A broad range of amphiphilic cyanine dyes are known to self-assemble into J-aggregates with diverse structures. The dye 3,3’-bis(2-sulfopropyl)-5,5’,6,6’-tetrachloro-1,1’-dioctylbenzimida-carbo-cyanine (C8S3) forms micrometer long double walled tubular aggregates with a uniform outer diameter of 13 ± 0.5 nm. These tubular aggregates of C8S3 are of particular interest for their extensive exciton delocalization and migration similar to that found in natural light harvesting systems. However, the optical properties of the aggregates are very sensitive to distortion of the aggregate structure, as can be observed upon drying. Previously, nanometer thick shells of silica with controlled and uniform thickness were synthesized around pre-formed C8S3 aggregates. This was shown to leave the aggregate absorbance and emission unaltered in solution. We now show that this silica coating stabilizes the tubular aggregates of C8S3 both against drying under ambient conditions, and against the vacuum conditions of an electron microscope. We also show that this coating can be applied to other J-aggregates with negative surface charge. Transmission electron microscope images confirm that the thickness of the coatings is 5 nm or less and energy dispersive X-ray spectroscopy confirms the presence of silica. Emission spectra of dried silica coated samples indicate that the supramolecular structure of the aggregates is preserved. Furthermore, the silica shell may serve as a base for further functionalization of the aggregates, such as dyes, nanoparticles, or polyelectrolytes.<br/>

Silica coating of tubular J-aggregates from amphiphilic cyanine dyes for stabilization and functionalization

2019 Fall National Meeting

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