Ionic aggregation-induced emission: bulky hydrophobic counterions light up dyes in polymeric nanoparticles

Ilya O Aparin (1) , Nina Melnychuk (1) , Andrey S Klymchenko (1)

1 LBP - Laboratoire de Bioimagerie et Pathologies

Dye-loaded polymeric nanoparticles emerge as powerful bioimaging tools, but their assembly is challenged by aggregation-caused quenching (ACQ) of flat fluorophores. Aggregationinduced emission (AIE) proposes an effective solution against ACQ by exploiting propellershaped neutral fluorophores without polymeric blending. Fighting ACQ of ionic dyes in polymeric nanoparticles can be achieved by bulky hydrophobic counterions. Here, we aim to generate an AIE phenomenon in poorly emissive ionic dyes using bulky counterions. Three cationic hemicyanine dyes of styryl pyridinium family have been synthesized: two planar fluorophores featuring ACQ and one propeller-shaped AIE fluorophore. We found that in water bulky fluorinated tetraphenylborates can light up all three dyes, including planar non-AIE fluorophores. The described "ionic" AIE (iAIE) with bulky counterions enables preparation of 50-nm dye-loaded polymeric NPs showing 40 % quantum yield at 500 mM dye loading, whereas small anions favor poorly emissive large aggregates. Single-particle microscopy reveals that these NPs emit without blinking 50-fold brighter than quantum dots-605 (at 470-nm excitation). iAIE opens the route to assembling charged intrinsically non-AIE fluorophores into bright fluorescent (nano)materials.

Mots clés: dye-loaded polymeric nanoparticles; aggregation-induced emission; aggregationcaused quenching; bulky hydrophobic counterions; single-particle microscopy

Domaines: Polymères; Chimie théorique et/ou physique

Ilya O Aparin, Nina Melnychuk, Andrey S Klymchenko. Ionic aggregation-induced emission: bulky hydrophobic counterions light up dyes in polymeric nanoparticles. Advanced Optical Materials, 2020, 8 (14), pp.2000027. ⟨10.1002/adom.202000027⟩. ⟨hal-03020565⟩