Reversible change between monomeric form and J-aggregate in vapor-evaporated merocyanine film

Merocyanine (MD 18) film prepared by vapor-evaporation formed J-aggregate (JA) by exposuring to dimethyl amine (DMA) aqueous vapor and/or soaking into aqueous solution containing various metallic ions. The reversible change between JA and monomeric/dimeric forms was observed by heat-treatment and acid treatment in HCl aqueous solution.