Atom-thick Sheets Research Articles

Graphene Oxide-based Magnetic Boronate-affinity Adsorbent for Extraction of Horseradish Peroxidase

Graphene oxide (GO) is a two-dimensional atom-thick sheet generated from an oxidation of graphene. GO possesses a range of reactive oxygen functional groups on the basal planes and edges, which makes it a good candidate in the field of separation and enrichment through chemical functionalization. In this work, GO-based Fe3O4 magnetic nanoparticles were prepared, and boronic acid groups were introduced by 3-aminophenylboronic acid (APBA) at the same time to improve the enrichment efficiency. Herein, the GO-based magnetic boronate-affinity adsorbent (Fe3O4@[email protected]) was developed focusing on the specific capture of low abundance of glycoprotein. The composites gathered excellent characters of large specific surface area and biocompatibility of GO, strong magnetic responsiveness, and enhanced affinity properties of boronic acid. The proposed system showed better specificity for glycoprotein even in the presence of non-glycoproteins. As a result, the prepared Fe3O4@[email protected] not only exhibited high selectivity for horseradish peroxidase (HRP), and an outstanding tolerance for interference, but also showed excellent rebinding rate for an extraction application. Furthermore, this method provided a reliable way to improve conventional magnetic adsorbent, and showed great potential in analysis of low-abundant glycoprotein from even complex samples.

Scale-Enhanced Magnetism in Exfoliated Atomically Thin Magnetite Sheets.

The discovery of ferromagnetism in atomically thin layers at room temperature widens the prospects of 2D materials for device applications. Recently, two independent experiments demonstrated magnetic ordering in two dissimilar 2D systems, CrI3 and Cr2 Ge2 Te6 , at low temperatures and in VSe2 at room temperature, but observation of intrinsic room-temperature magnetism in 2D materials is still a challenge. Here a transition at room temperature that increases the magnetization in magnetite while thinning down the bulk material to a few atom-thick sheets is reported. DC magnetization measurements prove ferrimagnetic ordering with increased magnetization and density functional theory calculations ascribe their origin to the low dimensionality of the magnetite layers. In addition, surface energy calculations for different cleavage planes in passivated magnetite crystal agree with the experimental observations of obtaining 2D sheets from non-van der Waals crystals.

ANTISTATIC PACKAGING OF PLASTICIZED BIODEGRADABLE POLYLACTIC ACID / GRAPHENE NANCOMPOSITES

Poly lactic acid is inexperienced various to organic compound artifact plastics, employed in packaging with graphene that being one atom thick sheet, composed of sp2 carbon atoms organized in an exceedingly flat honeycomb structure .In this analysis victimization plasticizer thymol with composites were ready by an answer casting technique with (0.5-10) % towers Graphene .Experimental work contain morphological (AFM,FTIR), mechanical(Tensile, Tear, Hardness),electrical conductivity Color , contact angle, and TGA . Results hyperbolic electrical physical phenomenon with hyperbolic Graphene and makes the composite less resistive and appropriate to be used as antistatic packaging , increase the strength and tensile modulus and elongation at (0.5-1)% and attenuate in (3-10%)%,Tear Resistance attenuate once the tensile decrease however hardness hyperbolic with graphene .The results of contact angle of pure PLA is 83◦ that hydrophobic and attenuate to 51◦ at PLA/thymol/Graphene 10% percent to get hydrophilic that able to dissipate or promote the decay of electricity and improve method ability of device. Color and Brightness show that attenuate however appropriate for antistatic packaging and have become opacity at 100 percent Graphene. Thermal stability shows that Graphene hydrolysis by oxidization and exfoliation of carbon and also by the functionalization of sheets graphene to hence on the mass loss of composites.

