Formation of pseudoisocyanine J-aggregates during thin-film formation

Thin-film formation of J-aggregated pseudoisocyanine iodide with long alkyl substituents C18H37 (PIC 2-18) and C10H21 (PIC 2-10) and ethyl substituents (PIC 2-2) with added \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$\text{B}_{10}\text{H}_{10}^{2-}$\end{document} anion was studied by spectrophotometry directly during spin-coating of its solutions. It is found that a bathochromic shift of the monomer dye absorption band maximum and extensive growth of a J-peak that is not compensated by the monomer decrease take place as the dye film forms. The refractive index and absorption coefficient of a solid dye thin film in monomeric (nmax = 2.1) and J-aggregated (nmax = 3.05) forms were measured as functions of the dispersion by spectral ellipsometry. The influence of a change in the local field factor on the spectral properties of the pseudoisocyanine dye solution in the course of both spin-coating and solid J-aggregated thin-film formation is considered.