Many chemical/biological processes can be tracked through monitoring the change of the electrostatic charge state. We developed a general methodology for designing nanoscale probes using nontoxic CuInS2/ZnS quantum dots (QDs) based on mediating the charge transfer process via the electrostatic interaction between the QD surface and the acceptors. The surface of this nanoprobe is covered with three types of ligands: 1) passivation ligands that protect the QD surface and ensure the solubility, 2) ligands with variable electrostatic charges that can respond to the change of the environment, 3) tethered acceptors that are anchored to the surface of QDs via flexible linkers and can be attracted/repelled by QDs depending on their surface electrostatic potential. Using this strategy, a pH probe was fabricated using mercaptoalkylamine-capped QDs by decorating their surface with a few tethered electron acceptors, methyl viologen (MV<sup>2+</sup>).(See the Figure) The change of the pH of the solution induces the protonation/deprotonation of the amine groups and varies the electrostatic potential of the surface. The electrostatic interaction between the MV<sup>2+ </sup>acceptor and the QD surface determines the average distance between them, and hence governs the rate of electron transfer, which is reflected as the change of the intensity of the photoluminescence of QDs. The structure of this probe was optimized to achieve the broad dynamic range and the best reversibility. By replacing the mercaptoalkylamine ligands with peptides which mimic the mitochondrial proteins, the probe can monitor the real-time level of protein acylation in mitochondria. This acylation probe showed the potential to diagnose important metabolic diseases.

An electrostatic strategy for designing quantum dot-based nanoprobes

256th National Meeting (2018)

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