Two-Color Emitting Colloidal Nanocrystals as Single-Particle Ratiometric Probes of Intracellular pH

Francesco Bruni, Jacopo Pedrini, Caterina Bossio, Beatriz Santiago-Gonzalez, Francesco Meinardi, Wan Ki Bae, Victor I. Klimov, Guglielmo Lanzani, Sergio Brovelli

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)


Intracellular pH is a key parameter in many biological mechanisms and cell metabolism and is used to detect and monitor cancer formation and brain or heart diseases. pH-sensing is typically performed by fluorescence microscopy using pH-responsive dyes. Accuracy is limited by the need for quantifying the absolute emission intensity in living biological samples. An alternative with a higher sensitivity and precision uses probes with a ratiometric response arising from the different pH-sensitivity of two emission channels of a single emitter. Current ratiometric probes are complex constructs suffering from instability and cross-readout due to their broad emission spectra. Here, we overcome such limitations using a single-particle ratiometric pH probe based on dot-in-bulk CdSe/CdS nanocrystals (NCs). These nanostructures feature two fully-separated narrow emissions with different pH sensitivity arising from radiative recombination of core- and shell-localized excitons. The core emission is nearly independent of the pH, whereas the shell luminescence increases in the 3–11 pH range, resulting in a cross-readout-free ratiometric response as strong as 600%. In vitro microscopy demonstrates that the ratiometric response in biologic media resembles the precalibralation curve obtained through far-field titration experiments. The NCs show good biocompatibility, enabling us to monitor in real-time the pH in living cells.

Original languageEnglish
Article number1605533
JournalAdvanced Functional Materials
Issue number12
Publication statusPublished - Mar 24 2017


  • bioimaging
  • colloidal quantum dots
  • pH sensing
  • ratiometric sensing
  • two-color emission

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

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