Ferrocyanide-Surface Ligands to Quantum Dots for Prussian Blue Composites Showing Efficient and Reversible Electrochemical Response

We employed a novel approach to fabricate quantum dot-in-Prussian blue analogue (QD-in-PBA) composites, encapsulating colloidal QDs into the electrical conducting metal organic framework PBA, which could provide a robust platform for efficient photochemical modulation of photoluminescence (PL) intensity. To achieve this, the surface of the QDs was engineered by attaching ferrocyanide ligands. This surface modification enabled the QDs to be seamlessly and uniformly incorporated into the PBA matrix. The ferrocyanide ligands on the QD surfaces played a pivotal role in initiating the in-situ formation of PBA, facilitated by the introduction of additional ferrocyanide ions and iron (III) ions as the building blocks of PBA. Alternatively applied external voltages to the QD-in-PBA electrode within an electrochemical cell demonstrated the reversible quenching and recovery of the PL intensity of the QDs embedded within the QD-in-PBA composite. Notably, we achieved the on/off modulation ratio over 7, which could be consistently repeated across multiple cycles. In contrast, the control sample, comprising a mixture of QDs and PBA, exhibited poor stability in terms of electrochemical performance, with a reduced modulation degree observed over repeating cycles. This diminished stability can be attributed to the fact that in the control sample, the QDs were merely attached to the surface of the PBA rather than being fully incorporated within the matrix and became redispersed into the electrolyte solution during the electrochemical reactions.