Chemiresistive Ion Sensors for Water Quality Applications

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This proposal aims to develop McMaster's chemiresistive technology for use in industrial water systems run by the client companies of our industrial partner, Magnus. Magnus Chemicals Ltd, a Canadian company founded in 1946, specializes in water treatment for industrial applications (steam boilers, cooling towers and closed loop cooling systems). For these applications, it is important to detect corrosion products and fouling, control alkalinity and water hardness, and monitor other parameters resulting from the water treatment processes. In most cases, reliable online sensors for monitoring these parameters are not available. Manual monitoring involves plant operators or technicians conducting chemical tests with reagents at regular intervals and comparing the results to specified chemical control limits. Some devices for online monitoring have been developed, mainly relying on colorimetric and electrochemical sensors. Colorimetric sensors require periodic maintenance for refills. Electrochemical sensors are typically reagentless, but nevertheless limited by the durability of their reference electrodes. In contrast, chemiresistors have a very simple and robust design and can operate without reagents or reference electrodes, thus reducing manufacturing and maintenance costs. The McMaster team (Kruse, Selvaganapathy groups) has worked over the last 8 years to develop chemiresistive sensors based on nanocarbon films such as carbon nanotubes (CNTs) or exfoliated few-layer graphene (FLG) modified with switchable dopant molecules, based on the notion of switching the doping characteristic of a molecule due to changes in its chemical environment. Due to the 2D nature of our nanocarbon films, and the change in doping behavior of our specific molecules, the state of the molecular switch can be read out by measuring the resistivity of the nanocarbon film. The read-out can occur at low voltages, enabling operation in aqueous analytes without inducing electro-chemical processes. This grant provides an opportunity to significantly broaden the utility of chemiresistors in water quality applications.