The formation mechanism and fluorophores of carbon dots synthesized <i>via</i> a bottom-up route

Qu, Dan; Sun, Zaicheng

doi:10.1039/c9qm00552h

Cited by 179 publications

(169 citation statements)

References 86 publications

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“…In the majority of the reported cases, IPCA-based fluorophores are only identified by spectroscopic (NMR and mass) and analytical techniques, and/or isolated in low yields from the prepared CNDs. 20,24,25 In order to access the engineered FCDs that avoid the drawback of the heterogeneity of the CNDs as a fluorescent material, we envisaged two different strategies for the synthesis of IPCA-appended CDs that are based on the reaction of CA with a suitable α,β-ethylenediamine molecular motif (Scheme 1).…”

Section: Chemical Synthesis and Characterization Of Ipcaappended Fcdsmentioning

confidence: 99%

“…A phosphate buffered solution of 6 (2400 µL, 2 µg mL −1 ) supplemented with pNP (10 µL, 2 mM) was combined with human serum (100 µL) from healthy volunteers. The samples were spiked with different amounts of Chol (20,40,60, and 80 µM). After incubation (10 min), the emission at 435 nm (excitation at 365 nm) was monitored.…”

Section: Detection Of Chol In Human Serum As a Matrixmentioning

confidence: 99%

“…Although the topic is still a subject of debate, some consensus has been established. [20][21][22] For bottom-up CNDs obtained by the co-pyrolysis of citric acid (CA) and an amine, it is accepted that luminescence primarily results from the molecular state rather than from size differences. 23 When α,β-bifunctional ethyleneamines (α,β-diamines, β-amino alcohols or α,β-aminothiols) are used, the formation of highly luminescent molecular fluorophores containing a five-membered fused 2-pyridone skeleton has been reported.…”

Section: Introductionmentioning

confidence: 99%

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Carbon dots-inspired fluorescent cyclodextrins: competitive supramolecular “off–on” (bio)sensors

et al. 2020

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Chromophore-appended cyclodextrins combine the supramolecular loading capabilities of cyclodextrins (CDs) with the optical properties of the affixed chromophores. Among fluorescent materials, carbon dots (CNDs) are attractive and the feasibility of CND-appended CDs as sensors has been demonstrated by different authors. However, CNDs are intrinsically heterogeneous materials and their ulterior functionalization yields hybrid composites that are not well defined in terms of structure and composition. Inspired by the fluorescence properties of 5-oxo-1,2,3,5-tetrahydroimidazo[1,2-a]pyridine-7-carboxylic acid (IPCA), the most paradigmatic of the molecular fluorophores detected in CNDs, herein we report two highly efficient synthetic chemical strategies for the preparation of IPCA-appended CDs that behave as CND-based CD "turn off-on" biosensors suitable for the analysis of cholesterol and β-galactosidase activity. We have deconstructed the CND-CD systems to demonstrate that (i) the role of CNDs is limited to acting as a support for the molecular fluorophores produced during their synthesis and (ii) the molecular fluorophores suffice for the determination of the enzymatic activity based on the quenching by p-nitrophenol as a sacrificial quencher. † Electronic supplementary information (ESI) available: Spectroscopic characterization of new compounds, and ESI schemes, figures, and tables. See

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Section: Chemical Synthesis and Characterization Of Ipcaappended Fcdsmentioning

confidence: 99%

Section: Detection Of Chol In Human Serum As a Matrixmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Carbon dots-inspired fluorescent cyclodextrins: competitive supramolecular “off–on” (bio)sensors

et al. 2020

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“…Although a substantial number of works have been already published on the topic, a controversial debate about the origin of C-dots fluorescence is still ongoing. Some authors attribute the C-dots emission properties to the functional groups on the dot surface, others to molecular-like fluorophores, which form during the thermal degradation process [11][12][13]. Conventionally, carbon dots can be divided into four classes [14].…”

Section: Introductionmentioning

confidence: 99%

Reversible Aggregation of Molecular-Like Fluorophores Driven by Extreme pH in Carbon Dots

et al. 2020

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The origin of carbon-dots (C‑dots) fluorescence and its correlation with the dots structure still lack a comprehensive model. In particular, the core-shell model does not always fit with the experimental results, which, in some cases, suggest a molecular origin of the fluorescence. To gain a better insight, we have studied the response of molecular-like fluorophores contained in the C‑dots at extreme pH conditions. Citric acid and urea have been employed to synthesize blue and green‑emitting C‑dots. They show a different emission as a function of the pH of the dispersing media. The photoluminescence has been attributed to molecular-like fluorophores: citrazinic acid and 4‑hydroxy‑1H‑pyrrolo[3,4‑c]‑pyridine‑1,3,6‑(2H,5H)-trione. 3D and time‑resolved photoluminescence, ultraviolet–visible (UV–vis) spectroscopy, and dynamic light scattering have been used to determine the aggregation state, quantum yield and emission properties of the C-dots. The dependence of the C-dots blue and green components on the chemical environment indicates that the origin of fluorescence is due to molecular-like fluorophores.

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“…Carbon quantum dots (CDs) have attracted significant attention in recent years 1,2 . They have been widely applied in fields such as light emitting diodes(LEDs) 3,4 , solar cells 5 , photocatalysts 6,7 , electrochemical sensing 8 , bioimaging 9 , photodetectors 10 , lasing 11 , and photothermal therapies 12 .…”

mentioning

confidence: 99%

Enhancing photoluminescence of carbon quantum dots doped PVA films with randomly dispersed silica microspheres

Zhao

Wang

Gao

et al. 2020

Sci Rep

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As a kind of excellent photoluminescent material, carbon quantum dots have been extensively studied in many fields, including biomedical applications and optoelectronic devices. They have been dispersed in polymer matrices to form luminescent films which can be used in LEDs, displays, sensors, etc. Owing to the total internal reflection at the flat polymer/air interfaces, a significant portion of the emitted light are trapped and dissipated. In this paper, we fabricate free standing flexible PVA films with photoluminescent carbon quantum dots embedded in them. We disperse silica microspheres at the film surfaces to couple out the total internal reflection. The effects of sphere densities and diameters on the enhancement of photoluminescence are experimentally investigated with a homemade microscope. The enhancement of fluorescence intensity is as high as 1.83 when the film is fully covered by spheres of 0.86 $${\boldsymbol{\mu }}$$µm diameter. It is worth noting that the light extraction originates from rather the scattering of individual spheres than the diffraction of ordered arrays. The mechanism of scattering is confirmed by numerical simulations. The simulated results show that the evanescent wave at the flat PVA/air interface can be effectively scattered out of the film.

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The formation mechanism and fluorophores of carbon dots synthesized via a bottom-up route

Abstract: Carbon dots (CDs) with incomparable optical properties have attracted extensive attention. However, some unclear issues remain, which has impeded the basic understanding and practical application of CDs.

Cited by 179 publications

References 86 publications

Carbon dots-inspired fluorescent cyclodextrins: competitive supramolecular “off–on” (bio)sensors

Carbon dots-inspired fluorescent cyclodextrins: competitive supramolecular “off–on” (bio)sensors

Reversible Aggregation of Molecular-Like Fluorophores Driven by Extreme pH in Carbon Dots

Enhancing photoluminescence of carbon quantum dots doped PVA films with randomly dispersed silica microspheres

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