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Abstract: This thesis highlights strategies for fiinctionalizing carbon nanomaterials with reactive metaspecies for applications in chemical sensing and electrocatalysis. In Chapter 1, we begin with anintroduction of chemiresistive sensing using functionalized carbon nanotubes (CNTs). Thisintroduction summarizes the design, fabrication, characterization, and evaluation of carbonnanotube-based chemiresistive sensors. Potential strategies for optimizing sensitivity andselectivity are also discussed. Typical applications of'CNT-based chemiresistive sensing are alsosurveyed. In Chapter 2, we report the synthesis of Pentiptycene Polymer/Single-Walled CarbonNanotube Complexes and their applications in the selective detection of benzene, toluene, and o.xylene using chemiresistive and quartz crystal microbalance-based methods. In Chapter 3. wereport a method to efiectively immobilize transition metal selectors in close proximity to theS WCN'T surface using pentiptycene polymers containing metal-chelating backbone structures. Wehave identified sensitive, selective, and robust copper-based chemiresistive ammonia sensorsdisplaying low parts per billion detection limits. We have added these hybrid materials into theresonant radio firequency circuits of commercial near-field communication (NFC) tags to achievewireless detection ofammonia at physiologically relevant levels, offering a non-invasive and cost.efiective approach for early detection and monitoring of chronic kidney diseases. In Chapter 4we report that iptycene-containing poly(arylene ether)s (PAEs) show to limit the palladiumnanoparticles (Pd NPs) growth and stabilize the Pd NPs dispersion. SWCNT-based chemiresistorsand graphene field-efect transistors (GFETs)using these PAE-supported small Pd NPs aresensitive, selective, and robust sensory materials for hydrogen gas under ambient conditions. InChapter 5, we describe chemiresistors based on SWCNTs containing small and highly reactivecopper-based nanoparticles in sulfonated pentiptycene poly(arylene ether)s (PAEs). The sensorsshow exceptional sensitivity to trace hydrogen sulfide in wet air with a low-ppb detection limithigh selectivity over a wide range of interferants, and month-long stability under ambientconditions. In Chapter 6, we report a SWCNT-based chemiresistor catalyst combination that candetect ppb levels of' ethylene in air, driven by the chemoselectivity ofthe catalytic transformationThe utility of this ethylene sensor is demonstrated in the monitoring of senescence in red carnationsand purple lisianthus flowers.In Chapter 7, we report SWCNT-based chemiresistive sensorsbased on a catalytic system comprising a copper complex and TEMPO cocatalyst, enabling thesensitive, selective, and robust detection of trace ethanol in air. In Chapter 8, we report thesynthesis of carbon-nanomaterial-based metal chelates that enable effective electronic coupling toelectrocatalytic transition metals. The defined ligands on the graphene surfaces enable theformation of structurally precise heterogeneous molecular catalysts. We demonstrate that thedensely functionalized metal-chelated carbon nanomaterials are eliective heterogeneous catalystsin the oxygen evolution reaction with low overpotentials and tunable catalytic activity.

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Abstract: Photoredox catalysis has traditionally been accomplished by using ruthenium or iridium polypyridyl complexes. These complexes, while robust in their application, can prove to be quite cost prohibitive. Additionally, their respective redox windows are relatively narrow, limiting the scope of substrates with which they can undergo photoinduced electron transfer. Visible light absorbing organic chromophores have proven to be cost effective alternatives to precious transition metal photoredox catalysts. Additionally, the excited state redox potentials of organic photoredox catalysts can be significantly greater than that of their inorganic counterparts allowing for the development of new methodologies on substrates that could not otherwise undergo photoinduced electron transfer. In particular, organic acridinium dyes possess photophysical properties that make them extremely potent excited state oxidants. More recently it has been demonstrated that the acridine radical in the excited state possesses and excited state oxidation potential comparable to that of dissolving metal reductants making it an excellent excited state reductant. Herein, we describe methods developed that leverage the 5.51 V of redox potential that acridinium complexes can access. Nucleophilic aromatic substitution (SNAr) is a common method for arene functionalization; however, reactions of this type are typically limited to electron-deficient aromatic halides. Herein, we describe a mild, metal_x005f_x0002_free, cation-radical accelerated nucleophilic aromatic substitution (CRA-SNAr) using a potent acridinium photoredox catalyst as an excited state oxidant. Selective substitution of arene C?O bonds on a wide array of aryl ether substrates was shown with a variety of primary amine nucleophiles. Mechanistic evidence is also presented that supports the proposed CRA-SNAr pathway. Ketone–olefin coupling reactions are common methods for the formation of carbon–carbon bonds. This reaction class typically requires stoichiometric or super stoichiometric quantities of metal reductants and catalytic variations are limited in application. Photoredox catalysis has offered an alternative method towards ketone–olefin coupling reactions, although most methods are limited in scope to easily reducible aromatic carbonyl compounds. Herein, we describe a mild, metal-free ketone–olefin coupling reaction using an excited state acridine radical super reductant as a photoredox catalyst. We demonstrate both intra and intermolecular ketone–olefin couplings of aliphatic and aromatic ketones and aldehydes. Mechanistic evidence is also presented supporting an “olefin first”ketone–olefin coupling mechanism.