In Situ N‐Doped Graphene and Mo Nanoribbon Formation from Mo2Ti2C3 MXene Monolayers

Since the advent of monolayered 2D transition metal carbide and nitrides (MXenes) in 2011, the number of different monolayer systems and the study thereof have been on the rise. Mo₂Ti₂C₃ is one of the least studied MXenes and new insights to this material are of value to the field. Here, the stability of Mo₂Ti₂C₃ under electron irradiation is investigated. A transmission electron microscope (TEM) is used to study the structural and elemental changes in situ. It is found that Mo₂Ti₂C₃ is reasonably stable for the first 2 min of irradiation. However, structural changes occur thereafter, which trigger increasingly rapid and significant rearrangement. This results in the formation of pores and two new nanomaterials, namely, N‐doped graphene membranes and Mo nanoribbons. The study provides insight into the stability of Mo₂Ti₂C₃ monolayers against electron irradiation, which will allow for reliable future study of the material using TEM. Furthermore, these findings will facilitate further research in the rapidly growing field of electron beam driven chemistry and engineering of nanomaterials.     

A new route to graphene starting from heavily ozonized fullerenes: Part 1—thermal reduction under inert atmosphere

It is shown that heavily ozonized C₆₀ or C₇₀ fullerenes (known also as “fullerene ozopolymers”) are suitable substrates for the preparation of graphene or nanographene in place of graphite oxide (GO) by thermal reduction in inert atmosphere. TGA-FTIR study shows that the release profile of CO₂ and CO from fullerene ozopolymers in the temperature range between 25°C and 900°C is comparable to that shown by GO. Furthermore, the FT-IR spectral evolution of fullerene ozopolymers from room temperature to 630°C under inert atmosphere is once again strikingly comparable to that observed on GO under the same conditions.     

Review of MXenes as new nanomaterials for energy storage/delivery and selected environmental applications

Energy and environmental issues presently attract a great deal of scientific attention. Recently, two-dimensional MXenes and MXene-based nanomaterials have attracted increasing interest because of their unique properties (e.g., remarkable safety, a very large interlayer spacing, environmental flexibility, a large surface area, and thermal conductivity). In 2011, multilayered MXenes (Ti₃C₂T_x, a new family of two-dimensional (2D) materials) produced by etching an A layer from a MAX phase of Ti₃AlC₂, were first described by researchers at Drexel University. The term “MXene” was coined to distinguish this new family of 2D materials from graphene, and applies to both the original MAX phases and MXenes fabricated from them. We present a comprehensive review of recent studies on energy and environmental applications of MXene and MXene-based nanomaterials, including energy conversion and storage, adsorption, membrane, photocatalysis, and antimicrobial. Future research needs are discussed briefly with current challenges that must be overcome before we completely understand the extraordinary properties of MXene and MXene-based nanomaterials.

     

Fabrication of Millimeter‐Scale,Single‐Crystal One‐Third‐Hydrogenated Graphene with Anisotropic Electronic Properties

Periodically hydrogenated graphene is predicted to form new kinds of crystalline 2D materials such as graphane, graphone, and 2D C_xH_y, which exhibit unique electronic properties. Controlled synthesis of periodically hydrogenated graphene is needed for fundamental research and possible electronic applications. Only small patches of such materials have been grown so far, while the experimental fabrication of large‐scale, periodically hydrogenated graphene has remained challenging. In the present work, large‐scale, periodically hydrogenated graphene is fabricated on Ru(0001). The as‐fabricated hydrogenated graphene is highly ordered, with a √3 × √3/R30° period relative to the pristine graphene. As the ratio of hydrogen and carbon is 1:3, the periodically hydrogenated graphene is named “one‐third‐hydrogenated graphene” (OTHG). The area of OTHG is up to 16 mm². Density functional theory calculations demonstrate that the OTHG has two deformed Dirac cones along one high‐symmetry direction and a finite energy gap along the other directions at the Fermi energy, indicating strong anisotropic electrical properties. An efficient method is thus provided to produce large‐scale crystalline functionalized graphene with specially desired properties.     

