Tetrapyrazinoindoloporphyrazine Langmuir-Blodgett films

We fabricated tetra(5-n-nonyl-8-tert-butyl-2,3-pyrazino[2,3-b]indolo)porphyrazinato copper(II) (Cu-Pc-C8) Langmuir-Blodgett (LB) films. We further investigated the influence of arachidic acid (AA) as a transfer promoter, as well as the effect of dipping speed, on the deposition of the films on hydrophilic and hydrophobic substrates. In the case of pure Cu-Pc-C8 LB deposition on a hydrophilic substrate, the transfer ratio was close to one for up-stroke depositions, but the previously deposited film was peeled off and re-spread onto water at down-stroke depositions. Whereas the stability of the Cu-Pc-C8 LB films was not improved by AA addition on hydrophilic substrates, the deposition of Cu-Pc-C8 was significantly improved by the presence of AA on a hydrophobic substrate. The AA-assisted deposition had transfer ratio of close to 1 and was essentially stable up to 10-layer depositions. Comparison of the UV-visible spectrum of a Cu-Pc-C8/AA LB film with that of Cu-Pc-C8/AA solution in dichloroethane revealed that the Soret and Q bands for the Cu-Pc-C8/AA LB film were broadened and red-shifted due to the aggregation of phthalocyanines upon assembly in the LB film.