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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.