Morphological Analysis of Self-assembled Structures of Merbromin Molecules Adsorbed on Titanium(IV) Oxide Nanoparticles
K. Adachi, N. Tsuru
BUNSEKI KAGAKU(分析化学), 2018, 67, 719-726.
DOI : 10.2116/bunsekikagaku.67.719

Abstract: A broad understanding of the adsorption and aggregation behavior of organic dye molecules on an inorganic semiconductor surface provides a new strategy for optical and electronic devices. We chose merbromin (Merb) and titanium(IV) oxide (TiO2) colloids in this study. The adsorption and aggregation behavior of Merb in a TiO2 colloid aqueous solution were spectrophotometrically investigated. The absorption spectra of Merb were significantly red-shifted in the visible region upon the addition of a TiO2 colloid solution. Detailed spectral analysis based on Kasha's exciton coupling theory and a modified Langmuir adsorption model revealed that dianionic Merb molecules are adsorbed flat on a positively charged TiO2 colloid surface by an electrostatic interaction, and eventually form "oblique" J-type dimers aligned in a head-to-tail fashion. We envisage new applications of this analysis in the development of advanced dye-sensitized solar cells, where the adsorption/aggregation morphology of organic dyes on the metal oxide is a crucial factor to be considered.