(Invited) Covalent Functionalization of Graphene and MoS2: Chemical Versus Electrochemical Routes

Atomically thin sheets of materials, the so-called two-dimensional (2D) materials arrived on the scene in early 2000s with the successful isolation of graphene as freestanding monolayer films. Graphene, a single atom thick sheet of sp2-hybridized carbon bonded in a honeycomb lattice, has exceptional electronic, optical, mechanical and thermal properties that outperform those of most of the existing materials. The research on graphene further fuelled emergence of related 2D materials such as black phosphorous, silicene, germanene and transition metal dichalcogenides (TMDs) such as MoS2. Due to their exotic properties, these materials offer virtually endless opportunities for fundamental research as well as cutting edge applications. Most of these 2D materials however exist as single layers only when supported by another solid surface or when stabilized by physisorbed or chemisorbed organic molecules. Given their layered nature, most 2D materials are extremely difficult to disperse in typical solvents. Chemisorption of organic molecules onto their basal plane allows dispersion of these materials in (organic) solvents thereby improving their solution processability. Such dispersions can be used in composite materials and as functional inks. Moreover, covalent functionalization allows modification of the intrinsic electrical, electronic and optical properties of these 2D materials. In this talk, I will discuss covalent modification graphene, graphite and MoS2 using diazonium chemistry. Two different routes for reductive decomposition of diazonium salts namely, chemical and electrochemical, will be discussed in detail. Special focus is on sub-nanometer characterization of modified materials using scanning tunneling and atomic force microscopy (STM and AFM). Initial results towards patterned covalent functionalization using physisorbed self-assembled templates will also be presented besides the discussion on the use of such surfaces as seed layers for atomic layer deposition (ALD).

Preparation of graphene nanoribbons (GNRs) from twisted structure carbon nanotubes using unzipping technique

This work deals with the preparation of graphene nano ribbons (GNRs), which are small bars or strips of graphene with narrow range width less than 50 nm and one atom thick sheet (approximately 140 °A). This material has many applications in electronics, polymer composite, contrast agent bio-imaging and others. This material was prepared from twisted structure of carbon nanotubes CNTs using oxidation process by acids and breaking down by high frequency ultrasonication (sonochemical unzipping). Pre-prepared twisted CNTs were characterized by scanning electron microscope (HRSEM) before treatment. The size, morphology, crystallinity of prepared graphene nanoribbons was also investigated using transmission electron microscope, high resolution transmission electron microscope, and X-ray diffraction and particle size analyzer. The results showed of formation of GNRs with narrow width as lower than 29 nm and uniform sizes. X-ray diffraction reveals Bragg reflections corresponding to the lattice planes (002), (100), (101), (004), and (110) matched with hexagonal system of graphite.

Effect of temperature and strain-rate on mechanical properties of defected graphene sheet: A molecular dynamics study

Graphene, a one atom thick sheet of carbon exhibits outstanding mechanical properties, but defects which are unavoidable at the time of synthesis may strongly affect, such as intrinsic properties and fracture toughness of graphene can be altered by topological defects such as vacancy, Stone-Thrower-Wales (STW) defects, dislocations and grain boundaries. In this research article, authors have extensively studied the effect of Stone-Thrower-Wales defect on mechanical properties of a single layer of graphene sheet at different temperature and strain-rates using classical molecular dynamics (MD) based simulations. Also, authors have studied the effect of defect-concentration on the mechanical properties of graphene at different temperature and strain rates. It has been observed that fracture strength and strain is not varying with temperature for STW-1 in zigzag direction and STW-2 in armchair direction respectively. Also, the same scenario was observed for different strain-rate values. Further-more it was observed that at 1K both STW-1 and STW-2 defects shows almost same fracture strength and strain in armchair and zigzag directions for higher strain-rates. On the other hand, at lower strain-rates both STW-1 and STW-2 defects showed different fracture strength and strain at 1K. Also, it was observed that at higher temperatures STW-1 in armchair direction and STW-2 in zigzag direction shows enormous decrease in mechanical properties, it shows STW-1 and STW-2 are not favourable in armchair and zigzag directions respectively. In addition, the effect of defects at different strain-rates and concentration on the fracture strength and failure morphology of graphene sheet has also been studied.

