Planar Carbon Research Articles

Sweet potato‑derived carbon nanosheets incorporate NiCo2O4 nanocomposite as electrode materials for supercapacitors

Since a composite electrode made of carbon and transition metal oxides has much potential to be the best electrode type for a future energy storage system, the low-temperature solution growth method was used to make a carbon framework from sweet potato with NiCo2O4 nanoparticles attached to it. This method is easy, cheap, and can be used for large-scale commercial production. FTIR spectra a peak band of Ni-O and Co-O and the bending functional group at wave number 857 cm−1. XRD shows the crystal planes (111), (220), (331), (222), (400), (422), (511), and (440) at 2θ = 18.97°, 31.97°, 37.51°, 38.10°, 44.55°, 55.51°, 58.65°, and 64.92°, which indicates the NiCo2O4. The typical broad peaks around 23.3° can be linked to (002) lattice planes of amorphous carbon. The average size of the grains in the NiCo2O4/C samples was found to be 21.5 ± 0.5 nm. VSM shows that NiCo2O4/C has strong magnet properties. Based on the CV curve formed, it can be seen that NiCo2O4/C-2.8 has a balanced cathodic and anodic curve and also a higher current density than the others. It shows that NiCo2O4/C-2.8 has a higher ability to move electrons. The addition of the number of variations in the carbon mixture in NiCo2O4 shows the specific capacitance. It shows that carbon can prevent the movement of electrons in NiCo2O4, causing a decrease in performance. The right amount of carbon can increase the electron transfer ability.

Planar pentacoordinate carbon in a 16-electron neutral CCu2Be3H4 cluster.

Planar hypercoordination in carbon is a fascinating area, which departs from the usual view of coordination geometry in carbon. Herein, we propose a planar pentacoordinate carbon species in the global minimum of the CCu2Be3H4 cluster. The cluster is a 16-electron species that is thermodynamically and kinetically very stable. Bonding analyses reveal 2π/6σ double aromaticity in the cluster. A low-energy isomerization pathway also reveals that the cluster has a sufficient lifetime for its experimental detection.

Revisiting the potential-energy surface of CnBe3n+2H2n+22+ (n = 2-4) clusters: are planar pentacoordinate carbon structures the global minima?

Using various exploration strategies, in this study, we investigated the potential energy surfaces (PES) of CBe5H5+ and CnBe3n+2H2n+22+ (n = 2-4) clusters. Previous studies proposed that the planar pentacoordinate carbons (ppCs) were the global minima of these clusters. However, our study identified new putative global minima and competitive isomers, refuting some previous assignments. We employed several methods, including evolutive-inspired stochastic approaches guided by "chemical criteria", and ab initio molecular dynamics simulations at elevated temperatures. Our results showed that the size of the scanned population significantly affected the evolutive method and that constrained or guided procedures showed an advantage in identifying better minima for larger systems. This study demonstrated that using multiple complementary strategies can result in a wider variety of minima in a given energy range. Our findings provide valuable insights into exploring the potential energy surfaces of clusters, mainly medium-sized clusters, which could be the connections between small clusters and nanomaterials.

18-valence-electron rule lighted planar tetracoordinate carbon and nitrogen: the global energy minima of CAl4Zn and NAl4Zn.

