Orientation of reduced graphene oxide in composite coatings

Composite coatings containing reduced graphene oxide (rGO) and 3-(aminopropyl)triethoxysilane functionalised rGO (APTES-rGO) were prepared by sol-gel technology and deposited on Al 2024 T-3. Covalent functionalisation of GO by APTES occurred by formation of amide bonds, accompanied by GO reduction. The thin sheets were retained. The hydrophilicity of the coating increased when APTES-rGO was added. The opposite was observed when GO was added. A key finding is that the rGO flakes agglomerate and lie in a random orientation in the coating, whereas the APTES-rGO flakes are more evenly distributed in the matrix and appear to lie along the plane of the substrate.

Nanodesigns for Na3V2(PO4)3-based cathode in sodium-ion batteries: a topical review

With the rapid development of sodium-ion batteries (SIBs), it is urgent to exploit the cathode materials with good rate capability, attractive high energy density and considerable long cycle performance. Na₃V₂(PO₄)₃(NVP), as a NASICON-type electrode material, is one of the cathode materials with great potential for application because of its good thermal stability and stable. However, NVP has the inherent problem of low electronic conductivity, and various strategies are proposed to improve it, moreover, nanotechnology or nanostructure are involved in these strategies, the construction of nanostructured active particles and nanocomposites with conductive carbon networks have been shown to be effective in improving the electrical conductivity of NVP. Herein, we review the research progress of NVP performance improvement strategies from the perspective of nanostructures and classifies the prepared nanomaterials according to their different nano-dimension. In addition, NVP nanocomposites are reviewed in terms of both preparation methods and promotion effects, and examples of NVP nanocomposites at different nano-dimension are given. Finally, some personal views are presented to provide reasonable guidance for the research and design of high-performance polyanionic cathode materials of SIBs.

Green approach for the synthesis of monolayer reduced graphene oxide: one-step protocol with simultaneous iodination and reduction

A schematic representation of iodinated GO and RGO formation in a single step.

Photocuring Graphene Oxide Liquid Crystals for High-Strength Structural Materials

Graphene is the strongest known material. However, the challenge of translating that strength from the microscale to the more useful macroscale remains unmet. Preparing solid structures from self-assembled graphene oxide liquid crystals has allowed the creation of paper and fibers with excellent mechanical properties. Conventionally, vacuum filtration, wet spinning, and freeze-drying are used to prepare such structures from graphene oxide liquid crystals. Here, we introduce photocuring as an additional option to create solid structures of self-assembled graphene oxide liquid crystals that allows for thicker samples and other shapes to be realized. The photocured graphene oxide paper prepared here exhibited mechanical properties comparable to those of benchmark samples prepared by vacuum filtration.

Spontaneous surface adsorption of aqueous graphene oxide by synergy with surfactants

The spontaneous adsorption of graphene oxide (GO) sheets at the air-water interface is explored using X-ray reflectivity (XRR) measurements. As a pure aqueous dispersion, GO sheets do not spontaneously adsorb at the air-water interface due to their high negative surface potential (-60 mV) and hydrophilic functionality. However, when incorporated with surfactant molecules at optimal ratios and loadings, GO sheets can spontaneously be driven to the surface. It is hypothesised that surfactant molecules experience favourable attractive interactions with the surfaces of GO sheets, resulting in co-assembly that serves to render the sheets surface active. The GO/surfactant composites then collectively adsorb at the air-water interface, with XRR analysis suggesting an interfacial structure comprising surfactant tailgroups in air and GO/surfactant headgroups in water for a combined thickness of 30-40 Å, depending on the surfactant used. Addition of too much surfactant appears to inhibit GO surface adsorption by saturating the interface, and low loadings of GO/surfactant composites (even at optimal ratios) do not show significant adsorption indicating a partitioning effect. Lastly, surfactant chemistry is also a key factor dictating adsorption capacity of GO. The zwitterionic surfactant oleyl amidopropyl betaine causes marked increases in GO surface activity even at very low concentrations (≤0.2 mM), whereas non-ionic surfactants such as Triton X-100 and hexaethyleneglycol monododecyl ether require higher concentrations (ca. 1 mM) in order to impart spontaneous adsorption of the sheets. Anionic surfactants do not enhance GO surface activity presumably due to like-charge repulsions that prevent co-assembly. This work provides useful insight into the synergy between GO sheets and molecular amphiphiles in aqueous systems for enhancing the surface activity of GO, and can be used to inform system formulation for developing water-friendly, surface active composites based around atomically thin materials.

