A review on recent progress in polymer composites for effective electromagnetic interference shielding properties - structures, process, and sustainability approaches

The rapid proliferation and extensive use of electronic devices have resulted in a meteoric increase in electromagnetic interference (EMI), which causes electronic devices to malfunction. The quest for the best shielding material to overcome EMI is boundless. This pursuit has taken different directions, right from materials to structures to process, up to the concept of sustainable materials. The emergence of polymer composites has substituted metal and metal alloy-based EMI shielding materials due to their unique features such as light weight, excellent corrosion resistance, and superior electrical, dielectric, thermal, mechanical, and magnetic properties that are beneficial for suppressing the EMI. Therefore, polymer nanocomposites are an extensively explored EMI shielding materials strategy. This review focuses on recent research developments with a major emphasis on structural aspects and processing for enhancing the EMI shielding effectiveness of polymer nanocomposites with their underlying mechanisms and some glimpses of the sustainability approaches taken in this field.

Defect healing and doping of CVD graphene by thermal sulfurization

CVD graphene layers are intrinsically polycrystalline; depending on grain size, their structure at the atomic level is scarcely free of defects, which affects the properties of graphene. On the one hand, atomic-scale defects act as scattering centers and lead to a loss of carrier mobility. On the other hand, structural disorder at grain boundaries provides additional resistance in series that affects material conductivity. Graphene chemical functionalization has been demonstrated to be an effective way to improve its conductivity mainly by increasing carrier concentration. The present study reports the healing effects of sulfur doping on the electrical transport properties of single-layer CVD graphene. A post-growth thermal sulfurization process operating at 250 °C is applied on single layers of graphene on Corning-glass and Si/SiO2 substrates. XPS and Raman analyses reveal the covalent attachment of sulfur atoms in graphene carbon lattice without creating new C-sp3 defects. Measurements of transport properties show a significant improvement in hole mobility as revealed by Hall measurements and related material conductivity. Typically, Hall mobility values as high as 2500 cm2 V-1 s-1 and sheet resistance as low as 400 Ohm per square are measured on single-layer sulfurized graphene.

Utilization of smartphones for the evaluation of Gr/Ni nanostructures magnetically controlled based on optical fibers surface plasmons

In the suggested optical fiber-based magnetoplasmonic system, we investigated the magnetic properties of graphene/nickel nanostructures. The plasmonic mode changes under the magnetic field observed in the intensity diagrams over time. To be accessible, cheap, and portable, we used a smartphone as a detector and processor. Considering the ambient noise and the light source, it was reported that the intensity of the changes improved up to 5 times. Further, the clad corrosion experiment carried out by pure dimethyl ketone in an intensity modulation by a smartphone camera and 10 seconds suggested removing fluorine polymer clad.

Novel magnetically separable tetrahedral Ag3PO4/NrGO/CuFe2O4 photocatalyst for efficient detoxification of 2,4-dichlorophenol

An effective as well as eco-friendly photodegradation methods by atoxic and easily reusable photocatalysts are essential for wastewater treatment. Silver phosphate (Ag₃PO₄) specifically in tetrahedral shape is one of the superior catalysts under visible light but its photocorrosion, poor electron transfer ability and low surface adsorption properties limits its applications. Combination of Ag₃PO₄ and nitrogen doped reduced graphene oxide (NrGO) having higher in surface area, ample functional groups and hetero atom doping is expected to get over the problem. Further addition of a spinel ferrite (CuFe₂O₄) could enhance the visible light response activity and helps in easy separation of catalyst for reuse. Given the merits of Ag₃PO₄, NrGO and CuFe₂O₄ we rationally integrated a novel magnetically separable stable Ag₃PO₄/NrGO/CuFe₂O₄ photocatalyst for efficient detoxification of 2,4-dichlorophenol (2,4-DCP). About 95.3% degradation efficiency was achieved by Ag₃PO₄/NrGO/CuFe₂O₄ (k = 0.01978 min^-1) which was ~2.6 times higher than pure Ag₃PO₄ (k = 0.00747 min^-1) in 60 min of visible light irradiation. The Ag₃PO₄/NrGO/CuFe₂O₄ heterojunction was able to separate and recycle easily using an external magnetic field due to its strong magnetism, and after 5 recycles it showed 88.6% of degradation efficiency revealed its higher stability and recyclability. The photocatalytic mechanism of Ag₃PO₄/NrGO/CuFe₂O₄ was explained by heterojunction energy-band theory. In addition, the plausible intermediate products of 2,4-dichlorophenol were analyzed by ESI/LC-MS and proposed the pathway. Moreover, the phytotoxicity was also studied on V. radiata in which GI (germination index) was found to be 11.97% before degradation, while 80.31% of GI was observed in 60 min of degradation which revealed that more significant reduction in toxicity was attained on this photodegradation.

