Langmuir-Blodgett (LB) films of 1-methyl-1'-octadecylquinocyanine bromide,
iodide and perchlorate were prepared from subphases containing NaClO4, KBr
and/or KI. Each sample consists of an arachidic cadmium layer and about 100
cyanine dye layers on a Si substrate. Anions incorporated into the film as
counter ions from the subphase were analyzed by particle induced X-ray emi
ssion (PIXE) using a 2.5 MeV He2+ beam. It was found that the dissociation
of the cationic dye molecule in the monolayer at the air/water interface le
ads to the substitution of counter anions of the dye molecules, and the sub
sequent incorporation of the counter anions in the LB films. Some of the di
ssociation constants of cyanine halide dyes were estimated. (C) 2000 Elsevi
er Science B.V. All rights reserved.