Development of oxygen and pH optical sensors using phase modulation technique.

In this paper we report the use of phase sensitive fluorometry to obtain preliminary results from micrometer-sized optical fiber oxygen sensors and a pH sensitive dye. Micrometer-sized (100 mu m and 10-20 mu m) oxygen sensors were prepared on the distal tip of an optical fiber using a dip-coating procedure to immobilize Tris(4,7-Diphenyl-1,10-Phenanthroline)Ru(II) Chloride (Ru(dpp)) within a sol-gel matrix. These optodes exhibit excellent performance towards both gaseous and dissolved oxygen. The sensor's intensity based excitation and emission spectra, as well as phase fluorometric measurements, were collected utilizing a back-detection set-up. These micro-optodes have many desirable features for minimally invasive bio-medical applications arising from the potential of miniaturization. Carboxynaphthofluorescein (CNF) solutions are shown to exhibit pH-dependent fluorescence decay times and analysis of the phase and the modulation values indicate a strong pH dependence in the physiological range, thus identifying this water-soluble dye as an attractive candidate for optical pH measurements in biomedical samples.