution pH of higher than the isoelectric point of the concerned nanomaterial, the higher the solution pH is, the greater the degree of stabilization of nanoparticles would be. On the contrary, nanoparticles aggregated as the ionic strength of the solution exceeded its critical aggregation concentration (CAC). CAC for each concerned nanomaterial could also be graphically determined as the attachment efficiency (£\) of nanoparticles increased with increasing ionic strength of the solution and then leveled off after reaching CAC. Experimental results also showed that Zn(OH)2(s) would form when nano-ZnO was in the solution of pH 10. The crystalline structure of the said precipitates was confirmed by X-ray diffraction. Likewise, Ce4+ dissolved from nano-CeO2 reacted with SO42- in aqueous solution yielding Ce(SO4)2(s). Clearly, transformation of nanomaterials might take place when they are in contact with various species in different aquatic environments. Humic acid in aqueous solution was found to be beneficial to the stability of nanomaterial of concern. Efforts have also been made to study the reaction behaviors among di(2-ethylhexyl)phthalate, erythromycin, and selected nanomaterials when they co-existed in the same solution. Their interactions, however, seemed to be unobvious. In this work it was found that under sunlight irradiation nano-ZnO did show its antibiotic effect due to photocatalysis. Nano-Ag was proven to have a strong antibacterial ability even in natural aquatic environments. It yielded the total bacteria survival ratio of less than 2% within one hour of reaction. In summary, the findings of this study showed that the behaviors of nano-ZnO, nano-Ag, and nano-CeO2 in aqueous solutions could be greatly influenced by different factors in different reaction systems.