A team of Foundry staff and users have used a combinatorial approach to broaden the scope of synthetic chemistry possible on quantum dot (QD) nanocrystals. Their results were recently published in the journal ACS Nano.
Surface functionalization of nanocrystals is essential for their practical application but nanocrystals are often are incompatible with key synthetic reagents. The copper-catalyzed azide-alkyne click reaction (CuAAC) is one of the most useful methods for attaching molecules to surfaces but has been largely useless for QDs because copper ions quickly and irreversibly quench QD fluorescence.
Copper ions will normally fully quench or extinguish QD fluorescence in under 10 seconds, even at low concentrations. To discover non-quenching synthetic conditions for CuAAC reactions on QD surfaces, Foundry scientists developed a 2000-reaction combinatorial fluorescence assay to identify conditions that enabled surface functionalization without significant quenching.
These conditions were then applied to the development of QD-based voltage sensors for recording electrical activity in neurons. This work demonstrates a combinatorial approach for adapting otherwise incompatible reactions to reagent-sensitive QDs, suggesting a more expansive view of synthetic possibilities on nanocrystal surfaces.