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In modern agriculture, nanotechnology has been at the forefront of agrochemical product innovation. For crop protection, researchers have turned to nano-zinc oxide (nano-ZnO) products that could potentially serve as an alternative to copper-based pesticides while mitigating micronutrient Zn deficiency. In this thesis, Zinkicide®, a nano-ZnO (4.5% Zn) based agriculture-grade product formulation has been investigated for their potential use as a broad-spectrum bactericide with systemic activity. Initial studies showed that Zinkicide® exhibits phytotoxicity to susceptible plants and experiences limited rainfastness. It is hypothesized that a suitable spray adjuvant will improve rainfastness and zinc absorption without compromising the antimicrobial efficacy. To test these hypotheses, the effect of three commercially available spray adjuvants – FitoFix®, Photon®, and AgriOil® – on Zinkicide®'s physico-chemical properties including wettability, zinc mobility and rainfastness were evaluated using citrus plants. Effects of adjuvant on Zinkicide® antimicrobial properties were also examined. Characterization results indicated that the composition of spray adjuvants has minimal effect on the deposition pattern (coffee ring effect) of Zinkicide® on glass and almost no effect on citrus leaf substrates. The wettability of Zinkicide® was slightly altered by the addition of adjuvants when tested on both substrates. FTIR data indicates that the adjuvants do not chemically interact with Zinkicide®. The effect of spray adjuvants on Zinkicide® antimicrobial properties were investigated using two model pathogens, Xanthamonas alfalfae and Pseudomonas syringae. The results suggest that the addition of adjuvants had no noticeable effect on the antimicrobial properties of Zinkicide®. The zinc in-planta mobility and rainfastness studies showed that the spray adjuvants have no observable effect on these properties. The above research findings could help advance Zinkicide® research in finding other potential adjuvant candidates in tank-mix settings.

Interest in nanoscale heat and mass transport has been augmented through current trends in nanotechnology research. The theme of this dissertation is to characterize electric charge, mass and thermal transport at the nanoscale using a fundamental molecular simulation method, namely molecular dynamics. This dissertation reports simulations of (1) ion intake by carbon nanotubes, (2) hydrogen storage in carbon nanotubes, (3) carbon nanotube growth and (4) nanoscale heat transfer. Ion transport is investigated in the context of desalination of a polar solution using charged carbon nanotubes. Simulations demonstrate that when either a spatially or temporally alternating charge distribution is applied, ion intake into the nanotubes is minimal. Thus, the charge distribution can either be maintained constant (for ion encapsulation) or varied (for water intake) in order to achieve different effects. Next, as an application of mass transport, the hydrogen storage characteristics of carbon nanotubes under modified conditions is reported. The findings presented in this dissertation suggest a significant increment in storage in the presence of alkali metals. The dependence of storage on the external thermodynamic conditions is analyzed and the optimal range of operating conditions is identified. Another application of mass transport is the growth mode of carbon nanostructures (viz. tip growth and base growth). A correct prediction of the dominant growth mode depends on the energy gain due to the addition of C-atoms from the carbon-metal catalyst solution to the graphene sheets forming the carbon nanostructures. This energy gain is evaluated through molecular dynamics simulations. The results suggest tip growth for Ni and base growth for Fe catalysts. Finally, unsteady nanoscale thermal transport at solid-fluid interfaces is simulated using non-equilibrium molecular dynamics simulations. It is found that the simulated temperature evolution deviates from an analytical continuum solution due to the overall system heterogeneity. Temperature discontinuities are observed between the solid-like interfaces and their neighboring fluid molecules. With an increase in the temperature of the solid wall the interfacial thermal resistance decreases. / Ph. D.

