Two-dimensional Carbon Sheets Research Articles

Oxidation two-dimensional porous carbon membrane for efficient and precise separation of mixed dyes solution

In actual production, dye wastewater typically contains a mixture of two or more dyes. Therefore, developing efficient and precise separation techniques for mixed dyes solution is of great value but still faces great challenges. In this study, we prepared two-dimensional porous carbon sheets (PCS) using Ti3C2 as the precursor through halogenation etching technology. Subsequently, the PCS was oxidized with nitric acid at room temperature to obtain oxidized porous carbon sheets (OPCS). When mixed dyes solution RB/MO and RB/MB were screened using OPCS vacuum filtration self-assembled porous carbon membrane (OPCSM), the rejection rate for the larger dye RB was 99.9 %, while the permeation rates for the smaller dyes MO and MB were 91.0 % and 99.5 %, respectively. Notably, OPCSM also exhibited much higher water flux than the previously reported. The combination of high water flux and precise screening make OPCSM a highly promising membrane for the separation and reuse of mixed dyes.

Differences in interaction of graphene/graphene oxide with bacterial and mammalian cell membranes.

Graphene, a single layer, hexagonally packed two-dimensional carbon sheet is an attractive candidate for diverse applications including antibacterial potential and drug delivery. One of the knowledge gaps in biomedical application of graphene is the interaction of these materials with the cells. To address this, we investigated the interaction between graphene materials (graphene and graphene oxide) and plasma membranes of cells (bacterial and mammalian cells). The interactions of four of the most abundant phospholipids in bacteria and mammalian plasma membranes with graphene materials were studied using density functional theory (DFT) at the atomic level. The calculations showed that the mammalian phospholipids have stronger bonding to each other compared to bacterial phospholipids. When the graphene/graphene oxide sheet is approaching the phospholipid pairs, the bacterial pairs exhibit less repulsive interactions, thereby a more stable system with the sheets was found. We also assembled bacterial and mammalian phospholipids into liposomes. We further observed that the bacterial liposomes and cells let the graphene flakes penetrate the membrane. The differential scanning calorimetry measurements of liposomes revealed that the bacterial liposomes have the lowest heat capacity; this strengthens the theoretical predictions of weaker interaction between the bacterial phospholipids compared to the mammalian phospholipids. We further demonstrated that graphene oxide could be internalized into the mammalian liposomes without disrupting the membrane integrity. The results suggest that the weak bonding among bacteria phospholipids and less repulsive force when graphene materials approach, result in graphene materials interacting differently with the bacteria compared to mammalian cells.

Theoretical characterization of tolanene: A new 2D sp-sp2 hybridized carbon allotrope

The search for new carbon allotrope forms has been the focus of much experimental and theoretical research. Some nonbenzenoid sp2-hybridized carbon allotropes have been proposed and synthesized, revealing properties unlike those observed for graphene. In the present work, first-principles calculations were performed to investigate a new two-dimensional (2D) carbon sheet — named tolanene — which may hypothetically be obtained from diphenylacetylene molecules as building blocks. The nonbenzenoid tolanene sheet has a periodic arrangement of four-, six-, eight-, and twelve-membered rings of sp and sp2 hybridized carbon atoms. Our calculations reveal that tolanene is mechanically and dynamically stable, and can potentially withstand a temperature as high as 1500 K quite easily. The structure presents a strong anisotropy in its mechanical properties, in a similar fashion to biphenylene. Additionally, we verify that the structure presents a metallic behavior, and its low-energy electronic structure is fully determined by pz orbitals, as in most carbon-based 2D materials. The application of tolanene as a potential anode material in Li-ion batteries is also explored. We find that it offers a competitive Li storage capacity and fast Li mobility along with other interesting electronic properties.

Corncob-Derived Two-Dimensional N-Doped Carbon Sheets as the Ultrabroadband Microwave-Absorbing Material

Corncob-Derived Two-Dimensional N-Doped Carbon Sheets as the Ultrabroadband Microwave-Absorbing Material

Synthesis and characterization of bio-nanocomposites: Functionalization of graphene oxide with a biocompatible amino acid

