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Title: Response characteristics of thin film optical oxygen sensors
Author: Eaton, K.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2002
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The development of a simple, semi-reversible, colorimetric oxygen sensor based on the redox chemistry of 2,6-dichloroindophenol in the presence of fructose and tetrabutylammonium hydroxide is described. The sensor is colourless in the absence of oxygen, but gives a strong blue coloration in oxygen at >30 Torr and quantitative analyses are possible between 0 and 50 Torr. The second type of sensor examined is based on the oxygen quenching of luminescence emitted from polymer encapsulated: platinum octaethylporphyrin, palladium octaethylporphyrin or tris(4,7-diphenyl-1,10-phenanthroline) ruthenium (II). Several means of collecting data from such sensors are evaluated. Gated fluorimeters can give erroneous data unless the natural and quenched lifetimes of the lumophores lie in the range 200 μs - 4ms. Several factors affect the oxygen sensitivity of these films including humidity, which depresses the sensitivity by 42% when using ethyl cellulose as the encapsulating matrix and by 14% when using cellulose acetate butyrate. No significant humidity effect is observed when using silicones, polyvinylchloride or polystyrene. The non-linear relationship between quenching efficiency (I0/I or τ0/τ) and partial pressure of oxygen observed in these films was examined and a simple Freuchlich power law shown to fit response data from six sensors which show a 600 fold variation in oxygen sensitivity. The non-linearity is a result of a site distribution in the sensor film and this has been further investigated using initial rate studies and distribution modelling. Such studies indicate that simulated data from a simple uniform distribution in the quenching rate constant (and/or oxygen solubility) gives good fits to experimental decay curves from the six different sensing systems examined. The required model parameters are easily accessible from experimental data and consistent with those calculated for diffusion controlled quenching by oxygen.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available