Photoluminescence mechanism of carbon dots: triggering high-color-purity red fluorescence emission through edge amino protonation

Zhang, Qing; Wang, Ruoyu; Feng, Bowen; Zhong, Xiaoxia; Ostrikov, Kostya Ken

doi:10.1038/s41467-021-27071-4

Cited by 327 publications

(239 citation statements)

References 32 publications

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confidence: 99%

Hydrothermal Synthesis of High‐Yield Red Fluorescent Carbon Dots with Ultra‐Narrow Emission by Controlled O/N Elements

Xian

2022

Advanced Materials

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are less than 30 nm, but only one is prepared by hydrothermal method, and the other reaction systems are organic solvents, as shown in Table S1 (Supporting Information). [6][7][8][9][10][11][12][13][14] However, low fluorescence quantum yield (QY) can limit their applications. For instance, white light emitting diodes only based on luminescent materials with low QY are difficult to realize. [15] Among the reports on the red fluorescent carbon dots (r-CDs) prepared by the environmentally friendly hydrothermal method, only four papers have QY over 40%, but their monochromaticity is very low (FWHMs > 80 nm, visual inspection) and purification requires the troublesome dialysis or column chromatography. [16][17][18][19] The higher product yield stands for a more economical method and the higher efficiency. But there are only four articles on the preparation of highyield CDs by hydrothermal method with a yield of >35%. [20][21][22][23] And three of them are blue emission, one is green emission, no red emission, and their FWHMs are all over 80 nm by visual inspection. There is no report on the preparation of r-CDs that simultaneously takes into account the environmental protection, the fluorescence monochromaticity, QY, and the yield. In this work, the hydrothermal method was used to prepare the r-CDs with double emission peaks (600 nm and 658-683 nm), ultra-narrow FWHMs (20 and 30 nm), and high yield (83.3%).At present, the several main emission mechanisms of CDs have been proposed, such as the quantum confineme effect, the surface state, the molecule state, and the aggregation-induced emission (AIE). [24][25] In this work, the long-wavelength side emission of r-CDs belongs to AIE, and its longest emission wavelength (683 nm) reaches the near infrared region, which benefits from deeper penetration due to the minimum autofluorescence and reduced light scattering, offering a great imaging contrast and spatial resolution. [7] The AIE regularly blue shifts with the decrease of r-CDs concentration and the logarithmic relationship of y = 8.853ln(x) + 688.53 is obtained for the first time, where y is emission wavelength and x is concentration of r-CDs. It may be caused by the regular decrease of r-CDs aggregate size with the decrease of r-CDs concentration in solution. And the presence of the r-CDs aggregates is confirmed by the light scattering phenomenon of different concentrations of r-CDs solution and the X-ray diffraction (XRD) analysis. Red fluorescent carbon dots (r-CDs) with narrow dual emissions (600 nm and 658-683 nm, full width at half-maximums (FWHMs) of 20 nm and 30 nm), fluorescence quantum yield of 41.0%, and yield of 83.3% are prepared by hydrothermal method using o-phenylenediamine as precursor and inorganic oxidant as yield enhancer, and they have graphite nitrate-like structures. The long-wavelength side emission is aggregation-induced emission (AIE). A logarithmic relationship between the AIE wavelength (y) and the concentration (x) (y = 8.853ln(x) + 688.53, R = 0.998) is found. This regularity and the hig...

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Hydrothermal Synthesis of High‐Yield Red Fluorescent Carbon Dots with Ultra‐Narrow Emission by Controlled O/N Elements

Xian

2022

Advanced Materials

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“…The high‐resolution XPS C1s peak of the CDs (Figure 1g ) could be deconvoluted into three peaks: C—C/C═C (≈284.80 eV), C—N (≈286.29 eV), and C═O (≈288.71 eV). [ 18 ] The N 1s of the CDs in Figure 1e exhibits three peaks ascribed to pyridinic N (≈399.05 eV), pyrrolic N (≈399.78 eV), and graphitic N (≈400.78 eV), suggesting that N was doped into the graphene cores. [ 19 ] The O1s spectra of the CDs (Figure 1f ) showed two peaks at ≈531.58 and ≈533.39 eV which could be attributed to C═O and C—O, respectively.…”

Section: Resultsmentioning

confidence: 99%

Toward Strong Near‐Infrared Absorption/Emission from Carbon Dots in Aqueous Media through Solvothermal Fusion of Large Conjugated Perylene Derivatives with Post‐Surface Engineering

Liu¹,

Lei

Wang³

et al. 2022

Advanced Science

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Carbon dots (CDs) have attracted significant interest as one of the most emerging photoluminescence (PL) nanomaterials. However, the realization of CDs with dominant near‐infrared (NIR) absorption/emission peaks in aqueous solution remains a great challenge. Herein, CDs with both main NIR absorption bands at 720 nm and NIR emission bands at 745 nm in an aqueous solution are fabricated for the first time by fusing large conjugated perylene derivatives under solvothermal treatment. With post‐surface engineering, the polyethyleneimine modified CDs (PEI‐CDs) exhibit enhanced PL quantum yields (PLQY) up to 8.3% and 18.8% in bovine serum albumin aqueous and DMF solutions, which is the highest PLQY of CDs in NIR region under NIR excitation. Density functional theory calculations support the strategy of fusing large conjugated perylene derivatives to achieve NIR emissions from CDs. Compared to the commercial NIR dye Indocyanine green, PEI‐CDs exhibit excellent photostability and much lower cost. Furthermore, the obtained PEI‐CDs illustrate the advantages of remarkable two‐photon NIR angiography and in vivo NIR fluorescence bioimaging. This work demonstrates a promising strategy of fusing large conjugated molecules for preparing CDs with strong NIR absorption/emission to promote their bioimaging applications.

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“…Therefore, it is very important to develop CDs with red/near-infrared emission properties for bioimaging to ensure good light penetration depth and to minimize photodamage to biological tissues. [136][137][138] Up-conversion photoluminescence (UCPL) can be useful in this context also. UCPL imaging (two-photon imaging) uses near-infrared photons to image cells or tissues, thus avoid tissue damage and autofluorescence interference commonly encountered with UV excitation.…”

Section: Bioimagingmentioning

confidence: 99%

Carbon Dots in Bioimaging, Biosensing and Therapeutics: A Comprehensive Review

et al. 2022

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Photoluminescence mechanism of carbon dots: triggering high-color-purity red fluorescence emission through edge amino protonation

Cited by 327 publications

References 32 publications

Hydrothermal Synthesis of High‐Yield Red Fluorescent Carbon Dots with Ultra‐Narrow Emission by Controlled O/N Elements

Hydrothermal Synthesis of High‐Yield Red Fluorescent Carbon Dots with Ultra‐Narrow Emission by Controlled O/N Elements

Toward Strong Near‐Infrared Absorption/Emission from Carbon Dots in Aqueous Media through Solvothermal Fusion of Large Conjugated Perylene Derivatives with Post‐Surface Engineering

Carbon Dots in Bioimaging, Biosensing and Therapeutics: A Comprehensive Review

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