Bioimaging based on Poly(ethylenimine)-Coated Carbon Dots and Gold Nanoparticles for pH Sensing and Metal Enhanced Fluorescence

Shweta Pawar, Hamootal Duadi, Moran Friedman Gohas, Yoram Cohen, Dror Fixler

Research output: Contribution to journalArticlepeer-review


When exposed to specific light wavelengths, carbon dots (CDs), which tend to be fluorescent, can emit colorful light. It provides them with a lot of adaptability for different applications including bioimaging, optoelectronics, and even environmental sensing. Poly(ethylenimine) (PEI) coated carbon dots (PEI-CDs) with a long emission wavelength were synthesized via the hydrothermal method. The resultant CDs show strong fluorescence with quantum yield up to 20.2%. The PEI-CDs exist with distinct pH-sensitive features with pH values in the range of 2-14. The optical characteristics of CDs are pH-responsive due to the presence of different amine groups on PEI, which is a functional polycationic polymer. One of the most widely employed nanoparticles for improving the fluorescence plasmonic characteristics of a nanocomposite is gold. Gold nanoparticles were coupled with PEI-CDs in this assay by using the EDC-NHS coupling to increase the photoluminescence property of the PEI-CDs by using the metal-enhanced fluorescence approach. In the presence of gold nanoparticles, the fluorescence is enhanced 5-6 times. The likely mechanism in our investigation was primarily derived from enhancement of the intrinsic radiative decay rate rather than the local electric field impact. Moreover, PEI-CDs can be used as a bioimaging agent, as these molecules are nontoxic to the cells, and the positively charged PEI-CDs have the potential for nuclear targeting, allowing for electrostatic contact with DNA in the nucleus. This finding will expand the application that the PEI-CDs can be used in the future for targeted imaging applications.

Original languageEnglish
Pages (from-to)4935-4943
Number of pages9
JournalACS Applied Bio Materials
Issue number11
StatePublished - 20 Nov 2023

Bibliographical note

Publisher Copyright:
© 2023 American Chemical Society.


  • bioimaging
  • carbon dots
  • gold nanoparticles
  • metal enhanced fluorescence
  • pH-sensitive


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