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Microtubules (MTs), whose basic units are a and ß tubulin proteins, are self-assembled proteinaceous filaments with nanometer scale diameters and micrometer scale lengths. Their aspect ratio, directionality, the reversibility of their assembly and their ability to be metallized by electroless plating make them good candidates to serve as templates for the fabrication of nanowires and other nanoscale devices. In addition, tubulin proteins can provide biological interactions with a naturally high specificity.Toward the goal of manufacturing MT-based metallic nanowires and networks of nanowires on a silicon wafer, I studied the influence of pH, temperature, and several biomolecules on the stability of MTs in solutions, as well as the surface effect on the dynamics of disassembly of microtubules. Secondly, I demonstrated the metallization of MTs by electroless nickel plating both in solution and on hydrophilic oxidized Si surface. After being activated by Pt, nickel coated MT surfaces during the electroless plating, with a thickness of several nanometers. Due to the different kinetics of the process, MTs metallized on the oxidized Si wafer are slightly different from MTs metallized in solutions. Finally, we explored controlled nucleation and growth of microtubules directly from a collection of g-tubulin monomers. g-tubulins bind to modified gold electrodes on a silicon wafer through an organic linker, Glutathione s-transferase, creating a g-tubulin layer for MT growth. MTs unambiguously originated from the surface-bound g-tubulin layer on the gold electrode, proving that the surface-bound g-tubulin retains its biological ability of nucleating MT growth.

One dimensional (1-D) metallic nanostructures (e.g. nanowires, nanorods) have stimulated great interest recently as important building blocks for future nanoscale electronic and electromechanical devices. In this thesis work, gold and nickel nanowires with various diameters were successfully fabricated, and two dedicated platforms, based on (1) a novel micro mechanical device (MMD) assisted with a quantitative nanoindenter and (2) a TEM-AFM sample holder system, were developed and adopted to perform in situ tensile tests inside SEM and TEM on samples with diameter ranging from a few nanometers to hundreds nanometers. Size-dependent mechanical behavior and different fracture mechanisms of gold nanowires had been revealed and discussed. In addition, we discovered cold welding phenomenon for ultrathin gold nanowires (diameter < 10nm), which is anticipated to have potential applications in the future bottom-up integration of metallic 1-D nanostructures and next-generation interconnects for extremely dense logic circuits.

Increasing energy demand makes the development of higher energy storage batteries, imperative. However, one of the major advantages of fossil fuels as an energy source is they can provide variably large quantities of power when desired. This is where electrochemical capacitors can continue to carve out a niche market supplying moderate energy storage, but with high specific power output. However, current issues with carbon precursors necessitate further development. Further, production requires high temperature, energy intensive carbonization to create the active pore sites and develop the pores. Double-layer capacitive materials researched to replace active carbons generally require properties that include: very high surface area, high pore accessibility and wettability, strong electrical conductivity, structural stability, and optionally reversible functional groups that lend to energy storage through pseudocapacitive mechanisms. In recent years, nanostructured carbon materials which could in future be tailored through bottom up processing have the potential to exhibit favourable properties have also contributed to the growth in this field. This thesis presents research on graphene, an emerging 2-dimensional carbon material. So far, production of graphene in bulk exhibits issues including restacking, structural damage and poor exfoliation. However, the high chemical stability, moderate conductivity and high electroactive behaviour even with moderate exposed surface area makes them an excellent standalone material or a potential support material. Two projects presented focus on enhancing the capacitance through functionality and controlling graphene formation to enhance performance. The first study addresses graphene enhancement possible with heteroatom functionality, produced by a single step low temperature hydrothermal reduction process. The dopant methodology was successful in adding nitrogen functionality to the reduced graphene oxide basal and the effect of nitrogen type was considered. The second study addresses the need for greater control of the rGO structure on the macro-scale. By harnessing the change in interactions between the GO intermediate and final rGO sheets we were able to successfully control the assembly of graphene, creating micro and macro-pore order and high capacitive performance. Further, self assembly directly onto the current collector eliminates process steps involved in the production of EDLC electrodes.