Graphene oxide (GO) is a complicated composite which can be synthesized from graphite or other carbon sources by a simple top-down method. Graphene is a two-dimensional carbon sheets which can be oxidized to synthesis its oxide structure. The graphene oxide sheets can be functionalized in order to be used actively in different areas. The graphene oxide nanocomposite materials have attracted researches and scientists’ attention due to their wade applications from electrochemical industry to drug delivery. In this novel work the authors have synthesized graphene oxide films and then functionalized with an amino acid, Lysine, and Cu in order to synthesize the Lysine-Cu-Graphene oxide combination. The novelty of this investigation is the authors have functionalized graphene oxide with l-lysine as an amino acid at diverse temperature. Also, this product is environmentally friendly product since it is soluble in aqueous medium and can be applied as an active antibacterial material. After the synthesizing process, the obtained materials had been characterized using different techniques such as Fourier-transform infrared spectroscopy (FTIR) to confirm the success of the functional reaction. Ultra violet visible (UV–Vis) spectroscopy, atomic force microscopy (AFM), X-ray diffraction (XRD), and thermal gravimetric (TG) analysis, were also utilized to approve the covalent attachment of Lysine and also to show the improvement in the thermal stability of GO.

Magnetic properties of 3d metal atoms embedded in a new two-dimensional carbon sheet

A first-principles study is performed to explore the magnetic properties of the 3d transition metal (TM) atoms embedded in a new two-dimensional(2D) nonmagnetic carbon sheet. By the adsorption of 3d metal atoms (M = Sc-Ni) on the single vacancy (SV) site of 2D carbon material, the M@SV complexes are nonmagnetic for M = Ti, Co and Ni. Other metal atoms doping can induce different magnetism. The magnetic moment of Sc@SV system mainly comes from the π electrons of carbon atoms, and these electrons virtual hopping leads to the ferromagnetic coupling interaction with Sc atom. For M = V, Cr, Mn and Fe systems, the more net spin electrons go the separate nonbonding d orbitals, giving the different magnetic moments. Meanwhile, due to the Hund’s rule, the metal atoms and the surrounding carbon atoms have the anti-ferromagnetic coupling interaction. By the simple spd hybridization model, we explore the origin of the various magnetism, and provide some new magnetic single-atom materials for the future spintronics devices and spin-dependent catalysts.

Lattice thermal conductivity of silicon monolayer in biphenylene network

Recently, the two-dimensional carbon sheet in a biphenylene network has been successfully fabricated by experiment [Fan et al., Science 372, 852 (2021)], promoting the study of silicon allotropes with similar structures. In this work, we investigate the lattice thermal conductivity of a silicon monolayer in a biphenylene network through first-principles calculations. It is found that the thermal conductivity is anisotropic and much lower than that of carbon sheets with a similar structure. At 300 K, the thermal conductivity is 2.46 and 3.25 W m−1 K−1 along the two crystallography directions, respectively. The phonon group velocity, relaxation time, and the contribution of each mode to total thermal conductivity are analyzed, to understand the underlying physical mechanisms of the low thermal conductivity. Our work provides fundamental insights into thermal transport in the silicon monolayer in the biphenylene network and should stimulate further experimental exploration of these materials for possible thermoelectric and thermal management applications.

Application of T4,4,4-graphyne for anode of Na-ion battery: first principle theoretical study

ABSTRACT The sodium (Na) storage behaviour of T4,4,4-graphyne of two-dimensional porous carbon sheet is explored using the density functional theory (DFT). The energy of adsorption and barrier, storage capacity, and open-circuit voltage are calculated. The calculations predict that Na atom is extraordinary mobile on T4,4,4-graphyne monolayer as a result of the relatively slight energy barrier. The Na storage capacity is as high as Na8C9, which exceeds the values reported for graphite and some other two-dimensional carbon-based materials. The high Na mobility and theoretical capacity make T4,4,4-graphyne monolayer suitable for implementation in rechargeable ion batteries. The electronic properties are also studied to ensure that T4,4,4-graphyne is suitable for Na-ion batteries as an anode material, and they revealed that semiconductor–metal transition is induced by Na adsorption. The favourable electronic conduction is another demand for promising Na-ion batteries. These results predict that the application of T4,4,4-graphyne sheet will increase efficiency of the Na-ion batteries.

