Mixed LB film

The suppression of C60 crystallite formation in mixed LB films was attempted by mixing C60 and amphiphilic electron donor compounds [259]. Observation of the C60 LB film transferred horizontally by TEM clearly showed 10-40-nm-size crystallites. The diffraction pattern gave an fee lattice with unit cell length 1.410 nm. Examination of the mixed films with arachidic acid by TEM showed extensive crystallite formation. Mixed LB films of three different amphiphilic derivatives of electron donors with C60 were examined. One particular derivative showed very little formation of C60 crystallites when LB films were formed from monolayers of it mixed with C60 in a 1 2 ratio, while two others reduced C60 crystallite formation but did not eliminate it. 

Molar fraction dependent effident energy transfer in mixed LB films... 

Figure 14 Fluorescence intensity ratio of acceptors at 417 nm and donors at 360 nm plotted against the molar fraction of MP-CUA in mixed LB films with (O) PA and ( ) AA The dotted line shows the calculated dependence by Forster energy transfer. 

Figure 15. Schematic representation of mixed LB films including carbazolyl donors ) and a small amount of acceptors (4SP) with (a) higher and (b) lower fc values. °...

Amplified photochemical quenching of carbazolyl fluorescence was observed in mixed LB films containing pure CUA and long-chain fatty adds [49,51], A pure CUA was synthesized from 2-nitrobiphenyl and 11-bromoundecanoic add methyl ester as reported previously [49,50]. Two monolayers of mixtures of CUA (fc= 0.02 - 0.50) and PA were deposited on five monolayers of cadmium arachidate at 15°C and 20 mN m 1 at pH 6.3. 

Upon irradiation of an IPCT band in degassed condition (Xex> 365 nm), the colour of both LB films changed from pale yellow to blue. The UV/vis absorption spectrum after irradiation is shown in Figure 25, which is characteristic of 4,4 -bipyridinium radical cation monomer[108]. Coloured species photogenerated in mixed LB films of AV2+/AA or HV2+/AA systems decayed almost exponentially in the dark in vacuo with a lifetime of about 4 h at 20 °C [93,94]. The lifetime of 4,4 -bipyridinium radical cations in LB films was almost... 

Figure 25 Absorption spectrum of mixed LB films (60x2) of HV2+ and AA (1 4) after excitation (>365 nm) in degassed condition at 20°C for 10 min using non-irradiated LB films as a reference. 

The latter was bleached after a subsequent independent irradiation at 420 nm for 30 h. The same selective photobleaching could be obtained by irradiating the same kind of mixed LB film at 420 nm for 30 h the 420 nm peak was bleached but no significant effect could be observed on the 476 nm peak the latter was bleached by irradiating the film at 467 nm for 30 h. The observed bleaching phenomenon was probably caused by the disrupture of the H-type molecular aggregates followed by the photochemical degradation of the monomers. 

A. Molar Fraction-Dependent Efficient Energy Transfer in Mixed LB Films... 

Figure 9 Fluorescence spectra of mixed LB films of pure CUA and PA with fc = 0.25 during irradiation in argon at 290 nm and 2.5 mW cm-2.

Figure 11 Schematic representation of the energy transfer to a trap site, formed during irradiation, depending on the molar fraction of CUA in mixed LB films with long chain fatty acids which are not shown for simplicity.

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