Sulfur Functionalization via Epoxide Ring Opening on a Reduced Graphene Oxide Surface to Form Metal (II) Organo-bis-[1,2]-oxathiin

The epoxide ring-opening reaction in graphene oxide (GO) by nucleophiles is a very fascinating and advanced methodology to develop novel functional material. Herewith, we report an advanced strategy for opening the epoxide ring on the rGO surface via easily an available nucleophile (Na₂S), which is further functionalized with O atom to obtain four-membered rings (FMRs). The Cd coordination with the S atom puts extra stress on the FMR leading to the C-C bond cleavage of the four-membered heteroatomic rings on the rGO surface. This strategic approach leads to the fabrication of an innovative metal (II) organo-bis-[1,2]-oxathiin (MOBOT) chemical moiety (M = Cd, Zn). The MOBOT compound further shows enhanced H₂ generation activity and hence is promising as a potential photocatalyst for solar hydrogen generation. This compound might also be a potential candidate for optoelectronic applications.

An Update on Graphene-Based Nanomaterials for Neural Growth and Central Nervous System Regeneration

Thanks to their reduced size, great surface area, and capacity to interact with cells and tissues, nanomaterials present some attractive biological and chemical characteristics with potential uses in the field of biomedical applications. In this context, graphene and its chemical derivatives have been extensively used in many biomedical research areas from drug delivery to bioelectronics and tissue engineering. Graphene-based nanomaterials show excellent optical, mechanical, and biological properties. They can be used as a substrate in the field of tissue engineering due to their conductivity, allowing to study, and educate neural connections, and guide neural growth and differentiation; thus, graphene-based nanomaterials represent an emerging aspect in regenerative medicine. Moreover, there is now an urgent need to develop multifunctional and functionalized nanomaterials able to arrive at neuronal cells through the blood-brain barrier, to manage a specific drug delivery system. In this review, we will focus on the recent applications of graphene-based nanomaterials in vitro and in vivo, also combining graphene with other smart materials to achieve the best benefits in the fields of nervous tissue engineering and neural regenerative medicine. We will then highlight the potential use of these graphene-based materials to construct graphene 3D scaffolds able to stimulate neural growth and regeneration in vivo for clinical applications.

Graphene oxide-controlled neutral versus cationic form of a red emitting dye: enhancement of fluorescence by graphene oxide

Fluorescence enhancement of fluorophores in neat solvent media in the presence of graphene oxide (GO) is less known. It is necessary to re-examine the role of GO from the fundamental scientific viewpoint. Herein, we have reported GO controlled conversion from the neutral to cationic form of a red emitting molecule. Besides this, the switching of the role of GO as an enhancer to a quencher of fluorescence depending on the concentration of GO in the presence of proton accepting solvent media was established. Intermolecular proton transfer from the GO surface to fluorophores is responsible for this phenomenon.

Welding partially reduced graphene oxides by MOFs into micro-mesoporous hybrids for high-performance oil absorption

Partially reduced graphene oxides (PRGOs) with a small number of COOH groups remaining at the edges were interlocked by UiO-66-NH2 nanoparticles into hierarchical porous hybrids (PRGO@UiO-66-NH2) during the synthesis of UiO-66-NH2 in the presence of PRGOs, in which the UiO-66-NH2 nanoparticles provide micropores and the interlocked PRGO skeletons provide mesopores. The peak intensity of the functional groups on the PRGO@UiO-66-NH2 hybrids decrease greatly when compared with the GO@UiO-66-NH2 hybrids and the UiO-66-NH2 nanoparticles, and the number of -COOH at the edge of the PRGOs are approximately 6.3% after reduction, which is confirmed by the FT-IR and XPS results. When the PRGO@UiO-66-NH2 hybrids were embedded in their macropores via hydrogen bonding, melamine foams (MFs) were able to effectively absorb a variety of water-immiscible organic solvents from oil/water biphasic mixtures and, at the same time, suppress water infusion due to Cassie-state surface superhydrophobicity with a water contact angle of 154.2° in air. After 10 cycles, the PRGO@UiO-66-NH2-laden MFs exhibited water contact angles of 148.3°, which indicated that the composite MFs had excellent stability and recycling ability after 10 cycles. The PRGO@UiO-66-NH2-laden MFs had an oil absorption capacity of >10 000 wt% of the dry mass of absorbents and water absorption capacity of ≈1.76 wt% of the adsorbate, thus highlighting the high absorption selectivity of oil over water.