Nitrogen-Doped Porous Carbon Nanosheets Based on a Schiff Base Reaction for High-Performance Lithium-Ion Batteries Anode

Lithium-ion batteries (LIBs) have already gained significant attention because they have satisfactory energy density and no memory effect, making them one of the most widely used energy storage systems. In commercial LIBs, graphite is widely used as an anode material due to its excellent electrical conductivity and structural stability; however, as they are limited by their restricted theoretical capacity, there is an urgent need for the development of novel anode materials for LIBs. For this purpose, we designed a nitrogen-doped two-dimensional layered porous carbon material (2D-PNC) based on a covalent organic framework (COF) generated by a Schiff base reaction as a precursor. The characterization analysis results show that 2D-PNC is made of stacked two-dimensional ultra-thin carbon sheets with a porous structure. This unique structure is beneficial for electrolyte impregnation and lithium-ion storage, resulting in excellent electrochemical performance of 2D-PNC, which shows a high specific capacity of 573 mAh g−1 after 380 cycles at 0.5 A g−1. The results show that 2D-PNC provides the possibility of a practical application of high-performance lithium-ion batteries.

A bottom-up fabrication for sulphur (S), nitrogen (N) co-doped two-dimensional microporous carbon nanosheets for high-performance supercapacitors and H2, CO2 storage

The synthesis of two-dimensional (2D) carbon sheets with sub-nanometer pore-rich microporous morphology and an understanding of the structure–performance relationship are important to develop an advanced device for supercapacitors and gas adsorption.

Ultrafine aluminum sulfide nanocrystals anchored on two-dimensional carbon sheets for high-performance lithium-ion batteries.

Aluminum sulfide is a novel light metal sulfide, which possesses multiple advantages for lithium storage, including high theoretical capacity, proper discharge potential and good conductivity. However, much research has not been done in areas related to light metal sulfide materials. Herein, we synthesized Al2S3/C nanocomposite by a facile one-step ball milling method. This simple method not only effectively achieves the uniform composite of Al2S3 nanoparticles and carbon sheets, but also controls Al2S3 into ultrafine nanocrystals. Al2S3/C electrode demonstrates very outstanding lithium storage performance with large reversible specific capacity (1249 mAh g-1 at 100mAg-1), remarkable rate capability (670 mAh g-1 at 5000mAg-1) and superior long-cycling stability (retaining 850 mAh g-1 even after 1000 cycles at 1000mAg-1). Moreover, the reversible lithium storage behavior and excellent diffusion kinetics of Al2S3/C are unveiled deeply. This work provides an inspiration to develop new light metal sulfide materials for the next-generation high-performance lithium ion battery.

Single-step salt-template-based scalable production of 2D carbon sheets heterostructured with nickel nanocatalysts for lowering overpotential of hydrogen evolution reaction

Non-precious metals have been considered as suitable alternatives for high-performance hydrogen evolution reactions (HER). Although the incorporation of carbon substances is shown to improve the number of active sites, electron transfer pathways, and long-term stability, there have been rare reports on their single-step scalable production. Herein, we realize free-standing two-dimensional (2D) carbon sheets heterostructured with nickel (Ni) nanocatalysts by pyrolyzing ultrathin layers of acetate tetrahydrate (i.e. the single precursor for both Ni and C sources) over water-soluble salt crystals. Such a salt-templated methodology is environmentally friendly and readily scalable without the implementation of sophisticated equipment. The resulting 2D carbon sheets exhibit an average small thickness of ∼ 3 nm and lateral dimensions with tens of micrometers, where a large number of nano-sized Ni particles with an average diameter of 14 nm are uniformly dispersed. Such 2D Ni-C sheets demonstrate a small overpotential of 111 mV at 10 mA/cm2 and a low Tafel slope of 86 mV/dec for HER in 1 M KOH, which is significantly improved over those of reported non-precious metals composited with carbon substances. This work offers new insight into the design and practical production of non-precious metal matrixes for economical HER.

The Diffusion and Clustering Formation of Gold Atoms on Alpha-Graphyne

Motivated by the experiment, high mobility of gold atoms on two-dimensional carbon sheets, we examine the ground-state structures, mobility, and clustering formations of small gold clusters (Au_n, n = 1-4) on monolayer alpha-graphyne using first-principles DFT calculations and finite temperature MD simulations. We reveal that Au_n cluster prefers to locate at the center of a hexagon in alpha-graphyne. The binding energy of Au_n on alpha-graphyne increases with increasing the number (n) of gold atoms. Moreover, we predict the step-wise formation of Au_2 out of two pre-adsorbed Au_1 ad-atoms. Likewise, the formation of Au_3 and Au_4 is also considered in the same way. The diffusion energy barrier of Au_1 on alpha-graphyne is found to be only 0.26 eV, indicating the high mobility of gold atoms on alpha-graphyne. Remarkably, the energy required for the cluster formation of gold atoms on alpha-graphyne is about less than 0.2 eV. According to our MD simulations at room temperature (RT), the Au_n cluster is subsequently formed on alpha-graphyne. Considering the high mobility of a single gold atom, the strong binding energy of small gold clusters, and the easy clustering of Au_n at RT on alpha-graphyne, we suggest that alpha-graphyne is a suitable substrate for gold cluster formation.

