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Graphitic Nitrogen Triggers Red Fluorescence in Carbon Dots
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SYSNO ASEP 0487128 Document Type J - Journal Article R&D Document Type Journal Article Subsidiary J Článek ve WOS Title Graphitic Nitrogen Triggers Red Fluorescence in Carbon Dots Author(s) Holá, K. (CZ)
Sudolská, M. (CZ)
Kalytchuk, S. (CZ)
Nachtigallová, Dana (UOCHB-X) RID, ORCID
Rogach, A. L. (CN)
Otyepka, M. (CZ)
Zbořil, R. (CZ)Source Title ACS Nano. - : American Chemical Society - ISSN 1936-0851
Roč. 11, č. 12 (2017), s. 12402-12410Number of pages 9 s. Language eng - English Country US - United States Keywords nitrogen-doped ; graphene dots ; red fluorescence ; fluorescence mechanism ; band-gap tuning Subject RIV CF - Physical ; Theoretical Chemistry OECD category Physical chemistry R&D Projects GBP208/12/G016 GA ČR - Czech Science Foundation (CSF) Institutional support UOCHB-X - RVO:61388963 UT WOS 000418990200067 EID SCOPUS 85040059908 DOI 10.1021/acsnano.7b06399 Annotation 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 (sp(2) 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. Workplace Institute of Organic Chemistry and Biochemistry Contact asep@uochb.cas.cz ; Kateřina Šperková, Tel.: 232 002 584 ; Jana Procházková, Tel.: 220 183 418 Year of Publishing 2018
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