Optical and Electronic Properties of Carbon-Based Nanomaterials and Composites

A special issue of C (ISSN 2311-5629).

Deadline for manuscript submissions: closed (30 September 2019) | Viewed by 79479

Special Issue Editors


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Guest Editor
Dipartimento di Fisica e Chimica—Emilio Segrè, Università degli Studi di Palermo, Via Archirafi 36, 90123 Palermo, Italy
Interests: 2D materials; optical; Raman and electron paramagnetic resonance spectroscopy studies of advanced materials for optics, electronics and photonics; irradiation effects on matter
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
Dipartimento di Fisica e Chimica—Emilio Segrè, Università degli Studi di Palermo, Via Archirafi 36, 90123 Palermo, Italy
Interests: nanomaterials; carbon nanodots; carbon dots; optical materials; ultrafast spectroscopy

Special Issue Information

Dear Colleagues,

We are pleased to present our project, a Special Issue of the Journal C, focusing on the optical and electronic properties of carbon-related nanomaterials. We would like to join the competences of researchers in the field of nanosized C-based structures, starting from 2D graphene and its ‘’extended family’’, like graphene oxide, nanotubes, and fullerenes, all the way to carbon dots (CDs) and diamond like carbon, thus covering the whole hierarchy of C-based 0D to 3D nanometric structures. The proposed Special Issue will also cover composites like graphene-nanoparticles, graphene-molecules, nanostructures and oxide, polymer included C-nanomaterials, and CD-based composites

The main focus of the project is on the electronic properties of the investigated materials, which means the following: transport, doping, energy gap modification, Fermi level shift, and on the optical properties targeting the absorption and fluorescence emission processes, also in connection to optical emitting, light harvesting, and photocatalytic devices, but not excluding fundamental aspects like charge and energy transfer dynamics. Within this framework, proper attention should also be given to the structural characterization of materials and the consideration of growth processes, as well as their exploitation for sensing and catalysis.

The reported manuscripts will represent both the experimental and the theoretical point of view, including simulative works. The final target is to give readers an overview of the hot topics and the state-of-the-art of C-related nanoscience, based on a largely interdisciplinary perspective typical of materials science.

Dr. Simonpietro Agnello
Dr. Fabrizio Messina
Guest Editors

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 1600 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

  • graphene
  • carbon dots
  • carbon nanotubes
  • diamond-like carbon
  • graphene derivatives
  • C-related nanomaterials
  • C-based nanocomposites
  • optical and electronic properties
  • structural characterization
  • optoelectronic devices
  • photocatalysis
  • electronic devices
  • sensors

Published Papers (18 papers)

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Editorial

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3 pages, 176 KiB  
Editorial
Optical and Electronic Properties of Carbon-Based Nanomaterials and Composites
by Simonpietro Agnello and Fabrizio Messina
C 2020, 6(2), 36; https://doi.org/10.3390/c6020036 - 29 May 2020
Cited by 2 | Viewed by 2137
Abstract
Dear Colleagues, [...] Full article