Interactions between Reduced Graphene Oxide with Monomers of (Calcium) Silicate Hydrates: A First-Principles Study

Graphene is a two-dimensional material, with exceptional mechanical, electrical, and thermal properties. Graphene-based materials are, therefore, excellent candidates for use in nanocomposites. We investigated reduced graphene oxide (rGO), which is produced easily by oxidizing and exfoliating graphite in calcium silicate hydrate (CSHs) composites, for use in cementitious materials. The density functional theory was used to study the binding of moieties, on the rGO surface (e.g., hydroxyl-OH/rGO and epoxide/rGO groups), to CSH units, such as silicate tetrahedra, calcium ions, and OH groups. The simulations indicate complex interactions between OH/rGO and silicate tetrahedra, involving condensation reactions and selective repairing of the rGO lattice to reform pristine graphene. The condensation reactions even occurred in the presence of calcium ions and hydroxyl groups. In contrast, rGO/CSH interactions remained close to the initial structural models of the epoxy rGO surface. The simulations indicate that specific CSHs, containing rGO with different interfacial topologies, can be manufactured using coatings of either epoxide or hydroxyl groups. The results fill a knowledge gap, by establishing a connection between the chemical compositions of CSH units and rGO, and confirm that a wet chemical method can be used to produce pristine graphene by removing hydroxyl defects from rGO.

Hydrogel-assisted delivery of lipophilic molecules into aqueous medium for transdermal medication based on environment-specific, regioselective adsorption of graphene oxides

Graphene oxide (GO)-laden agarose composite hydrogels (GOACHs) were utilized to deliver lipophilic molecules from organic to aqueous media without alteration of the lipophilic nature of the molecules and the hydrophilic nature of the GOACHs. After the agarose host networks of the GOACHs were impregnated with the non-polar organic solution of lipophilic molecules via stepwise solvent exchange, their GO guests wielded the edge polar groups to effectively adsorb the lipophilic molecules via hydrogen bonding. After being transferred to aqueous media, the GOACHs were able to not only release the loaded lipophilic molecules but also to adsorb the released lipophilic molecules on the GO non-polar carbon lattice planes via hydrophobic interactions, thus resulting in deliberately balanced release of lipophilic molecules in aqueous media. Based on this environment-specific, regioselective adsorption of their GO guests, the GOACHs were harnessed as carriers for sustained delivery of ibuprofen across rat skin, underpinning their applicability in transdermal medication.

Long-acting photocatalytic degradation of crude oil in seawater via combination of TiO2 and N-doped TiO2/reduced graphene oxide

N-doped TiO₂/ reduced graphene oxide (N/TiO₂/rGO) composite was prepared and used together with the commercial TiO₂ for comparative research on photocatalytic degradation of crude oil in seawater. Five test conditions were designed including a combined catalyst of TiO₂ and N/TiO₂/rGO (4:1) under UV-A light irradiation with a duration of 28 days. The changing trend of the water-soluble fraction (WSF) of crude oil in seawater was monitored by ultraviolet spectroscopy and fluorescence spectroscopy as well as dissolved organic carbon (DOC) measurement. The SARA fractions of oil residues were analysed by column chromatography, and the chemical composition changes of saturates and aromatics were investigated by gas chromatography-mass spectroscopy (GC-MS). The results reveal that although it had high efficiency in the degradation of aromatics, the nano-TiO₂ tended to self-agglomerate, which enhanced agglomeration of crude oil, causing its catalytic process actually terminating within seven days. By comparison, the N/TiO₂/rGO composite consistently dispersed crude oil in the whole experimental duration, subsequently, it presented a higher photocatalytic degradation rate than TiO₂. The combination of TiO₂ and N/TiO₂/rGO (4:1) shows concerted catalysis on photocatalytic degradation of crude oil, and the oil degradation rate reached to 54.80% while the aromatic degradation rate was 74.83%. The fluorescent components in WSFs were preferentially degraded, and the degradation products of aromatic fraction were CO₂ and H₂O as well as saturates, mainly C₂₀∼C₃₁ alkanes. Considering its long-acting photocatalysis, the N/TiO₂/rGO composite possesses practical utilization potentiality together with TiO₂ in spilled oil treatment in the marine environment.