In situ growth of 1D carbon nanotubes on well-designed 2D Ni/N co-decorated carbon sheets toward excellent electromagnetic wave absorbers

Rational construction of complex hierarchical structure with dielectric/magnetic components is an effective strategy to achieve outstanding electromagnetic wave (EMW) absorbers. In this work, Ni/N-doped two-dimensional carbon sheets (Ni-NC) were subtly prepared through a facile coordination-exfoliation process based on a bulk precursor ethylenediaminetetraacetic acid-nickel (EDTA-Ni). Subsequently, carbon nanotubes (CNTs) were catalytically grown in situ on the surface of the carbon sheet to fabricate a series of forest-like three-dimensional (3D) structured composites (Ni-NC/CNTs) which combine multiple advantages of well-dispersed Ni particles, massive interfacial polarization and rich air contact within the skeleton. The composites exhibit different EMW attenuation capabilities by tuning impedance matching, interfacial polarization, dipole polarization, 3D conductive loss and magnetic loss that manipulated by changing the calcination temperature. Amongst them, Ni-NC/CNTs(700) has a strong absorption capacity in the X-band region, where the minimum reflection loss can reach −55.3 dB at 8.72 GHz with the thickness of 2.7 mm. More extraordinarily, this composite material exhibits an effective absorption bandwidth of 14.32 GHz by adjusting the thickness from 1.5 mm to 5.0 mm. This work provides a simple design and feasible synthesis strategy for light EMW absorber with wide band and strong absorption.

Biphenylene carbon sheets

Nanomaterials Although graphene forms two-dimensional carbon sheets, other arrangements of carbon rings could also assemble as flat sheers. Fan et al. synthesized an ultraflat biphenylene carbon sheet consisting of sp2-hybridized carbon atoms forming four-, six-, and eight-membered rings on a gold surface. An adsorbed halogenated terphenyl molecule undergoes a two-step interpolymer dehydrofluorination polymerization that creates the four- and eight-membered rings through carbon–carbon bond formation. Scanning tunneling spectroscopy revealed that this carbon allotrope is metallic. Science , abg4509, this issue p. [852][1] [1]: /lookup/doi/10.1126/science.abg4509

Biphenylene network: A nonbenzenoid carbon allotrope.

The quest for planar sp2-hybridized carbon allotropes other than graphene, such as graphenylene and biphenylene networks, has stimulated substantial research efforts because of the materials' predicted mechanical, electronic, and transport properties. However, their syntheses remain challenging given the lack of reliable protocols for generating nonhexagonal rings during the in-plane tiling of carbon atoms. We report the bottom-up growth of an ultraflat biphenylene network with periodically arranged four-, six-, and eight-membered rings of sp2-hybridized carbon atoms through an on-surface interpolymer dehydrofluorination (HF-zipping) reaction. The characterization of this biphenylene network by scanning probe methods reveals that it is metallic rather than a dielectric. We expect the interpolymer HF-zipping method to complement the toolbox for the synthesis of other nonbenzenoid carbon allotropes.

Boosting lithium storage performance of Si nanoparticles via thin carbon and nitrogen/phosphorus co-doped two-dimensional carbon sheet dual encapsulation

Silicon (Si) is a promising anode candidate for next-generation lithium-ion batteries (LIBs), but it suffers from poor electronic conductivity and dramatic volume variation during cycling, which poses a critical challenge for stable battery operation. To mitigate these issues simultaneously, we propose a “double carbon synergistic encapsulation” strategy, namely thin carbon shell and nitrogen/phosphorus co-doped two-dimensional (2D) carbon sheet dual encapsulate Si nanoparticles (denoted as 2D NPC/C@Si). This double carbon structure can serve as a conductive medium and buffer matrix to accommodate the volume expansion of Si nanoparticles and enable fast electron/ion transport, which promotes the formation of a stable solid electrolyte interphase film during cycling. Through structural advantages, the resulting 2D NPC/C@Si electrode demonstrates a high reversible capacity of 592 mAh·g−1 at 0.2 A·g−1 with 90.5% excellent capacity retention after 100 cycles, outstanding rate capability (148 mAh·g−1 at 8 A·g−1), and superior long-term cycling stability (326 mAh·g−1 at 1 A·g−1 for 500 cycles, 86% capacity retention). Our findings elucidate the development of high-performance Si@C composite anodes for advanced LIBs.

