OPTICAL SENSOR FOR MOISTURE AND AMMONIA GAS IN AMBIENT USING PH INDICATOR POLYMER COMPOSITE FILMS

For calcein-poly (ethylene oxide) composite, the fluorescence with lambda(max) similar to 540 nm is enhanced by sorption of water and hardly influenced by ammonia concentrations less than about 50 ppm. The absorbance at 510 nm of calcein-poly (vinyl pyrrolidone) composite increases with increasing ammonia concentration and humidification induced an enhancement of the absorbance at lambda(max) = 480 nm. For calcein-poly(vinyl pyridine) composites, the absorbance at 510 nm is influenced both by humidity and ammonia. For bromocresol purple-poly(vinyl pyrrolidone) composites, the absorbance (Abs) at lambda(max) = 605 nm increases with ammonia concentration and is expressed as Abs = K[InN][%RH][log C-NH3]. Under ammonia free conditions, the absorbance at lambda(max) = 605 nm remains almost constant when the humidity is less than 60 %RH. By selecting proper sensing materials, it is possible to determine both humidity and low levels of ammonia concentration in ambient air.