Interaction between nitroxyl radicals and CdTe quantum dots: Determination of fluorescence-quenching mechanisms in aqueous solution

Quantum Dot Metal Salt Interactions Unraveled by the Sphere of Action Model

Postsynthetic metal salt treatments are frequently employed in the luminescence enhancement of quantum dots (QDs); however, its microscopic picture remains unclear. CsPbBr₃-QDs, featuring strong excitonic absorption and high photoluminescence (PL) quantum yield, are ideal QDs to unravel the intricate interaction between QDs and such surface-bound metal salts. Herein, we study this interaction based on the controlled PL quenching of CsPbBr₃-QDs with BiBr₃. Upon the addition of BiBr₃, an instant and complete PL quenching is observed, which can be fully recovered after the addition of an excess of PbBr₂. This, together with the complete preservation of the excitonic absorption suggests a surface-driven adsorption equilibrium. Additionally, time-resolved studies reveal a non-homogeneous surface trap formation. Based on the so-called sphere of action model for the adsorption process, we show that already a single BiBr₃ adsorption suffices to completely quench a QD's luminescence. This approach is expanded to analyze size-, ligand-, and metal-dependent quenching dynamics. Facet junctions are identified as regions of enhanced surface reactivity. A Langmuir-type ligand coverage is exposed with a strong impact on adsorption. Our results provide a detailed mechanistic insight into postsynthetic interaction of QDs with metal salts, opening pathways for future surface manipulations.