Solvent-Assisted Interfacial Assembly of Copper Tetra-(tert-Butyl)-Phthalocyanine into Ultrathin Films

Nowadays, the assembling of metallophthalocyanines into well-structured thin films via wet-processing techniques is a topic of active research. This process is addressed in the present study devoted to Langmuir-Schaeffer (LS) films of copper tetra-(tert-butyl)-phthalocyanine. The LS films were prepared by using o-xylene as a spreading solvent and, concurrently, as a modulator of the film growth. The film formation process was monitored by Brewster angle microscopy from the 2D solution on the water surface to the five-layer solid films deposited on silicon at various surface pressures. The morphological data are rationalized in terms of the clathrate-like species prefabricated on the water surface and transferred onto solid substrates with both solvent and water molecules trapped. The film growth mechanism is further detailed by means of polarized optical spectroscopy and the water uptake measurement performed on the thicker LS films. The pros and cons of o-xylene as a dual-purpose solvent are revealed, and promising alternatives are proposed.