Research

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13 pages, 2755 KiB  
Article
On the Colloidal Stability of Nitrogen-Rich Carbon Nanodots Aqueous Dispersions
by Thiago Fiuza, Guilherme Gomide, Alex Fabiano Cortez Campos, Fabrizio Messina and Jérôme Depeyrot
C 2019, 5(4), 74; https://doi.org/10.3390/c5040074 - 16 Nov 2019
Cited by 15 | Viewed by 3446
Abstract
The present survey reports on the colloidal stability of aqueous dispersions of nitrogen-rich carbon nanodots (N-CDs). The N-CDs were synthesized by thermally induced decomposition of organic precursors and present an inner core constituted of a β C 3 N 4 crystalline structure [...] Read more.
The present survey reports on the colloidal stability of aqueous dispersions of nitrogen-rich carbon nanodots (N-CDs). The N-CDs were synthesized by thermally induced decomposition of organic precursors and present an inner core constituted of a β C 3 N 4 crystalline structure surrounded by a surface shell containing a variety of polar functional groups. N-CDs size and structure were checked by combined analysis of XRD (X-ray Diffraction) and TEM (Transmission Electron Microscopy) measurements. FTIR (Fourier-Transform Infrared Spectroscopy) experiments revealed the presence of carboxyl and amide groups on N-CDs surface. Towards a better understanding of the relation between colloidal stability and surface charge development, zetametry experiments were applied in N-CDs dispersions at different pHs and constant ionic strength. The increase of the absolute values of zeta potential with the alkalinization of the dispersion medium is consistent with the deprotonation of carboxyl groups on N-CDs surface, which agrees with the macroscopic visual observations of long-term colloidal stability at pH 12. The saturation value of N-CDs surface charge density was evaluated by means of potentiometric-conductometric titrations. The difference between carboxyl-related surface charge and the one determined by zeta potential measurements point to the presence of oxidized nitrogen functionalities onto the N-CDs surface in addition to carboxyl groups. These novel results shed light on the electrostatic repulsion mechanism that allows for the remarkable colloidal stability of N-CDs dispersions. Full article
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11 pages, 1376 KiB  
Article
Evaluation of Commercial “Carbon Quantum Dots” Sample on Origins of Red Absorption and Emission Features
by Weixiong Liang, Lin Ge, Xiaofang Hou, Xianyan Ren, Liju Yang, Christopher E. Bunker, Christopher M. Overton, Ping Wang and Ya-Ping Sun
C 2019, 5(4), 70; https://doi.org/10.3390/c5040070 - 1 Nov 2019
Cited by 22 | Viewed by 3883
Abstract
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 [...] Read more.
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. Full article
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11 pages, 2439 KiB  
Article
Recycling Oxacillin Residues from Environmental Waste into Graphene Quantum Dots
by Maria Laura Soriano and Soledad Cárdenas
C 2019, 5(4), 68; https://doi.org/10.3390/c5040068 - 1 Nov 2019
Cited by 4 | Viewed by 2639
Abstract
Of great concern are the residual antibiotics from dirt that can be found in farm soil and wastewater. This kind of emerging pollutant into engineered nanomaterials is riveting. This work proposes the elimination and transformation of a beta-lactam antibiotic, oxacillin, from environmental waste [...] Read more.
Of great concern are the residual antibiotics from dirt that can be found in farm soil and wastewater. This kind of emerging pollutant into engineered nanomaterials is riveting. This work proposes the elimination and transformation of a beta-lactam antibiotic, oxacillin, from environmental waste to graphene quantum dots (GQDs). Two protocols were followed in which the use of ethylenediamine (EDA) in the transformation leads to GQDs with excellent optical properties. Therefore, two types of GQDs were synthesized in a Teflon-lined stainless autoclave by a thermal procedure using oxacillin in the absence and presence of EDA. The ensuing e-GQDs from oxacillin and EDA display a stronger fluorescence emission in comparison to those synthesized without EDA (o-GQDs). The combination of Kaiser test analyses, infrared (IR) and Raman measurements revealed the presence of oxygen-containing groups and primary amines at the edges of the graphitic nanolayer for e-GQDs. This straightforward strategy brings hope and opens a new interest in waste recycling by means of extracting residual contaminants from the environment for their further transformation into adequate non-toxic graphitic nanomaterials with potential applications. Full article
