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20 February 2017 A pH sensing system using fluorescence-based fibre optical sensor capable of small volume sample measurement
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Proceedings Volume 10110, Photonic Instrumentation Engineering IV; 101101C (2017)
Event: SPIE OPTO, 2017, San Francisco, California, United States
In this work, a low cost optical pH sensing system that allows for small volume sample measurements was developed. The system operates without the requirement of laboratory instruments (e.g. laser source, spectrometer and CCD camera), this lowers the cost and enhances the portability. In the system, an optical arrangement employing a dichroic filter was used which allows the excitation and emission light to be transmitted using a single fibre thus improving the collection efficiency of the fluorescence signal and also the ability of inserting measurement. The pH sensor in the system uses bromocresol purple as the indicator which is immobilised by sol-gel technology through a dip-coating process. The sensor material was coated on the tip of a 1 mm diameter optical fibre which makes it possible for inserting into very small volume samples to measure the pH. In the system, a LED with a peak emission wavelength of 465 nm is used as the light source and a silicon photo-detector is used to detect the uorescence signal. Optical filters are applied after the LED and in front of the photo-detector to separate the excitation and emission light. The fluorescence signal collected is transferred to a PC through a DAQ and processed by a Labview-based graphic-user-interface (GUI). Experimental results show that the system is capable of sensing pH values from 5.3 to 8.7 with a linear response of R2=0.969. Results also show that the response times for a pH changes from 5.3 to 8.7 is approximately 150 s and for a 0.5 pH changes is approximately 50 s.
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Shijie Deng, Michael A. P. McAuliffe, Urszula Salaj-Kosla, Raymond Wolfe, Liam Lewis, and Guillaume Huyet "A pH sensing system using fluorescence-based fibre optical sensor capable of small volume sample measurement", Proc. SPIE 10110, Photonic Instrumentation Engineering IV, 101101C (20 February 2017);

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