25th Anniversary Article: Exploring Nanoscaled Matter from Speciation to Phase Diagrams: Metal Phosphide Nanoparticles as a Case of Study

The notions of nanoscale “phase speciation” and “phase diagram” are defined and discussed in terms of kinetic and thermodynamic controls, based on the case of metal phosphide nanoparticles. After an overview of the most successful synthetic routes for these exotic nanomaterials, the cases of InP, Ni₂P, Ni₁₂P₅ and Pd_xP_y are discussed in detail to highlight the relationship between composition, structure, and size at the nanoscale. The influence of morphology is discussed next by comparing the behavior of Cu₃P nanophases with those of Ni_xP_y, FeP/Fe₂P, and CoP/Co₂P. Perspectives provide the reader with methodological guidelines for further investigation of nanoscale “phase diagrams”, and their use for optimized synthesis of new functional nanomaterials.     

Sand-Fixation Model for Interface Engineering of Layered Titania and N/O-Doped Carbon Composites to Enhance Potassium/Sodium Storage

Layered titania (L-TiO₂) holds great potential for potassium-ion batteries (PIBs) and sodium-ion batteries (SIBs) due to their high specific capacity. Synthesizing L-TiO₂ functional materials for high-capacity and long cyclability battery remains challenging due to the unstable and poor conductivity of bare L-TiO₂. In nature, plant growth can stabilize land by preventing sands from dispersing following desertification. Inspired by nature's “sand-fixation model,” Al³⁺ “seeds” are in situ grown on layered Ti₃C₂T_x “land.” Subsequently, NH₂-MIL-101(Al) “plants” with Al as metal nodes are grown on the Ti₃C₂T_x “land” by self-assembly. After annealing and etching processes (similar to desertification), NH₂-MIL-101(Al) is transformed into interconnected N/O-doped carbon (MOF-NOC), which not only acts as a plant-like function to prevent the pulverization of L-TiO₂ transformed from Ti₃C₂T_x but also improves the conductivity and stability of MOF-NOC@L-TiO₂. Al species are selected as seeds to improve interfacial compatibility and form intimate interface heterojunction. Systematic ex situ analysis discloses that the ions storage mechanism can be endowed by mixed contribution of non-Faradaic and Faradaic capacitance. Consequently, the MOF-NOC@L-TiO₂ electrodes exhibit high interfacial capacitive charge storage and outstanding cycling performance. The interface engineering strategy inspired by “sand-fixation model” provides a reference for designing stable layered composites.     

Multivalent Interactions between 2D Nanomaterials and Biointerfaces

2D nanomaterials, particularly graphene, offer many fascinating physicochemical properties that have generated exciting visions of future biological applications. In order to capitalize on the potential of 2D nanomaterials in this field, a full understanding of their interactions with biointerfaces is crucial. The uptake pathways, toxicity, long‐term fate of 2D nanomaterials in biological systems, and their interactions with the living systems are fundamental questions that must be understood. Here, the latest progress is summarized, with a focus on pathogen, mammalian cell, and tissue interactions. The cellular uptake pathways of graphene derivatives will be discussed, along with health risks, and interactions with membranes—including bacteria and viruses—and the role of chemical structure and modifications. Other novel 2D nanomaterials with potential biomedical applications, such as transition‐metal dichalcogenides, transition‐metal oxide, and black phosphorus will be discussed at the end of this review.     

C3N—A 2D Crystalline,Hole‐Free,Tunable‐Narrow‐Bandgap Semiconductor with Ferromagnetic Properties

Graphene has initiated intensive research efforts on 2D crystalline materials due to its extraordinary set of properties and the resulting host of possible applications. Here the authors report on the controllable large‐scale synthesis of C₃N, a 2D crystalline, hole‐free extension of graphene, its structural characterization, and some of its unique properties. C₃N is fabricated by polymerization of 2,3‐diaminophenazine. It consists of a 2D honeycomb lattice with a homogeneous distribution of nitrogen atoms, where both N and C atoms show a D_6h‐symmetry. C₃N is a semiconductor with an indirect bandgap of 0.39 eV that can be tuned to cover the entire visible range by fabrication of quantum dots with different diameters. Back‐gated field‐effect transistors made of single‐layer C₃N display an on–off current ratio reaching 5.5 × 10¹⁰. Surprisingly, C₃N exhibits a ferromagnetic order at low temperatures (<96 K) when doped with hydrogen. This new member of the graphene family opens the door for both fundamental basic research and possible future applications.     