Integrated nano-architectured photocatalysts for photochemical CO2 reduction

Recent advances in nanotechnology, especially the development of integrated nanostructured materials, have offered unprecedented opportunities for photocatalytic CO2 reduction. Compared to bulk semiconductor photocatalysts, most of these nanostructured photocatalysts offer at least one advantage in areas such as photogenerated carrier kinetics, light absorption, and active surface area, supporting improved photochemical reaction efficiencies. In this review, we briefly cover the cutting-edge research activities in the area of integrated nanostructured catalysts for photochemical CO2 reduction, including aqueous and gas-phase reactions. Primarily explored are the basic principles of tailor-made nanostructured composite photocatalysts and how nanostructuring influences photochemical performance. Specifically, we summarize the recent developments related to integrated nanostructured materials for photocatalytic CO2 reduction, mainly in the following five categories: carbon-based nano-architectures, metal-organic frameworks, covalent-organic frameworks, conjugated porous polymers, and layered double hydroxide-based inorganic hybrids. Besides the technical aspects of nanostructure-enhanced catalytic performance in photochemical CO2 reduction, some future research trends and promising strategies are addressed.

A quantum study on novel azo-dyes containing a fullerene C60 unit as a smart material for optoelectronic applications

Quantum chemical calculations of some novel azo-dyes containing a fullerene C60 unit as a smart material have been carried out with the aims to determine their cis and trans electronic properties and to describe the change of their quantum parameters as a result of the trans/cis isomerization of these molecules. The effects of electron-withdrawing or electron-releasing groups on the R-position of these molecules on electronic, optical, spectroscopic, and other properties of these molecules have been considered with DFT and TDDFT calculations. The obtained results of the calculations show that compounds "b" and "c" with the strongest electron-releasing groups in the R-position of these molecules, particularly the trans isomers of these compounds, with higher chemical softness, higher electrophilicity index, higher thermodynamic properties, and higher charge transfer values, have the better electronic and optical properties and therefore the better chemical reactivity compared to the other compounds. Graphical abstract.

High-performance humidity sensor based on a micro-nano fiber Bragg grating coated with graphene oxide

A high-performance relative humidity (RH) sensor based on a micro-nano fiber Bragg grating (MFBG) coated with a graphene oxide (GO) film is fabricated with a chemical corrosion technique and optically driven deposition method. The diameter of MFBG is corroded to about 12 µm. GO film with the thickness of about 2.5 µm is uniformly coated on the MFBG surface. The change of RH results in the change of refractive index (RI) of GO film, that is, the change of effective RI of MFBG, which will at last result in the shift of reflected wavelength. The experimental results show that there is a good linear relationship between the wavelength shift of MFBG and RH changes in the RH range of 20% to 80% at constant temperature. The sensitivity is 17.361 pm/RH% and the linear correlation coefficient is 99.89%. In order to eliminate the impact of temperature cross sensitivity, the relative measurement is adopted and similar results are obtained. The average response and recovery times are measured to be about 3.2 s and 8.3 s, respectively. The sensor has the advantages of long stability, reversibility, quick response and simple structure. With such high performance, it can be used in widespread potential fields, such as biology, chemical processing and food processing.

Assembly and application advancement of organic-functionalized graphene-based materials: A review

Owing to the remarkable physicochemical properties such as hydrophobicity, conductivity, elasticity, and light weight, graphene-based materials have emerged as one of the most appealing carbon allotropes in materials science and chemical engineering. Unfortunately, pristine graphene materials lack functional groups for further modification, severely hindering their practical applications. To render graphene materials with special characters for different applications, graphene oxide or reduced graphene oxide has been functionalized with different organic agents and assembled together, via covalent binding and various noncovalent forces such as π-π interaction, electrostatic interaction, and hydrogen bonding. In this review, we briefly discuss the state-of-the-art synthetic strategies and properties of organic-functionalized graphene-based materials, and then, present the prospective applications of organic-functionalized graphene-based materials in sample preparation.

