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AuthorReckmeier, Claas J.
AuthorSchneider, Julian
AuthorXiong, Yuan
AuthorHäusler, Jonas
AuthorKasák, Peter
AuthorSchnick, Wolfgang
AuthorRogach, Andrey L.
Available date2020-08-20T08:06:21Z
Publication Date2017
Publication NameChemistry of Materials
ResourceScopus
ISSN8974756
URIhttp://dx.doi.org/10.1021/acs.chemmater.7b03344
URIhttp://hdl.handle.net/10576/15699
AbstractRecently, molecular fluorophores were shown to be formed in the bottom-up chemical synthesis, contributing to the emission of carbon dots (CDs), derived from a citric acid precursor. We applied an ammonothermal synthesis toward CDs, employing two reactants citric acid and supercritical ammonia functioning as both solvent and precursor. The resulting nanoparticles are identified as amorphous aggregates of molecular fluorophores based on citrazinic acid derivatives, which resemble many of the emission features typically reported to be characteristic for CDs. The aggregates absorb and emit at short and long wavelengths of the spectrum, a feature prior ascribed to intrinsic CD core and surface states, respectively. We identify three emission states: a high energy and a low energy aggregate state as well as an energy transfer state between both. Energy transfer is triggered only upon excitation within a narrow high energy spectral range, resulting in a characteristic blue-green double emission. The high energy aggregate state exhibits a trapping mechanism elongating emission lifetime. To further analyze aggregated molecular fluorophores, we studied aqueous solutions and films of citrazinic acid and polyvinylpyrrolidone and demonstrated their concentration dependent optical behavior. Since fluorophore aggregates reproduce the emissive features of CDs, the contribution of sp2/sp3 carbonized products and graphitic domains to the emission features of CDs must be carefully evaluated in future studies. 2017 American Chemical Society.
SponsorThe authors thank Dr. Klaus Speck (Ludwig-Maximilians-Universität, Munich) for valuable discussions regarding the chemistry of citric acid. This work was funded by NPRP grant no. 8-878-1-172 from the Qatar National Research Fund (a member of the Qatar Foundation).
Languageen
PublisherAmerican Chemical Society
SubjectCarbon Quantum Dots
Nanodots
Carbon Nanoparticles
TitleAggregated Molecular Fluorophores in the Ammonothermal Synthesis of Carbon Dots
TypeArticle
Pagination10352-10361
Issue Number24
Volume Number29
dc.accessType Open Access


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