Special Issue "Graphene and Carbon Quantum Dots, and Related 2D Quantum Dots"

A special issue of C (ISSN 2311-5629). This special issue belongs to the section "Carbon Materials and Carbon Allotropes".

Deadline for manuscript submissions: closed (31 March 2021).

Special Issue Editor

Prof. Dr. Yoke Khin Yap
E-Mail Website
Guest Editor
Department of Physics, Michigan Technological University, 118 Fisher Hall, 1400 Townsend Drive, Houghton, Michigan, 49931-1295, USA
Interests: fundamentals of synthesis; characterization; applications of functional nanomaterials, including B–C–N nanostructures (carbon, boron nitride, boron carbon–nitride, carbon nitride, boron, etc.)
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

Two-dimensional (2D) van der Waals nanostructures such as graphene, hexagonal boron nitride (h-BN) sheets, and transition metal dichalcogenides (TMDCs) have gained tremendous research interest in physical, chemical, and biological applications. Carbon dots (CDs) are nanoparticles of graphene and thin graphite with diameters of several nanometers. It has been demonstrated that CDs are emerging new fluorescent materials, which are biologically compatible. The structurally similar boron nitride dots (BNDs) are of nanoparticle h-BN sheets. Similar to CDs, BNDs also attained excitation-dependent fluorescent properties and are biologically compatible. This Special Issue shall focus on highlighting latest research discovery of CDs, BNDs, as well as nanoparticles of other van der Waals materials, such as TMDCs. Articles related to the synthesis, characterization, and application of these CDs and related van der Waals nanostructures will be included into the Special Issue.

Prof. Dr. Yoke Khin Yap
Guest Editor

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. C is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Carbon
  • Boron nitride
  • Graphene
  • Transition metal dichalcogenides
  • TMDCs
  • van der Waals

Published Papers (5 papers)

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Research

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Open AccessArticle
Functionalized Graphene Quantum Dots Modulate Malignancy of Glioblastoma Multiforme by Downregulating Neurospheres Formation Viewed by 441
Abstract
Glioblastoma multiforme (GBM) is the most aggressive brain cancer. We previously demonstrated the effect of biocompatible surface functionalized graphene quantum dots (GQDs) on GBM cells as chemotherapy enhancers in combination with the antitumor drug doxorubicin (Dox). However, traditional two-dimensional cultures could not represent [...] Read more.
Glioblastoma multiforme (GBM) is the most aggressive brain cancer. We previously demonstrated the effect of biocompatible surface functionalized graphene quantum dots (GQDs) on GBM cells as chemotherapy enhancers in combination with the antitumor drug doxorubicin (Dox). However, traditional two-dimensional cultures could not represent a reliable model of tumor behavior. In this work, we investigated the effect of carboxylated (COOH-GQDs), aminated (NH2-GQDs) and unfunctionalized GQDs on a three-dimensional model of neurospheres. Neurospheres are clusters of GBM cells, which formation is driven by the presence of a stem subpopulation involved in cancer malignancy. Tumor recurrence after surgical resection, chemotherapy and radiotherapy indeed depends on the presence of cancer cells with stem properties. We measured a significant reduction in number and size of neurospheres after two weeks of monitoring in the presence of COOH-GQDs and GQDs. Previous works pointed out how variations of membrane fluidity could affect membrane stability and cell-to-cell interactions, thus influencing cell clustering. Therefore, we measured changes in membrane fluidity after administration of GQDs. We found that COOH-GQDs and GQDs significantly increased membrane fluidity with respect to the treatment with NH2-GQDs or compared to untreated cells. Shifts in the phase of phospholipid bilayer were in accordance with the negative surface net charge of GQDs. We depicted a strong correlation between negatively charged GQDs-induced increase in membrane fluidity and the downregulation of neurospheres formation. Our results indicate that COOH-GQDs and GQDs significantly modulate tumor malignancy by increasing fluidity of cell membrane, with a consequent inhibition of cell-to-cell interaction. Full article
(This article belongs to the Special Issue Graphene and Carbon Quantum Dots, and Related 2D Quantum Dots)
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Open AccessArticle
Nitrogen-Doped Arginine Carbon Dots and Its Metal Nanoparticle Composites as Antibacterial Agent
C 2020, 6(3), 58; https://0-doi-org.brum.beds.ac.uk/10.3390/c6030058 - 21 Sep 2020
Cited by 1 | Viewed by 849
Abstract
Nitrogen (N)-doped arginine carbon dots (Arg CD) were successfully synthesized using arginine as the amine source and citric acid as the carbon source via a one-pot green synthesis microwave-assisted technique in 2 min. Ag and Cu nanoparticles (NP) were generated within N-doped Arg [...] Read more.
Nitrogen (N)-doped arginine carbon dots (Arg CD) were successfully synthesized using arginine as the amine source and citric acid as the carbon source via a one-pot green synthesis microwave-assisted technique in 2 min. Ag and Cu nanoparticles (NP) were generated within N-doped Arg CDs as composite Arg-Ag CDs and Arg-Cu CDs to render enhanced antibacterial properties. TEM analysis revealed that Arg CDs are in graphitic structures with d spacing ranging from 0.5 nm to 10 nm. The minimum inhibition concentration (MIC) values of Arg CDs with 6.250 mg/mL were decreased by about 100-fold for Arg-Ag CDs and ten-fold for Arg-Cu CDs with 0.062 and 0.625 mg/mL MIC values against Staphylococcus aureus (S. aureus). The highest antibacterial susceptibility was observed for the Arg-Ag CD composite with 0.125 and 0.312 mg/mL minimum bactericidal concentration (MBC) values against Gram negative S. aureus and Gram positive Escherichia coli (E. coli) bacteria strains, respectively. It was found that the metal NPs within Arg CDs significantly increased the antibacterial properties of CDs making them available in the treatment of infections caused by different bacterial species. Furthermore, Arg-Ag CD and Arg-Cu CD composites were tested for Acetylcholinesterase (AChE, E.C. 3.1.1.7) that break down acetylcholine (ACh) into choline and acetic acid leading to the loss of ACh which plays an essential role as neurotransmitter in Alzheimer disease. It was found that Arg-Cu CDs inhibited 74.9 ± 0.8% and Arg-Ag CDs inhibited 52.1 ± 3.8% of AChE at a 1.82 mg/mL concentration versus no inhibition for Arg-CD. Moreover, the chelating activity of Arg-Cu CDs and Arg-Ag CDs were tested for Fe(II) and it was found that almost 100% chelating was attained at 116 μg composites versus no measurable chelation for bare Arg CDs, suggesting the potential neurodegenerative disease treatment properties of these composite CDs in the brain. Full article
(This article belongs to the Special Issue Graphene and Carbon Quantum Dots, and Related 2D Quantum Dots)
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Open AccessCommunication
Graphene-Quantum-Dot-Mediated Semiconductor Bonding: A Route to Optoelectronic Double Heterostructures and Wavelength-Converting Interfaces
C 2020, 6(2), 28; https://0-doi-org.brum.beds.ac.uk/10.3390/c6020028 - 09 May 2020
Cited by 2 | Viewed by 863
Abstract
A semiconductor bonding technique that is mediated by graphene quantum dots is proposed and demonstrated. The mechanical stability, electrical conductivity, and optical activity in the bonded interfaces are experimentally verified. First, the bonding scheme can be used for the formation of double heterostructures [...] Read more.
A semiconductor bonding technique that is mediated by graphene quantum dots is proposed and demonstrated. The mechanical stability, electrical conductivity, and optical activity in the bonded interfaces are experimentally verified. First, the bonding scheme can be used for the formation of double heterostructures with a core material of graphene quantum dots. The Si/graphene quantum dots/Si double heterostructures fabricated in this study can constitute a new basis for next-generation nanophotonic devices with high photon and carrier confinements, earth abundance, environmental friendliness, and excellent optical and electrical controllability via silicon clads. Second, the bonding mediated by the graphene quantum dots can be used as an optical-wavelength-converting semiconductor interface, as experimentally demonstrated in this study. The proposed fabrication method simultaneously realizes bond formation and interfacial function generation and, thereby, can lead to efficient device production. Our bonding scheme might improve the performance of optoelectronic devices, for example, by allowing spectral light incidence suitable for each photovoltaic material in multijunction solar cells and by delivering preferred frequencies to the optical transceiver components in photonic integrated circuits. Full article
(This article belongs to the Special Issue Graphene and Carbon Quantum Dots, and Related 2D Quantum Dots)
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Review

