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Keywords:

  • sensor;
  • Langmuir–Blodgett film;
  • chromoionophore;
  • crown ether;
  • complex formation;
  • stability constant;
  • absorbance;
  • water;
  • metal cation;
  • silver;
  • mercury;
  • lead;
  • barium

Abstract

Langmuir–Blodgett films built up from an amphiphilic derivative of benzothiazolium styryl dye containing a 1,10-dithia-18-crown-6 ether group have been found to complex with ‘soft’ polarisable ions such as Ag+ and Hg2+ in water. The films exhibited high sensitivity (stability constant of complex formation K ≈ 105 M−1) and high selectivity (e.g. K(Ag+)/K(Pb2+)> 105) compared with aqueous solutions of similar ionophores. This was attributed to the predominant formation of complexes with ligand–cation stoichiometries of 2:1 in the films.