Fibre optic sensing techniques for the detection of lead (II) ions

Guillemain, Henri (2009). Fibre optic sensing techniques for the detection of lead (II) ions. (Unpublished Doctoral thesis, City University London)

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Abstract

Lead is an element with harmful effects to man and whose uses are being increasingly subject to legislations. This thesis describes the incorporation of two lead-sensitive reagents in different fibre optic sensing configurations. The reagents were carefully selected for their response towards lead. A probe was built for each reagent and a sensor system designed, constructed and tested with each probe followed by analysis of the experimental data obtained from them.

The first reagent is a chromogenic dye whose absorption spectrum changes in the presence of lead ions. In this work, a reflectance-based probe is built and tested to exploit this feature. A robust referencing technique based on the performance of the probe is developed that allows the sensor to operate amid unstable conditions.

The second reagent is a fluorophore whose fluorescence mechanism and affinity to lead ions are explained in detail. Based on its binding properties with lead, the sol-gel matrix is selected to encapsulate this reagent and a probe is thus constructed but in subsequent tests, no response to lead ion is detected. A hypothesis is put forward to explain the lack of reaction between lead and the fluorophore in its entrapped environment.

As a result, the fluorophore is then utilised in solution where its characteristics have already been established and a capillary probe which exploits the capillary effect for its operation is constructed and evaluated. Existing analytical techniques are reviewed in this work and compared to fibre optic sensors whose various sensing configurations are then described. The instrumentation and measurement techniques used throughout this work are also discussed.

Item Type: Thesis (Doctoral)
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
Divisions: School of Engineering & Mathematical Sciences > Engineering
URI: http://openaccess.city.ac.uk/id/eprint/12440

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