Abstract:
This project involved the continued development of a unique sensing platform capable of producing a visible optical signal in the presence of volatile organic compounds. Rugate porous silicon samples appear coloured to human eye under white light illumination, and this colour can change upon incorporation of material into the pores. This has been used as the basis of gas and sensors in this research. In order to achieve this goal, validation of a vapour dosing system was completed for later use in the vapour dosing research. The performance of the vapour dosing system was examined for performance parameters such as vaporisation temperature, and dosing and purge phase timing, and development of calibration curves for all intended analytes was completed. To characterize the pore wall surface-composition gradient, porous silicon samples were exposed to titrations of ethanol in water. The optical responses of suitable samples were subsequently monitored during exposure to analyte vapours. Spectral imaging, standard RGB camera, and a raw Bayer image camera mode (Mode 0) were examined to assess suitability for detection of porous silicon sensor response during vapour dosing experiments. Porous silicon samples were analysed by examining the change in calculation variables: the change in rugate peak wavelength, and two measures of change in green and red response. Results demonstrate the ability of porous silicon rugate sensors to detect of analyte vapours over the concentration range 100 - 800 mg/m³. Spectral imaging of porous silicon sample produced a quantifiable change in rugate peak wavelength upon exposure to ethanol, decane, heptane, toluene and 2-butanone vapours. In comparison, RGB, and Mode 0 imaging analyses demonstrated a reduced average response, which was confounded by the variation in background noise for the sensor, suggesting that either these analyses, or these calculation variables may not be suitable for analysis of low vapour concentrations of ethanol, heptane, toluene and 2-butanone. However, for both RGB and Mode 0 analyses, the derived variables did demonstrate a clear response during decane vapour dosing across this concentration range. This suggests that these imaging modes, and/or variables may be suitable for the detection of decane at these levels