Excitation-Independent Dual-Color Carbon Dots: Surface-State Controlling and Solid-State Lighting

Chen, Daqin; Gao, Haobo; Chen, Xiao; Fang, Gaoliang; Yuan, Shuo; Yuan, Yong‐Jun

doi:10.1021/acsphotonics.7b00675

Cited by 93 publications

(45 citation statements)

References 36 publications

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“…When they are synthesized in the same reaction pot, the nanoparticle formation may proceed along two or more parallel routes in well-resolved discrete forms with recognizable spectroscopic properties, instead of the expected broadly heterogeneous species [134,157,158]. The observed dual emissions can be excitation wavelength-independent, and these properties can be retained in the solid state [158]. It was reported that the two blue and orange excitation-emission channels can be disconnected and excited at two different wavelengths [158].…”

Section: What Determines the Excitation And Emission Peak Positions?mentioning

confidence: 99%

Excitons in Carbonic Nanostructures

Demchenko

2019

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Unexpectedly bright photoluminescence emission can be observed in materials incorporating inorganic carbon when their size is reduced from macro–micro to nano. At present, there is no consensus in its understanding, and many suggested explanations are not consistent with the broad range of experimental data. In this Review, I discuss the possible role of collective excitations (excitons) generated by resonance electronic interactions among the chromophore elements within these nanoparticles. The Förster-type resonance energy transfer (FRET) mechanism of energy migration within nanoparticles operates when the composing fluorophores are the localized electronic systems interacting at a distance. Meanwhile, the resonance interactions among closely located fluorophores may lead to delocalization of the excited states over many molecules resulting in Frenkel excitons. The H-aggregate-type quantum coherence originating from strong coupling among the transition dipoles of adjacent chromophores in a co-facial stacking arrangement and exciton transport to emissive traps are the basis of the presented model. It can explain most of the hitherto known experimental observations and must stimulate the progress towards their versatile applications.

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Section: What Determines the Excitation And Emission Peak Positions?mentioning

confidence: 99%

Excitons in Carbonic Nanostructures

Demchenko

2019

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“…Although plentiful researches have proposed that the structural defects help to create bandgaps within the structure of CDs, the relationship between structural defects and bandgaps is still controversial. In the view of long‐wavelength emissions, many previous efforts have indicated that the defect states originated from surface groups are highly responsible for energy gaps changes, and thus releasing energy in the forms of multiple PL emissions …”

Section: Resultsmentioning

confidence: 99%

Orange‐Emissive Carbon Quantum Dots: Toward Application in Wound pH Monitoring Based on Colorimetric and Fluorescent Changing

Yang

Zhu

Zhang

et al. 2019

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152

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Monitoring of wound pH is critical for interpreting wound status, because early identification of wound infection or nonhealing wounds is conducive to administion of therapies at the right time. Here, novel orange‐emissive carbon quantum dots (O‐CDs) are synthesized via microwave‐assisted heating of 1,2,4‐triaminobenzene and urea aqueous solution. The as‐prepared O‐CDs exhibit distinctive colorimetric response to pH changing, and also display pH‐sensitive fluorescence. Benefiting from the response of O‐CDs over a wound‐relevant pH range (5–9), medical cotton cloth is selected to immobilize O‐CDs through hydrogen bond interactions, the resultant O‐CDs‐coated cloth with emission at 560 nm shows a high response to pH variation in the range of 5–9 via both fluorescence and visible colorimetric changes. Moreover, the sensitivity of fluorescence to pH is capable of establishing an analytical mode for determining pH value. Further, the O‐CDs‐based pH indicator possesses not only superior biocompatibility and drug compatibility but also excellent resistance leachability and high reversibility. Importantly, the usage of O‐CDs‐coated cloth to detect pH is free from the interference of blood contamination and long‐term storage, thus providing a valuable strategy for wound pH monitoring through visual response and quantitative determination.

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“…The center of emission spectra of PCD‐based LED was located at 434 nm for 1 wt% and at 484 nm for 50 wt% that are blue region (Figure S15, Supporting Information). The red‐shift with concentration increase may be due to the inner filter effect or energy transfer, which is arising from additional emissive states formed during sonication and annealing. While PCD‐based LED showed almost same blue emission irrespective of loading amounts of PCD, RCD‐based LED showed obvious color change from blue to red as the loading fraction increased.…”

Section: Resultsmentioning

confidence: 99%

“…However, like organic molecular fluorophores, the real application of CD in solid‐state lighting has been retarded by aggregation‐caused quenching (ACQ), a phenomenon that luminescence intensity of the aggregated fluorophores weakens dramatically and even disappears . Because ACQ of CD results from π–π stacking or resonance energy transfer between nearby fluorophores, a routine way to prevent solid‐state quenching used dispersion matrices like polymer to secure sufficient distance between fluorophores . But, high CD concentration still leads to dead CD, and only 0.1–1 wt% of fluorophores has been employed in the supporting media .…”

Section: Introductionmentioning

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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Excitation-Independent Dual-Color Carbon Dots: Surface-State Controlling and Solid-State Lighting

Cited by 93 publications

References 36 publications

Excitons in Carbonic Nanostructures

Excitons in Carbonic Nanostructures

Orange‐Emissive Carbon Quantum Dots: Toward Application in Wound pH Monitoring Based on Colorimetric and Fluorescent Changing

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

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