The dissolution of the cyanine dye 3,3’-bis(2-sulfopropyl)-5,5’,6,6’-tetrachloro-1,1’-dioctylbenzimida-carbo-cyanine (C8S3) in aqueous solution leads to the formation of tubular J-aggregates with a uniform outer diameter of 13.0 ± 0.5 nm and length exceeding microns. A strong excitonic coupling between the dyes within the aggregates makes them prospective as model systems to study excitation energy migration in comparison to natural light harvesting complexes. However, for any functionalization beyond the internal properties of the J-aggregates, it becomes necessary to attach different chemical compounds to the tubes. For many applications inorganic materials, such as semiconducting nanoparticles, are preferred due to their photochemical stability. Here we demonstrate two different approaches to expand the aggregates into complex hybrid inorganic/organic systems (HIOS) by means of self-assembly in aqueous solution:<br/>One approach is electrostatic adsorption of polyelectrolyte materials. It is shown that adsorption of linear polycations leave the optical spectra, hence the molecular structure of the aggregates, unaffected if preparation-conditions obey certain limits. Furthermore, anionic CdTe nanoparticles were added to the aggregates using polycations as a glue. These nanoparticles, depending on their size, serve as donors or acceptors for highly efficient Förster resoncane energy transfer (FRET).<br/>Another approach is direct synthesis of inorganic material at or within the tubular aggregates. As examples, we show the growth of CdS nanoparticles on top of the outer surface of the aggregates and we discuss the appearance of AgI nanowires within the aggregates. These wires grow after addition of silver nitrate to the solution and were initially described as silver nanowires. It is demonstrated by structure analysis of single wires that they actually consist of silver iodine, a finding that was completely surprising. A further possibility for stabilization and functionalization that will briefly be discussed is addition of a silica shell around the aggregates.<br/>The large variety of possibilities demonstrated here to grow more complex structures form the tubular J-aggregates may lay the foundations for building functional structures to mimic natural light harvesting systems.

Tubular J-aggregates of amphiphilic cyanine dyes as functional scaffolds for self-assembly of complex hybrid inorganic/organic systems

2019 Fall National Meeting

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