Optical properties of cresyl violet–polymer composites for quantification of humidity and ammonia gas in ambient air

Abstract

The optical spectra of various cresyl violet–polymer composites have been investigated. For dye–poly(ethylene oxide) the spectrum was sensitive to the concentration of ammonia in air, i.e. the absorbance at 600 nm decreased but at 460 nm it increased with increasing ammonia content in the air. The ammonia molecule interacts chemically with the monocationic form of the dye and forms a weak charge-transfer complex. For the dye–Nafion composite, the absorbance at 610 nm increased as the humidity increased. An increase in the water content of the film induced the formation of lower protonated forms of the dye trapped within the Nafion matrix.