<p>The main objective of this work it to produce membrane electrode assemblies (MEAs) that have improved performance over MEAs produced by the conventional manner, by producing highly efficient, electroactive, uniform catalyst layers with lower quantities of platinum electrocatalyst. The catalyst coated membrane (CCM) method was used to prepare the MEAs for the PEM fuel cell as it has been reported that this method of MEA fabrication can improve the performance of PEM fuel cells. The MEAs performances were evaluated using polarisation studies on a single cell. A comparison of polarisation curves between CCM MEAs and MEAs produced in the conventional manner illustrated that CCM MEAs have improved performance at high current densities (&gt / 800 mA/cm2).</p>

Amyloid fibrils are an insoluble, highly ordered, fibrous protein structure, which have increasingly been recognised as having bionanotechnology applications. Their ability to selfassemble allows a bottom-up approach to material design. Their nanometre dimensions affords them a high surface-to-volume ratio and their proteinaceous building blocks from which they are assembled allow for decoration with biomolecules and chemicals through amino acid residues. Amyloid fibrils are therefore a potential nanoscaffold for immobilisation of biomolecules. Immobilisation offers a solution to the problems associated with the use of enzymes in in vitro applications, by increasing their stability, reusability, and in some cases, enhancing catalytic activity. Nanosupports offer a high surface-to-volume ratio compared to classical planar 2-D supports, potentially affording them dramatic increases in immobilisation capacity. To investigate the potential of amyloid fibrils as a novel nanoscaffold, organophosphate hydrolase (OPH), cytochrome P450BM3 (P450BM3), green fluorescent protein (GFP), tobacco etch virus protease (TEV), and glucose oxidase (GOD) were immobilised in solution to the model amyloid fibril forming protein, bovine insulin. Covalently immobilised OPH was found to have a ~300 % increase in relative thermostability at 40 and 50 °C. P450BM3 was not successfully immobilised in its active state, most likely due to unfolding of the enzyme on the amyloid fibril surface. Covalently immobilised GFP retained full fluorescence and acted as a fluorescent protein tag. TEV was shown to have a physical interaction with the nanoscaffold and retain activity. GOD was immobilised and retained activity. Although not all proteins retained activity, a range of different protein structures were successfully immobilised onto the insulin amyloid fibril nanoscaffold. Attachment to the crystallin amyloid fibril nanoscaffold remains a work in progress due to the complexities associated with post-translational modifications of these fibrils. Crystallin amyloid fibrils were assembled on a surface for the first time. Their surface assembled structure was found to resemble spherulites, not previously seen before with crystallin amyloid fibrils. Bovine insulin amyloid fibrils were assembled on the surface of glass beads to increase the available surface area for biomolecule immobilisation. The surface assembled bovine insulin nanoscaffold was first functionalised with GOD, demonstrating that the nanoscaffold provides more surface area for biomolecule immobilisation, although in this case the increase was limited due to high non-specific binding of GOD to the unmodified glass surface. GFP was successfully employed as a fluorescent protein tag to assess the degree of nanoscaffold coverage, confirming the nanoscaffold affords the glass bead a greater surface area. Moreover, a reusable immobilised TEV protease-bead system was developed that was able to sequentially cleave the poly-histidine tags of three different proteins. In conclusion, bovine insulin amyloid fibrils have been shown to be a versatile nanoscaffold for the immobilisation of a range of biomolecules. The surface characteristics of the nanoscaffold allows for both covalent and physical immobilisation of biomolecules. Thus, amyloid fibrils have exciting potential in the creation of novel bionanotechnologies.

<p> Nanofluids, stable colloidal suspensions of nanoparticles in a base fluid, have potential applications in the heat transfer, combustion and propulsion, manufacturing, and medical fields. Experiments were conducted to determine the evaporation rate of room temperature, millimeter-sized pendant drops of ethanol laden with varying amounts (0-3% by weight) of 40-60 nm aluminum nanoparticles (nAl). Time-resolved high-resolution drop images were collected for the determination of early-time evaporation rate (D²/D₀² > 0.75), shown to exhibit D-square law behavior, and surface tension. Results show an asymptotic decrease in pendant drop evaporation rate with increasing nAl loading. The evaporation rate decreases by approximately 15% at around 1% to 3% nAl loading relative to the evaporation rate of pure ethanol. Surface tension was observed to be unaffected by nAl loading up to 3% by weight. </p><p> A model was developed to describe the evaporation of the nanofluid pendant drops based on D-square law analysis for the gas domain and a description of the reduction in liquid fraction available for evaporation due to nanoparticle agglomerate packing near the evaporating drop surface. Model predictions are in relatively good agreement with experiment, within a few percent of measured nanofluid pendant drop evaporation rate. </p><p> The evaporation of pinned nanofluid sessile drops was also considered via modeling. It was found that the same mechanism for nanofluid evaporation rate reduction used to explain pendant drops could be used for sessile drops. That mechanism is a reduction in evaporation rate due to a reduction in available ethanol for evaporation at the drop surface caused by the packing of nanoparticle agglomerates near the drop surface. Comparisons of the present modeling predictions with sessile drop evaporation rate measurements reported for nAl/ethanol nanofluids by Sefiane and Bennacer [11] are in fairly good agreement. Portions of this abstract previously appeared as: W. J. Gerken, A. V. Thomas, N. Koratkar and M. A. Oehlschlaeger, Int. J. Heat Mass Transfer, vol. 74, no. 1, pp. 263-268, July 2014. W. J. Gerken, M. A. Oehlschlaeger, "Nanofluid Pendant Droplet Evaporation", in Proceedings of the ASME 2013 Summer Heat Transfer Conference, Minneapolis, MN, 2013, pp. V001T03A018.</p>

