Ethanothermal Synthesis ofDual Emissive Supramolecular Carbon Dots from Naphthalenedioland Quinones with Aggregate Tuned Fluorescence

Abstract

Carbon dots (CDs) haveattracted considerable interest due to their unique photoluminescence and broadpotential in sensing, bioimaging, and optoelectronics. However, precise controlof their emission properties through molecular design and understanding ofsupramolecular aggregation remain challenging. Here, nitrogen-doped carbon dots(H-CDs) with green fluorescence are synthesized via an ethanol-mediatedsolvothermal method using 1,3-dihydroxynaphthalene as a rigid π-conjugatedcarbon source and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) as both oxidantand nitrogen donor. The synthesis involves complexmolecular transformations yielding amorphous supramolecular carbon dotsstabilized mainly by noncovalent interactions. Characterization confirmedabundant oxygen- and nitrogen-containing functional groups and an amorphous structuredevoid of crystalline residues. Hierarchical H-type aggregation driven by π-πstacking and hydrogen bonding governs the photophysical behavior of the H-CDs,inducing a concentration-dependent evolution from blue-emitting monomers togreen-emitting supra-CDs, accompanied by particle growth, red-shifts in theemission spectrum, and a pronounced elongation of the fluorescence lifetime. Temperature- and salt-dependent studies reveal thatemission intensity increases with rising temperature and low ionic strength,due to distorted H'-aggregates with weak excitonic coupling and electrostaticscreening of surface charges. These insights deepen the understanding ofstructure-property relationships in carbon dots and offer guidance fortailoring their photophysical properties for advanced optoelectronicapplications.

Keywords

Nitrogen-doped carbon dots / Supramolecular aggregation / Photoluminescence / Fluorescence lifetime / π–πstacking

Acknowledgments

We thank Dongmao Zhang of the Department of Chemistry at Mississippi State University for helpful discussions and suggestions.

Author Contributions

Conceptualization, C.W. and W.Z.; Methodology, C.W., X.Z. and Z.Y.; Validation, W.F.; Formal Analysis, C.W. and M.Z.; Data Curation, Z.Y.; Original Draft Preparation, C.W.; Review & Editing, W.Z.; Visualization, X.Z.; Supervision, Project Administration, and Funding Acquisition, W.Z.

Ethics Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

All research data related to the paper are accessible and provided by the authors.

Funding

This research was funded by [the Key Science and Technology Program of Kaifeng City] grant number [2301002].

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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