Nanotechnology has enormous potential to transform a wide variety of sectors, e.g., energy, electronics, healthcare, and environmental sustainability. At the same time, there are concerns about the health and environmental impacts of nanotechnology and uncertainties about the fate and toxicity of nanomaterials. Life cycle assessment (LCA), a quantitative framework for evaluating the cumulative environmental impacts associated with all stages of a material or process, has emerged as a decision-support tool for analyzing the environmental burdens of nanotechnology. The objective of this research was to combine laboratory techniques with LCA modeling to reduce the life cycle impacts of gold nanoparticle (AuNP) production. The LCA studies were focused on three aspects of AuNP synthesis: 1) the use of bio-based ("green") reducing agents; 2) the potential for recycling gold from nanomaterial waste; and, 3) the reduction of the life cycle impacts of AuNP production by conducting the synthesis at reduced temperature. The LCA models developed for AuNPs can inform future nanotechnology-focused LCA studies. Comparative LCA showed that in some cases, the environmental impacts associated with green synthesis methods may be worse than those of conventional synthesis approaches. The main driver of the environmental burdens associated with AuNP synthesis is the large embodied energy of gold, and so-called green synthesis methods do not offset those impacts. In addition, the reaction yield, which is seldom reported in the literature for green synthesis of nanomaterials, was found to greatly influence the life cycle impacts of AuNP synthesis. Gold from nanomaterial waste was successfully recovered by using host-guest inclusion complex formation facilitated by alpha-cyclodextrin. This recycling approach involved room temperature conditions and did not require the toxic cyanide or mercury commonly used in the selective recovery of gold. A major advantage offered by this approach for selective gold recovery over conventional approaches is that the recovery does not involve the use of toxic cyanide or mercury. To reduce the energy footprint of citrate-reduced AuNP synthesis, the synthesis was conducted at room temperature. LCA models showed significant reduction in the energy footprint. The findings of this research can inform future LCAs of other nanomaterials. / Ph. D.

Background: Photothermal therapy is an actively researched cancer treatment alternative to chemotherapy and resection due to its potential as a minimally invasive treatment with fewer health complications than high energy radiation therapies. The effectiveness of photothermal therapy may be enhanced with the use of photoabsorbtive nanoparticles by increasing heat generation and improving spatial selectivity. While photothermal therapy is a spatially distributed treatment, traditional experimental analysis methods used to assess photothermal therapy have either lacked spatial assessment such as is the case with standard viability assays of cell monolayers, or they only provide macroscopic treatment information, such as the measurement of the diameters of implanted mice flank tumors post-treatment. Goals: This work aims to accomplish two major goals. The first is to determine the therapeutic impact of combining Single Walled Carbon Nanohorns (SWNHs) with photothermal therapy. The second is to advance the measurement tools used to assess photothermal therapy by developing viability measurement methods which incorporate detailed quantitative spatial information Methods: Photothermal therapy was tested with and without SWNHs in in vitro cell monolayers, in vitro tissue phantoms, and ex-vivo tissue. Digital image analysis methods were developed which allowed for the use of viability assays and histological information to be identified and organized spatially. These methods were then used to compare the impact of cellular microenvironment and heating method on Arrhenius parameters. Results: The inclusion of SWNHs dramatically increased the temperatures reached in each experiment. Digital image analysis methods were shown to quantify spatial viability with a high degree of accuracy and precision in 2D and 3D. Experimental data indicated that there were areas of collateral damage (partially treated tissue) surrounding areas of completely treated tissue ranging which were between 46% and 78% of the completely treated volume. In each case the heat transfer properties of the experimental system had a large impact on the area of treatment. Variation in the temperature and viability response of photothermal therapy for specific laser and nanoparticle treatment parameters was quantified. Conclusions: This research has brought an experimental cancer treatment procedure from experiments in cell monolayers to tests in ex-vivo tissue to analyze viability response. The strengths of photothermal therapy such as its minimally invasive nature, and effectiveness at killing cells were experimentally demonstrated. This research has also developed the tools necessary to assess the spatial impact in vitro and lay the foundations for assessing spatial impact in vivo. These tools may be used to assess other treatments beyond photothermal therapy, and serve as a basis for improving the analysis of biological systems both in vitro and in vivo. / Ph. D.