Kisholoy Goswami

Fiber-optic fluorescence carbon dioxide sensor for environmental monitoring

Fiber-optic sensors were developed for monitoring dissolved carbon dioxide in water samples in the 0 to 900 ppm concentration range. A pH-sensitive fluorescent dye (HPTS) was reacted with a cationic quaternary ammonium salt to form an ion pair which was electrostatically bound to the surface of particles of aminocellulose which then were dispersed into a gas-permeable silicone polymer. The green fluorescence of the base form was monitored using a fiber optic fluorometer. The use of the aminocellulose enhanced the stability and lifetime of the sensor and also increased the fluorescence of the sensor membrane because the particles act as scattering centers. The characteristics of the sensors are described with respect to dynamic range, reproducibility, long-term stability and temperature dependence.

Fiber Optic Chemical Sensor For The Measurement Of Partial Pressure Of Oxygen

The estimation of partial pressure of oxygen in gaseous samples, aqueous samples and biological fluids has very important ramifications in environmental, medicinal and analytical chemistry. We have devised a fiber optic chemical sensor for the determination of oxygen concentration based on the dynamic luminescence quenching of a fluorophore bx oxygen. Ruthenium(II)tris(bipyridine), [Ru(bpy)3]4+, has been employed in our studies as the oxygen sensitive dye. The emission of Ru(bpy)32+ is centered at 610 nm and has a lifetime of 685 ns in argon purged aqueous solution. Our fiber optic chemical sensor consists of a custom built spectrometer containing argon ion laser light source, detector and associated electronics. A fiber optic cable is employed to guide light into and out of the spectrometer. A known amount of the sensing material in solution is used in a specially designed cell which has a gas permeable membrane at one end and the other end is coupled with the long cable to the spectrometer. Further research is being continued in improving the sensor chemistry and its dynamic detection range.

Development Of A Fiber Optic Chemical Sensor For The Monitoring Of Trichloroethylene In Drinking Water

A fiber optic chemical sensor (FOCS) has been developed for the monitoring of trichloroethylene in drinking water. The sensor is based upon refractive index changes, where the amount of light refracted varies as the analyte interacts with the coated surface. Response is specific for TCE, reversible, and can be used for monitoring TCE in the vapor or aqueous phase.

In-situ monitoring for hydrocarbons using fiber optic chemical sensors

The use of FOCS for environmental applications, namely, for monitoring spills of HC or leaking underground HC storage tanks, is discussed. The current FOCS design comes in two configurations: the field unit, permanently installed at one or more monitoring sites, and connected to a central monitoring station, and the hand-held unit, designed for rapid on-site evaluation. The sensors performance in HC vapor at 100 percent relative humidity and at 20 C, and at the vapor-water interface is illustrated.

A Fiber Optic Chemical Sensor For Carbon Dioxide Dissolved In Sea Water

A fluorescence based fiber optic chemical sensor has been developed to measure the concentration of dissolved carbon dioxide in sea water. The sensor configuration involves a single strand of step index multimode silica fiber, one end of which is terminated with a conical ferrule connector while the other end is incorporated with a special reservoir cell. This special cell contains a CO2 permeable membrane at the tip. An aqueous solution of 8-hydroxy-1,3,6- pyrenetrisulfonic acid-trisodium salt has been employed as the sensing reagent. CO2 dissolved in water permeates through the membrane into the sensing solution and alters its pH causing modulation in the emission intensity of the dye. Linear response is observed for this sensor over 0-600 ppm range. Measurements are done with a custom made filter fluorimeter.