Long-Life Dendrite-Free Lithium Metal Electrode Achieved by Constructing a Single Metal Atom Anchored in a Diffusion Modulator Layer

Lithium metal electrodes have shown great promise for high capacity and the lowest potential. However, wide application is restricted by uncontrollable plating/stripping lithium behaviors, an uneven solid electrolyte interphase, and a lithium dendrite. Herein, the highly active single metal atom anchored in vacant catalyst is synthesized on the hierarchical porous nanocarbon (SACo/ADFS@HPSC). Acting as an artificial protective modulation layer on the lithium surface, the numerous atomic sites show the superiority in modulating lithium ion behaviors and smoothing the lithium surface without dendrite growth. As a consequence, the SACo/ADFS@HPSC-modified Li electrode lowers nucleation barrier (15 mV), extends the smooth plating lifespan (1600 h), and improves Coulombic efficiency, significantly accelerating the horizonal deposition of plated lithium. Coupled with a sulfur cathode, the fabricated pouch cell with 5.4 mg cm^-2 delivers a high capacity of 3.78 mA h cm^-2 corresponding to 1505 Wh kg^-1, showing the promising practical application.

Construction of activated carbon-supported B3N3 doped carbon as metal-free catalyst for dehydrochlorination of 1,2-dichloroethane to produce vinyl chloride

Metal-free catalysts synthesized by impregnating activated carbons with B₃N₃-containing arylacetylene resin showed good catalytic performance for industrial dehydrochlorination of 1,2-dichloroethane to produce vinyl chloride monomer.

Chemiresistive Properties of Imprinted Fluorinated Graphene Films

The electrical conductivity of graphene materials is strongly sensitive to the surface adsorbates, which makes them an excellent platform for the development of gas sensor devices. Functionalization of the surface of graphene opens up the possibility of adjusting the sensor to a target molecule. Here, we investigated the sensor properties of fluorinated graphene films towards exposure to low concentrations of nitrogen dioxide NO₂. The films were produced by liquid-phase exfoliation of fluorinated graphite samples with a composition of CF_0.08, CF_0.23, and CF_0.33. Fluorination of graphite using a BrF₃/Br₂ mixture at room temperature resulted in the covalent attachment of fluorine to basal carbon atoms, which was confirmed by X-ray photoelectron and Raman spectroscopies. Depending on the fluorination degree, the graphite powders had a different dispersion ability in toluene, which affected an average lateral size and thickness of the flakes. The films obtained from fluorinated graphite CF_0.33 showed the highest relative response ca. 43% towards 100 ppm NO₂ and the best recovery ca. 37% at room temperature.

Single Si-Doped Graphene as a Catalyst in Oxygen Reduction Reactions: An In Silico Study

Single Si-doped graphene C₅₃H₁₈Si with one carbon atom replaced by a three-coordinate silicon atom is studied by density functional theory (DFT) calculations as a catalyst for the oxygen reduction reactions (ORRs) in both acidic and alkaline media. The active sites for oxygen adsorption were determined from the distribution of the charge density difference analysis. At the equilibrium electrode potential, the most stable intermediate was found to have the structure HO*O*-C₅₃H₁₈Si with both oxygen atoms bound to the support, one of them being incorporated in between Si and C atoms, corresponding to the transfer of one hydrogen atom [H⁺ + e^-]. The 2e ORR mechanism is shown to be very unlikely because the alternative 4e ORR pathway occurring via intermediates with a broken O-O bond is much more exothermic. In addition to the commonly adopted ORR mechanism, new reaction pathways have been discovered and shown to be potentially preferable over the traditional mechanism. The new proposed four-electron ORR route was predicted to proceed spontaneously in acidic media at U < 0.99 V and in alkaline media at U < 0.22.

