Spacer-Controlled Aggregation and Surface Morphology of a Selenacarbocyanine Dye on Gemini Monolayers

The adsorption and aggregation of a selenacarbocyanine dye (3,3-disulfopropyl-9-methyl-selenacarbocyanine, SeCy) onto Langmuir monolayers of a series of gemini amphiphiles with different methylene spacers were investigated. When the monolayers of the gemini amphiphiles were spread on the dye-containing subphase, the dye could be easily adsorbed and aggregated onto the monolayers through the electrostatic and π−π interaction. The dye formed complexes with gemini amphiphiles and stacked as J-aggregates in all the transferred multilayers, regardless of the structure of gemini amphiphiles. However, the surface morphologies of the complex monolayers showed a significant dependence on the spacer length of the gemini amphiphiles and the temperature of the subphase. Nanorods were observed for the complex films with spacer lengths ranged from 4 to 10 methylenes. With the temperature of the subphases increased from 20 °C to 30 °C, aligned longer nanofibers were formed instead. Although both the gemini amphiphiles a...