Recent progress and advances in the environmental applications of MXene related materials

MXenes are a new type of two-dimensional (2D) transition metal carbide or carbonitride material with a 2D structure similar to graphene. The general formula of MXenes is M_n+1X_nT_x, in which M is an early transition metal element, X represents carbon, nitrogen and boron, and T is a surface oxygen-containing or fluorine-containing group. These novel 2D materials possess a unique 2D layered structure, large specific surface area, good conductivity, stability, and mechanical properties. Benefitting from these properties, MXenes have received increasing attention and emerged as new substrate materials for exploration of various applications including, energy storage and conversion, photothermal treatment, drug delivery, environmental adsorption and catalytic degradation. The progress on various applications of MXene-based materials has been reviewed; while only a few of them covered environmental remediation, surface modification of MXenes has never been highlighted. In this review, we highlight recent advances and achievements in surface modification and environmental applications (such as environmental adsorption and catalytic degradation) of MXene-based materials. The current studies on the biocompatibility and toxicity of MXenes and related materials are summarized in the following sections. The challenges and future directions of the environmental applications of MXene-based materials are also discussed and highlighted.

Reduced holey graphene oxide film and carbon nanotubes sandwich structure as a binder-free electrode material for supercapcitor

A novel carbon nanotubes (CNTs) and reduced holey graphene oxide film (RHGOF) sandwich structure has been fabricated to enhance its electrochemical properties. CNTs are grown by a catalyst assisted chemical vapor deposition technique, interpenetrated between the RHGOF layers. A RHGOF/CNTs hybrid film is used as a binder-free supercapacitor electrode. The grown CNTs in the graphene layers structure act as spacers and bridges to increase the counductivity of RHGOF, while the grown CNTs on the surfaces of the graphene contribute to increase the specific surface area of RHGOF. The results demonstrate that the synthesized porous, flexible and binder free hybrid electrode has advantages of higher ion diffusion rate, longer diffusion length and larger ion accessible surface area as compared to the pristine graphene which results in an extra ordinary galvanostatic charge-discharge specific capacitance of 557 F/g at a current density of 0.5 A/g, with excellent rate capabilities and superior cyclic stabilities.

Enhanced electrochemical performance of α-MoO3/graphene nanocomposites prepared by an in situ microwave irradiation technique for energy storage applications

Nanoparticles of α-molybdenum oxide (α-MoO₃) are directly grown on graphene sheets using a surfactant-free facile one step ultrafast in situ microwave irradiation method.

Energy storage: The future enabled by nanomaterials

Lithium-ion batteries, which power portable electronics, electric vehicles, and stationary storage, have been recognized with the 2019 Nobel Prize in chemistry. The development of nanomaterials and their related processing into electrodes and devices can improve the performance and/or development of the existing energy storage systems. We provide a perspective on recent progress in the application of nanomaterials in energy storage devices, such as supercapacitors and batteries. The versatility of nanomaterials can lead to power sources for portable, flexible, foldable, and distributable electronics; electric transportation; and grid-scale storage, as well as integration in living environments and biomedical systems. To overcome limitations of nanomaterials related to high reactivity and chemical instability caused by their high surface area, nanoparticles with different functionalities should be combined in smart architectures on nano- and microscales. The integration of nanomaterials into functional architectures and devices requires the development of advanced manufacturing approaches. We discuss successful strategies and outline a roadmap for the exploitation of nanomaterials for enabling future energy storage applications, such as powering distributed sensor networks and flexible and wearable electronics.

Flexible all-in-one zinc-ion batteries

The recent development of flexible and wearable electronic devices has increased the demand for energy storage devices with excellent flexibility and structural stability. Aqueous zinc-ion batteries (ZIBs) are promising energy storage devices due to their low cost, high safety, and eco-friendliness. Therefore, flexible ZIBs have to be considered. Herein, we design the flexible all-in-one ZIBs, where the reduced graphene oxide/polyaniline (rGO/PANI) cathode, cellulose nanofiber (CNF) separator, and exfoliated graphene (EG)/Zn anode are integrated together using an all-freeze-casting strategy. The continuous seamless connection of such all-in-one ZIBs can avoid displacing and detaching between the electrodes and separator under different bending states and improve the load-transfer capacity and interface strength between the neighboring component layers. As a result, the all-in-one ZIBs show excellent flexibility and superior electrochemical stability under different bending states.