<p> Magnetic nanoparticle hyperthermia (mNPH) is an emerging cancer therapy which has shown to be most effective when applied in the adjuvant setting with chemotherapy, radiation or surgery. Although mNPH employs heat as a primary therapeutic modality, conventional heat may not be the only cytotoxic effect. As such, my studies have focused on the mechanism and use of mNPH alone and in conjunction with cisplatinum chemotherapy in murine breast cancer cells and a related in vivo model. MNPH was compared to conventional microwave tumor heating, with results suggesting that mNPH (mNP directly injected into the tumor and immediately activated) and 915 MHz microwave hyperthermia, at the same thermal dose, result in similar tumor regrowth delay kinetics. However, mNPH shows significantly less peri-tumor normal tissue damage. MNPH combined with cisplatinum also demonstrated significant improvements in regrowth delay over either modality applied as a monotherapy. Additional studies demonstrated that a relatively short tumor incubation time prior to AMF exposure (less than 10 minutes) as compared to a 4-hour incubation time, resulted in faster heating rates, but similar regrowth delays when treated to the same thermal dose. The reduction of heating rate correlated well with the observed reduction in mNP concentration in the tumor observed with 4 hour incubation. The ability to effectively deliver cytotoxic mNPs to metastatic tumors is the hope and goal of systemic mNP therapy. However, delivering relevant levels of mNP is proving to be a formidable challenge. To address this issue, I assessed the ability of cisplatinum to simultaneously treat a tumor and improve the uptake of systemically delivered mNPs. Following a cisplatinum pretreatment, systemic mNPs uptake was increased by 3.1 X, in implanted murine breast tumors. Additional in vitro studies showed the necessity of a specific mNP/ Fe architecture and spatial relation for heat-based cytotoxicity in cultured cells.</p>

<p> Optical rectennas, which are micro-antennas to convert optical-frequency radiation to alternating current combined with ultrahigh-speed diodes to rectify the current, can in principle provide high conversion efficiency solar cells and sensitive detectors. Currently investigated optical rectennas using metal/insulator/metal (MIM) diodes are limited in their RC response time and poor impedance matching between diodes and antennas. A new rectifier, the geometric diode, can overcome these limitations. The thesis work has been to develop geometric diode rectennas, along with improving fabrication processes for MIM diode rectennas. The geometric diode consists of a conducting thin-film, currently graphene, patterned into a geometry that leads to diode behavior. In contrast with MIM diodes that have parallel plate electrodes, the planar structure of the geometric diode provides a low RC time constant, on the order of 10^-15 s, which permits operation at optical frequencies. Fabricated geometric diodes exhibit asymmetric DC current-voltage characteristics that match well with Monte Carlo simulations based on the Drude model. The measured diode responsivity at DC and zero drain-source bias is 0.012 A/W. Since changing the gate voltage changes the graphene charge carrier concentration and can switch the majority charge type, the rectification polarity of the diode can be reversed. Furthermore, the optical rectification at 28 THz has been measured from rectennas formed by coupling geometric diodes with graphene and metal bowtie antennas. The performance of the rectenna IR detector is among the best reported uncooled IR detectors. The noise equivalent power (NEP) of the rectenna detector using geometric diode was measured to be 2.3 nW Hz^-1/2. Further improvement in the diode and antenna design is expected to increase the detector performance by at least a factor of two. Applications for geometric diodes and graphene bowtie antennas include detection of terahertz and optical waves, ultra-high speed electronics, and optical power conversion.</p>

<p>Planar transistors have been the important building block of integrated circuits for decades, during which the size of transistors has steadily decreased. We will evaluate energy released due to recombination and also evaluate energy stored in the electric field for the step junction case, and then calculate the net energy of formation for the step junction. Also, we have calculated the change in temperature due to the energy of formation. </p>