Abstract
This dissertation presents the carboxylation of GUITAR particles using spontaneous chemical diazonium grafting. GUITAR (pseudo-Graphite from the University of Idaho Thermalized Asphalt Reaction) is a graphite-like material that has shown excellent electrochemical properties, including fast basal plane heterogeneous electron transfer rate (HET), wide potential window, and excellent corrosion resistance. These properties stem from the unique structure of GUITAR, particularly its high density of basal plane defects, which results in a wavy basal plane. This waviness combined with GUITAR’s resistance to corrosion makes spontaneous diazonium grafts easier to perform, with higher coverage, and results in a more stable and consistent functionalized material. Chapter 1 will introduce GUITAR, its properties, and current issues facing the functionalization of graphitic materials. Additionally, it will provide background information on particle-based GUITAR. Chapter 2 will present the formation and spectroscopic characterization of the carboxylated GUITAR particles (GUITAR-COOH). This chapter will explore the availability of the carboxylic acid groups for amide bond coupling reactions by using carbodiimide chemistry to attach aminoferrocene to the particles. The resulting material GUITAR-Fc allows probing of the bonding stability and surface coverage through ferrocene electrochemistry and shows the material’s utility as a hydrogen peroxide sensor. Chapter 3 will examine the electrochemistry of GUITAR-COOH as well as the ability to resist organic fouling agents through its use as an electrochemical detector for dopamine oxidation. The presence of only one functional group creates a consistent chemical environment that allows for the highly sensitive dopamine transducer. This sensor is reproducible for dopamine oxidation, resulting in a nM detection limit and no current loss from dopamine fouling or interferents. Finally, Chapter 4 will use GUITAR-COOH combined with an ascorbic acid-based chemical oxygen scavenger for the electrochemical detection for lead. The interaction between carboxylic acid groups and Pb2+ strengthens the preconcentration of lead, while the chemical oxygen scavenger removes trace O2, the most prevalent interferent. This results in a lead detector with a 1 parts-per billion (ppb) detection limit and a wide linear range of 5-700 ppb for a fraction of the cost of standard detection methods. Additionally, GUITAR-COOH shows strong resilience against interfering ions and accurately determined lead concentration in a complex real sample.