Perturbation theory for weakly coupled two-dimensional layers

Abstract

Molecular dynamics study on the mechanical response and failure behaviour of graphene: performance enhancement via 5–7–7–5 defects

A one atom-thick sheet of carbon exhibits outstanding elastic moduli and tensile strength in its pristine form but structural defects which are inevitable in graphene due to its production techniques can alter its structural properties.

Chemical synthesis of graphene nanoribbons

Graphene is a two-dimensional atom-thick sheet of graphite composed of an sp-hybridized carbon atom network. Its isolation in 2004 and the extensive research that followed have led, amongst others, to graphene nanoribbons (GNRs), a graphene-based structure having nano-scale dimensions and semiconducting or metallic electronic properties that depend on its geometry and dimensions. These characteristics of GNRs are in stark contrast to those of graphene, which is a carbon sheet with semimetal, zero band gap characteristics. In the present article, we discuss the progress that has been reported towards producing GNRs with predefined dimensions, by using bottom-up chemical synthesis approaches.

Synthesis of mono layer graphene oxide from sonicated graphite flakes and their Hall effect measurements

Abstract Graphene, a single atom thick sheet is considered a key candidate for the future nanotechnology, due to its unique extraordinary properties. Researchers are trying to synthesize bulk graphene via chemical route from graphene oxide precursor. In the present work, we investigated a safe and efficient way of monolayer graphene oxide synthesis. To get a high degree of oxidation, we sonicated the graphite flakes before oxidation. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) results confirmed graphene oxide formation and high degree of oxidation. Raman spectroscopy and atomic force microscopy (AFM) results revealed a monolayer of graphene oxide (GO) flakes. The sheet like morphology of the GO flakes was further confirmed by scanning electron microscopy (SEM). The Hall effect measurements were performed on the GO film on a silica substrate to investigate its electrical properties. The results obtained, revealed that the GO film is perfectly insulating, having electrical resistivity up to 8.4 × 108 (Ω·cm) at room temperature.

Graphene‐Like Single‐Layered Covalent Organic Frameworks: Synthesis Strategies and Application Prospects

Two-dimensional (2D) nanomaterials, such as graphene and transition metal chalcogenides, show many interesting dimension-related materials properties. Inspired by the development of 2D inorganic nanomaterials, single-layered covalent organic frameworks (sCOFs), featuring atom-thick sheets and crystalline extended organic structures with covalently bonded building blocks, have attracted great attention in recent years. With their unique graphene-like topological structure and the merit of structural diversity, sCOFs promise to possess novel and designable properties. However, the synthesis of sCOFs with well-defined structures remains a great challenge. Herein, the recent development of the bottom-up synthesis methods of 2D sCOFs, such as thermodynamic equilibrium control methods, growth-kinetics control methods, and surface-assisted covalent polymerization methods, are reviewed. Finally, some of the critical properties and application prospects of these materials are outlined.

Research updates on graphene oxide‐based polymeric nanocomposites

Graphene oxide (GO) is a carbon‐based material, which is one atom thick sheet of graphite. The nanofillers have exceptional stiffness and strength owing to the presence of two‐dimensional graphene backbone. Especially owing to this reason, nanocomposites have been developed using GO for several applications. This review article explores the synthesis of GO from flake graphite. Main emphasis has been afforded on the preparation and characterization of GO nanocomposites, utilizing various industrial polymers for wide application in aerospace, biomedical, military, supercapacitors, electrical, sensor, and so on. Morphological characterization exploring the interaction and extent of dispersion of GO nanosheets in the polymer matrices is extensively accounted. From the reports, it is clear that exfoliation and strong interaction of GO tremendously improved the physical, mechanical, thermal, electrochemical, biocompatibility, and tribological properties of the added polymer. POLYM. COMPOS., 35:2297–2310, 2014. © 2014 Society of Plastics Engineers