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10 pages, 1949 KiB  
Article
Effect of Halogen Ions on the Photocycle of Fluorescent Carbon Nanodots
by Alice Sciortino, Roberto Pecorella, Marco Cannas and Fabrizio Messina
C 2019, 5(4), 64; https://doi.org/10.3390/c5040064 - 24 Oct 2019
Cited by 1 | Viewed by 2539
Abstract
Carbon dots (C-dots) are well-known for their strong sensitivity to the environment, which reflects on intensity and shape changes of their fluorescence, induced by various interacting ions and molecules in solution. Although these interactions have been extensively studied in the last few years, [...] Read more.
Carbon dots (C-dots) are well-known for their strong sensitivity to the environment, which reflects on intensity and shape changes of their fluorescence, induced by various interacting ions and molecules in solution. Although these interactions have been extensively studied in the last few years, especially in view of their possible sensing applications, the existing works have mostly focused on the quenching of C-dot fluorescence induced by metal cations. In fact, these latter easily bind to C-dots surfaces, which are negatively charged in most cases, promoting an electron transfer from the surface to them. Much less is known from the literature on the effect induced on C-dots by prototypical negative species in solutions, motivating more systematic studies on this different class of interactions. Here, we analyzed the effect of halogen ions on the fluorescence of C-dots, by combining steady-state optical absorption and photoluminescence, time-resolved fluorescence and femtosecond pump/probe spectroscopy. We demonstrate a quenching effect of C-dots fluorescence in the presence of halogen ions, which becomes more and more pronounced with increasing atomic number of the halogens, being negligible for chloride, appreciable for bromide and stronger for iodide. We find that quenching is mostly static, due to the binding of halogen ions on suitable surface sites at C-dots surfaces, while collisional quenching becomes obvious only at very high iodide concentrations. Finally, nanosecond and femtosecond time-resolved spectroscopies provide information on the quenching mechanism and time scales. Based on these data, we propose that the fluorescent state is deactivated by intersystem crossing to a dark triplet state, induced by close-range interactions with the heaviest halogen ions. Full article
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13 pages, 1621 KiB  
Article
Near-Infrared, Light-Triggered, On-Demand Anti-Inflammatories and Antibiotics Release by Graphene Oxide/Elecrospun PCL Patch for Wound Healing
by Nicolò Mauro, Salvatore Emanuele Drago, Gennara Cavallaro and Gaetano Giammona
C 2019, 5(4), 63; https://doi.org/10.3390/c5040063 - 23 Oct 2019
Cited by 29 | Viewed by 3350
Abstract
Very recently, significant attention has been focused on the adsorption and cell adhesion properties of graphene oxide (GO), because it is expected to allow high drug loading and controlled drug release, as well as the promotion of cell adhesion and proliferation. This is [...] Read more.
Very recently, significant attention has been focused on the adsorption and cell adhesion properties of graphene oxide (GO), because it is expected to allow high drug loading and controlled drug release, as well as the promotion of cell adhesion and proliferation. This is particularly interesting in the promotion of wound healing, where antibiotics and anti-inflammatories should be locally released for a prolonged time to allow fibroblast proliferation. Here, we designed an implantable patch consisting of poly(caprolactone) electrospun covered with GO, henceforth named GO–PCL, endowed with high ibuprofen (5.85 mg cm−2), ketoprofen (0.86 mg cm−2), and vancomycin (0.95 mg cm−2) loading, used as anti-inflammatory and antibiotic models respectively, and capable of responding to near infrared (NIR)-light stimuli in order to promptly release the payload on-demand beyond three days. Furthermore, we demonstrated the GO is able to promote fibroblast adhesion, a key characteristic to potentially provide wound healing in vivo. Full article
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9 pages, 3216 KiB  
Article
First-Principles Modeling of Atomic Structure and Chemical and Optical Properties of β-C3N4
by Xue Lei, Danil W. Boukhvalov and Anatoly F. Zatsepin
