A Highly Luminescent Nitrogen-Doped Nanographene as an Acid- and Metal-Sensitive Fluorophore for Optical Imaging

Due to the complex core–shell structure and variety of surface functional groups, the photoluminescence (PL) mechanism of carbon dots (CDs) remain unclear. o-Phenylenediamine (oPD), as one of the most common precursors for preparing red emissive CDs, has been extensively studied. Interestingly, most of the red emission CDs based on oPD have similar PL emission characteristics. Herein, we prepared six different oPD-based CDs and found that they had almost the same PL emission and absorption spectra after purification. Structural and spectral characterization indicated that they had similar carbon core structures but different surface polymer shells. Furthermore, single-molecule PL spectroscopy confirmed that the multi-modal emission of those CDs originated from the transitions of different vibrational energy levels of the same PL center in the carbon core. In addition, the phenomenon of “spectral splitting” of single-particle CDs was observed at low temperature, which confirmed these oPD-based CDs were unique materials with properties of both organic molecules and quantum dots. Finally, theoretical calculations revealed their potential polymerization mode and carbon core structure. Moreover, we proposed the PL mechanism of red-emitting CDs based on oPD precursors; that is, the carbon core regulates the PL emission, and the polymer shell regulates the PL intensity. Our work resolves the controversy on the PL mechanism of oPD-based red CDs. These findings provide a general guide for the mechanism exploration and structural analysis of other types of CDs.

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“…1i and Fig. S14 ) 30 . Structural characterizations indicated that there was a PAH structure in the CDs, which existed in the carbon core.…”

Section: Resultsmentioning

confidence: 98%

Electron–phonon coupling-assisted universal red luminescence of o-phenylenediamine-based carbon dots

et al. 2022

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“…A striking demonstration of the wide applicability of heteroatom doped PAHs is provided by the synthesis of the diaza derivative of dibenzo[ hi,st ]ovalene (compound 33 , Scheme 7 ) [ 47 ]. Notably, in compound 33 , the two nitrogen atoms are located on the zig zag edges; nonetheless, compound 33 is stable as its all carbon parent compound [ 48 ].…”

Section: N-doped Polycyclic Aromatic Hydrocarbonsmentioning

confidence: 99%

Novel Synthetic Approach to Heteroatom Doped Polycyclic Aromatic Hydrocarbons: Optimizing the Bottom-Up Approach to Atomically Precise Doped Nanographenes

et al. 2021

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The success of the rational bottom-up approach to nanostructured carbon materials and the discovery of the importance of their doping with heteroatoms puts under the spotlight all synthetic organic approaches to polycyclic aromatic hydrocarbons. The construction of atomically precise heteroatom doped nanographenes has evidenced the importance of controlling its geometry and the position of the doping heteroatoms, since these parameters influence their chemical–physical properties and their applications. The growing interest towards this research topic is testified by the large number of works published in this area, which have transformed a once “fundamental research” into applied research at the cutting edge of technology. This review analyzes the most recent synthetic approaches to this class of compounds.

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“…Furthermore, the insertion of heteroatoms into PAHs significantly improves their electronic properties without changing their frameworks [11] . Thus, heteroatom doping in such nonplanar PAHs is a key method to prepare a series of compounds for emergency applications [4d,12] …”

Section: Introductionmentioning

confidence: 99%

Synthesis of Distorted Nitrogen‐Doped Nanographenes by Partially Oxidative Cyclodehydrogenation Reaction

Varghese

Gao

Chang

et al. 2022

Chemistry An Asian Journal

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A series of partially fused N‐doped nanographenes (2–4) are synthesized via the oxidative cyclodehydrogenation of oligoaryl‐substituted dibenzo[e,l]pyrene (1), and five, six, and seven new C−C bonds are formed, respectively, implying stepwise C−C bond fusion and extended π‐conjugation. Single‐crystal X‐ray diffraction analysis of compound 4 a revealed that the presence of sterically demanding groups hindered the formation of planar and fully fused nanographene in the oxidative cyclodehydrogenation reaction step. Optical study of compounds 2 to 4 showed that extended π‐conjugation leads to a regular stepwise bathochromic shift in the absorption and emission spectra. Furthermore, the HOMO–LUMO gaps of these compounds exhibit a decrease as C−C bond formation proceeds. Thus, the optoelectronic properties of nanographenes are highly dependent on the formation of new C−C bonds in the molecular skeleton.

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A Highly Luminescent Nitrogen-Doped Nanographene as an Acid- and Metal-Sensitive Fluorophore for Optical Imaging

Cited by 55 publications

References 91 publications

Electron–phonon coupling-assisted universal red luminescence of o-phenylenediamine-based carbon dots

Electron–phonon coupling-assisted universal red luminescence of o-phenylenediamine-based carbon dots

Novel Synthetic Approach to Heteroatom Doped Polycyclic Aromatic Hydrocarbons: Optimizing the Bottom-Up Approach to Atomically Precise Doped Nanographenes

Synthesis of Distorted Nitrogen‐Doped Nanographenes by Partially Oxidative Cyclodehydrogenation Reaction

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