A smart drug-delivery nanosystem based on carboxylated graphene quantum dots for tumor-targeted chemotherapy

Aim: Constructing a new drug-delivery system using carboxylated graphene quantum dots (cGQDs) for tumor chemotherapy in vivo. Materials & methods: A drug-delivery system was synthesized through a crosslink reaction of cGQDs, NH2-poly(ethylene glycol)-NH2 and folic acid. Results: A drug delivery system of folic acid-poly(ethylene glycol)-cGQDs was successfully constructed with ideal entrapment efficiency (97.5%) and drug-loading capacity (40.1%). Cell image indicated that the nanosystem entered into human cervical cancer cells mainly through macropinocytosis-dependent pathway. In vivo experiments showed the outstanding antitumor ability and low systemic toxicity of this nanodrug-delivery system. Conclusion: The newly developed drug-delivery system provides an important alternative for tumor therapy without causing systemic adverse effects.

Porous Nb4N5/rGO Nanocomposite for Ultrahigh-Energy-Density Lithium-Ion Hybrid Capacitor

To meet the increasing demands for high-performance energy storage devices, an advanced lithium-ion hybrid capacitor (LIHC) has been designed and fabricated, which delivers an ultrahigh energy density of 295.1 Wh kg^-1 and a power density of 41 250 W kg^-1 with superior cycling stability. The high-performance LIHC device is based on the uniform porous Nb₄N₅/rGO nanocomposite, which has an intimate interface between the firmly contacted Nb₄N₅ and rGO through the Nb(Nb₄N₅)-O(rGO)-C(rGO) bonds, significantly improving the electron transport kinetics. Moreover, the introduction of rGO nanosheets can prevent the Nb₄N₅ nanoparticles from agglomeration, not only resulting in a larger specific surface area to provide more active sites but also accommodating the strain during Li ion insertion/deinsertion. Therefore, the Nb₄N₅/rGO nanocomposite exhibits a higher reversible specific capacity and better rate and cycling performance than the Nb₄N₅ nanoparticle. In view of the scalable preparation and superior electrochemical characteristics, the Nb₄N₅/rGO nanocomposite would have great potential practical applications in the future energy storage devices.

Electrical Conductivity of Films Formed by Few-Layer Graphene Structures Obtained by Plasma-Assisted Electrochemical Exfoliation of Graphite

Current-voltage characteristics of few-layer graphene structures (FLGS) obtained by plasma-assisted electrochemical exfoliation of graphite in Na2SO4 solution were measured. FLGS are shown to possess electronic conductivity, which indicates the predominant functionalization of the edges of graphene planes and the preservation of the structure of basal planes in obtained nanostructures as in the source graphite. The effect of humidity on the conductivity of FLGS films was studied. The resistance of films was found to increase with an increase in the relative humidity of the environment due to the shielding of FLGS flakes by a film of water. The effect of different solvents on the current-voltage characteristics of FLGS was analyzed. The conductivity of films significantly decreased in vapors of polar protic solvents, while there was a minor effect of nonpolar aprotic solvents on the conductivity of FLGS films.

Cobalt-Doped Porous Carbon Nanosheets Derived from 2D Hypercrosslinked Polymer with CoN₄ for High Performance Electrochemical Capacitors

Cobalt-doped graphene-coupled hypercrosslinked polymers (Co-GHCP) have been successfully prepared on a large scale, using an efficient RAFT (Reversible Addition-Fragmentation Chain Transfer Polymerization) emulsion polymerization and nucleophilic substitution reaction with Co (II) porphyrin. The Co-GHCP could be transformed into cobalt-doped porous carbon nanosheets (Co-GPC) through direct pyrolysis treatment. Such a Co-GPC possesses a typical 2D morphology with a high specific surface area of 257.8 m² g^-1. These intriguing properties of transition metal-doping, high conductivity, and porous structure endow the Co-GPC with great potential applications in energy storage and conversion. Utilized as an electrode material in a supercapacitor, the Co-GPC exhibited a high electrochemical capacitance of 455 F g^-1 at a specific current of 0.5 A g^-1. After 2000 charge/discharge cycles, at a current density of 1 A g^-1, the specific capacitance increased by almost 6.45%, indicating the excellent capacitance and durability of Co-GPC. These results demonstrated that incorporation of metal porphyrin into the framework of a hypercrosslinked polymer is a facile strategy to prepare transition metal-doped porous carbon for energy storage applications.

