Controlled Assembly of Fluorescent Molecules

Controlled Assembly of Fluorescent Molecules

Author: ChemNanoMat

Nanomaterials made by the self-assembly of organic molecules are interesting due to their low processing costs and tunable electronic and optical properties. Since the size and shape of the nanomaterials strongly affect these properties, the ability to control the particles’ morphology would be useful.

Raquel Giménez, Teresa Sierra, University of Zaragoza, Spain, Enrique Ortí, University of Valencia, Spain, and colleagues have developed a method to control the morphology and emission properties of aggregates formed by star-shaped fluorescent compounds based on the 2,4,6‐tris(1,2,3‐triazol‐4‐yl)‐1,3,5‐triazine (TTT) moiety. The compounds used are the T3C4 and TB3C4 (pictured) TTT derivatives, which differ in the chains attached to the central triazole ring. They behave differently in their self‐assembly and their fluorescent properties.

T3C4 and TB3C4 were prepared by a reprecipitation method. Simple variations in some preparation parameters, such as the selection of the solvent/non‐solvent pair or the relative amount of both solvents, lead to a variety of aggregate shapes, such as spherical particles, one-hole hollow spheres, toroids, twisted fibers, and helical nanotubes in a controlled way (examples pictured). The various morphologies have a significant impact on the optical behavior.

The two derivatives allowed the study of the effect of the chemical structure on the aggregation and the optical properties. Compared to T3C4, the introduction of an additional benzoyloxy moiety with the ability to rotate in TB3C4 completely changed the emissive behavior. Interestingly, aggregation has opposite effects on the fluorescent properties of the two compounds: T3C4 acts as a conventional fluorescent molecule, showing an aggregation-caused quenching effect, while TB3C4 shows aggregation-induced emission (AIE).


 

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