Carbon dots with high fluorescence quantum yield: the fluorescence originates from organic fluorophores

Shi, Lei; Yang, Jian; Zeng, Hai Bo; Chen, Yong Mei; Yang, Sheng; Wu, Chao; Zeng, Hao; Osada, Yoshihito; Zhang, Qiqing

doi:10.1039/c6nr00451b

Cited by 235 publications

(202 citation statements)

References 31 publications

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“…Still, the debate regardingt he exact origin of this upconversion mechanism in carbon-based nanoparticles is open and not completely unraveled as additional fluorescent compounds linked to the carbogenic cores may participate in the observed optical response. [38,[49][50][51][52] Timeresolved photoluminescence decay measurements fitted well to as um of three-exponential functions with an averagel ifetime of 6.5ns. The shortest fitting components have been previously attributed to intrinsic recombination of populated core states whilst the longer( slower) fitting components are usually related to surface defects, which give rise to surfacet raps and surfaces tates.…”

Section: Synthesis and Characterization Of Edta-derived Carbon Nanodotsmentioning

confidence: 66%

Upconverting Carbon Nanodots from Ethylenediaminetetraacetic Acid (EDTA) as Near‐Infrared Activated Phototheranostic Agents

Ortega‐Liebana

Encabo‐Berzosa

Casanova

et al. 2019

Chemistry A European J

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This work describes the synthesis of nitrogendoped carbon nanodots (CNDs) synthesized from ethylenediaminetetraacetic acid (EDTA) as aprecursor and their application as luminescent agentsw ith ad ual-mode theranostic role as near-infrared (NIR)t riggered imaging and photodynamic therapy agents.I nterestingly,t hese fluorescent CNDs are more rapidlya nd selectively internalized by tumorc ells and exhibit very limited cytotoxicity until remotelya ctivated with aN IR illumination source. These CNDsa re excellent candidates forp hototheranostic purposes, for example, si-multaneousi maging and therapy can be carriedo ut on cancer cells by using their luminescent properties and the in situ generation of reactive oxidative species(ROS) upon excitation in the NIR range. In the presence of CNDs,N IR remote activation induces the in vitro killing of U251MG cells. Through the use of flow imaging cytometry,w eh ave been able to successfully mapa nd quantify the different types of cell deaths induced by the presence of intracellular superoxide anions (CO 2 À )a nd hydrogen peroxide (H 2 O 2 )R OS generated in situ upon NIR irradiation. [a] Dr.M.C.O rtega-Liebana, Dr.M.M.Encabo-Berzosa,D r.Supporting information and the ORCID identification number(s) for the author(s) of this articlecan be found under: https://doi.

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Section: Synthesis and Characterization Of Edta-derived Carbon Nanodotsmentioning

confidence: 66%

Upconverting Carbon Nanodots from Ethylenediaminetetraacetic Acid (EDTA) as Near‐Infrared Activated Phototheranostic Agents

Ortega‐Liebana

Encabo‐Berzosa

Casanova

et al. 2019

Chemistry A European J

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“…[29–33] Recently, due to the importance of small molecular fluorophores formed by CA and amine based molecules, various citrate-based fluorescent molecules have also been developed. [32, 34–36] …”

Section: Introductionmentioning

confidence: 99%

Citrate‐Based Fluorescent Biomaterials

Shan

Hsieh

Bai

et al. 2018

Adv Healthcare Materials

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Fluorescence imaging has emerged as a promising technique for monitoring and assessing various biologically relevant species in cells and organisms, driving the demand for effective fluorescent agents with good biocompatibility and high fluorescence performance. However, traditional fluorescent agents, such as quantum dots (QDs) and organic dyes, either suffer from toxicity concerns or poor fluorescence performance (e.g., low photobleaching-resistance). In this regard, citrate-based fluorescent biomaterials, which are synthesized from the natural and biocompatible precursor of citric acid (CA), have become competitive alternatives for fluorescence imaging owing to their biocompatibility, cost effectiveness, straightforward synthetic routes, flexible designability, as well as strong fluorescence with adjustable excitation/emission wavelengths. Accordingly, numerous citrate-based biomaterials, including carbon dots (CDs), biodegradable photoluminescent polymers (BPLPs), and small molecular fluorophores, have been developed and researched in the past few decades. This review discusses recent progress in the research and development of citrate-based fluorescent materials with emphasis on their design and synthesis considerations, material properties, fluorescence properties and mechanisms, as well as biomedical applications. It is expected that this review will provide an insightful discussion on the citrate-based fluorescent biomaterials, and lead to innovations for the next generation of fluorescent biomaterials and fluorescence-based biomedical technology.