The exploration of planar hypercoordinate carbon (phC) is challenging and significant. It is often puzzling to chemists whether the designed phC species should satisfy the 18-valence-electron rule, an authoritative rule in the phC field. In this study, we introduced a zinc atom into the extremely unstable 16-valence-electron planar tetracoordinate carbon (ptC) species CAl4 and its isoelectronic structure NAl4+ with a planar tetracoordinate nitrogen (ptN), and designed the 18-valence-electron CAl4Zn and NAl4Zn+ possessing a ptC and ptN, respectively. The thermodynamic results indicate that the ptC/N species CAl4Zn and NAl4Zn+ are the global energy minima, and also showed that the 18-valence-electron rule is more appropriate in designing ptC/N species having the CAl4 and NAl4+ skeletons, compared with the 16-valence-electron rule. Simultaneously, the BOMD simulations found that CAl4Zn is dynamically stable. Although NAl4Zn+ was isomerized at 298 and 500 K, it is dynamically viable. The excellent stability may be explained by the perfect electronic structure. First, the HOMO-LUMO gaps became much wider after the introduction of the Zn atom. Second, AdNDP analysis indicated that the introduction of the Zn atom promoted the formation of peripheral Al-Al and Al-Zn covalent bonds, providing a stable and comfortable bonding environment for ptC/N. In addition, the σ and π double aromaticity further stabilized the ptC/N species. Hence, as dynamic global energy minima display σ and π double aromaticity, the ptC/N species CAl4Zn and NAl4Zn+ are promising in gas phase generation.

Planar carbon electrodes for real-time quantification of hydrogen sulfide release from cells.

A planar electrode system was developed to permit the real-time, selective detection of hydrogen sulfide (H2S) from stimulated cells. Planar carbon electrodes were produced via stencil printing carbon ink through a laser cut vinyl mask. Electrodes were preconditioned using a constant potential amperometry methodology to prevent sensor drift resulting from elemental sulfur adsorption. Modification with a bilaminar coating (electropolymerized ortho-phenylenediamine and a fluorinated xerogel) facilitated high selectivity to H2S. To demonstrate the biological application of this planar sensor system, H2S released from 17β-estradiol-stimulated human umbilical vein endothelial cells (HUVECs) was quantified in situ in real-time. Stimulated HUVECs released sustained H2S levels for hours before returning to baseline. Cellular viability assays demonstrated negligible cell cytotoxicity at the electrochemical potentials required for analysis.

Transverse magnetoconductance in two-terminal chiral spin-selective devices.

The phenomenon of chirality induced spin selectivity (CISS) has triggered significant activity in recent years, although many aspects of it remain to be understood. For example, most investigations are focused on spin polarizations collinear to the charge current, and hence longitudinal magnetoconductance (MC) is commonly studied in two-terminal transport experiments. Very little is known about the transverse spin components and transverse MC - their existence, as well as any dependence of this component on chirality. Furthermore, the measurement of the CISS effect via two-terminal MC experiments remains a controversial topic. Detection of this effect in the linear response regime is debated, with contradicting reports in the literature. Finally, the potential influence of the well-known electric magnetochiral effect on CISS remains unclear. To shed light on these issues, in this work we have investigated the bias dependence of the CISS effect using planar carbon nanotube networks functionalized with chiral molecules. We find that (a) transverse MC exists and exhibits tell-tale signs of the CISS effect, (b) transverse CISS MC vanishes in the linear response regime establishing the validity of Onsager's relation in two-terminal CISS systems, and finally (c) the CISS signal remains present even in the absence of electric magneto chiral effects, suggesting the existence of an alternative physical origin of CISS MC.

Structure and Bonding in Planar Hypercoordinate Carbon Compounds

The term hypercoordination refers to the extent of the coordination of an element by its normal value. In the hypercoordination sphere, the element can achieve planar and/or non-planar molecular shape. Hence, planar hypercoordinate carbon species violate two structural rules: (i) The highest coordination number of carbon is four and (ii) the tetrahedral orientation by the connected elements and/or groups. The unusual planar orientations are mostly stabilized by the electronic interactions of the central atom with the surrounding ligands. In this review article, we will talk about the current progress in the theoretical prediction of viable planar hypercoordinate carbon compounds. Primary knowledge of the planar hypercoordinate chemistry will lead to its forthcoming expansion. Experimental and theoretical interests in planar tetracoordinate carbon (ptC), planar pentacoordinate carbon (ppC), and planar hexacoordinate carbon (phC) are continued. The proposed electronic and mechanical strategies are helpful for the designing of the ptC compounds. Moreover, the 18-valence electron rule can guide the design of new ptC clusters computationally as well as experimentally. However, the counting of 18-valence electrons is not a requisite condition to contain a ptC in a cluster. Furthermore, this ptC idea is expanded to the probability of a greater coordination number of carbon in planar orientations. Unfortunately, until now, there are no such logical approaches to designing ppC, phC, or higher-coordinate carbon molecules/ions. There exist a few global minimum structures of phC clusters identified computationally, but none have been detected experimentally. All planar hypercoordinate carbon species in the global minima may be feasible in the gas phase.