Self-Assembled Graphene-Based Architectures and Their Applications

Due to unique planar structures and remarkable thermal, electronic, and mechanical properties, chemically modified graphenes (CMGs) such as graphene oxides, reduced graphene oxides, and the related derivatives are recognized as the attractive building blocks for "bottom-up" nanotechnology, while self-assembly of CMGs has emerged as one of the most promising approaches to construct advanced functional materials/systems based on graphene. By virtue of a variety of noncovalent forces like hydrogen bonding, van der Waals interaction, metal-to-ligand bonds, electrostatic attraction, hydrophobic-hydrophilic interactions, and π-π interactions, the CMGs bearing various functional groups are highly desirable for the assemblies with themselves and a variety of organic and/or inorganic species which can yield various hierarchical nanostructures and macroscopic composites endowed with unique structures, properties, and functions for widespread technological applications such as electronics, optoelectronics, electrocatalysis/photocatalysis, environment, and energy storage and conversion. In this review, significant recent advances concerning the self-assembly of CMGs are summarized, and the broad applications of self-assembled graphene-based materials as well as some future opportunities and challenges in this vibrant area are elucidated.

Carbon Domains on MoS2/TiO2 System via Catalytic Acetylene Oligomerization: Synthesis, Structure, and Surface Properties

Carbon domains have been obtained at the surface of a MoS2/TiO2 (Evonik, P25) system via oligomerization and cyclotrimerization reactions involved in the interaction of the photoactive material with acetylene. Firstly, MoS2 nanosheets have been synthesized at the surface of TiO2, via sulfidation of a molybdenum oxide precursor with H2S (bottom-up method). Secondly, the morphology and the structure, the optical and the vibrational properties of the obtained materials, for each step of the synthesis procedure, have been investigated by microscopy and spectroscopy methods. In particular, transmission electron microscopy images provide a simple tool to highlight the effectiveness of the sulfidation process, thus showing 1L, 2L, and stacked MoS2 nanosheets anchored to the surface of TiO2 nanoparticles. Lastly, in-situ FTIR spectroscopy investigation gives insights into the nature of the oligomerized species, showing that the formation of both polyenic and aromatic systems can be taken into account, being their formation promoted by both Ti and Mo catalytic sites. This finding gives an opportunity for the assembly of extended polyenic, polyaromatic, or mixed domains firmly attached at the surface of photoactive materials. The presented approach, somehow different from the carbon adding or doping processes of TiO2, is of potential interest for the advanced green chemistry and energy conversion/transport applications.

One-Pot Synthesis of Reduced Graphene Oxide/Metal (Oxide) Composites

Graphene, one of the most attractive two-dimensional nanomaterials, has demonstrated a broad range of applications because of its excellent electronic, mechanical, optical, and chemical properties. In this work, a general, environmentally friendly, one-pot method for the fabrication of reduced graphene oxide (RGO)/metal (oxide) (e.g., RGO/Au, RGO/Cu₂O, and RGO/Ag) composties was developed using glucose as the reducing agent and the stabilizer. The glucose not only reduced GO effectively to RGO but also reduced the metal precursors to form metal (oxide) nanoparticles on the surface of RGO. Moreover, the RGO/metal (oxide) composites were stabilized by gluconic acid on the surface of RGO. The developed RGO/metal (oxide) composites were characterized using STEM, FE-SEM, EDS, UV-vis absorption spectroscopy, XRD, FT-IR, and Raman spectroscopy. Finally, the developed nanomaterials were successfully applied as an electrode catalyst to simultaneous electrochemical analysis of l-ascorbic acid, dopamine, and uric acid.

