Luminescence-Based Optical Fiber Chemical Sensors

Abstract

A scheme for the simultaneous determination of temperature and analyte concentration for application in luminescence-based chemical sensors is proposed. This scheme is applied to an optical oxygen sensor, which is based on the quenching of the fluorescence of a ruthenium complex. Temperature measurement is performed using the excitation radiation and an absorption long-pass filter. Preliminary results are presented that show the viability of an oxygen measurement that is independent of temperature and optical power level. The possibility of self-referenced temperature measurements with semiconductor nanoparticles is also investigated. In order to optimize the sensor design, several different optical fiber probe geometries for oxygen sensing are tested and compared, including different methods of coupling radiation 202 P. A. S. Jorge et al. into the optical fiber system. Polyvinyl alcohol (PVA) and polyacrylamide membranes are tested as supports for sensor immobilization in fiber-optical pH sensing devices in aqueous solution. Some results are presented that show the feasibility of using fiber-optical pH indicators for remote monitoring.

Improved fluorescence signal with tapered polymer optical fibers under side-illumination

“…These larger diameters can be obtained through the use of polymer optical fibers, since diameters as wide as 3 mm are commercially available. In our proposal, we use a tapered polymer optical fiber to improve the collection efficiency since the tapering of glass fibers has proved to be an useful method to increase a fluorescence signal [14,16]. Additionally, the direct excitation of the fluorophore without the use of the evanescent field guided by the fiber also provides an increase in the fluorescence signal, since the intensity of the incident light is higher than the provided by the evanescent field.…”

“…Therefore, to get a fluorescence signal with a good signal to noise ratio, it is important to use a high intensity excitation source and a high fluorophore concentration together with high collection efficiency from the emitted luminescence. For these kinds of sensors the collection efficiency of the fluorescence signal can also be improved through tapered fibers [16,17] or sandwiched-fibers, where a negative fiber is placed between two positive ones [18]. As for the excitation source, the usual configurations employ the evanescent wave of the guided light through the fiber or the backscattered luminescence from the fluorophore placed on the fiber tip.…”

Optical Fiber Sensing Using Quantum Dots

“…Later on, a similar principle was used to provide an oxygen sensor with a temperature reference [139]. In this case, a colored glass filter (GG455 –cut-off 455nm) from Schott was placed at the distal end of one of the fiber tips of a 50/50 fiber coupler (multimode fiber with 550/600 μm core/cladding diameters).…”

Characterization of tapered polymer optical fibers under side illumination for fluorescence sensing applications

“…The most used configurations to excite a fluorophore are based either on evanescent wave interaction or directly at the fiber tip, being the fluorescence signal gathered by the same fiber and guided to the detector [3]. In both cases, the fluorophore is attached to the fiber surface (either lateral surface or end surface) which renders the sensors useless when the outer medium acts as a solvent of the fluorophore.…”