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(2022)ThesisConverting natural resources or greenhouse gases into value-added species with low carbon footprint, is essential for the development and sustainability of modern society. However, the goal for sustainable and cost-effective conversion by using many current technologies, including photo-, electro- and thermal-based catalytic reaction systems, has been largely underachieved. Hence, it is a necessity to explore and develop new approaches to fulfill this objective. In this thesis, three hybrid catalytic systems, containing liquid gallium (Ga) and solid materials as co-catalysts, are demonstrated, which realize the gaseous and liquid feedstocks conversion through nano-tribo-electrochemical reaction pathways. In the first stage of this PhD thesis, the author reports a green carbon capture and conversion technology for mitigating CO2 emissions. The technology uses suspensions of Ga liquid metal to reduce CO2 into solid carbonaceous products and O2 at near room temperature. The solid co-contributor of silver-Ga rods ensures a cyclic sustainable process. The overall process relies on mechanical energy as the input, which drives nano dimensional triboelectrochemical reactions. In the next stage, for the gaseous feedstock conversion, the author demonstrates an approach based on Ga liquid metal droplets and Ni(OH)2 co-catalysts for CH4 conversion into H2 and carbon. Mainly driven by the triboelectric voltage, originating from the joint contributions of the co-catalysts during agitation, CH4 is converted at the Ga and Ni(OH)2 interfaces. The efficiency of the system is enhanced when the reaction is performed at an increased pressure. The dehydrogenation of other non-gaseous hydrocarbons using this approach is also demonstrated. In the final stage, the author explores and realizes the liquid biofuels conversion, including canola oil and other liquid hydrocarbons, with H2 and C2H4 as the main products by employing Ga and nickel particles as the co-catalysts and mechanical energy as the stimulus. Altogether, the work of this PhD research offers novel pathways for low energy and green conversion of gaseous and liquid feedstocks that can be implemented in large scale conversion systems of the future.
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(2022)ThesisLiquid metals (LMs) are a class of metals and their alloys which have low melting points near or below room temperature, and they are mainly composed of post-transition elements. The low melting points of LMs make them easily stay in a liquid state and readily be broken into tens or hundreds of nanometers, which are called LM nanoparticles (LMNPs). In this thesis, the author investigates LMNPs for three exciting applications of creating conductive polymer-LMNPs compositions and explores the potential utilization of LMNPs in biological applications. In the first phase of this research, the author develops nanocomposites of Ga-based LMNPs (EGaIn NPs) with conductive polymer polyaniline (PANI). This work reports a method of growing PANI nanofibers on the EGaIn NPs by firstly providing initial functionalization sites at the interfaces for the formation of PANI nanofibrous network. The nanocomposites provide synergistic effects of PANI nanofibers and EGaIn NPs for the applications of environmental sensing and molecular separation. In the second phase of the research, the author focused on the exploration of LMNPs for their anti-inflammatory applications. Considering that Ga ions (Ga3+), have been historically utilized as anti-inflammatory agents by interfering with the Fe homeostasis of immune cells. The study presents the anti-inflammatory effects of Ga by delivering Ga nanoparticles (Ga NPs) into lipopolysaccharide-induced macrophages. The Ga NPs show a selective anti-inflammatory effect by modulating nitric oxide production without disturbing other pro-inflammatory mediators. This work reveals the different anti-inflammatory effects between Ga NPs and Ga3+ come from their different endocytic pathways: transferrin receptor independent and dependent endocytosis for Ga NPs and Ga3+, respectively. In the final phase, the author studies the interactions between LMNPs and macrophages at a light microscopic level. The mechanistic responses of macrophages to LMNPs with different densities were observed, in comparison to some other commonly studied nanoparticles. This work discovers the mobility of macrophages is very much density-dependent. This thesis comprehensively studies the interactions between LMNPs and polymeric and biological systems, at both molecular and microscopic levels, which provides a basis and road map for utilizing LMNPs in various fields such as electronics and biomedical engineering.
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(2022)ThesisNitric oxide (NO) plays pivotal roles in various physiological systems and has immense therapeutic potential. NO, however, has a short half-life (<5 s) and a short diffusion distance of ~160 μm in vivo, and its physiological functions are highly dependent on its concentrations. Current NO delivery strategies can be generally categorized into non-catalytic and catalytic (enzymatic) approaches. For the former, the longevity of the NO delivery systems principally relies on the finite NO donor reservoir, while the latter is limited by the low stability of natural enzymes. Another important challenge in NO delivery is the difficulty in accurately detecting circulating NO reservoir in blood. To address these challenges, this thesis focuses on the design, synthesis, and applications of nano-biomaterials to enable sustained NO delivery and accurate detection of endogenous circulating NO reservoir. This thesis revealed ceria nanoparticles as a new class of nanomaterials with the unique ability to catalyze NO generation from NO donors. The therapeutic activity of ceria-induced NO was demonstrated to inhibit cancer cell proliferation. This unique NO-generating feature stood in contrast to the well-established understanding of ceria to scavenge NO. This study provided deeper insights into the bio-functions of ceria nanoparticles and broadened their biomedical applications. Then this thesis reported the first catalytic polymers that generate NO, in particular amine-containing polymers, e.g., polyethyleneimine (PEI). These polymers can be easily integrated into a suite of biomaterials (e.g. hydrogels) to equip them with NO delivery capability. The therapeutic application of polymer-induced NO was demonstrated to prevent the formation of Pseudomonas aeruginosa biofilm. Finally, the thesis tackled the demand for rapid and accurate detection of human serum albumin (HSA, the most abundant circulating NO reservoir in blood) by developing a fluorescent paper-based sensor. This sensing platform allowed sensitive (detection limit of 0.91 g/L) and rapid (20 minutes) point-of-care detection of HSA and HSA-related disease diagnosis by visible color change, and could be extended to the detection of a spectrum of biomarkers. Collectively, these findings open new routes to produce next generation nano-biomaterials for the diverse biomedical applications of NO such as anticancer, antibacterial, and sensing applications.