A Hybrid of FeS2 Nanoparticles Encapsulated by Two-Dimensional Carbon Sheets as Excellent Nanozymes for Colorimetric Glucose Detection.

Recently, the development of nanozymes with high catalytic performance is gaining more and more attention due to the ever-growing demands for their practical applications. The elaborate design of its morphology has demonstrated to be an effective approach to improve the performance of these nanozymes. Herein, a hybrid of iron disulfide nanoparticles (FeS2 NPs) encapsulated by two-dimensional (2D) carbon nanosheets (NSs), denoted as FeS2@C NSs, demonstrates both superior peroxidase-like activity and excellent stability. The incorporation of 2D carbon sheets endows the proposed FeS2@C nanozymes with high specific surface area, providing abundant active sites to facilitate the contact with substrates. Moreover, the embedded FeS2 NPs are kept from aggregation due to the encapsulation and confinement of 2D carbon sheets, avoiding the conventional failure of single-component nanozymes. Based on glucose oxidase (GOx) and the elaborately designed FeS2@C nanozymes, a colorimetric method for glucose detection is then developed with excellent simplicity and sensitivity. The detection limit of the sensing platform is as low as 0.19 μM for a glucose assay. More notably, this method can be successfully employed for the glucose assay in some real samples, indicating the great potential of this FeS2@C NS-based nanozymes in the fields of biotechnology and clinical diagnostics.

Nitrogen self-doped carbon sheets anchored hematite nanodots as efficient Li-ion storage anodes through pseudocapacitance mediated redox process

The evolution of ultrathin carbon layers self-doped by nitrogen assists the formation of α-Fe2O3 nanodots embedded in N-rich carbon sheets by a surfactant-less self-assembly approach and they are reported as anode materials for lithium-ion batteries. The resulting Fe2O3 nanodots confine to size of 3–7nm with evenly embedding in a two-dimensional N-rich carbon sheets. As an anode material, the Fe2O3ND/NC electrode delivers a reversible capacity of 917mAhg−1 at 0.1C rate after 100 cycles and a good rate capability and long term cyclability of 476mAhg−1 at 3C rate after 325 cycles. Detailed investigation through the differential capacity (dQ/dV) and galvanostatic charge/discharge techniques reveal and distinguish the dual role of charge storage, i.e., faradaic and pseudocapacitive processes are involved in realizing improved electrochemical performances. The contribution of the pseudocapacitive capacity from the electrochemical processes accounts for 216mAhg−1, which are due to the Li storages in both the tiny size Fe2O3 and the defective sites of N-doped carbon sheets as portrayed through a model schematic. Altogether, the report paves way for accomplishing multiple avenues, such as in-situ nitrogen doping, preparation of nanodots and ultrathin N-doped carbon sheets for applications in energy conversion and storage devices.

Three-Dimensional Graphene Enhances Neural Stem Cell Proliferation Through Metabolic Regulation.

Graphene consists of two-dimensional sp2-bonded carbon sheets, a single or a few layers thick, which has attracted considerable interest in recent years due to its good conductivity and biocompatibility. Three-dimensional graphene foam (3DG) has been demonstrated to be a robust scaffold for culturing neural stem cells (NSCs) in vitro that not only supports NSCs growth, but also maintains cells in a more active proliferative state than 2D graphene films and ordinary glass. In addition, 3DG can enhance NSCs differentiation into astrocytes and especially neurons. However, the underlying mechanisms behind 3DG's effects are still poorly understood. Metabolism is the fundamental characteristic of life and provides substances for building and powering the cell. Metabolic activity is tightly tied with the proliferation, differentiation, and self-renewal of stem cells. This study focused on the metabolic reconfiguration of stem cells induced by culturing on 3DG. This study established the correlation between metabolic reconfiguration metabolomics with NSCs cell proliferation rate on different scaffold. Several metabolic processes have been uncovered in association with the proliferation change of NSCs. Especially, culturing on 3DG triggered pathways that increased amino acid incorporation and enhanced glucose metabolism. These data suggested a potential association between graphene and pathways involved in Parkinson's disease. Our work provides a very useful starting point for further studies of NSC fate determination on 3DG.