Stable and reliable operation of an optical sensor for pH monitoring is important for many industrial applications. This dissertation reports a series of studies on the development of novel and highly sensitive fibre optic sensors which are based on wavelength, instead of intensity changes and the development of thin film optical fibre working combinations for effectively enhancing the durability and value of the sensor probe. Several novel optical fibre sensors were fabricated and evaluated in this work. In order to measure the pH of a solution using optical methods, the sensor probes were prepared using layer~by-layer deposition techniques, a simple and versatile method to deposit a sensitive thin film i.e. active pH indicators on such optical fibre-based devices. In further work, the selection of a charged and water-soluble. pH indicator which introduces the highest wavelength shift, while varying the pH of the media, was investigated since the wavelength shift was considered as the basis of the sensitivity index. Brilliant yellow (BY) was applied as an indicator because of its greater wavelength shift with pH change compared to the use of other indicators. Poly (allylamine hydrochloride) (P AH) was also used as a crosslinker. To this end, the layers of BYIPAH were deposited on the bare silica core optical fibre using the layer-by-Iayer technique. The research was then developed to optimize the design factors that have an important effect on the sensitivity of the device. Utilizing V-shaped fibre with small radius which coated six bilayers of (BY IP AB) prepared from a polyion solution of low concentration was seen to provide a sensor with wider range of sensitivity which presents a highly sensitive device working over a smaller pH range offering higher resolution.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:612698 |
| Date | January 2014 |
| Creators | Raoufi, N. |
| Publisher | City University London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://openaccess.city.ac.uk/3668/ |
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