<p>Lithium-ion batteries provide a more cost-effective and non-toxic source of reusable energy compare to other energy sources. Several research studies have lead to production of some more promising cathode components for lithium ion batteries. Recently, a new series of pyrophosphate-based composition Li₂FeP₂O₇ and Li₂MnP₂O₇ has been reported as cathode materials. They have shown a 3D framework structure and the two Lithium-ions in the three-dimensional tunnel structure make it possible that more than one lithium ion be extracted during cycling. Lithium solid state nuclear magnetic resonance (NMR) is an effective technique to study this cathode material, not only for analyzing local structure, but also for investigation of the microscopic processes that take place in the battery.</p> <p>In this work, Li₂FeP₂O₇ and Li₂MnP₂O₇ have been synthesized. The lithium environment of these materials is studied using 1D ^6,7Li NMR. Assignment of Li₂MnP₂O₇ spectrum has been made based on Fermi-contact interaction and crystal structure. Both variable temperature experiment and 1D selective inversion NMR are used to establish Li-ion pathways as well as Li hopping rates for Li₂MnP₂O₇. Also, ⁷Li MAS NMR measurements are used to characterize Li environments in LixFeP₂O₇after being electrochemically cycled to different points, and preliminary results regard to changes to ion mobility in LixFeP₂O₇at different electrochemical cycled points are presents here, solid-solution (de)lithetiation process is confirmed for this material.</p> / Master of Science (MSc)

<p>Silicone polymers, particularly PDMS (poly(dimethylsiloxane)) exhibit a wide range of exceptional properties including optical transparency, biostability, hydrophobicity and excellent oxygen transmissibility that make them extremely useful in a wide range of applications, particularly as biomaterials. Current methods for the preparation of silicone elastomers have been well documented, however, silicone elastomers are thermoset materials and once cured, they cannot be reformed without chemical intervention. The properties of silicones that make them a popular material choice in a wide variety of industries also make them un-responsive and non-reusable often limiting their application to one primary purpose.</p> <p>This thesis aims to further understand the mechanisms of silicone polymer chain interactions and how the chemistry of polymer modification can alter the mechanical and chemical properties of materials. The effects of distinctive functional groups (coumarin) on silicone chains to allow for both the formation of thermoplastic silicone elastomers and stimuli-responsive elastomers for reversible crosslinking are explored.</p> <p>A companion study examined a different way to form silicone elastomers. The Piers- Rubinsztajn reaction was used to create elastomers and foams rapidly and under relatively mild conditions using very small quantities of the catalyst B(C6F5)3. The factors required to create – on demand – a foam or an elastomer, and the strategies to control physical properties, including bubble density and modulus, are explored.</p> <p>Silicone foams that were structured in a completely different way are described. Allyl- modified PEG (poly(ethylene glycol)) was found to structure foam mixtures precure. The product foam after cure was amphiphilic, due to the presence of both silicone and PEG constituents. The origins of bubble stabilization and the ability to control foam properties are described.</p> / Doctor of Science (PhD)

<p>The development of both silica and silicones has led to enormous improvements in available products over the last 50 years: the compounds have now found practical applications in fields ranging from electronics to biomaterials. Both of these materials have several desirable intrinsic properties. The compounds can be combined as a blend, in a composite or at an interface with other compounds to tune the chemical and physical properties to those desired. On their own, silica and silicones also have many applications. Their utility would be enhanced if it was possible to improve morphological control of the materials independently or together.</p> <p>This thesis explores various parameters and factors that enable the structuring of elastomers, colloids/suspensions, films and foams with the use of unconventional or new organosilicon chemistries. Specifically, amine and boron based catalysts are utilized to catalyze silicone and silica formation at different interfaces to create the materials mentioned above. Potential applications for these materials include drug delivery, GC chromatography and paper-based diagnostics.</p> / Doctor of Philosophy (PhD)

Self-assembly of colloidal microparticles is one of the strategies for making characteristic patterns. These versatile self-assemblies provide a route to elevate the efficiency of an electronic device. Silsesquioxane particles with various functionalities were synthesized by a modified Stöber condensation method. This thesis describes the synthesis of benzylchloride silsesquioxanes, benzylchloride-amine silsesquioxanes and amine-functionalized silsesquioxane particles with multi-fluorescent tags. The size and morphology of the particles were controlled by varying the concentration of base and anhydrous ethanol (solvent). The size distribution of particles was controlled by adjusting the molar ratios of organotrialkoxy silane, base, and ethanol concentrations. Through selective post-functionalization with fused arenes of anthracene and rhodamine, multifluorescent particles were obtained. Morphologies and optical properties of particles were characterized by TEM, SEM, fluorescence optical microscopy, and absorption and fluorescence spectroscopies. The composition of silsesquioxanes was confirmed by FTIR, thermogravimetric analysis, and elemental analysis. A versatile technique was developed for the self-assembly of particles on different polymer substrates by changing the colloidal suspension concentration and the polymer substrate.