Lithiophilic single-atom Co on carbon nanosheets synergistically modulates Li deposition enable dendrite-free lithium metal batteries

Lithium metal batteries with proud energy density gained wide research interest in the past decades. Unfortunately, the uneven lithium deposition and the uncontrollable lithium dendrites growth leading to low coulombic efficiency and poor cycling stability remain unresolved. Herein, advanced approach via constructing 3D hierarchical single-atom Co anchored nitrogen carbon nanosheets-carbon fiber cloth (CC@CN-SACo) is reported that enables uniform Li deposition and offers high performance of Li metal batteries. The design of active single-atom in CC@CN-SACo achieves enhanced lithophilicity that effectively reduces the nucleation overpotential. Owing to the enlarge specific area and numerous lithophilic single atom Co sites, the current density is significantly reduced and the Li+ ion flux is uniformly distributed. Density functional theory calculations also reveal that the electron-delocalized sp2 hybridized 2D carbon plane between Co sites on the CN-SACo nanosheet and the active s(Li)-dz2/dxz(Co) interactions takes a pivotal role in improving Li deposition thermodynamics as well as the diffusion kinetics of Li+ and effectively modulates the deposition/stripping behavior of Li at lithium metal anode, thereby preventing the formation of Li dendrites. As a consequence, CC@CN-SACo@Li electrode assembled with Li foil delivers a superior cycling stability with 2000 h, 1400 h, and 500 h at 1 mA cm−2/1mAh cm−2, 2 mA cm−2/1mAh cm−2, and 5 mA cm−2/5mAh cm−2, respectively. The full cells assembled with LiFePO4 achieve a capacity retention of 96.6% with 2 mg cm−2 LiFePO4 and 81% with N/P ratio of 5 at 1C is attained. Surprisingly, CC@CN-SACo@Li also presents superior performances with 718.4 mAh g−1 reversible capacity after 300 cycles when applied in lithium-sulfur batteries, suggesting its universality for different high-energy batteries.

Dynamic crush response of compression molded planar isotropic carbon fiber reinforced composites

AbstractVehicle mass reduction can be achieved through the utilization of carbon fiber reinforced composites within the vehicle body structure. In this study, planar isotropic compression molded carbon fiber reinforced composites are studied for their potential utilization as automotive primary energy absorbing structures. The energy absorption behavior of a discontinuous randomly oriented 2‐D planar isotropic carbon fiber reinforced nylon 6 thermoplastic composite and a continuous 2 × 2 twill quasi‐isotropic carbon fiber reinforced epoxy thermoset composite are studied by dynamic flat plaque crush testing. Post‐mortem failure modes of both materials are related back to their load‐displacement and energy‐displacement curves under different test conditions. It is shown that crush fixture support length dictates the failure mode and specific energy absorption (SEA) of all fiber reinforced composites tested. In addition, elevated temperature testing of the nylon 6 carbon fiber reinforced composites reduces the SEA in all test configurations. Finally, an automotive carbon fiber composite front end energy absorbing structure is considered as the replacement over a legacy metallic energy absorbing structure. Mass reduction benefits beyond the improved SEA of the composite as compared to the metallic structure it replaces are discussed by considering the increased crush length efficiency of the composite structure which can reduce the vehicle front end length, and therefore the mass of the vehicle. These results are expected to direct the future development of fiber reinforced composites structures in energy absorbing automotive structures.

