Chemiresistive Detection of Metal Cations in Water

Abstract

Metal cations serve an important physiological purpose in humans, and one of the most abundant sources of these cations is water. Many cations beneficial to human life are found in water. However, many cations that are deemed detrimental to health may also be present in these water sources. Currently, many methods exist to detect, quantify, and monitor metal cations in water ranging from simple visual tests to more elaborate lab-based methods. The method of metal cation detection employed in this thesis relies on the use of chemiresistive sensors. These sensors monitor the changes in the transductive portion of the sensor, which can be observed through the changes in the current resistance of the sensor. One example of a transducing film is graphene, which is known for its high conductivity. Herein, chemiresistive sensors based on a few layer graphene transducing film have been employed for the detection of metal cations, namely copper, silver, lead, and mercury. The films were functionalized with molecules specific to each cation to ensure selectivity. Charge transfer between the metal-molecule complex and the few layer graphene film drives the sensing mechanism. An investigation was also made into the efficient selection of sensor molecules to be used for functionalization by observing four different phenanthroline derivatives. This was done to allow for a smarter way to select sensor molecules. The work presented in this thesis suggests that the detection of metal cations using these few layer graphene based chemiresistive sensors is a viable pathway towards cheap online water quality monitoring.