Red carbon dots: Optical property regulations and applications

Zhu, Zhijun; Zhai, Yanling; Li, Zhenhua; Zhu, Peiyuan; Sui, Mao; Zhu, Chengzhou; Du, Dan; Belfiore, Laurence A.; Tang, Jianguo; Lin, Yuehe

doi:10.1016/j.mattod.2019.05.003

Cited by 251 publications

(146 citation statements)

References 227 publications

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“…Nowadays, the emissive carbon dots covering the whole visible spectral range down to the near infrared have been reported [133,134]. They emit bright fluorescence with band maxima observed in yellow [135,136], orange [137,138], and red [78,139,140] colors. The near-IR absorbing and emitting nanoparticles were recently obtained [141,142].…”

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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“…The optical absorption spectrum of the as-supplied solution was measured in a standard 1.0 cm cuvette, and the observed absorbances were ~0.12 at 400 nm and ~0.054 at 480 nm ( Figure 2). The absorption spectrum featured a very broad band around 480 nm, which would probably qualify the sample to be in the rank of "red-absorptive" (or more accurately "longer wavelength-absorptive" for the absorption band not quite in the red yet) [22][23][24][25][26][27][28][29][30]. Since it is well known that electronic transitions responsible for the observed optical absorptions in solid carbon nanoparticles are dominated by π-plasmons [32][33][34][35] the known absorption spectrum of aqueous dispersed carbon nanoparticles is shown for comparison [31].…”

Section: Resultsmentioning

confidence: 99%

“…In fact, recent investigations in the literature have raised questions on some reported dot samples obtained from "one-pot" carbonization syntheses [16,[18][19][20][21] especially on those from thermal processing under very mild conditions such as "cooking a simple organic mixture at lower than 200 • C for a few hours". Similarly mild one-pot carbonization conditions were used in some reported experiments on the synthesis of "red-absorptive and emissive" samples from some selected specific precursor mixtures [22][23][24][25][26][27][28][29][30] such as mixtures of citric acid with formamide [22,24] on which there are understandably concerns with respect to not only the content of nanoscale carbon domains and dot structures in such samples but also the potentially substantial interference from dye-like species produced in the processing. Meanwhile, the scientific chemical supplier MilliporeSigma has recently started to market the dot sample of red absorption and emission features from unspecified source(s) or production method.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Commercial “Carbon Quantum Dots” Sample on Origins of Red Absorption and Emission Features

Liang

Hou

et al. 2019

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The commercially acquired aqueous solution of “carbon quantum dots” sample was evaluated by optical absorption and fluorescence emission methods; in reference to aqueous dispersed small carbon nanoparticles and representative carbon dots prepared from chemical functionalization of the carbon nanoparticles. The results suggest a very low content of carbon that is associated with nanoscale carbon particles/domains in the as-supplied sample; and likely significant contamination by dye-like species/mixtures. In the absence of any information on the synthesis and history of the commercial sample, the possible cause of the contamination was illustrated by an example on similar dye formation in the one-pot carbonization synthesis of “red carbon dots” from citric acid–formamide precursor mixtures under too mild processing conditions that were insufficient for the intended carbonization. The negative impacts to the carbon dots research field by the apparent proliferation and now commercial availability of carbon-deficient or even largely carbon-less “carbon quantum dots”, which are more susceptible to dye contamination or dominance, are discussed.

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“…6F) has been proved as an efficient way to boost their catalytic performance. [62,63] With this in mind, the catalytic performance of metal-free SACs for NERR has been explored. compared to that of G, and higher B doping leads to improved N2 adsorption.…”

Section: Au Sacsmentioning

confidence: 99%

Single-atom catalysts boost nitrogen electroreduction reaction

Zhai

Zhu

et al. 2020

Materials Today

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Ammonia (NH3) is mainly produced through the traditional Haber-Bosch process under harsh conditions with huge energy consumption and massive carbon dioxide (CO2) emission. The nitrogen electroreduction reaction (NERR), as an energy-efficient and environment-friendly process of converting nitrogen (N2) to NH3 under ambient conditions, has been regarded as a promising alternative to the Haber-Bosch process and has received enormous interest in recent years. Although some exciting progress has been made, considerable scientific and technical challenges still exist in improving the NH3 yield rate and Faradic efficiency, understanding the mechanism of the reaction and promoting the wide commercialization of NERR. Single-atom catalysts (SACs) have emerged as promising catalysts because of its atomically dispersed activity sites and maximized atom efficiency, unsaturated coordination environment, and its unique electronic structure, which could significantly improve the rate of reaction and yield rate of NH3. In this review we briefly introduce the unique structural and electronic features of SACs, which contributes to comprehensively understand the reaction mechanism owing to their structural simplicity and diversity, and in turn expedite the rational design of fantastic catalysts at the atomic scale. Then, we summarize the most recent experimental and computational efforts on developing novel SACs with excellent NERR performance, including precious metal-, nonprecious metal-and nonmetal-based SACs. Finally, we present challenges and perspectives of SACs on NERR, as well as some potential means for advanced NERR catalyst.

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Red carbon dots: Optical property regulations and applications

Cited by 251 publications

References 227 publications

Excitons in Carbonic Nanostructures

Excitons in Carbonic Nanostructures

Evaluation of Commercial “Carbon Quantum Dots” Sample on Origins of Red Absorption and Emission Features

Single-atom catalysts boost nitrogen electroreduction reaction

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