Phthalocyanine thin films

Liquid crystalline phthalocyanines which are formally amphiphilic, with substituents which between them provide hydrophilic headgroups and hydrophobic tailgroups, deposit as well-ordered films by the Langmuir-Blodgett method. A comparison of normal incidence transmission Fourier transform infrared (FTIR) spectra and Reflection absorption infrared (RAIR) spectra shows that the molecules are arranged with the cores essentially perpendicular to the surface. Atomic Force Microscopy (AFM) of the surface of films of the compounds reveals columnar structures which are anisotropically aligned. Spin-coated films of various phthalocyanines and analogues, which contain either a thiophene or pyridine ring in place of one of the benzenoid rings, also contain columnar assemblies. Phthalocyanine derivatives incorporating a thiol or disulfide unit at the end of an alkyl chain substituent can be deposited by self-assembly from solution onto a thin gold film supported on a glass slide or silicon wafer. FTIR measurements of the self-assembled monolayer (SAM) films demonstrate that orientation of the macrocylic ring within these films is dependent upon the length of the mercaptoalkyl tethering chain. Evanescent wave stimulated fluorescence can be detected from the films when the support is used as a waveguide. The potential applications of examples of these films in the area of gas sensing is discussed.