Oxygen fluorescence quenching

The dye is excited by light suppHed through the optical fiber (see Fiber optics), and its fluorescence monitored, also via the optical fiber. Because molecular oxygen, O2, quenches the fluorescence of the dyes employed, the iatensity of the fluorescence is related to the concentration of O2 at the surface of the optical fiber. Any glucose present ia the test solution reduces the local O2 concentration because of the immobilized enzyme resulting ia an iacrease ia fluorescence iatensity. This biosensor has a detection limit for glucose of approximately 100 ]lM , response times are on the order of a miaute. 

Bergman I., Rapid-response atmospheric oxygen monitor based on fluorescence quenching, Nature 1968 218 396. 

A.K. McEvoy, C.M. McDonagh and B.D. MacCraith, Dissolved oxygen sensor based on fluorescence quenching of oxygen-sensitive ruthenium complexes immobilized in sol-gel-derived porous silica coatings, Analyst, 121(6) (1996) 785-788. 

Fluorescence quenching resulting from the collision of the analyte with a fluorescent compound (see Chapter 4). This method is particularly well suited to the detection of gases such as oxygen (dissolved in water or blood), SO2, H2S, ammonia, HC1, Cl2, chlorocarbons, etc. 

K. A. Hagaman and M. R. Eftink, Fluorescence quenching ofTrp-314 of liver alcohol dehydrogenase by oxygen, Biophys. Chem. 20, 201-207 (1984). 

The apphcation of an optical transducer based on the fluorescence quenching effect of oxygen was described by Preininger et al. [3]. Another interesting technique is represented by the use of the luminous bacterium Photobacterium phos-phoreum [34]. This device is based on the correlation of the intensity of luminescence to the cellular assimilation of organic compounds from the wastewater. 

Effective fluorescence quenching of polycyclic hydrocarbons by oxygen was observed by Terenin,45,46 who proposed a quenching mechanism according to which the overall result was the production of an electronically excited hydrocarbon-oxygen complex. 

Since the efficiency of fluorescence quenching of the sensitizer paralleled the oxidizability of the arene in a series of substituted alkyl benzenes, the reaction was thought to proceed through electron transfer followed by protonation and trapping of the radical by oxygen. 

The participation of the singlet states of dyes such as rose bengal (RB, tetraiodotetrachlorofluorescein, sodium salt) and MB during the sensitized oxygenation of amines was demonstrated by Davidson (40). Fluorescence quenching Stem-Volmer constants were reported for several amines, halide anions, and for 3-carotene and were consistent with charge transfer stabilization of an exciplex quenching intermediate. 

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