This research explores the synthesis of anthracene and stilbene-based metal-organic framework (MOF) structures as potential scintillating (radioluminescent) materials for use in the detection of gamma radiation. The organic molecules 9,10-anthracenedicarboxylic acid (ADCH2) and trans-4,4’-stilbenedicarboxylic acid (SDCH2), were each used as a linker, in combination with a range of lanthanide metal ions, to synthesize novel three dimensional MOF structures under hydrothermal conditions. With ADCH2, the early period lanthanides yield isostructures with the metal ion in higher coordination (nine) than for those with late period metals (seven). The ADC-MOFs show linker-based photoluminescence properties with well defined vibronic peaks in their emission profile and their emission (λmax~435 nm) blue shifting from that of the ADCH2 powder (~500 nm) and closer to the organic molecule in monomer arrangement (λmax ~ 420 nm). The structures also show photoluminescence lifetimes between 1 and 2 ns, which is similar to the reported value for monomeric anthracene units. The blue-shift and reduction in lifetime, compared to ADCH2, are indicative of minimal π-π interactions amongst the aromatic moieties, thereby limiting the non-radiative relaxation pathways. On exposure to ionizing radiation (protons and g- rays), the ADC-MOFs demonstrated scintillation properties, with a radioluminescence lifetime of ~ 6 ns which is similar to that of the ADCH2 powder. A combination of SDCH2 and lanthanide metal ions produced two isostructured MOFs containing Tm3+ and Er3+, under the hydrothermal synthesis conditions explored. The 3-D structure contained ultra large diamond-shaped pores with dimensions of 16 Å x 30 Å. A blue-shift of fluorescence spectra was observed for the SDC-MOF structures (λmax ~ 425 nm) compared to that of bulk SDCH2 powder (λmax ~475 nm), and closely resembling that of monomeric isolated SDC units (λmax~475 nm). Their photoluminescence lifetime is ~0.76 ns, about half of that observed for SDCH2 powder. The blue shift and reduction in lifetime (compared to SDCH2) is attributed to minimal π-π interactions between SDC units in the MOF structure, thus minimizing associated non-radiative relaxation pathways. The isolation of anthracene and stilbene in MOF structures therefore has the potential to improve their performance as scintillators.

Two novel materials have been developed: TiO2/poly(dimethylsiloxane) (PDMS) beads as buoyant photocatalyst materials for water remediation, and copper rhodamine‑B silane (Cu‑RBS) as an n ‑type organic/inorganic hybrid for thermoelectric applications. The approach to incorporate TiO2 into low‑density PDMS beads addresses many of the challenges traditionally encountered when creating buoyant photocatalysts, an area which is crucial for wide‑spread remediation of water resources, including natural bodies of water. The performance and reusability of the buoyant photocatalyst materials, demonstrated by using methylene blue as a model degradation target, is strong enough for environmental application. The use of a kinetic model and the introduction of a parameter to allow comparison of buoyant photocatalysts is also included as part of the analysis. The performance of Cu‑RBS was investigated as a low‑temperature thermoelectric material. Clear improvements in the electrical conductivity and Seebeck coefficient are observed for RBS upon coordination to Cu2+. Evidence explaining this improvement is provided by computational analysis and by concentration‑dependent optical absorption and fluorescent emission measurements, all of which indicate that a metal‑to‑ligand charge transfer occurs from Cu2+ to RBS. Although the power factor of Cu‑RBS is low compared to other materials reported in the literature, these results provide a promising approach to increasing both the Seebeck coefficient and electrical conductivity of n‑type small molecule organic systems.