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“…Those similar spectroscopic results between solution and solid PCD indicate that our PCD shares the same PL origin irrespective of its phase. The small fluorescent molecule has been reported as a main PL origin of citric acid‐derived CD because the fluorophore has spectroscopic characteristics resembling those of CD . In particular, the inverted shape between PL and PLE spectra is a common feature of molecular fluorophore .…”

Section: Resultsmentioning

confidence: 99%

“…Between the components, the τ 1 (14.0 ns for PCD and 14.3 ns for RCD) had almost 100% contribution to PL than the τ 2 (6.9 ns for PCD and 2.4 ns for RCD). With the existence of molecular fluorophore as a PL origin and the similar time scale (≈10 ns) of fluorescent organic molecules, we assigned the τ 1 as the molecular‐state. In powder form, PCD had two lifetime components of τ 1 (10.6 ns) and τ 2 (4.8 ns) with an average lifetime of 8.7 ns, while RCD showed three components of τ 1 (8.2 ns), τ 2 (2.1 ns), and τ 3 (0.6 ns) with an average value of 1.0 ns.…”

Section: Resultsmentioning

confidence: 99%

Quenching‐Resistant Polymer Carbon Dot Preserving Emission Color Consistency in Solid‐State

Kwak

Yoo

Kim

2019

Advanced Optical Materials

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Recently, Rogach's group realized solidstate-luminescent CD/silica composite, which possessed high quantum yield (QY) and PL output with relatively high CD loading (19.2 wt%) by gelation. [18] However, this process was limited to hydroxyl-rich CD only and still suffered from aggregation in extremely high concentration.Fundamental solution is to develop a selfquenching-resistant CD even without dispersion matrices. Polymer CD (PCD), a polymer-like CD consisting of crosslinked matrix and sub-fluorophores, has been studied for solid-state luminescence because crosslinking may prevent π-π interaction. [20][21][22][23] Several groups synthesized quenching-resistant PCD, but those showed red-shifted emission with noticeable color change compared to solutionstate fluorescence. [24][25][26][27] Such spectral shift in solid-state usually occurs with nonradiative decay competitively, which leads to a decrease of QY. In addition, the emission color change in solidstate needs additional optimization process for the fabrication of optoelectronics, so that the energy transfer as an origin for ACQ and red-shift should be strictly avoided.Herein, we synthesized a blue-emitting PCD with the same emission center at 434 nm in both solution-and solid-state through a hydrothermal reaction. By structural and spectroscopic analysis, the origin of solid-state luminescence was investigated. We further identified a reason for the emission color consistency of PCD from dilute solution to powder form by comparing with CD that showed red-shifted emission in solid-state. We also fabricated LED using PCD as a color-converting layer, and it had a luminous efficacy of 12.03 lm W −1 without significant color change even with extremely high loading fraction of 50 wt%. With the increased loading fraction (20 wt%), we enhanced brightness of our LED up to four times compared to the LED fabricated with conventional low loading fraction (0.1-5 wt%) using PCD. Compared to red-shifted CD (RCD)-based LED with the conventional loading fraction, the luminous flux of PCD-based LED with 20 wt% increased by 3 to 15 times. This result would be a great interest to those who study CD-based LED. Results and DiscussionSolid-state luminescent polymer carbon dot (PCD) was synthesized using citric acid (CA) and diethylenetriamine (DETA) through a hydrothermal reaction at 70 °C (Figure 1a). Product Solid-state luminescent carbon dot without dispersion matrices is studied to overcome aggregation-caused quenching, but it usually shows spectral shift between solution-and solid-state accompanying a dramatic decrease of fluorescence intensity, which hinders a real application. Herein, polymer carbon dot (PCD) showing solid-state luminescence without red-shift is synthesized by low-temperature reaction. The PCD solution and solid have the same emission peaks at 434 nm and similar absolute quantum yields of 68.2% and 62.7%, respectively, which is uncommon feature compared to other carbon dots. The mechanism for solid-state luminescence and emission color consistency is invest...

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Carbon dots with high fluorescence quantum yield: the fluorescence originates from organic fluorophores

Cited by 235 publications

References 31 publications

Upconverting Carbon Nanodots from Ethylenediaminetetraacetic Acid (EDTA) as Near‐Infrared Activated Phototheranostic Agents

Upconverting Carbon Nanodots from Ethylenediaminetetraacetic Acid (EDTA) as Near‐Infrared Activated Phototheranostic Agents

Citrate‐Based Fluorescent Biomaterials

Quenching‐Resistant Polymer Carbon Dot Preserving Emission Color Consistency in Solid‐State

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