Fabrication and characterization of polyamide 6-functionalized graphene nanocomposite fiber

Graphene oxide was prepared by the Hummers’ method and then functionalized with 4-substituted benzoic acid via “direct Friedel–Crafts” acylation in a mild reaction medium of polyphosphoric acid/phosphorous pentoxide (P₂O₅). Raman spectroscopy, differential scanning calorimetry, thermo-gravimetric analysis, and transmission electron microscopy were used to characterize the resultant structure. The results show that 4-substituted benzoic acid functionalized graphene (FG) sheets were achieved without pretreatment of oxidation. Polycaprolactam (PA6)-FG composites were prepared by in situ polymerization of ε-caprolactam in the presence of FG. Nanocomposite fiber with 0.01–0.5?wt% content of FG was prepared with a piston spinning machine and hot-roller drawing machine. A significant enhancement of mechanical properties of the PA6-FG composites’ fiber is obtained at low graphene loading; that is, a 29?% improvement of tensile strength and a three times increase of Young’s modulus are achieved at a graphene loading of only 0.1?wt%. The “graft-from” methodologies pave the way to prepare graphene-based nanocomposites of condensation polymers with promising performance and functionality.     

Pd Single‐Atom Catalysts on Nitrogen‐Doped Graphene for the Highly Selective Photothermal Hydrogenation of Acetylene to Ethylene

The selective hydrogenation of acetylene to ethylene in an ethylene‐rich gas stream is an important process in the chemical industry. Pd‐based catalysts are widely used in this reaction due to their excellent hydrogenation activity, though their selectivity for acetylene hydrogenation and durability need improvement. Herein, the successful synthesis of atomically dispersed Pd single‐atom catalysts on nitrogen‐doped graphene (Pd₁/N‐graphene) by a freeze‐drying‐assisted method is reported. The Pd₁/N‐graphene catalyst exhibits outstanding activity and selectivity for the hydrogenation of C₂H₂ with H₂ in the presence of excess C₂H₄ under photothermal heating (UV and visible‐light irradiation from a Xe lamp), achieving 99% conversion of acetylene and 93.5% selectivity to ethylene at 125 °C. This remarkable catalytic performance is attributed to the high concentration of Pd active sites on the catalyst surface and the weak adsorption energy of ethylene on isolated Pd atoms, which prevents C₂H₄ hydrogenation. Importantly, the Pd₁/N‐graphene catalyst exhibits excellent durability at the optimal reaction temperature of 125 °C, which is explained by the strong local coordination of Pd atoms by nitrogen atoms, which suppresses the Pd aggregation. The results presented here encourage the wider pursuit of solar‐driven photothermal catalyst systems based on single‐atom active sites for selective hydrogenation reactions.     

Facile synthesis of graphene@NiMoO<Subscript>4</Subscript> nanosheet arrays on Ni foam for a high-performance asymmetric supercapacitor

Honeycomb-like NiMoO₄ with nanosheet arrays is grown on reduced graphene oxide, which is supported on Ni foam having successfully fabricated by a simple hydrothermal treatment followed by a calcined process. In the as-synthesized Ni foam@reduced graphene oxide@NiMoO₄, Ni foam served as “skeleton” to support reduced graphene oxide and reduced graphene oxide directly grown on Ni foam served as the “skin” to provide high passway of electrons and ions, which simultaneously accommodated the volume change during the process of charge–discharge and NiMoO₄ acted as active substance to provide high areal capacitance. It shows a high areal capacitance of 2165.9 mF cm^?2 at a current density of 1 mA cm^?2 and long cycle stability with 93.8% capacitance retained over 1000 charge–discharge cycles. Moreover, an asymmetric supercapacitor has been constructed by using Ni foam@reduced graphene oxide and Ni foam@reduced graphene oxide@NiMoO₄ as negative and positive electrodes. The energy density of this asymmetric supercapacitor is 0.579 mWh cm^?2, and it retains 93.1% capacitance over charge–discharge 5000 cycles. Therefore, it reveals great promise for practical applications in energy storage devices.     

