Tapered Optical Fiber Sensor for Detection of pH in Microscopic Volumes

• Main Authors: Ondřej PODRAZKÝ, Vlastimil MATĚJEC, Jan MRÁZEK, Tomáš MARTAN, an AUBRECHT, Ivan KAŠÍK
• Format: Article
• Language: English
• Published: IFSA Publishing, S.L. 2014-05-01
• Series: Sensors & Transducers
• Subjects: Optical sensor; Ph; Microfiber tip; Fluorescence; HPTS; Ratiometrc method.
• Online Access: http://www.sensorsportal.com/HTML/DIGEST/may_2014/Special_issue/P_SI_521.pdf

A compact and robust tapered optical fiber microsensor is presented for detection of pH in a range from 5.8 to 7.5 in sub-microliter volumes. The sensor is based on a pH transducer 8- hydroxypyrene-1,3,6-trisulfonic acid trisodium salt immobilized in a xerogel matrix onto the tip of a optical fiber taper with a tip diameter below 20 mm. The sol-gel method and two silicon alkoxides is used for preparing the matrix. A ratio of the fluorescence emission intensities measured at 518 nm after the excitation at 400 and 450 nm is used for evaluating the sensor response to pH. This ratiometric approach enables to reduce effects of ambient light, bleaching of the sensitive layer and geometry of the probe to the fluorescence signal and achieve the resolution of about 0.07 pH units.