Revealing the Molecular Origin of Green Fluorescence in meta-Phenylenediamine Derived Carbon Dots

Le résumé fourni par la source

Understanding and controlling long-wavelength emission in carbon dots (CDs) remains a key challenge that limits their rational design for optoelectronic and energy conversion applications. In this study, we elucidate the mechanism of green emission in CDs derived from metaphenylenediamine (mPDA). Through sequential synthesis, purification, and spectroscopic analysis, we isolate and assign the emissive species to amidated 2,7-diaminophenazine derivatives, demonstrating that molecular fluorophores, rather than graphitic domains, dictate the green emission. Density functional theory (DFT) and time-dependent DFT calculations further support this assignment, showing excellent agreement with the experimental absorption and emission energies. Further thermal and optical studies support a dual core-shell architecture for those CDs, in which the sp2-rich carbon core enhances structural robustness and photostability, while surface-anchored fluorophores govern the green photoluminescence. To illustrate the practical implications of this structural-optical interplay, integration of greenemitting CDs into TiO2 photoanodes is shown to enhance photocurrent generation and light harvesting efficiency in photoelectrochemical water splitting. This molecular-level understanding establishes a rational design framework for engineering carbon nanomaterials with tailored photophysical and optoelectronic properties.

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