Fullerene-like CPx: A first-principles study of the relative stability of precursors and defect energetics during synthetic growth

Inherently nanostructured CP_x compounds were studied by first-principles calculations. Geometry optimizations and cohesive energy comparisons show stability for C₃P, C₂P, C₃P₂, CP, and P₄ (P₂) species in isolated form as well as incorporated in graphene layers. The energy cost for structural defects, arising from the substitution of C for P and intercalation of P atoms in graphene, was also evaluated. We find a larger curvature of the graphene sheets and a higher density of cross-linkage sites in comparison to fullerene-like (FL) CN_x, which is explained by differences in the bonding between P and N. Thus, the computational results extend the scope of fullerene-like thin film materials with FL-CP_x and provide insights for its structural properties.     

Liquid exfoliation — new low-temperature method of nanotechnology

Two-dimensional nano-crystals, nanosheets, are a new special type of nanomaterials recently discovered. They have attracted interest due to their unique potential applications especially in electronics. In this mini review, we present the current status of liquid exfoliation of layered crystals — an original new method of production of nanosheets. This “top down” synthesis is a low-temperature physico-chemical process already used to graphene production.     

Understanding Interactions of Functionalized Nanoparticles with Proteins: A Case Study on Lactate Dehydrogenase

Nanomaterials in biological solutions are known to interact with proteins and have been documented to affect protein function, such as enzyme activity. Understanding the interactions of nanoparticles with biological components at the molecular level will allow for rational designs of nanomaterials for use in medical technologies. Here we present the first detailed molecular mechanics model of functionalized gold nanoparticle (NP) interacting with an enzyme (l ‐lactate dehydrogenase (LDH) enzyme). Molecular dynamics (MD) simulations of the response of LDH to the NP binding demonstrate that although atomic motions (dynamics) of the main chain exhibit only a minor response to the binding, the dynamics of side chains are significantly constrained in all four active sites that predict alteration in kinetic properties of the enzyme. It is also demonstrated that the 5 nm gold NPs cause a decrease in the maximal velocity of the enzyme reaction (V_max) and a trend towards a reduced affinity (increased K_m) for the β‐NAD binding site, while pyruvate enzyme kinetics (K_m and V_max) are not significantly altered in the presence of the gold NPs. These results demonstrate that modeling of NP:protein interactions can be used to understand alterations in protein function.     

A new route to graphene starting from heavily ozonized fullerenes: Part 2—oxidation in air

Graphite oxide (GO) and heavily ozonized C₆₀ and C₇₀ fullerenes known as “fullerene ozopolymers” were studied by TGA-FTIR (Thermogravimetry coupled with FT-IR spectroscopy), DTG (Differential Thermogravimetry) and DTA (Differential Thermal Analysis) in air flow. It was found that GO burns at 70°C higher temperature than the fullerene ozopolymers. This different behavior toward the thermal oxidation of GO is due to the size of the oxidized and staked graphene layers which are expected to be significantly larger than those of the fullerene ozopolymers. Furthermore, the latter should necessarily have a buckybowl shaped structure which should favor their reactivity with oxygen.     

The safer and scalable mechanochemical synthesis of edge-chlorinated and fluorinated few-layer graphenes

Halogen functionalization of the edges of the graphene sheets can improve processability, add new properties, and enhance its interactions with other materials. Through functionalization, improved materials can be realized. Typically, halogenated graphenes are produced from pure or reactive halogen sources. Current approaches present significant safety challenges. By generating reactive dichlorine monoxide (Cl₂O) in situ, a chlorinated graphene with the nominal composition C₁₇Cl₂OH can be realized safely and scalably. Chlorinated graphene can be used as a precursor for an array of functionalized materials by mechanically driven solid-state metathesis reactions. For example, nearly 75% of the chlorine in chlorinated graphene can be exchanged with fluorine by using the safer fluorine-containing compound ammonium fluoride (NH₄F) as a reagent. A material with the composition C₃₄Cl₃F(OH)₂ is realized. Preliminary work shows that F–graphene has oxygen reduction properties and Cl–graphene can improve existing zinc–air fuel cells. A scalable production of chlorinated and fluorinated graphenes and graphites will accelerate their adoption in fuel cells, batteries, polymer composites, and catalysts.     

