Nanoaggregates in floating layers of azaporphyrins

Abstract

An analysis of compression isotherms of floating layers of copper tetra-tert-butylphthalocyanine ( CuPctBu4 ) and copper tetrabenzotriazaporphyrine, obtained at varied initial conditions, is carried out. The structure of layers is determined by three methods: the traditional one (direct estimation of area per molecule from a π-A isotherm), by a quantitative analysis of compression isotherms (with the use of Volmer equation), and by Brewster angle microscopy. It is shown that in layers with edge-on arrangement of molecules (initial surface concentrations N0 > 0.15 μmol.m-2), the layer structure, determined by the quantitative method, may differ drastically from the structure obtained by the traditional one. The equation of state of the floating layer generalized to the case when structural units of 2D gas are molecular aggregates is used to describe the layer of azaporphyrines. Boundaries of existence and characteristics of structure and properties of floating layers in stable states (size of nanoaggregates formed in a layer, number of molecules in them, interaggregate spacing, compressibility) are determined. The quantitative model of floating layer of copper tetra-tert-butylphthalocyanine is proposed. Constants characterizing a stable monolayer, as well as the region where it may be formed, are determined on the base of the model created.