Fabrication of graphdiyne and its analogues for photocatalytic application

AbstractGraphdiyne (GDY), an emerging two‐dimensional all‐carbon allotrope, features the coexistence of sp and sp2 hybridized planar carbon atoms. GDY and GDY‐based materials exhibit unique physical and chemical properties, such as well‐defined molecular skeleton, π‐conjugated structure, high specific surface area with porosity, and good electrical conductivity, which have aroused widespread interest in various disciplines. As an emerging field, in this work, we summarize important synthesis strategies of GDY and GDY‐based materials including classical synthesis, chemical vapor deposition, explosion approach, and interface‐assisted methods. We also elaborate the recent modifications to regulate the structure and properties of GDY from the viewpoint of metal doping, non‐metal doping, and heterostructure construction. Meanwhile, recent achievements and progress in the development of energy and environmental applications in photocatalysis are highlighted. Lastly, the challenges and potential developments of GDY in the catalytic research are given at the end of this article.image

Theoretical Study of Oxygen Reduction Reaction Mechanism in Metal-Free Carbon Materials: Defects, Structural Flexibility, and Chemical Reaction.

Metal-free carbon materials are attractive Pt-based catalyst alternatives. However, despite efforts, the reaction mechanism remains elusive. Thus, we investigated the role of defects (dopant nitrogen and carbon vacancy) on the catalytic oxygen reduction reaction in a metal-free carbon material focusing on the effect of structural flexibility. Crucially, defects lower the energy barrier for the sp2/sp3 transition of the carbon-centered O2-adsorption sites by releasing structural strain during the reaction. In particular, low-coordinated pyridinic-N displaces from the carbon plane to release the strain, whereas weak C-C bonds around the carbon vacancy change the bond lengths to release the strain. Defects indirectly promote the adsorption of oxygen by enhancing structural flexibility. Thus, the nonlocal structural environment is as critical as the direct interaction between adsorption sites and adsorbate in the chemical reaction. Molecular dynamics simulations reveal that pyridinic-N doping is a facile route to introduce stable catalytic active sites. Overall, our results provide a deeper understanding of chemical processes on defective carbon materials.

Synthesizing a nanographyne

The synthesis of γ-graphyne, a planar carbon allotrope, has been a long-standing challenge in organic synthesis. In this issue of <i>Chem</i>, Wu and co-workers report an efficient synthesis of a molecular nano γ-graphyne, which provides remarkable insight into the aromaticity of the sp-sp²-hybridized carbon network.

Lignite-Based N-Doped Porous Carbon as an Efficient Adsorbent for Phenol Adsorption

The treatment of phenolic-containing wastewater has received increased attention in recent years. In this study, the N-doped porous carbons were prepared from lignite with tripolycyanamide as the N source, and their phenol adsorption behaviors were investigated. Results clearly showed that the addition of tripolycyanamide largely improved the surface area, micropore volume, N content and thus the phenol adsorption capacity of lignite-based carbons. The N-doped sample prepared at 700 °C showed a surface area of 1630 m2/g and a phenol adsorption capacity as high as 182.4 mg/g at 20 °C, which were 2.0 and 1.6 times that of the lignite-based carbon without N-doping. Pseudo-second order and Freundlich adsorption isotherm models could better explain the phenol adsorption behaviors over lignite-based N-doped porous carbon. Theoretical calculations demonstrated that phenol adsorption energies over graphitic-N (−72 kJ/mol) and pyrrolic-N (−74 kJ/mol) groups were slightly lower than that over the N-free graphite layer (−71 kJ/mol), supporting that these N-containing groups contribute to enhance the phenol adsorption capacity. The adsorption mechanism of phenol over porous carbon might be interpreted by the π–π dispersion interactions between aromatic-ring and carbon planes, which could be enhanced by N-doping through increasing π electron densities in the carbon plane.

