Rapid on-site colorimetric determination of drinking water safety in the developing world

Abstract

The purpose of this thesis is the development of sustainable colorimetric sensors for the detection of toxins in aqueous media. These sensors are based on azulene and guaiazulene, two molecules with unique optical and chemical properties.

Due to natural and man-made processes, many drinking water reservoirs in developing countries have been contaminated with toxins such as mercury, lead, fluoride or arsenic. The areas affected can be very remote and difficult to access. The affected population may not have the economic means to check the safety of their water by conventional methods. There is subsequently a need for cheap and easy-to-use sensors that are highly selective and sensitive. Colorimetry is the ideal technique for this purpose as the chemosensors can be synthesised from cheap organic molecules and the signal is easy-to-read and does not require further instrumentation apart from the human eye.

A selective fluoride sensor was synthesised using boronic esters as sensing element. The sensor was able to work in real samples of water contaminated with fluoride thanks to the addition of a surfactant.

A family of azulene- and guaiazulene-based mercury sensors using hydrocarbon chains containing sulfur atoms as sensing element was developed. These molecules showed excellent selectivity towards mercury (with copper as the only significant interference) and gave a clear signal -a colour change from blue to orange- in mixtures of organic solvents and water.

A mercury sensor was developed, based on the conversion of dithiane into aldehyde. The clear colour change, from blue to red, was observed only after the addition of mercury or silver. This sensor worked in mixtures of organic solvents and water, but also in 100 \% aqueous media when accompanied by a surfactant.

Azulene derivatives containing DPA-Zn groups were synthesised as arsenate sensors. They failed at detecting arsenate, however, an increase of fluorescence was observed when they were in the presence of ADP. After this, they were developed as selective fluorescent ADP sensors.

Date of Award	19 Feb 2020
Original language	English
Awarding Institution	University of Bath
Supervisor	Simon Lewis (Supervisor), Tony James (Supervisor) & Jannis Wenk (Supervisor)