C 2019, 5(4), 58; https://doi.org/10.3390/c5040058 - 24 Sep 2019
Cited by 1 | Viewed by 2810
Abstract
In our work, we report the results of first-principles modeling of optical and chemical properties of β-C3N4 in bulk (pristine and defected), surface, and nanoclusters. We demonstrate significant sensitivity of adsorption spectra of β-C3N4 to [...] Read more.
In our work, we report the results of first-principles modeling of optical and chemical properties of β-C3N4 in bulk (pristine and defected), surface, and nanoclusters. We demonstrate significant sensitivity of adsorption spectra of β-C3N4 to any kinds of disorder in atomic structure. Formation and passivation of the surface provides similar changes in optical properties. The value of the indirect bandgap depends on the chemical structure of the surface. The surface of the bulk crystal and nanocluster is chemically active and unavoidably passivated at ambient conditions. Partial oxidation of the surface of β-C3N4 provides decreasing of the bandgap. Functionalization of the active sites on the surface by monovalent species (hydrogen and fluorine) leads to vanishing of the bandgap in the case of (001) surface and changes the value of the bandgap in the case of nanoclusters. Results of our calculations also demonstrate the appearance of magnetic moments in hydrogenated and fluorinated (001) surface of β-C3N4. Full article
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7 pages, 1217 KiB  
Article
Macroscopic Behavior and Microscopic Factors of Electron Emission from Chained Nanocarbon Coatings
by Daleri Boqizoda, Anatoly Zatsepin, Evgeny Buntov, Anatoly Slesarev, Daria Osheva and Tatiana Kitayeva
C 2019, 5(3), 55; https://doi.org/10.3390/c5030055 - 9 Sep 2019
Cited by 3 | Viewed by 2513
Abstract
The carbyne-containing films based on linear-chain carbon are promising materials for the manufacture of electronic equipment components. These carbyne-containing materials can be used as active elements of computational electronics and as ultra-miniature sensors of gaseous environment. The temperature studies of the electrical characteristics [...] Read more.
The carbyne-containing films based on linear-chain carbon are promising materials for the manufacture of electronic equipment components. These carbyne-containing materials can be used as active elements of computational electronics and as ultra-miniature sensors of gaseous environment. The temperature studies of the electrical characteristics of carbyne-containing films by most of the scientific groups are limited to the low temperature range in which the quantum properties of nanostructures are most pronounced. We studied carbyne-containing films with a thickness of 20 and 400 nm on copper and silicon substrates using optically stimulated electron emission (OSEE) in the temperature range from room temperature (RT) to 400 °C. Theoretical modeling explains the dependence of work function on termination groups and substrate lattice. Experimental data revealed a relationship between the spectral characteristics of electron emission and temperature. The spectral contributions of both surface states and bulk interband transitions were clearly distinguishable. Full article
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14 pages, 3100 KiB  
Article
Changing Contents of Carbon Hybridizations in Amorphous Hydrogenated Carbon Layers (a-C:H) on Sustainable Polyhydroxybutyrate (PHB) Exhibit a Significant Deterioration in Stability, Depending on Thickness
by Torben Schlebrowski, Lucas Beucher, Hadi Bazzi, Barbara Hahn, Stefan Wehner and Christian B. Fischer
C 2019, 5(3), 52; https://doi.org/10.3390/c5030052 - 30 Aug 2019
Cited by 14 | Viewed by 2909
Abstract
PHB is a biodegradable polymer based on renewable raw materials that could replace synthetic polymers in many applications. A big advantage is the resulting reduction of the waste problem, as well as the conservation of fossil resources. To arrange it for various applications, [...] Read more.