In recent years, research has focused on reducing the cost of catalysts in a variety of ways including using less expensive materials, improving the synthetic method, and increasing the catalytic activity, recovery, and recyclability. Typically with nanoparticles, the size, shape, composition, and surface coating have an effect on catalytic activity.1-2 In this work, we focused on reducing the cost of precious metal based catalysts by altering the synthetic methods. One way to lower the cost of synthesizing precious metal nanoparticles is by debasing the precious metal with a second cheaper more abundant metal. CuPd nanoparticles were synthesized in oleylamine and displayed catalytic activity in several cross-coupling reactions. Due to copper being present in the nanoparticle, a copper halide co-catalyst was not needed for Sonogashira cross coupling to be successful.3 While this method produced reactive catalysts, low product yield hinders its application for industry. Solution based synthesis of metallic nanoparticles typically require long reaction times and high temperatures, which make large scale production of nanoparticles on an industrial scale difficult.4-5 The use of continuous flow microreactors provides greater control of synthetic parameters, leading to lower batch-to-batch variability and increasing the efficient of heat and mass transfer and have been applied to the synthesis of metals, semiconductors, zeolites, organic compounds, and semiconductors.5-7 To compare continuous flow methods to benchtop reactions, a well-characterized benchtop reaction synthesizing Cu@Ni core/shell nanoparticles was successfully transferred to a flow reactor set-up. Cu@Ni nanoparticles were synthesized using a capillary microreactor in under 1 minute compared to the 1 hour reaction on benchtop with similar properties in a green solvent.2 The Cu@Ni nanocomposites were active towards the Fischer Tropsch reaction.8 2 nm platinum nanoparticles and platinum bimetallic alloys were synthesized in water using a capillary microwave flow reactor. Investigations showed the nanoparticles were activity toward hydrogenation of octene. With further development, continuous flow synthesis of metallic nanoparticles can be applied to the synthesis of a wide variety of catalysts on an industrial scale. Continuous flow methods provide greater control of reaction parameters, increased safety by reacting smaller volumes of chemicals at a given time, and decreasing the batch-to-batch variability.

The fascinating physical properties that arise in materials limited to dimensions of 1-100 nm have gained noteworthy interest from the scientific community. Accordingly, there has been a lot of attention paid to the synthesis of discrete nanoparticles (NPs) and they are being investigated for a range of advanced technologies. Nonetheless, efficient use of nanomaterials in device applications require them to be assembled into solid state macro-structures while retaining their unique, nanoparticulate properties. To date, most commonly investigated assembling techniques include: covalent coupling of NPs surface groups, control evaporation of the solvent to produce ordered supercrystals or non-ordered glassy films, and polymer or bimolecular mediated self-assembly. However, in each of these cases, the interactions among discrete NPs are mediated by intervening ligands, the presence of which are detrimental for efficient electronic transport and interparticle coupling that limit performance in optoelectronic,electro-catalytic, and chemical sensor studies. Thus, novel and efficient strategies that can be predictably manipulated for direct, self-supported assembly of NPs are of critical need. A method that has proved useful to construct direct interfacial linkages of colloidal NPs is the sol-gel technique.Oxidative removal of surfactant ligands has been shown to produce self-supported NP monoliths that in most cases retain the physical properties of primary NPs.The ability to create direct interfacial bonds contributes to enhanced electrical and thermal transport as well as tunable interparticle interactions, expanding the potential range of NP technologies. During oxidation, low coordinated active sites are produced on the NP surface that interacts with a nearby NP to reduce the surface energy. The formed active sites are highly reactive allowing the NPs to establish direct interfacial linkages, polymerize into low dimensional clusters, and consequently highly porous superstructures that augment the unique, nanoparticulate properties. An added advantage of this chemistry is the ability to couple chemically similar or dissimilar systems with the potential to achieve novel/tunable physical properties. In this dissertation, application of sol-gel chemistry in efficient integration of similar and dissimilar nanoscale materials will be discussed with an aim of achieving improved optoelectronic and electro-catalytic properties. Hybrid nanomaterials composed of metal-semiconductor components exhibit unique properties in comparison to their individual counterparts, making them of great interest for optoelectronic technologies. The direct cross-linking of NPs via sol-gel chemistry provides a versatile route to tune interfacial interactions in a manner that has not been thoroughly investigated. Thus, the first part of the dissertation will illustrate the synthesis of CdSe/Ag hetero-nanostructures (aerogels) via oxidation induced self-assembly of thiol-coated NPs and investigate the evolution of optical properties as a function of Ag composition. Two hybrid systems were investigated, where the first and second excitonic energies of CdSe were matched with plasmonic energy of Au and Ag NPs. The optical properties of the CdSe/Ag hybrids were systematically examined through UV-visible, photoluminescence, and time resolved photoluminescence spectroscopy. A new emission (640 nm) from CdSe/Ag aerogels was emerged at Ag loading as low as 0.27 % whereas absorption band tailing and PL quenching effects were observed at higher Ag and Au loading, respectively. The TRPL decay time of the new emission (~600 ns) is markedly different from those of the band-edge (1.83 ± 0.03 ns) and trap state (1190 ± 120 ns) emission maxima of phase pure CdSe, supporting the existence of alternate radiative relaxation pathways in sol-gel derived CdSe/Ag hybrids. An added benefit of newly developed sol-gel chemistry is the potential to produce porous, conducting nanoarchitectures that provide a facile pathway for efficient transfer of charge carriers and small molecules. Thus, aerogels composed entirely of noble metal NPs are expected to exhibit high electrical conductivity making them promising for electrocatalysis. Thus, the second part of the dissertation will describe the extension of NP condensation strategy for the fabrication of ternary noble metal (Au/Ag/Pd, Au/Ag/Pt) aerogels for electro-oxidation of alcohols. The precursor alloy NPs were produced via stepwise galvanic replacement of thiol-coated Ag NPs. The resultant alloy NPs were self-assembled into large, free-standing aerogels that exhibit direct interparticle connectivity, high surface area (282 – 98 m2/g) and mesoporosity (2 – 50 nm) via controlled oxidation of the surfactant ligands. The gelation kinetics has been controlled by varying the oxidant/surfactant molar ratio that governs the dealloying of Ag from ternary superstructures with in-situ generated HNO3. The monolithic Au/Ag/Pd alloy aerogels exhibit higher catalytic activity and durability compared to the discrete alloy NPs (~ 20-30 times) and commercial Pd/C catalyst (2-3 times). On the other hand, Au/Ag/Pt alloy aerogels showed excellent stability at higher concentration of methanol (12 M) during electro-oxidation studies, suggesting its superior electro-catalytic activity. The synergistic effect of tri-metallic alloy mitigates the catalyst poisoning and increases the stability and durability whereas the self-supported superstructure with direct interparticle connectivity, high surface area and porosity offers a facile conduit for molecular and electronic transport, enabling the ternary aerogels an efficient electro-catalyst.

