Graphitic Nitrogen Triggers Red Fluorescence in Carbon Dots

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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  • Kateřina Holá
  • Mária Sudolská
  • Sergii Kalytchuk
  • Dana Nachtigallová
  • Michal Otyepka
  • Radek Zbořil


Original languageEnglish
Pages (from-to)12402-12410
Journal / PublicationACS Nano
Issue number12
Online published14 Nov 2017
Publication statusPublished - 26 Dec 2017


Carbon dots (CDs) are a stable and highly biocompatible fluorescent material offering great application potential in cell labeling, optical imaging, LED diodes, and optoelectronic technologies. Because their emission wavelengths provide the best tissue penetration, red-emitting CDs are of particular interest for applications in biomedical technologies. Current synthetic strategies enabling red-shifted emission include increasing the CD particle size (sp2 domain) by a proper synthetic strategy and tuning the surface chemistry of CDs with suitable functional groups (e.g., carboxyl). Here we present an elegant route for preparing full-color CDs with well-controllable fluorescence at blue, green, yellow, or red wavelengths. The two-step procedure involves the synthesis of a full-color-emitting mixture of CDs from citric acid and urea in formamide followed by separation of the individual fluorescent fractions by column chromatography based on differences in CD charge. Red-emitting CDs, which had the most negative charge, were separated as the last fraction. The trend in the separation, surface charge, and red-shift of photoluminescence was caused by increasing amount of graphitic nitrogen in the CD structure, as was clearly proved by XPS, FT-IR, Raman spectroscopy, and DFT calculations. Importantly, graphitic nitrogen generates midgap states within the HOMO-LUMO gap of the undoped systems, resulting in significantly red-shifted light absorption that in turn gives rise to fluorescence at the low-energy end of the visible spectrum. The presented findings identify graphitic nitrogen as another crucial factor that can red-shift the CD photoluminescence.

Research Area(s)

  • band-gap tuning, fluorescence mechanism, graphene dots, nitrogen-doped, red fluorescence

Citation Format(s)

Graphitic Nitrogen Triggers Red Fluorescence in Carbon Dots. / Holá, Kateřina; Sudolská, Mária; Kalytchuk, Sergii et al.

In: ACS Nano, Vol. 11, No. 12, 26.12.2017, p. 12402-12410.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review