Bulky Barbiturates as Non‐Toxic Ionic Dye Insulators for Enhanced Emission in Polymeric Nanoparticles

Bulky hydrophobic counterions (weakly coordinating anions) can insulate ionic dyes against aggregation-caused quenching (ACQ) and enable preparation of highly fluorescent dye-loaded nanoparticles (NPs) for bioimaging, biosensing light harvesting. Here, we introduce a family anions based on fluorinated C-acyl barbiturates with delocalized negative charge bulky non-polar groups. Similarly to tetraphenylborates, these prevent ACQ cationic dye alkyl rhodamine B inside polymer NPs made biodegradable poly(lactic-co-glycolic acid) (PLGA). Their efficiency increases analogues higher acidity bulkiness. structure controls dye-dye communication, yielding bright on/off switching or stable emission. They enhance encapsulation NPs, allowing intracellular imaging without leakage. Compared tetraphenylborates known as cytotoxic transmembrane ion transporters, the display significantly lower cytotoxicity. These chemically available versatile barbiturate derivatives are promising counterion scaffolds non-toxic nanomaterials.