Fabrication and characterization of electrochemical ammonia and nitrite sensors for water quality monitoring

Franco, Fabiane Fantinelli (2023) Fabrication and characterization of electrochemical ammonia and nitrite sensors for water quality monitoring. PhD thesis, University of Glasgow.

Abstract

High levels of dissolved inorganic nitrogen (NH3 and NO2 - /NO3 - ions) in water can lead to eutrophication and negatively impact human health and aquatic ecosystems, making it an important parameter to monitor. The development of affordable, continuous sensors for NH3 and NO2 - /NO3 - ion detection in water has been an ongoing challenge due to the limitations and high cost of standard monitoring techniques. Voltammetric sensors have been presented as an alternative, however, achieving high sensitivity while maintaining long-term stability and low/no signal interference remains a significant challenge. Moreover, the environmental impact of the sensor lifecycle and the materials used during the fabrication steps are crucial considerations when designing new sensors for continuous use in water bodies but are often not investigated. In this manner, printed voltametric sensors are a good alternative to standard monitoring techniques due to their versatility and costeffective nature. The work described here focus on two main aspects of the development of printed sensors: the electrode material choice and the synthesis of new sensing material for the detection of NH3 and NO2 - ions. In the electrode material aspect, screen-printing and laser induced graphene (LIG) techniques were used to develop new sensors and to investigate the effect of silver and carbon materials on the electrode tracks. It was inferred that silver, a material that is commonly used as a conductive paste in screen-printed sensors, can interfere with the electrochemical response of the sensor. In this manner, carbon electrode tracks were explored as a more stable and sustainable alternative. To improve the conductivity of the track, LIG electrodes were developed and compared to carbon screen-printed electrodes (SPEs). The LIGs demonstrated improved stability and sensitivity compared to the SPE in the oxidation of NO2 - ions, revealing they can be an alternative to disposable carbon-based SPEs. In the sensing material aspect, materials that are easy to incorporate with current sensor fabrication techniques were prioritised. Different metal oxides were explored to detect NH3, a challenging parameter to detect due to effects of pH and temperature on the ion dissociation. From the materials synthesised, the Cu-BDC metal-organic framework presented the best performance, although further improvements on material stability and reproducibility are necessary. For the NO2 - ion monitoring, the unmodified LIGs showed enhanced sensitivity and fast detection, important parameters to achieve when detecting unstable ions such as NO2 - . Furthermore, the use of unmodified LIGs facilitate the fabrication of NO2 - sensors. Overall, by researching the materials employed in both the electrode pathway and the sensing electrode, improved printed electrochemical sensors were achieved.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Colleges/Schools: College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
• Supervisor's Name: Smith, Professor Cindy and Gauchotte-Lindsay, Professor Caroline
• Date of Award: 2023
• Depositing User: Theses Team
• Unique ID: glathesis:2023-83872
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 26 Oct 2023 10:02
• Last Modified: 20 May 2024 14:15
• Thesis DOI: 10.5525/gla.thesis.83872
• URI: https://theses.gla.ac.uk/id/eprint/83872