Triazole-functionalized hydrochar-stabilized Pd nanocatalyst for ullmann coupling

Biomass valorization is essential, particularly in emerging countries. Here, hydrochar from arabica coffee straw was functionalized with a triazole group (HD-TRz) for use as a support of palladium nanoparticles (PdNPs-HD-TRz) applied in the Ullmann coupling reaction for the first time. It provided remarkably excellent selectivities, conversions at a temperature as low as 45 °C and catalyst recyclability, surpassing previous literature performances. Hydrochar was obtained by one-pot reaction via hydrothermal synthesis, using NaOH solution as activating agent and functionalized with a 1,3-triazole group by CuAAC “click” reaction. The PdNPs were prepared via reduction of hydrochar-bound Pd(II) using NaBH4. Hydrochar functionalization was monitored by infrared spectroscopy, and X-ray diffraction (XRD) allowed to observe carbon and palladium planes in hydrochar and PdNPs HD-TRz structures. The PdNPs presented a spherical shape with 2.1 ± 0.1 nm size, homogeneously distributed in the carbon coverslips. The HD-TRz-supported PdNPs were used as a catalyst in the Ullmann reaction of iodobenzene, using ethanol as solvent with 100% of conversion and 91% selectivity at 45 °C. The material was reused, presenting 100% of conversion and selectivities of 92, 84 and 73% for the 1st, 2nd and 3rd cycle, respectively. The scope of the reaction was expanded to other molecules showing the potential of this and other triazole-hydrochar-supported nanocatalysts.

Study of the properties of nanocomposites based on thermally-treated-polyacrylonitrile (review)

Organic semiconductors and novel carbon forms (fullerene, carbon nanotubes, carbon foam, graphene) promote synthesis of carbon nanocomposites with modified properties based on thermally treated polyacrylonitrile (TPAN) that comprises curved (spherical, ring-like, and tube-like) carbon planes. Here we present a review of the studies regarding the properties of TPAN-based nanocomposites. The features of the IR irradiation procedure with a synergetic effect and the mechanism of polyacrylonitrile (PAN) transformation into carbon nanocrystalline material (CNM) have been analyzed. The developed method is promising for the synthesis of luminescent carbon nanostructures and biocompatible carbon nanostructures with high sensitivity to pH medium; metal-polymer nanocomposites (Ag/PAN, Cu/PAN, Fe3O4/TPAN), which can be used in electronics, catalysis, and in water purification from heavy metals, etc. The results obtained may be used to synthesize TPAN-based novel nanocomposites with modified properties.

Planar carbon allotrope B-graphyne as lithium-ion battery anode materials

We study the application of the new carbon allotrope B-graphyne (B-GY) as the anode material for lithium-ion batteries (LIBs) by density functional theory. A high lithium storage capacity of 525 mAhg-1 has been predicted. The average open-circuit voltage (OCV) is moderate of 0.73 V. In addition, it is found that the diffusion of Li atoms at the adjacent sites on the B-GY surface has a moderate diffusion barrier of 0.17 to 0.87 eV. Moderate transition potential barriers and OCV indicate superior mobility of the B-GY membrane. Based on these excellent features, B-GY is a suitable anode material for LIBs.

(Digital Presentation) Carbon Quantum Dot Assisted Enhancement of S2 Fluorescence of Near-Infrared Dyes through Immobilization-Induced Emission Effect