Electronic Structure of Nitrogen- and Phosphorus-Doped Graphenes Grown by Chemical Vapor Deposition Method

Heteroatom doping is a widely used method for the modification of the electronic and chemical properties of graphene. A low-pressure chemical vapor deposition technique (CVD) is used here to grow pure, nitrogen-doped and phosphorous-doped few-layer graphene films from methane, acetonitrile and methane-phosphine mixture, respectively. The electronic structure of the films transferred onto SiO₂/Si wafers by wet etching of copper substrates is studied by X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy using a synchrotron radiation source. Annealing in an ultra-high vacuum at ca. 773 K allows for the removal of impurities formed on the surface of films during the synthesis and transfer procedure and changes the chemical state of nitrogen in nitrogen-doped graphene. Core level XPS spectra detect a low n-type doping of graphene film when nitrogen or phosphorous atoms are incorporated in the lattice. The electrical sheet resistance increases in the order: graphene < P-graphene < N-graphene. This tendency is related to the density of defects evaluated from the ratio of intensities of Raman peaks, valence band XPS and NEXAFS spectroscopy data.

Microwave exfoliation of organic-intercalated fluorographites

Microwave (MW) irradiation is often used in preparation of nanomaterials. Here, we investigate MW exfoliation patterns of intercalated fluorinated graphite (C₂F) depending on the nature of the "guest". The resulting highly exfoliated graphites (multi-layer graphenes) show advantageous characteristics, as compared to the products of convective heating.

Tuning the properties of boron-doped reduced graphene oxide by altering the boron content

Boron-doping enhanced the occurrence of the energy bandgap, the pore structure and interfacial charge transfer characteristics.

Pristine-Graphene-Supported Nitrogen-Doped Carbon Self-Assembled from Glucaminium-Based Ionic Liquids as Metal-Free Catalyst for Oxygen Evolution

For the first time, graphene-supported N-doped carbon (G@NC) with a high degree of N doping was synthesized by in situ self-assembly of a glucaminium-based ionic liquid on pristine graphene under hydrothermal conditions. This 2D, metal-free nanohybrid exhibited much higher catalytic activity than most reported metal-free catalysts for the oxygen evolution reaction (OER) and even state-of-the-art Ir- and Ru-based catalysts because the high content of graphitic N greatly increased the number of OER-active sites, the pristine graphene significantly promoted the OER activity of the C sites adjacent to the graphitic N atoms, and N-doped graphitic carbon remarkably enhanced the charge-transfer rate. This work not only creates a facile and economical approach to controllably fabricate pristine-graphene-supported carbon with a high N-doping level for the development of highly efficient metal-free OER catalysts but also provides insight into the mechanisms for both the in situ self-assembly and the high OER catalytic activity of G@NC.

Construction of Layered B3N3-Doped Graphene Sheets from an Acetylenic Compound Containing B3N3 by a Semisynthetic Strategy

The structural modification of graphene at the atomic level is crucial for electrochemical applications. Doping heteroatoms to modify the structure of graphene has widely been adopted. However, the construction and controllable doping of heteroatom-doped graphene remains a challenge. Herein, a novel semisynthetic method is developed to synthesize a borazine (B₃N₃)-containing acetylenic compound as a precursor, and a series of B₃N₃-doped few-layered graphene nanosheets are prepared after annealing at different temperatures. To form graphene sheets, the in situ-forming MgBrCl salt is used as an intercalation agent to enlarge the mutual distance between molecules, which can inhibit the unwanted cross-linking reaction. Nanosheets with different thicknesses of 2.5, 3.5, and 4.1 nm can be obtained at annealing temperatures of 1500, 1200, and 1000 °C, respectively. The results demonstrate that the B and N atoms are co-doped in the graphene by the structure of B₃N₃, and the doping site can be changed with different annealing temperatures. The optical gap of graphene can be successfully opened by doping with B₃N₃, and the resultant material can be potentially utilized as a catalyst and semiconductor material. Furthermore, this new semisynthetic strategy will offer the opportunity to fabricate more carbon materials via controllable heteroatom doping.

