HIGHLY SENSITIVE CHITOSAN-BASED OPTICAL FLUORESCENT SENSOR FOR GASEOUS METHYLAMINE DETECTION.

An optical fluorescent sensor based on a chitosan thin film co-doped with Eu³⁺ and a bromothymol blue pH indicator has been developed. Near-UV to visible (350-400 nm) excitation of the europium (III) chelate complexes with 1,3-diphenyl-1,3-propanedione exhibits a typical lanthanide emission with maximum at 618 nm. Luminescent spectra of the Eu³⁺ complex were found to be insensitive to the presence of methylamine gas. Therefore, bromothymol blue, a non-fluorescent pH indicator with an absorbance maximum of deprotonated form close to the Eu³⁺ emission band was added to the film to provide a non-fluorescent reversible response to different methylamine concentrations, which can be detected by measuring the Eu³⁺ emission. [ABSTRACT FROM AUTHOR]