Efficient Graphene Production by Combined Bipolar Electrochemical Intercalation and High-Shear Exfoliation

In this study, we demonstrate that bipolar electrochemistry is a viable strategy for "wireless" electrochemical intercalation of graphite flakes and further large-scale production of high-quality graphene suspensions. Expansion of the graphite layers leads to a dramatic 20-fold increase in the yield of high-shear exfoliation. Large graphite flakes, which do not produce graphene upon high shear if left untreated, are exfoliated in a yield of 16.0 ± 0.2%. Successful graphene production was confirmed by Raman spectroscopy and scanning transmission electron microscopy, showing that the graphene flakes are 0.4-1.5 μm in size with the majority of flakes consisting of 4-6 graphene layers. Moreover, a low intensity of the D peak relative to the G peak as expressed by the I _D/I _G ratio in Raman spectroscopy along with high-resolution transmission electron microscopy images reveals that the graphene sheets are essentially undamaged by the electrochemical intercalation. Some impurities reside on the graphene after the electrochemical treatment, presumably because of oxidative polymerization of the solvent, as suggested by electron energy loss spectroscopy and X-ray photoelectron spectroscopy. In general, the bipolar electrochemical exfoliation method provides a pathway for intercalation on a wider range of graphite substrates and enhances the efficiency of the exfoliation. This method could potentially be combined with simultaneous electrochemical functionalization to provide graphene specifically designed for a given composite on a larger scale.

2D Black Phosphorus for Energy Storage and Thermoelectric Applications

Recent progress in the currently available methods of producing black phosphorus bulk and phosphorene are presented. The effective passivation approaches toward improving the air stability of phosphorene are also discussed. Furthermore, the research efforts on the phosphorene and phosphorene-based materials for potential applications in lithium ion batteries, sodium ion batteries, and thermoelectric devices are summarized and highlighted. Finally, the outlook including challenges and opportunities in these research fields are discussed.

Graphene and Other 2D Colloids: Liquid Crystals and Macroscopic Fibers

Two-dimensional colloidal nanomaterials are running into renaissance after the enlightening researches of graphene. Macroscopic one-dimensional fiber is an optimal ordered structural form to express the in-plane merits of 2D nanomaterials, and the formation of liquid crystals (LCs) allows the creation of continuous fibers. In the correlated system from LCs to fibers, understanding their macroscopic organizing behavior and transforming them into new solid fibers is greatly significant for applications. Herein, we retrospect the history of 2D colloids and discuss about the concept of 2D nanomaterial fibers in the context of LCs, elaborating the motivation, principle and possible strategies of fabrication. Then we highlight the creation, development and typical applications of graphene fibers. Additionally, the latest advances of other 2D nanomaterial fibers are also summarized. Finally, conclusions, challenges and perspectives are provided to show great expectations of better and more fibrous materials of 2D nanomaterials. This review gives a comprehensive retrospect of the past century-long effort about the whole development of 2D colloids, and plots a clear roadmap - "lamellar solid - LCs - macroscopic fibers - flexible devices", which will certainly open a new era of structural-multifunctional application for the conventional 2D colloids.

Understanding Surface and Interfacial Chemistry in Functional Nanomaterials via Solid-State NMR

Surface and interfacial chemistry is of fundamental importance in functional nanomaterials applied in catalysis, energy storage and conversion, medicine, and other nanotechnologies. It has been a perpetual challenge for the scientific community to get an accurate and comprehensive picture of the structures, dynamics, and interactions at interfaces. Here, some recent examples in the major disciplines of nanomaterials are selected (e.g., nanoporous materials, battery materials, nanocrystals and quantum dots, supramolecular assemblies, drug-delivery systems, ionomers, and graphite oxides) and it is shown how interfacial chemistry can be addressed through the perspective of solid-state NMR characterization techniques.

N-Doped CDs–GP nanospheres as a drug delivery nanocarrier system with carbon dots and a fluorescent tracer

In this study, a carbon dots-genipin covalent conjugate (CDs–GP) was synthesized, characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and fluorescence spectroscopy (FL).

Controllable decoration of palladium sub-nanoclusters on reduced graphene oxide with superior catalytic performance in selective oxidation of alcohols

Sub-nanosized Pd/rGO catalyst prepared by impregnation with PdCl₂ is highly active in alcohols oxidation.

Chemical Tailoring of Functional Graphene-Based Nanocomposites by Simple Stacking, Cutting, and Folding

Got your work cut out: Stacking, cutting, and folding have been demonstrated to be a viable approach for the fabrication of robust nanocomposites from large-area graphene films and polymers. This method opens up an effective route towards strong, durable, and multifunctional nanomaterials with fascinating properties.