The monitoring of pH and free chlorine concentration in drinking water is important for
water safety and public health. However, existing laboratory-based analytical methods are
laborious, inefficient, and costly. This thesis focuses on the development of an easy-to-use,
sensitive, and low-cost drinking water quality monitoring system for pH and free chlorine.
An inkjet printing technology with a two-step thermolysis process in air is developed to
deposit palladium/palladium oxide (Pd/PdO) films as potentiometric pH sensing electrodes.
The redox reaction between PdO and hydronium ions generates the sensor output voltage.
A large PdO percentage in the film provides a high sensitivity of ~60 mV/pH. A defect-free
Pd/PdO film with small roughness contributes to a fast response and a high stability.
When the Pd ink is thermalized in low vacuum, the deposited Pd/PdO film shows a bilayer
structure. The residual oxygen in the low vacuum environment assists the decomposition
of organic ligands for Pd to form a thin and continuous layer beneath submicron Pd
aggregates. The oxidized bilayer film behaves as a temperature sensor with a sensitivity of
0.19% resistance change per °C, which can be used to compensate the sensed pH signals.
Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is drawn by hand
to form a free chlorine sensor. Free chlorine oxidises PEDOT:PSS, whose resistivity
increment indicates the free chlorine concentration in the range of 0.5-500 ppm. Also, we
simplified an amperometric free chlorine sensor based on amine-modified pencil leads. The
simplified sensor is calibration-free, potentiostat-free, and easy-to-use.
The pH, temperature, and free chlorine sensors are fabricated on a common substrate and
connected to a field-programmable gate array board for data processing and display. The
sensing system is user-friendly, cheap, and can accurately monitor real water samples. / Thesis / Doctor of Philosophy (PhD) / Sensitive, easy-to-use, and low-cost pH and free chlorine monitoring systems are important
for drinking water safety and public health. In this thesis, we develop an inkjet printing
technology to deposit palladium/palladium oxide films for potentiometric pH sensors and
resistive temperature sensors. The different electrical and electrochemical properties of the
palladium/palladium oxide films are realized by creating different film morphologies using
different ink thermolysis atmospheres. The developed pH and temperature sensors are
highly sensitive, fast in response, and stable. For free chlorine sensors, a hand drawing
process is used to deposit poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), which
is an indicator for the free chlorine concentration over a wide range. We also developed a
calibration-free free chlorine sensors based on modified pencil leads. Such a free chlorine
sensor is integrated with the pH and temperature sensors, and an electronic readout system
for accurate on-site drinking water quality monitoring at low cost is demonstrated.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/21465 |
| Date | January 2017 |
| Creators | Qin, Yiheng |
| Contributors | Howlader, Matiar M. R., Deen, M. Jamal, Haddara, Yaser M., Electrical and Computer Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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