Improved Environmental Operation of Alcohol Breathalyzers with Functionalized Graphene Nanocomposite Membranes

Abstract

Driving under the influence of alcohol is prohibited or restricted in almost every country on the planet. In Canada, a Blood Alcohol Content (BAC) of 0.08 g dL-1 results in a Criminal Code offense and vehicle impoundment. Critical to this charge and its associated consequences is the technology assessing alcoholic content. Modern police forces use handheld or stationary breath analysis tools to evaluate alcohol ingestion. In order for punitive measures to be enforced, the reliability and accuracy of breathalyzers must go without question. However, methods employed to improve the reliability of modern sensors waste significant energy to control the test environment; namely humidity and temperature of the test cell. Through a more thorough investigation of the parameters which govern an ethanol fuel cell sensor (FCS) response, we can design a testing cell itself which is insensitive to its environment while improving the specificity. Modern FCS are based on acid-soaked poly-vinyl chloride (PVC) with a platinum on carbon catalyst hot-pressed directly to the membrane interface. More recently, Nafion by Dupont has been investigated as an alternative, strongly conductive and stable membrane material. Both of these fall prey to water loss, limiting their response to varied environmental conditions and requiring frequent calibration. This project designs and tests engineered nanocomposite membranes to enhance the reliability of the FCS response. Increasing the thickness of Nafion nanocomposite membranes correlated with improved sensor responses. Integration of 5 wt% 1:1 ratio of sulfonic-acid functionalized nanoporous silicon dioxide to functionalized graphene oxide in Nafion best enhanced a FCS response in low humidity, showing stability even at 100 days in a low humidity environment.