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Open AccessReview
A Review on van der Waals Boron Nitride Quantum Dots
C 2021, 7(2), 35; https://0-doi-org.brum.beds.ac.uk/10.3390/c7020035 - 27 Mar 2021
Viewed by 374
Abstract
Boron nitride quantum dots (BNQDs) have gained increasing attention for their versatile fluorescent, optoelectronic, chemical, and biochemical properties. During the past few years, significant progress has been demonstrated, started from theoretical modeling to actual application. Many interesting properties and applications have been reported, [...] Read more.
Boron nitride quantum dots (BNQDs) have gained increasing attention for their versatile fluorescent, optoelectronic, chemical, and biochemical properties. During the past few years, significant progress has been demonstrated, started from theoretical modeling to actual application. Many interesting properties and applications have been reported, such as excitation-dependent emission (and, in some cases, non-excitation dependent), chemical functionalization, bioimaging, phototherapy, photocatalysis, chemical, and biological sensing. An overview of this early-stage research development of BNQDs is presented in this article. We have prepared un-bias assessments on various synthesis methods, property analysis, and applications of BNQDs here, and provided our perspective on the development of these emerging nanomaterials for years to come. Full article
(This article belongs to the Special Issue Graphene and Carbon Quantum Dots, and Related 2D Quantum Dots)
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Open AccessFeature PaperReview
Citric Acid Derived Carbon Dots, the Challenge of Understanding the Synthesis-Structure Relationship Cited by 1 | Viewed by 708
Abstract
Carbon dots (CDs) are highly-emissive nanoparticles obtained through fast and cheap syntheses. The understanding of CDs’ luminescence, however, is still far from being comprehensive. The intense photoluminescence can have different origins: molecular mechanisms, oxidation of polyaromatic graphene-like layers, and core-shell interactions of carbonaceous [...] Read more.
Carbon dots (CDs) are highly-emissive nanoparticles obtained through fast and cheap syntheses. The understanding of CDs’ luminescence, however, is still far from being comprehensive. The intense photoluminescence can have different origins: molecular mechanisms, oxidation of polyaromatic graphene-like layers, and core-shell interactions of carbonaceous nanoparticles. The citric acid (CA) is one of the most common precursors for CD preparation because of its high biocompatibility, and this review is mainly focused on CA-based CDs. The different parameters that control the synthesis, such as the temperature, the reaction time, and the choice of solvents, were critically described. Particular attention was devoted to the CDs’ optical properties, such as tunable emission and quantum yields, in light of functional applications. The survey of the literature allowed correlating the preparation methods with the structures and the properties of CA-based CDs. Some basic rules to fabricate highly luminescent nanoparticles were selected by the metanalysis of the current literature in the field. In some cases, these findings can be generalized to other types of CDs prepared via liquid phase. Full article
(This article belongs to the Special Issue Graphene and Carbon Quantum Dots, and Related 2D Quantum Dots)
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