Pd Nanoparticles Confined in the Porous Graphene-like Carbon Nanosheets for Olefin Hydrogenation

As a novel type of defective graphene, porous graphene has been considered an excellent support material for metal clusters, as the interaction between defective carbon atoms surrounded with the metal nanoparticles (NPs) is very different from that on the ordinary supported catalyst. In this work, we reported a facile three-step method to confine the Pd NPs and grow the graphene-like carbon nanosheets (GLCs) in the same interlayer space of the layered silicate, generating embedded Pd NPs in the pores of porous GLCs in situ. The Pd@GLC nanocomposite exhibited not only high activity and stability than the common commercial Pd/C catalyst for the hydrogenation of olefins but also superior ability of resisting high temperature, which benefitted from the two-dimensional structure of layered GLCs, the confinement of Pd, and the increased edge and defect of the unsaturated carbon atoms in GLCs.

Nitrogen-doped graphene and graphene quantum dots: A review onsynthesis and applications in energy, sensors and environment

Doping of nitrogen is a promising strategy to modulate chemical, electronic, and structural functionalities of graphene (G)and graphene quantum dots (GQDs) for their outstanding properties in energy and environmental applications.This paper reviews various synthesis approaches of nitrogen-doped graphene (N-G) and nitrogen-doped graphene quantum dots (N-GQDs).;Thermal, ultrasonic, solvothermal, hydrothermal, and electron-beam methods have been applied to synthesize N-G and N-GQDs.These nitrogen-doped carbon materials are characterized to obtain their structural configurations in order to achieve better performance in their applications compared to only either graphene or graphene quantum dots.Both N-G and N-GQDs may be converted into functional materials by integrating with other compounds such as metal oxides/nitrides, polymers, and semiconductors.These functional materials demonstrate superior performance over N-G and N-GQDs materials.Examples of applications of N-G and N-GQDs include supercapacitors, batteries, sensors, fuel cells, solar cells, and photocatalyst.

Recent advances in the nanoengineering of electrocatalysts for CO2 reduction

Emissions of CO2 from fossil fuel combustion and industrial processes have been regarded as the dominant cause of global warming. Electrochemical CO2 reduction (ECR), ideally in aqueous media, could potentially solve this problem by the storage of energy from renewable sources in the form of chemical energy in fuels or value-added chemicals in a sustainable manner. However, because of the sluggish reaction kinetics of the ECR, efficient, selective, and durable electrocatalysts are required to increase the rate this reaction. Despite considerable progress in using bulk metallic electrodes for catalyzing the ECR, greater efforts are still needed to tackle this grand challenge. In this Review, we highlight recent progress in using nanoengineering strategies to promote the electrocatalysts for the ECR. Through these approaches, considerable improvements in catalytic performance have been achieved. An outlook of future developments in applying and optimizing these strategies is also proposed.

Synthesis and Characterization of "Ravine-Like" BCN Compounds with High Capacitance

A series of "ravine-like" boron carbonitrides (abbreviation: BCN) were synthesized by a green precursor pyrolysis method at different temperatures (about 700-1100 °C). The highest electrochemical performance of BCN-800 (Named BCN-temperature) electrode was observed, because the "ravine-like" structure can significantly increase the contact area and improve the wettability between electrode and electrolyte. The BCN electrode exhibited ultrahigh specific capacitance 805.9 F/g (at a current density of 0.2 A/g), excellent rate capability, and good cycling stability (91%) after 3000 cycles at a current density of 8 A/g, showing high potential applications in supercapacitors.

