Detector Development for Particle Physics and Applications to Environmental Monitoring

This thesis reports on the development of a novel device, called PlomBOX, employing a CMOS
sensor and lead-sensing bacteria to assay lead in drinking water, up to the World Health Organisation (WHO)’s upper limit of 10 ppb. As a first step, a scientific CMOS was used to demonstrate the capability of detecting gamma energies in an Si detector from a lead-210 (210Pb) sample through calorimetry methods. While this technique is promising for dosimetry applications, it is not able to reach the WHO level in sensitivity. A second step was to explore how the sensitivity range of any device could be improved by increasing the concentration of the substance of interest in a sample. Lead doped water samples were boiled to explore if an increase in heavy metal concentration was observed. This technique was able to retain 99 ± 9% of 210Pb, allowing for an increase of its concentration. The third step involved the development of the PlomBOX. The project followed three development paths: a) Certain bacteria can change colour when in the presence of lead. A genetically modified strain of Escherichia coli sensitive to lead concentrations up to 10 ppb was developed together with a team of biologists. This constitutes the biosensor that emits colour in proportion to the presence of lead. b) Bacteria response is imaged using a microprocessor (ESP32) with a camera module. This constitutes the optical metrology component of the PlomBOX. c) Data acquisition and control of the PlomBOX is achieved through a Bluetooth connection with the
PlomApp, a custom-developed mobile phone application. Data are sent from the PlomApp to a database where a bespoke automated analysis software provides a result of the lead concentration in a sample of water. A full description of the experimental set up and analysis software is provided and results of the first in situ assay are discussed.