Optical properties in Langmuir–Blodgett films of crystal violet dyes adsorbing cyanine dyes

Langmuir–Blodgett (LB) films of crystal violet (CV) dyes incorporating cyanine (Cy) dyes (CVCy LB films) have been prepared by the diffusion–adsorption LB method, and the optical properties have been investigated. In the photoluminescence (PL) spectrum of the CVCy LB films, a weak, narrow peak at around 470 nm and an intense peak at around 700 nm were observed, which were caused by the Cy and the CV dyes, respectively. The PL peak at about 470 nm became more intense as the irradiation time of the laser excitation light increased. The PL peak initially appearing at about 700 nm, broadened and moved to lower wavelength with increasing irradiation time. CV/DSACy LB heterofilm of the CV LB film without Cy dyes on distearyldimethylammonium bromide (DSA) LB film with adsorbed Cy dyes (DSACy LB film) was also prepared for the comparison. The absorption spectrum was similar to that of the CVCy LB film. On the contrary, in the PL spectrum of the CV/DSACy LB hetrofilm, the peak at around 470 nm was more intense and the peak at around 700 nm was weaker. From the results, the PL properties of the CVCy LB films were thought to be related to the energy transfer between the CV and the Cy dyes.