Luminescence origin of carbon based dots obtained from citric acid and amino group-containing molecules

Fang, Qingqing; Dong, Yongqiang; Chen, Yingmei; Lü, Chunhua; Chi, Yuwu; Yang, Huanghao; Yu, Ting

doi:10.1016/j.carbon.2017.03.061

Cited by 137 publications

(82 citation statements)

References 41 publications

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“…Part of recent studies relate the fluorescence of CDs to the detection of conjugated fluorophores, such as IPCA (1,2,3,5-tetrahydro-5-oxo-imidazo[1,2-α]pyridine-7-carboxylic acid), [28][29][30] derivatives or citrazinic acid [31][32] or pyridine-like structures. [33][34] On the other hand, the group of B. Yang put under closer scrutiny the polymeric structure of the CDs. The observation that also non-conjugated polymers cause a bright photoluminescence, regardless of the presence of other emissive sources such as molecular fluorophores or a carbon core was ascribed to the so-called cross-link enhanced emission (CEE) effect.…”

Section: Introductionmentioning

confidence: 99%

Supramolecular-Enhanced Charge Transfer within Entangled Polyamide Chains as the Origin of the Universal Blue Fluorescence of Polymer Carbon Dots

et al. 2018

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The emission of a bright blue fluorescence is a unique feature common to the vast variety of polymer carbon dots (CDs) prepared from carboxylic acid and amine precursors. However, the difficulty to assign a precise chemical structure to this class of CDs yet hampers the comprehension of their underlying luminescence principle. In this work, we show that highly blue fluorescent model types of CDs can be prepared from citric acid and ethylenediamine through low temperature synthesis routes. Facilitating controlled polycondensation processes, the CDs reveal sizes of 1-1.5 nm formed by a compact network of short polyamide chains of about 10 monomer units. Density functional theory calculations of these model CDs uncover the existence of a spatially separated highest occupied molecular orbital and a lowest unoccupied molecular orbital located at the amide and carboxylic groups, respectively. Photoinduced charge transfer between these groups thus constitutes the origin of the strong blue fluorescence emission. Hydrogen-bond-mediated supramolecular interactions between the polyamide chains enabling a rigid network structure further contribute to the enhancement of the radiative process. Moreover, the photoinduced charge transfer processes in the polyamide network structure easily explain the performance of CDs in applications as revealed in studies on metal ion sensing. These findings thus are of general importance to the further development of polymer CDs with tailored properties as well as for the design of technological applications.

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Section: Introductionmentioning

confidence: 99%

Supramolecular-Enhanced Charge Transfer within Entangled Polyamide Chains as the Origin of the Universal Blue Fluorescence of Polymer Carbon Dots

et al. 2018

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“…Carbon quantum dots (CQDs), a new class of carbon nanoparticles with size less than 10 nm, 4,5 have uorescence properties similar to QDs, but do not contain toxic metal elements, and have outstanding advantages such as easy functionalization, low cost, very low toxicity and favorable biocompatibility. [5][6][7][8] Recently, research on chiral CQDs has attracted great attention and achieved some good achievements. The researches on chiral CQDs indicated that levogyration-CQDs (L-CQDs) and dextrorotation-CQDs (D-CQDs) present different biological effects.…”

Section: Introductionmentioning

confidence: 99%

Investigation on the chirality mechanism of chiral carbon quantum dots derived from tryptophan

et al. 2019

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“…For the detailed investigation of optical properties, spectroscopic analysis for solution and solid PCD was performed. In absorption spectra, PCD in solution‐state showed distinct peaks at ≈250 and 351 nm that correspond to π–π* transition from sp 2 ‐hybridized carbon for the former peak while n–π* and π–π* transition from heteroatom‐containing groups and pyridine derivatives for the latter peak, respectively (Figure S1, Supporting Information) . The absorbance of solid PCD had quite different feature with several distinct peaks, showing higher intensity near ≈400 nm compared to other visible region.…”

Section: Resultsmentioning

confidence: 99%

“…In high‐performance liquid chromatography‐mass spectrometry (HPLC‐MS) result of PCD, an intense peak at 243 m z −1 and weak peaks at 260 and 278 m z −1 , which means the existence of small molecules (Figure S3, Supporting Information). It has been known that hydrothermal reaction between CA and several amines forms highly emissive organic fluorophores such as citrazinic acid . Ding's group identified that a fluorescent organic fluorophore, 1‐(2‐aminoethyl)‐5‐oxo‐1,2,3,5‐tetrahydroimidazo[1,2‐a]‐pyridine‐7‐carboxylic acid (AEIOP) was synthesized during the hydrothermal reaction between CA and DETA .…”

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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Luminescence origin of carbon based dots obtained from citric acid and amino group-containing molecules

Cited by 137 publications

References 41 publications

Supramolecular-Enhanced Charge Transfer within Entangled Polyamide Chains as the Origin of the Universal Blue Fluorescence of Polymer Carbon Dots

Supramolecular-Enhanced Charge Transfer within Entangled Polyamide Chains as the Origin of the Universal Blue Fluorescence of Polymer Carbon Dots

Investigation on the chirality mechanism of chiral carbon quantum dots derived from tryptophan

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

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