Shock Exfoliation of Graphene Fluoride in Microwave

An unprecedented microwave‐based strategy is developed to facilitate solid‐phase, instantaneous delamination and decomposition of graphite fluoride (GF) into few‐layer, partially fluorinated graphene. The shock reaction occurs (and completes in few seconds) under microwave irradiation upon exposing GF to either “microwave‐induced plasma” generated in vacuum or “catalyst effect” caused by intense sparking of graphite at ambient conditions. A detailed analysis of the structural and compositional transformations in these processes indicates that the GF experiences considerable exfoliation and defluorination, during which sp²‐bonded carbon is partially recovered despite significant structural defects being introduced. The exfoliated fluorinated graphene shows excellent electrochemical performance as anode materials in potassium ion batteries and as catalysts for the conversion of O₂ to H₂O₂. This simple and scalable method requires minimal energy input and does not involve the use of other chemicals, which is attractive for extensive research in fluorine‐containing graphene and its derivatives in laboratories and industrial applications.     

Addition of “Living” Polymers onto C60.

Abstract

Various “living” polymers were grafted onto C₆₀ The number of arms of the so obtained “star” molecules can be controlled by stoechiometry and/or by varying the reactivity of the carbanion on the “living” chain against a double bond on the C₆₀. Even the oxanion of “living” polyethylenoxide is able to add onto the reactive double bonds on C₆₀. In some conditions, the carbanions present on these alkaline salts of grafted fullerenes becomes able to initiate anionic polymerization of vinyl monomers. Using “living” poly(phenylvinylsulfoxide) as a precursor polymer for PA, polyacetylene chains could be attached to the fullerene.     

Functionalized Fullerene for Inhibition of SARS-CoV-2 Variants

As virus outbreaks continue to pose a challenge, a nonspecific viral inhibitor can provide significant benefits, especially against respiratory viruses. Polyglycerol sulfates recently emerge as promising agents that mediate interactions between cells and viruses through electrostatics, leading to virus inhibition. Similarly, hydrophobic C₆₀ fullerene can prevent virus infection via interactions with hydrophobic cavities of surface proteins. Here, two strategies are combined to inhibit infection of SARS-CoV-2 variants in vitro. Effective inhibitory concentrations in the millimolar range highlight the significance of bare fullerene's hydrophobic moiety and electrostatic interactions of polysulfates with surface proteins of SARS-CoV-2. Furthermore, microscale thermophoresis measurements support that fullerene linear polyglycerol sulfates interact with the SARS-CoV-2 virus via its spike protein, and highlight importance of electrostatic interactions within it. All-atom molecular dynamics simulations reveal that the fullerene binding site is situated close to the receptor binding domain, within 4 nm of polyglycerol sulfate binding sites, feasibly allowing both portions of the material to interact simultaneously.     

Study on the Corrosion and High-Temperature-Resistant Coating for In Situ Crosslinking Reaction Catalyzed by a Special “Egg Inlaid Egg Tray” Structure

A new type of water corrosion-resistant coating which is similar to the “egg inlaid egg tray” structure is successfully prepared. Modified chitosan (MCS) and graphene oxide (GO) are crosslinked with waterborne epoxy resin to form a unique 3D “tray” hybrid structure, and the crosslinking reaction is catalyzed by modified nano-SiO₂ (MSiO₂) with an egg-like morphology. The uniformly dispersed MSiO₂ can provide crosslinking reaction sites and is firmly “fixed” in the composite coating, thus not only catalyzing the crosslinking reactions with good performance, but also improving the interaction between itself and the as-formed GO-MCS structure. Consequently, with the help of “fixed catalytic in situ crosslinking reactions” and synergistic effect between MSiO₂ and GO-MCS, the coating not only shows an improved corrosion resistance with a large impedance modulus at low frequency (|Z|_{0.01 Hz}) of 1.8 × 10⁶ Ω cm², but also possesses good thermal stability and high hydrophobicity. The protective effect of the composite coating on the substrate is more comprehensive and multiple.