Multi-functional nano-electronics constructed using boron phosphide and silicon carbide nanoribbons

First-principles density functional theory and non-equilibrium Green function calculations provide theoretical support for the promising applications of multi-functional nano-electronics constructed using zigzag boron phosphide (BP) nanoribbons (zBPNRs) and silicon carbide nanoribbons (zSiCNRs). The results indicate that zBPNRs are non-magnetic direct bandgap semiconductors with bandgaps of ∼1 eV. Devices constructed using hybrid zSiC-BP-SiC nanoribbon structures are found to exhibit not only significant field-effect characteristics but also tunable negative differential resistance. Moreover, ‘Y’- and ‘Δ’-shaped nano-structures composed of zBPNRs and zSiCNRs exhibit pronounced spin polarization properties at their edges, suggesting their potential use in spintronic applications. Interestingly, a transverse electric field can convert zBPNRs to non-magnetic indirect bandgap semiconductors, ferrimagnetic semiconductors or half-metals depending on the strength and direction of the field. This study may provide a new path for the exploration of nano-electronics. Graphene has sparked such interest among the scientific and technology community that it has been called a ‘wonder material’. The one-dimensional, atom-thick sheet of carbon holds particular promise for nanoelectronics — in field-effect transitors for example — but its zero bandgap hinders practical application. Strategies to circumvent this issue include cutting graphene into nanoribbons or turning to materials that feature boron, nitrogen, silicon or phosphorus — all elements that neighbour carbon in the periodic table. Through first-principles density functional theory and nonequilibrium Green's function calculations, Hui Li from Shandong University, China, and co-workers have predicted interesting electron transport properties for a peculiar material consisting of two zigzag silicon carbide (SiC) nanoribbons connected by a central zigzag boron phosphide (BP) nanoribbon. A variety of configurations were investigated, and the hybrid SiC-BP nanostructures were found to exhibit versatile electronic properties that may be suitable for the construction of multifunctional optoelectronic or spintronic devices. In this article, we propose several kinds of simple nano-structures constructed by BP and SiC nanoribbons, which show peculiar electronic properties and might have promising applications in nano-electronics. SiC-BP-SiC nanoribbons are found to exhibit not only significant field-effect characteristics but also tunable negative differential resistance. ‘Y’- and ‘Δ’-shaped SiC-BP structures show significant spin polarization at their edges. Under the transverse electric field, the non-magnetic direct bandgap zigzag BP nanoribbons can change to non-magnetic indirect bandgap semiconductors, ferrimagnetic semiconductors or half-metals depending on the field strength and direction. These findings reveal the possibility of using SiC-BP nano-structures to construct multi-functional electronics.

Flexible nanocircuits can be drawn with heat

A hot nanoscale pen can draw circuits on graphene – atom-thick sheets of carbon – opening the way to electronics more compact than silicon allows

ANOTHER ONE-ATOM-THICK MATERIAL

GRAPHENE ISN’T THE ONLY material capable of existing as a free-standing one-atom-thick film. The widely studied carbon material now shares that distinction with boron nitride, according to researchers in Germany ( Nano Lett., DOI: 10.1021/nl9011497). Scientists had long predicted that single-atom-thick sheets of materials like graphene would spontaneously roll up into tubes or other curved structures if, indeed, the superthin films could be formed at all. Just a few years ago, however, researchers showed that not only is it possible to separate atom-thick sheets of graphene from graphite, but it’s also easy to do. That discovery touched off an explosion of studies that uncovered outstanding and potentially useful mechanical, electronic, and chemical properties of the thinnest material (C&EN, March 2, page 14). Now, atom-thick boron nitride films may be poised to share the spotlight with graphene. Many other types of atom-thick monolayers have been grown on solid supports. But unlike graphene, other films ...

Carbon makes super-tough paper

Atom-thick sheets stacked to make strong ultra-thin material.