The rapid development of polymer nanocomposites has received extensive attention over the last few decades. The ability to alter functionalities of composites, dramatically improving properties and performance at low filler content creates flexibility in designing materials for advanced applications in various industrial fields. This work focuses on nanocomposites relevant to the packaging and aerospace industries. This work evaluated the ability to homogeneously distribute nanomaterials into a polymer matrix, understand the effects on rheological properties, understand changes to microstructure and effects, and characterize properties of resulting nanocomposite. High torque melt mixing was used to disperse surface modified cellulose nanocrystals in a poly(lactic acid) (PLA) resin and graphene in a phenylethynyl terminated imide resin, PETI 298, using bulk graphite. Rheology, Raman spectroscopy, and X-Ray powder diffraction were applied for the understanding of changes to the microstructure and location of optimum loading by the determination of the percolation threshold. Thermomechanical performance was evaluated through TGA, DMA, and DSC. It was determined that graphene and short stacks of graphene could be dispersed and distributed at low loadings in PETI 298. As expected, the addition of graphitic material led to an increase in viscosity, but also caused a retardation of the cure which could be attributed to increased viscosity or quenching of free radicals. Changes to the microstructure were difficult to evaluate because of the competing chemistry occurring in the system but it could be determined that something significant occurs around 1 wt % at which the melt rheology and the microstructure behavior was different from other composites. It was further determined that the melt mixing process led to the formation of an ordered structured. Modification of the cellulose nanocrystals (m-CNC) with Cardura, glycidyl ester, provided no improvement to mechanical properties of PLA composites. However, m-CNCs were found to nucleate the crystallization of PLA. Lack of improvement to mechanical properties could be attributed to the degradation of polymer during processing.

Phloridzin, an antidiabetic and antineoplastic agent usually found in fruit trees, is a dihydrochalcone constituent that has a clinical/pharmaceutical significance as a sodiumglucose linked transport 2 (SGLT2) inhibitor. Phloridzin never experienced widespread clinical usage in the pharmaceutical market due to its side effects and poor bioavailability when compared to other antidiabetic therapeutics. The poor bioavailability is primarily attributed to the degradation of the glycosidic bond of the phloridzin, resulting in the formation of phloretin, the aglycone of phloridzin and glucose. While phloretin displays a reduced capacity of SGLT2 inhibition, this nutraceutical shows enhanced antineoplastic activity in comparison to phloridzin. Gold nanoparticles (AuNPs) have been explored in improving the bioavailability of many drugs and therefore we opt for gold nanoparticle mediated delivery of phloridzin and phloretin and exploration of their anticancer mechanism. In this study, we have synthesized phloridzin and phloretin conjugated gold nanoparticles (Phl-AuNP and Pht-AuNP) in a single-step, rapid, biofriendly processes. The synthesized AuNPs morphology and elemental composition was characterized via transmission electron microscopy, UV-Vis spectroscopy, scanning electron microscopyenergy dispersive x-ray spectroscopy, and thermogravimetric analysis. Assessment of the antineoplastic potency of the dihydrochalcone-conjugated AuNPs against cancerous cell lines was accomplished through monitoring via flow cytometry. We posit that the functionalization of these chalcones onto the gold nanoparticles’ surface has improved the pharmacokinetic profile of phloridzin and phloretin.