Spectroscopic studies of Langmuir–Blodgett films of 3,4,9,10-tetra(heptyloxycarbonyl)perylene and its mixtures with a liquid crystal

Spectral properties of naphthalimide dyes mixed with 4-heptyl-4′-cyanobiphenyl (7CB) in Langmuir-Blodgett films

“…Similar observation was made for dyes 1−12 mixed with 7CB in the Langmuir films [10,20], although the molecules were aligned more vertically with respect to the water sur− face than to the quartz surface. This indicates that during the transfer of the floating monolayer from the air−water inter− face onto the solid substrate the molecular rearrangement can take place, as it was also previously reported for other compounds [12,28,30,34].…”

“…In these case, the exciton is delocalized over several molecules due to the large intermolecular interactions. Therefore the excimer creation was observed also in the LB films, where the high dye concentration and molecular or− dering favour the aggregation process [12,18,[27][28][29][30][31]. The excimer states decay with a much smaller radiative effi− ciency as compared to monomer states and this effect is re− ferred as to "dye self−quenching" [25,26].…”

Intermolecular interactions in Langmuir-Blodget films of liquid crystalline perylene derivatives

“…6(b) and 7(b)]. As the concentration of the dye rises, small broadening of the fluorescence band at the red side appeared, especially for the dyes with short alkyl chains (1-3), similar as it was observed for the monolayer of pure 3,4,9,10-tetra-(n-alkoxy--carbonyl)-perylenes on quartz slides [8][9][10]14,15]. Thus, taking into account the shape of the fluorescence spectrum we can suggest that Y-type emission with only small contribution of E-type emission occur for LB films made of one layer of dyes 1-6 and their mixtures with arachid acid.…”

“…In these spectra we observe the structureless broad fluorescence band with the maximum around 550-600 nm and, in some cases, small shoulder at shorter wavelength (»520 nm). A shape of the band depends on the length of the alkyl In our previous papers [8][9][10]14,15] we reported about the fluorescence spectra of LB films formed of dyes 2-6, pure and mixed with two liquid crystals, and supposed that the main emitters in LB films are excimers, which originate from interaction of neighbouring molecules after one is excited. Benning et al [2] have found that the maximum of the excimer fluorescence band of 3,4,9,10-tetra-(n-alkoxy--carbonyl)-perylenes in the crystalline state appears at 582-600 nm (depending on the alkyl chain length).…”

Spectral and orientational properties of new group of naphthalene derivatives of bicarboxylic acid in liquid crystal 7CB

“…The fluorescence measurements were carried out by using a photon-counting spectrofluorimeter built in our laboratory and described in detail in Ref. 11. The exciting light was the 436 nm line from a high-pressure mercury lamp.…”