| Abstract
| - We present here a study of the effects of surface modification on the efficiency of transfer of ultrathinLangmuir−Blodgett films of rodlike aggregates of the phthalocyanine (Pc) (2,3,9,10,16,17,23,24-octakis((2-benzyloxy)ethoxy)phthalocyaninato)copper (1) to gold and silicon substrates. These surface modificationsimpact on (i) the molecular orientation of the individual Pcs within the rodlike aggregates, (ii) the coherenceof the aggregates (providing for coherence lengths of some Pc rods of over 100 nm), and (iii) the opticalanisotropy and the overall uniformity and lack of pinholes in Pc bilayer films, on the 100 μm distance scale.Methyl-terminated and phenyl-terminated surface modifiers were added to both Au and Si surfaces throughthiol and silane chemistries, respectively. The phenyl-terminated modifier for Au surfaces, benzyloxyethanethiol, 2, mimics the side chain composition of Pc 1. Both methyl- and phenyl-terminated modifiersproduced hydrophobic surfaces, as revealed by high water contact angles. FT-IR spectroscopy and AFMcharacterization of horizontally transferred bilayer LB thin films of 1 consistently showed higher degreesof coverage on the surfaces with phenyl-terminated modifiers. Reflection−absorption FT-IR of 1−5 bilayerfilms on modified Au substrates showed that the average tilt angle (ψ) and rotation angle (θ) of the individualPc chromophores within these films varied with increasing Pc film coverage but that changes to ψ weresignificantly less on Au surfaces modified with 2. Phenyl−phenyl intermolecular interactions have beenhypothesized to lead to the unique formation of rodlike aggregates of 1 and are shown here to be criticalin establishing coherent thin films of this material during the transfer of the first bilayer.
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