METAL-ION SENSOR BASED ON DIOCTADECYLDITHIOCARBAMATE-METAL COMPLEX INDUCED ENERGY-TRANSFER

The complex formation of dioctadecyldithiocarbamate (DOTC) monolayers at the air-water interface by reaction with metal ions from the subphase was investigated using surface pressure/area (pi/A) and surface potential/area (DELTA-V/A) isotherms and reflection spectroscopy. Metal ion complexation leads to metal specific changes in the pi/A and DELTA-V/A isotherms and also to either a shift of the DOTC reflection spectrum or to the appearance of a new band in the UV-vis reflection spectrum. These properties were utilized for the construction of a CU2+ -ion sensor based on the Langmuir- Blodgett (LB) technique. The sensor uses energy transfer (Forster type) from fluorescent oxacyanine dye layer to a DOTC layer with the complexing group in contact with the aqueous phase containing the CU2+ ions. Copper complexes with the specific absorption band were formed instantaneously at the solid-liquid interface of the LB film. The quenching of the fluorescence of the oxacyanine layer increases with the surface density of the copper complexes in the top layer of the LB film,