PHB is a biodegradable polymer based on renewable raw materials that could replace synthetic polymers in many applications. A big advantage is the resulting reduction of the waste problem, as well as the conservation of fossil resources. To arrange it for various applications, the surface is arranged by plasma-enhanced chemical vapor deposition (PECVD) with amorphous hydrogenated carbon layers (a-C:H). Here, on a 50 µm thick PHB-foil, a-C:H layers of different thicknesses (0–500 nm) were deposited in 50 nm steps. Surface topography was investigated by scanning electron microscopy (SEM), chemical composition by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and wettability checked by contact angle. In addition, layers were examined by synchrotron supported X-ray photoelectron spectroscopy (XPS) and near edge X-ray absorption fine structure (NEXAFS), which revealed thickness dependent changes of the sp2/sp3 ratio. With increasing thickness, even the topography changes show internal, stress-induced phenomena. The results obtained provide a more detailed understanding of the predominantly inorganic a-C:H coatings on (bio)polymers via in situ growth. Full article
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14 pages, 3975 KiB  
Article
Insights into the Electrochemical Behavior of Mercury on Graphene/SiC Electrodes
by Ivan Shtepliuk, Mikhail Vagin and Rositsa Yakimova
C 2019, 5(3), 51; https://doi.org/10.3390/c5030051 - 22 Aug 2019
Cited by 9 | Viewed by 3830
Abstract
Fast and real time detection of Mercury (Hg) in aqueous solutions is a great challenge due to its bio-accumulative character and the detrimental effect on human health of this toxic element. Therefore, development of reliable sensing platforms is highly desirable. Current research is [...] Read more.
Fast and real time detection of Mercury (Hg) in aqueous solutions is a great challenge due to its bio-accumulative character and the detrimental effect on human health of this toxic element. Therefore, development of reliable sensing platforms is highly desirable. Current research is aiming at deep understanding of the electrochemical response of epitaxial graphene to Mercury exposure. By performing cyclic voltammetry and chronoamperometry measurements as well as density functional theory calculations, we elucidate the nature of Hg-involved oxidation-reduction reactions at the graphene electrode and shed light on the early stages of Hg electrodeposition. The obtained critical information of Hg behavior will be helpful for the design and processing of novel graphene-based sensors. Full article
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12 pages, 5647 KiB  
Article
Fluence Enhanced Optical Response of Ag Implanted Amorphous Carbon Thin Films
by Shunmugam Ramsamy Naidoo and Abdulsalam Ismaila
C 2019, 5(3), 45; https://doi.org/10.3390/c5030045 - 5 Aug 2019
Cited by 7 | Viewed by 3162
Abstract
Silver nanoparticles (NPs) are known to exhibit strong interaction with light photons because their surface conduction electrons undergo collective oscillations once photo-excited at specific wavelengths; the so-called surface plasmon resonance (SPR). Their incorporation into carbon-based material is shown to greatly influence the overall [...] Read more.
Silver nanoparticles (NPs) are known to exhibit strong interaction with light photons because their surface conduction electrons undergo collective oscillations once photo-excited at specific wavelengths; the so-called surface plasmon resonance (SPR). Their incorporation into carbon-based material is shown to greatly influence the overall optical response of the matrix due to aggregation. In this paper, we studied the optical response of silver-irradiated amorphous carbon films due to varying fluence of 25 keV Ag ions in the range 2.5–3.4 × 1016 ions/cm2. Raman spectroscopy provided an insight into the microstructural details of the Ag:a-C nanocomposites such that access to bond characteristics of the films is enabled by directly linking the Raman information with sp2/sp3 configurations. Atomic force microscopy (AFM) analysis show significant increase in particle grain size and surface roughness of the films with increasing fluence while transmission electron microscopy (TEM) confirmed fluence-induced particle aggregation due to irradiation. Optical absorption studies revealed that the SPR of Ag NPs occurs in the wavelength range 418–395 nm in the irradiated films. The blue shift in plasmonic wavelength response is explained with respect to the fluence-induced increase in the particulate grain size and particle density as confirmed by AFM and TEM. The optical band gap energy ( E g ) of the pristine carbon film decreased from 1.79 eV to 1.41 eV while Urbach parameter ( E u ) increased from 0.01 eV to 12.0 eV, respectively with increasing fluence. These tunable optical parameters can be tailored into applications in surface coatings and as functional materials for solar cell efficiency enhancement. Full article
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Review