Graphene-Based Functional Architectures: Sheets Regulation and Macrostructure Construction toward Actuators and Power Generators

Graphene, with large delocalized π electron cloud on a two-dimensional (2D) atom-thin plane, possesses excellent carrier mobility, large surface area, high light transparency, high mechanical strength, and superior flexibility. However, the lack of intrinsic band gap, poor dispersibility, and weak reactivity of graphene hinder its application scope. Heteroatom-doping regulation and surface modification of graphene can effectively reconstruct the sp² bonded carbon atoms and tailor the surface chemistry and interfacial interaction, while microstructure mediation on graphene can induce the special chemical and physical properties because of the quantum confinement, edge effect, and unusual mass transport process. Based on these regulations on graphene, series of methods and techniques are developed to couple the promising characters of graphene into the macroscopic architectures for potential and practical applications. In this Account, we present our effort on graphene regulation from chemical modification to microstructure control, from the morphology-designed macroassemblies to their applications in functional systems excluding the energy-storage devices. We first introduce the chemically regulative graphene with incorporated heteroatoms into the honeycomb lattice, which could open the intrinsic band gap and provide many active sites. Then the surface modification of graphene with functional components will improve dispersibility, prevent aggregation, and introduce new functions. On the other hand, microstructure mediation on graphene sheets (e.g., 0D quantum dots, 1D nanoribbons, and 2D nanomeshes) is demonstrated to induce special chemical and physical properties. Benefiting from the effective regulation on graphene sheets, diverse methods including dimension-confined strategy, filtration assembly, and hydrothermal treatment have been developed to assemble individual graphene sheets to macroscopic graphene fibers, films, and frameworks. These rationally regulated graphene sheets and well-constructed assemblies present promising applications in energy-conversion materials and device systems focusing on actuators that can convert different energy forms (e.g., electric, chemical, photonic, thermal, etc.) to mechanical actuation and electrical generators that can directly transform environmental energy to electric power. These results reveal that graphene sheets with surface chemistry and microstructure regulations as well as their rationally designed assemblies provide a promising and abundant platform for development of diverse functional devices. We hope that this Account will promote further efforts toward fundamental research on graphene regulation and the wide applications of advanced designed assemblies in new types of energy-conversion materials/devices and beyond.

Controlled Chemical Synthesis in CVD Graphene

Due to the unique properties of graphene, single layer, bilayer or even few layer graphene peeled off from bulk graphite cannot meet the need of practical applications. Large size graphene with quality comparable to mechanically exfoliated graphene has been synthesized by chemical vapor deposition (CVD). The main development and the key issues in controllable chemical vapor deposition of graphene has been briefly discussed in this chapter. Various strategies for graphene layer number and stacking control, large size single crystal graphene domains on copper, graphene direct growth on dielectric substrates, and doping of graphene have been demonstrated. The methods summarized here will provide guidance on how to synthesize other two-dimensional materials beyond graphene.

Sandwiches of N-doped diamondoids and benzenevialone pair–cation and cation–pi interaction: a DFT study

Cation–lone pair and cation–pi interactions in the complexes of N-doped dimondoids.

Derivatization and interlaminar debonding of graphite–iron nanoparticle hybrid interfaces using Fenton chemistry

Physico-chemical phenomena endure in the nanoscale domains of organic–inorganic interfaces for exfoliation, interfacial debonding and cracking of the graphite sheets.

Understanding reactivity, aromaticity and absorption spectra of carbon cluster mimic to graphene: a DFT study

Effect of doping B and/or N on the reactivity, aromaticity and absorption spectra of graphene and functionalized (–OH and –COOH) carbon cluster mimicking graphene is studied using DFT, DFRT and TD-DFT.

Nitrogen-doped reduced graphene oxide and aniline based redox additive electrolyte for a flexible supercapacitor

Nitrogen-doped reduced graphene oxide (N-rGO) with a flexible structure was prepared by simple hydrothermal method. The N-rGO flexible supercapacitor fabricated and improved the performance using aniline as redox additive.