Aggregation-induced emission of organic dyes is a phenomenon in which organic luminophores show higher photoluminescence (PL) efficiency in the aggregated state than in a free molecule, due to the freezing rotational degrees of freedom of the luminophore which otherwise quench the PL emission. In many cases, however, coupling of molecules leads to quenching of their emission due to the concentration quenching or self-quenching (exciton-exciton annihilation) effect. Therefore, in order to realize an enhanced PL emission as a result of molecule-molecule interaction a fine balance should be achieved between freezing rotational degrees of freedom of the molecule and escaping self-quenching effect. This could be realized via immobilization of the luminophore onto the inert surface.Here, we demonstrate an enhancement of specific S2 emission of the near-infrared (NIR) dyes of tricarbocyanine family due to their immobilization on the surface of carbon nanoparticles that induce freezing a specific planar conformation of the molecule imposed by the carbon plane of the particle it interact with. Carbon quantum dots serve as inert particles that render an opposite influence on the S1 and S2 emission of the tricarbocyanine dyes. We demonstrate a dual emission of the NIR tricarbocyanine dyes with a bright green S2 fluorescence, which is relatively weak for the free dye molecule but whose quantum yield increases by 2-4 times, together with a strong enhancement of the spontaneous rate of S2 fluorescence, whereas the quantum yield of S1 emission in the NIR decreases by 2-7 times, respectively, as a result of immobilization of the dye molecule via the interaction with carbon quantum dots. The above changes are dependent on the terminal and meso-groups of the dye and the solvent used. The dye immobilization due to interaction with carbon quantum dots causes freezing rotational degrees of freedom of the molecule as indicated by suppression of the dye hot band absorption-assisted anti-Stokes S1 emission.The observed “lighting up” of an anti-Kasha emission, i.e., the emission from Sn (n>1) excited levels, of the NIR chromophores which possess intensive S1 absorption and emission in the NIR region, but which are spectrally silent in the visible, can lead to their potential applications in the fields such as energy conversion, bio-imaging and bio-sensing, sensitization of solar cells, etc.

Deep‐Sea Discovery and Detective Work: Towards Solving the Hemicalide Structural Enigma through Computational NMR Analysis and Stereocontrolled Synthesis

AbstractThe marine natural product hemicalide displays potent anticancer activity. While detailed NMR experiments established the planar carbon skeleton, its full configurational assignment proved enigmatic. This Review summarises ongoing synthetic efforts and NMR studies on hemicalide, which have succeeded in reducing the number of possible stereoisomers from more than one million to a more manageable eight structures, setting the stage for a focused total synthesis campaign.

Hyperbranched Polyborate: A Non‐conjugated Fluorescent Polymer with Unanticipated High Quantum Yield and Multicolor Emission

AbstractNon‐conjugated fluorescent polymers have attracted great attention due to their excellent biocompatibility and environmental friendliness. However, it remains a huge challenge to obtain a polymer with high fluorescence quantum yield (QY) and multicolor emission simultaneously. Herein, we reported three kinds of nonaromatic hyperbranched polyborates (P1–P3) with multicolor emission, surprisingly, P2 also exhibits an unanticipated high QY (54.1 %). The natural bond orbital (NBO) analysis and density functional theory (DFT) calculation results revealed that the synergistic effect of rigid BO3 planar and flexible carbon chain, as well as the through‐space dative bond in supramolecular aggregate, were the key factors contributing to the ultrahigh QY of P2. Moreover, the applications of P2 in Fe3+ ions detection and cell imaging were also investigated. This work provides a new perspective for designing non‐conjugated fluorescent polymers with both high QY and multicolor emission.

Hyperbranched Polyborate: A Non-conjugated Fluorescent Polymer with Unanticipated High Quantum Yield and Multicolor Emission.

Non-conjugated fluorescent polymers have attracted great attention due to their excellent biocompatibility and environmental friendliness. However, it remains a huge challenge to obtain a polymer with high fluorescence quantum yield (QY) and multicolor emission simultaneously. Herein, we reported three kinds of nonaromatic hyperbranched polyborates (P1-P3) with multicolor emission, surprisingly, P2 also exhibits an unanticipated high QY (54.1 %). The natural bond orbital (NBO) analysis and density functional theory (DFT) calculation results revealed that the synergistic effect of rigid BO3 planar and flexible carbon chain, as well as the through-space dative bond in supramolecular aggregate, were the key factors contributing to the ultrahigh QY of P2. Moreover, the applications of P2 in Fe3+ ions detection and cell imaging were also investigated. This work provides a new perspective for designing non-conjugated fluorescent polymers with both high QY and multicolor emission.