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13 pages, 1760 KiB  
Review
Recent Advancements on the CVD of Graphene on Copper from Ethanol Vapor
by Giuliana Faggio, Giacomo Messina, Caterina Lofaro, Nicola Lisi and Andrea Capasso
C 2020, 6(1), 14; https://doi.org/10.3390/c6010014 - 19 Mar 2020
Cited by 18 | Viewed by 5028
Abstract
Chemical vapor deposition (CVD) on metal foils is regarded as the most effective method to produce large-area graphene with properties in line with the requirements of an extensive range of electronic and optical applications. For the CVD of graphene, ethanol is a versatile [...] Read more.
Chemical vapor deposition (CVD) on metal foils is regarded as the most effective method to produce large-area graphene with properties in line with the requirements of an extensive range of electronic and optical applications. For the CVD of graphene, ethanol is a versatile carbon source alternative to the widely used methane. In this review we report on the current progress in this field showing how the CVD parameters can be modulated to gain full microstructural control on graphene grown on Cu foils. Using ethanol vapor, graphene can be grown as a continuous film with mono- or multi-layer thickness, and also in the form of isolated crystals on pre-oxidized Cu substrates. Overall, ethanol-CVD allows a controllable degree of crystallinity and tunable electrical/optical characteristics in the grown samples. In turn, this control translates into a superior versatility for device design and related applications. Full article
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50 pages, 4726 KiB  
Review
Excitons in Carbonic Nanostructures
by Alexander P. Demchenko
C 2019, 5(4), 71; https://doi.org/10.3390/c5040071 - 12 Nov 2019
Cited by 46 | Viewed by 5512
Abstract
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 [...] Read more.
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. Full article
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37 pages, 4952 KiB  
Review
Two-Dimensional Carbon: A Review of Synthesis Methods, and Electronic, Optical, and Vibrational Properties of Single-Layer Graphene
by Angelo Armano and Simonpietro Agnello
C 2019, 5(4), 67; https://doi.org/10.3390/c5040067 - 1 Nov 2019
Cited by 51 | Viewed by 12208
Abstract
Graphite has been widely used by humans for a large part of their history. Nevertheless, it has only recently been possible to isolate its basic unit: carbon atoms arranged in a honeycomb structure on a single plane, namely graphene. Since its discovery, many [...] Read more.
Graphite has been widely used by humans for a large part of their history. Nevertheless, it has only recently been possible to isolate its basic unit: carbon atoms arranged in a honeycomb structure on a single plane, namely graphene. Since its discovery, many techniques have been developed and improved to properly synthesize graphene and its derivatives which are part of the novel class of two-dimensional materials. These advanced materials have imposed themselves in nanotechnology thanks to some outstanding physical properties due to their reduced dimensions. In the case of graphene, its reduced dimension gives rise to a high electrical mobility, a large thermal conductivity, a high mechanical resistance, and a large optical transparency. Therefore, such aspect is of great scientific interest for both basic and applied research, ranging from theoretical physics to surface chemistry and applied solid state physics. The connection between all these fields is guaranteed by spectroscopy and especially by Raman spectroscopy which provides a lot of information about structural and electronic features of graphene. In this review, the authors present a systematized collection of the most important physical insights on the fundamental electronic and vibrational properties of graphene, their connection with basic optical and Raman spectroscopy, and a brief overview of main synthesis methods. Full article
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15 pages, 4419 KiB  
Review
On the Emission Properties of Carbon Dots: Reviewing Data and Discussing Models
by Carlo Maria Carbonaro, Riccardo Corpino, Marcello Salis, Francesca Mocci, Swapneel Vijay Thakkar, Chiara Olla and Pier Carlo Ricci
C 2019, 5(4), 60; https://doi.org/10.3390/c5040060 - 2 Oct 2019
Cited by 115 | Viewed by 9006
Abstract
The emission properties of carbon dots (CDs) have already found many potential applications, from bio-imaging and cell labelling, to optical imaging and drug delivery, and are largely investigated in technological fields, such as lighting and photonics. Besides their high efficiency emission, CDs are [...] Read more.
The emission properties of carbon dots (CDs) have already found many potential applications, from bio-imaging and cell labelling, to optical imaging and drug delivery, and are largely investigated in technological fields, such as lighting and photonics. Besides their high efficiency emission, CDs are also virtually nontoxic and can be prepared through many green chemistry routes. Despite these important features, the very origin of their luminescence is still debated. In this paper, we present an overview of sounding data and the main models proposed to explain the emission properties of CDs and their tunability. Full article
