Organic J-Aggregate Nanodots with Enhanced Light Absorption and Near-Unity Fluorescence Quantum Yield

Development of biocompatible fluorophores with small size, bright fluorescence, and narrow spectrum translate directly into major advances in fluorescence imaging and related techniques. Here, we discover that a small donor-acceptor-donor-type organic molecule consisting of a carbazole (Cz) donor and benzothiazole (BT) acceptor (CzBTCz) assembles into quasi-crystalline J-aggregates upon a formation of ultrasmall nano-particles. The 3.5 nm CzBTCz Jdots show a narrow absorption spectrum (fwhm = 27 nm), near-unity fluorescence quantum yield (phi(fi) = 0.95), and enhanced peak molar extinction coefficient. The superior spectroscopic characteristics of the CzBTCz Jdots result in two orders of magnitude brighter photoluminescence of the Jdots compared with semiconductor quantum dots, which enables continuous single-Jdots imaging over a 1 h period. Comparison with structurally similar CzBT nanoparticles demonstrates a critical role played by the shape of CzBTCz on the formation of the Jdots. Our findings open an avenue for the development of a new class of fluorescent nanoparticles based on J-aggregates.

Automated summary

The development of biocompatible fluorophores with small size, bright fluorescence, and narrow spectrum has led to significant advancements in fluorescence imaging technologies. A recent discovery showed that a small donor-acceptor-donor-type organic molecule can assemble into quasi-crystalline J-aggregates upon formation of ultrasmall nano-particles, resulting in bright and narrow-spectrum CzBTCz Jdots that are two orders of magnitude brighter than semiconductor quantum dots, allowing for continuous single-Jdots imaging.