Direct Formation of Carbocyanine J-Aggregates in Organic Solvent

J-aggregates are molecular nanoscale self-assemblies with distinct excitonic properties, such as highly delocalized excitons, making them main candidates for designing excitonic energy transfer systems. Here, we show a technique to form J-aggregates of the cyanine dye 1,1′-dioctyl-3,3′-di(4sulfobutyl)-5,5′,6,6′-tetrachloro-benzimidazolocarbocyanine (C8S4) in organic solutions of chloroform and acetone. These J-aggregates have a spectrum with three red-shifted absorption peaks and two sharp emission peaks. Spin-coated thin films of C8S4 aggregates have similar spectra. Investigation of the thin films via electron microscopy shows two morphologies of aggregates, which partially explains the complicated spectra. We have shown two ways for isolating the type of aggregate with the lowest transition energy. Atomic force microscopy and high-resolution transmission electron microscopy images of the aggregates reveal a 2D brickstone arrangement. Finally, J-aggregating C8S4 from organic solvent will enable mixing J-aggregates directly with various fluorescent organic compounds, thereby expanding the options for designing energy transfer systems based on J-aggregates.