An Electrochemical Impedance Spectroscopy Study Of Epitaxial Graphene For Use In A Breath Alcohol Analyzer

Breath alcohol analyzers are commonly used by law enforcement officers to estimate blood alcohol concentration with the goal of identifying drunk drivers. Such tests are quick and efficient. However, results can be inaccurate, sometimes leading to unfair arrests and wasted law enforcement resources. Improvement in the accuracy and reliability of breath alcohol analyzers would benefit the criminal justice system. Graphene, a two-dimensional carbon molecule, shows promise for use as an electrochemical sensor due to its large surface area, excellent electrical conductivity, and sensitivity to changes in local environment. Graphene can be grown epitaxially, which involves the desorption Si atoms from the surface of a SiC wafer, leaving behind a layer of graphene on a SiC substrate. Electrochemical impedance spectroscopy is a process in which the impedance across a conductor is measured over a range of electrical frequencies. In this study, electrochemical impedance spectroscopy was used to analyze epitaxial graphene exposed to various substances. The objectives of this research were to detect and differentiate changes in graphene in response to the presence of ethanol, water, and acetone. Experimentation revealed that contact with these substances changes the way the impedance of graphene responds to changes in the frequency of AC current. The resistance across graphene at any electrical frequency in the 0.1 Hz-1000 Hz range was significantly different during exposure to each substance. It was shown that the resistance was lowest for acetone, highest for water while ethanol produced intermediate values