Interaction of an Oxa- and Thiacarbocyanine Dye and Silver Halide Nanoparticles Synthesized in a Microemulsion System†

Silver halide particles were synthesized in a water-in-oil microemulsion consisting of AOT (sodium bis 2-ethylhexylsulfosuccinate)/n-heptane/water. The study of the interaction of an oxa- and a thiacarbocyanine with the particles suggested that only the thiacarbocyanine was adsorbed. To determine the site of adsorption of the thiacarbocyanine, the influence of the particle charge on the adsorption was investigated. The adsorption of the 1,1‘-sulfopropyl-5,5‘-dichloro-9-ethyl thiacarbocyanine occurs by the interaction between the ring sulfur atom and the silver ion in the case of silver bromide and by the interaction between the nitrogen atom and the chloride ion in the case of silver chloride. NMR experiments have shown the adsorption of water and methanol molecules on the particles. Finally, stationary and time-resolved fluorescence measurements indicate a quenching effect of the dye fluorescence by the particles, suggesting that the dye molecules could be suitable for the spectral sensitization.