Construction of Amphiphilic Indocyanine-Green-Based Langmuir Film and Drop-Casting Film with Photoelectric Conversion Properties

Molecular self-assembly is the automatic formation of functional assemblies of different structural components through weak, reversible, non-covalent interactions on the basis of molecular recognition. Amphiphilic molecules have a natural advantage in self-assembly at the gas/liquid interface. In this work, two amphiphilic molecules with a special molecular structure, indocyanine green (ICG) and a derivative of indocyanine green (CCS), were combined with two dye molecules (tetraphenylporphyrin tetrasulfonic acid hydrate (TPPS) and nickel (II) phthalocyanine-tetrasulfonic acid tetrasodium salt (TsNiPc) for self-assembly through the Langmuir-Blodgett (LB) technique. The nanostructure and assembly behavior in ordered self-assembled films are effectively regulated by inducing dye molecules to form different types of aggregates (H- and J-aggregates). In addition, we prepared composite films containing the same functional components using the conventional drop-casting technique and performed a series of comparative experiments with LB films. The degree of hydrophilicity was found to be related to roughness, with LB composite films being flatter and denser, with the lowest roughness and the best hydrophobicity compared to drop-casting films. Notably, the LB films showed better optoelectronic properties under the same conditions, providing new clues for the application of optoelectronic functional ultrathin film devices.