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12 pages, 2033 KiB  
Review
Porphyrinoid–Fullerene Hybrids as Candidates in Artificial Photosynthetic Schemes
by Vasilis Nikolaou, Asterios Charisiadis, Christina Stangel, Georgios Charalambidis and Athanassios G. Coutsolelos
C 2019, 5(3), 57; https://doi.org/10.3390/c5030057 - 18 Sep 2019
Cited by 20 | Viewed by 4222
Abstract
Natural photosynthesis inspired the scientific community to design and synthesize molecular assemblies that possess advanced light-harvesting and electron-transfer features. In this review, we present the preparation and the photophysical investigation of novel porphyrin–fullerene hybrids acting as artificial photosynthetic systems. Porphyrinoids stand as chlorophyll [...] Read more.
Natural photosynthesis inspired the scientific community to design and synthesize molecular assemblies that possess advanced light-harvesting and electron-transfer features. In this review, we present the preparation and the photophysical investigation of novel porphyrin–fullerene hybrids acting as artificial photosynthetic systems. Porphyrinoids stand as chlorophyll analogues and have emerged as suitable photosensitizers in supramolecular electron donor–acceptor hybrids. Fullerenes (C60) are versatile electron acceptors with small reorganization energy and low reduction potentials. The novel derivatives presented herein mimic the fundamental features of the photosynthetic reaction center, namely, light harvesting, charge separation, and charge transport. To this end, a comprehensive analysis on these key processes that occur in various porphyrin–fullerene entities is illustrated in this work. Full article
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11 pages, 3541 KiB  
Review
Structure and Properties of Chained Carbon: Recent Ab Initio Studies
by Evgeny Buntov, Anatoly Zatsepin, Tatiana Kitayeva and Alexander Vagapov
C 2019, 5(3), 56; https://doi.org/10.3390/c5030056 - 11 Sep 2019
Cited by 5 | Viewed by 4509
Abstract
Carbon chains or carbyne-like structures represent the next generation of 1D materials whose properties can be tuned by the chain length, doping, and the type of termination. Currently inaccessible technology of the macroscopic carbyne synthesis and characterization makes theoretical work especially valuable. The [...] Read more.
Carbon chains or carbyne-like structures represent the next generation of 1D materials whose properties can be tuned by the chain length, doping, and the type of termination. Currently inaccessible technology of the macroscopic carbyne synthesis and characterization makes theoretical work especially valuable. The state of the art methods being applied in the field are density functional theory and molecular dynamics. This paper provides a review of the current state of research on modeling linear carbon structures and related materials. We show that even though the “static” properties of carbon chains (mechanical strength, thermal conduction, band gaps, and phonon spectra) are extensively described, there are only a few simulations of the synthesis processes that constitute the next challenge in 1D research. Full article
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17 pages, 4763 KiB  
Review
Recent Advances in Seeded and Seed-Layer-Free Atomic Layer Deposition of High-K Dielectrics on Graphene for Electronics
by Emanuela Schilirò, Raffaella Lo Nigro, Fabrizio Roccaforte and Filippo Giannazzo
C 2019, 5(3), 53; https://doi.org/10.3390/c5030053 - 2 Sep 2019
Cited by 24 | Viewed by 4775
Abstract
Graphene (Gr) with its distinctive features is the most studied two-dimensional (2D) material for the new generation of high frequency and optoelectronic devices. In this context, the Atomic Layer Deposition (ALD) of ultra-thin high-k insulators on Gr is essential for the implementation of [...] Read more.
Graphene (Gr) with its distinctive features is the most studied two-dimensional (2D) material for the new generation of high frequency and optoelectronic devices. In this context, the Atomic Layer Deposition (ALD) of ultra-thin high-k insulators on Gr is essential for the implementation of many electronic devices. However, the lack of out-of-plane bonds in the sp2 lattice of Gr typically hinders the direct ALD growth on its surface. To date, several pre-functionalization and/or seed-layer deposition processes have been explored, to promote the ALD nucleation on Gr. The main challenge of these approaches is achieving ultra-thin insulators with nearly ideal dielectric properties (permittivity, breakdown field), while preserving the structural and electronic properties of Gr. This paper will review recent developments of ALD of high k-dielectrics, in particular Al2O3, on Gr with “in-situ” seed-layer approaches. Furthermore, recent reports on seed-layer-free ALD onto epitaxial Gr on SiC and onto Gr grown by chemical vapor deposition (CVD) on metals will be presented, discussing the role played by Gr interaction with the underlying substrates. Full article
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