On the myth of “red/near-IR carbon quantum dots” from thermal processing of specific colorless organic precursors

Liang, Weixiong; Wang, Ping; Meziani, Mohammed J.; Ge, Liya; Yang, Liju; Patel, Amankumar K.; Morgan, Sabina O.; Sun, Ya‐Ping

doi:10.1039/d1na00286d

Cited by 24 publications

(37 citation statements)

References 46 publications

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“…[103,104] Recently, the origins of the red/near IR optical absorption observed in some precursor mixtures have been proposed to be from the molecular chromophore of thermally induced chemical reactions and have nothing to do with any nanoscale carbon entities produced by carbonization. [105] It overturns the previous understanding of the carbon core as emission center which is worthy of further discussion.…”

Section: Origin Of Luminescencesupporting

confidence: 57%

Carbon dots: An innovative luminescent nanomaterial

Shi

Yuan

et al. 2021

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In recent years, carbon dots (CDs), including carbon nanodots, carbonized polymer dots, carbon quantum dots, and graphene quantum dots have attracted a mounting interest as readily accessible, nontoxic, and relatively inexpensive carbon-based nanomaterials. Yet, despite intense research for a number of years, a unifying picture is still lacking to clarify the exact definition, clear chemical structure, and unique optical properties of this family of nanomaterials. In this review, we systematically summarize the recent development of CDs from molecular design to related properties of excited states as well as their applications in optoelectronic devices and biology. We point out the current challenges, including exploring precise synthesis, clarifying the structure-property relationship, and regulating singlet and triplet states of fluorescence, phosphorescence, and delayed fluorescence. Moreover, the structural optimization of optoelectronic devices, tumor targeting mechanism, selective imaging, and drug delivery of CDs are also highlighted. We hope that the information provided in this review will inspire more exciting research on CDs from a brand-new perspective and promote practical application of CDs in multiple directions of current and future research.

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Section: Origin Of Luminescencesupporting

confidence: 57%

Carbon dots: An innovative luminescent nanomaterial

Shi

Yuan

et al. 2021

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“…On the other hand, most of the research groups have pursued investigations only on a particular set (or subset) of carbon dots. This diversity continues to lead to apparent FL mechanism controversies and purification issues (with red-emissive CDs being recently referred as "mythical", 29 due to presence of molecular dyes in the mixture), 20,165 and there continues to be a lack of deep understanding of how operating conditions can be translated into versatile methodologies towards tailorable properties.…”

Section: Perspectivesmentioning

confidence: 99%

“…28 When working with electronrich arene precursors (such as o-phenylenediamine) special care should be taken since red-emitting molecules have been reported to form in the same synthetic conditions. 20,29 The introduction of heteroatoms, their location, as well as the choice of heteroatom are also known approaches to tune the emission wavelength of CDs (Fig. 2d).…”

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confidence: 99%

A multifunctional chemical toolbox to engineer carbon dots for biomedical and energy applications

et al. 2022

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Photoluminescent carbon nanomaterials, or carbon dots (CDs), are an emerging class of materials that has recently attracted considerable attention for biomedical and energy applications. They are defined by characteristic sizes of <10 nm, a carbon-based core, and the possibility to add various functional groups at their surface for targeted applications. These nanomaterials possess many interesting physicochemical and optical properties, including tuneable light emission, dispersibility and low toxicity. In this Review, we categorize how chemical tools impact the properties of CDs. We look for pre-and post-synthetic approaches for the preparation of CDs and their derivatives or composites. We then showcase examples to correlate structure, composition, and function and use them to discuss the future development for this class of nanomaterials. monomer/polymer as starting materials. Historically, the top-down strategy was first exploited and consisted mainly of electrochemical or chemical oxidation of graphite. 7 While these approaches can yield relatively large quantities of CDs, they usually employ harsh conditions (in terms of voltage applied or chemical oxidant used), long synthetic times, and still need post-synthetic procedures to tune the optoelectronic properties. From the fluorescence perspective, oxidative cutting of carbon sources leads to more structural defects, resulting in less appealing photoluminescence properties.Currently, the bottom-up syntheses are more popular and will be the focus of this Review. In addition to the multitude of molecular precursors available, other benefits include multiple choices of thermal treatments, quicker reaction times, and more uniform properties in the final material. The choice of precursors and synthetic procedures (i.e. pre-synthetic control) affects the physicochemical properties of CDs in terms of size, graphitization degree, surface functional groups, and doping. Nevertheless, the structural features of the precursors can be retained in the nanoparticles, allowing for some degree of predictability. Single-component, to a certain extent, and multi-component reactions enable the use of straightforward doping strategies. These include heteroatoms (examples here include boron, nitrogen, sulfur, selenium, or a combination of them) and metals (such as lanthanides).Besides pre-synthetic control, engineering the surface composition via post-synthetic approaches is a promising way to optimize and expand the utilization of CDs (Fig. 1b). Post-synthetic strategies usually affect the surface functional groups of the CDs since they are generally inefficient in changing properties and chemical composition of the core. Exploiting their surface chemistry also prompted the development of multifunctional CD-based materials (Fig. 1c).There are many excellent sources of information about the intricacies of CDs properties [7][8][9][10][11] and their applications, [12][13][14][15][16] as well as their progress in comparison to traditional inorganic quantum dots. 17 At first, emphas...

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“…40–42 Molecular fluorophores have been proven to be formed in situ during the initial synthesis steps of numerous blue- and green-emitting CA-based CDs, 38 and the most recent literature indicates that similar low molecular weight compounds might impart the optical properties of red-emitting CDs prepared from CA and specific amine precursors. 21,43,44…”

Section: Introductionmentioning

confidence: 99%

The role of molecular fluorophores in the photoluminescence of carbon dots derived from citric acid: current state-of-the-art and future perspectives

et al. 2022

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On the myth of “red/near-IR carbon quantum dots” from thermal processing of specific colorless organic precursors

Abstract: Carbon dots were originally found and reported as surface-passivated small carbon nanoparticles, where the effective surface passivation was the chemical functionalization of the carbon nanoparticles with organic molecules. Understandably, the...

Cited by 24 publications

References 46 publications

Carbon dots: An innovative luminescent nanomaterial

Carbon dots: An innovative luminescent nanomaterial

A multifunctional chemical toolbox to engineer carbon dots for biomedical and energy applications

The role of molecular fluorophores in the photoluminescence of carbon dots derived from citric acid: current state-of-the-art and future perspectives

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