Graphene Oxide Papers Simultaneously Doped with Mg(2+) and Cl(-) for Exceptional Mechanical, Electrical, and Dielectric Properties

Enhanced Gas Barrier and Mechanical Properties of Styrene-Butadiene Rubber Composites by Incorporating Electrostatic Self-Assembled Graphene Oxide @ Layered Double Hydroxide Hybrids

Rubber composites with a high gas barrier and mechanical properties have received considerable attention due to their potential applications. Constructing complex filler networks in a rubber matrix is an effective strategy to simultaneously enhance the gas barrier and mechanical properties. In this work, graphene oxide layered double hydroxide (GO@LDHs) hybrids were obtained by the electrostatic self-assembly method. A unique interspersed and isolated structure was formed in GO@LDHs hybrids due to the chemical interactions between the functional groups on GO sheets and the metal cations on LDH layers. Subsequently, the GO@LDHs hybrids were incorporated into a styrene-butadiene rubber (SBR) matrix using a green latex compounding method. The results showed that the GO@LDHs hybrids were uniformly embedded in the SBR matrix, constructing an overlapped filler network and forming physical bonding points that reduced the free volume of the composites. The electrostatic interactions between GO@LDHs hybrids facilitated energy dissipation during stretching, thereby improving the mechanical performance of the rubber composites. More importantly, the N2 gas permeability and fracture toughness of GO@LDHs/SBR composites decreased by 52.2% and increased by 845%, respectively, compared to those of a pure SBR matrix. The construction of GO@LDHs hybrids offers new insights for designing rubber composites with a high gas barrier and mechanical properties.

Crystallization Retardation and Synergistic Trap Passivation in Perovskite Solar Cells Incorporated with Magnesium-Decorated Graphene Quantum Dots

One of the encouraging strategies for enhancing the efficiency of perovskite solar cells (PSCs) is to reduce defects, trap states of pinholes, and charge recombination rate in the light absorber layer of perovskite, which can be addressed by increasing the perovskite grain size. The utilization of Mg-decorated graphene quantum dots (MGQD) or graphene quantum dots (GQDs) into a perovskite precursor solution for further crystal modification is introduced in this study. Studies on the crystalline structure and morphology of MGQD generated from GQDs demonstrate that MGQD has a greater crystal size than GQD. Therefore, higher light absorption in the whole UV-vis spectrum and a larger grain size for the perovskite/MGQD layer compared to the perovskite/GQD sample are achieved. Moreover, more photoluminescence peak quenching of perovskite/MGQD and extended carrier recombination lifetime (from 3 to 40 ns) verify the surface and grain boundary trap passivation compared to pristine perovskite. Consequently, PSCs in an n-i-p configuration containing perovskite/MGQD show a higher performance of 10.2% in comparison to the pristine perovskite at 7.2%, attributed to the enhanced JSC from 13.2 to 19.1 mA cm-2. Thus, incorporating MGQDs into the perovskite layer is a hopeful approach for obtaining a superior perovskite film with impressive charge extraction and decreased nonradiative charge recombination.

High-kerbium oxide film prepared by sol-gel method for low-voltage thin-film transistor

In this work, high-dielectric-constant (high-k) erbium oxide（Er₂O₃）film is fabricated using the spin coating method, and annealed at a series of temperatures (from 400 °C to 700 °C). The effect of annealing temperature on the microstructural and electrical properties of Er₂O₃nanofilm is investigated. To demonstrate the applicability of the Er₂O₃film, the indium oxide (In₂O₃) thin film transistor (TFT)-based amorphous Er₂O₃dielectric film is fabricated at different temperatures. The TFT-based EO-600 shows a low-operating voltage and good electrical properties. The inverter demonstrates that the Er₂O₃nanofilm synthesized by the sol-gel method could be a promising candidate as the dielectric layer in a low-voltage electronic device.

Ultrastrong Carbon Nanotubes/Graphene Papers via Multiple π-π Cross-Linking

Considering the extraordinary properties of graphene nanosheets, graphene-based materials from a molecular level to a macroscopic level as paper-like graphene films have recently grown for promising applications in many fields. However, there is still a major challenge in the design of the interface between adjacent graphene nanosheets so as to achieve high strength, high toughness, and high conductivity. Herein, we construct the high-performance graphene-based papers by using graphene as the matrix, carbon nanotubes (CNTs) as the reinforcement, and a long-chain molecule (1-pyrenylbutyric acid-linear diamine-1-pyrenylbutyric acid, PBA-diamine-PBA) as the bridging agent. The multiple π-π interactions between the fused rings, graphene nanosheets, and CNTs are generated among the aromatic rings of PBA, rGO, and CNTs, which significantly improve the mechanical properties and electrical properties of the cross-linked composite papers (abbreviated to CLP-X, where X is the carbon chain length). Furthermore, the linear diamines with different lengths of carbon chain affect the properties of papers after cross-linking. Especially, the as-obtained graphene-based paper (CLP-6) shows a high tensile strength (625.2 MPa), high toughness (28.5 MJ/m³), and high electrical conductivity (233.4 S/cm) as well as high solvent stability, which maintains the premium stability in different solvents. The improvement of strengthening and toughening mainly comes from the effective stress transfer and the reduction of slipping distance between rGO and CNTs during the stretching, with the help of multiple π-π cross-linking by in situ Raman analysis and simulation calculations. In addition, the high electrical conductivity leads to an excellent electromagnetic interference shielding capability (44,502 dB·cm²/g). The distinguished electric heating performance with rapid response to temperature changes is also recognized. Therefore, the proposed interface design is demonstrated as an effective way for developing a graphene-based paper with superior properties.

Coordination-Driven Hierarchical Assembly of Hybrid Nanostructures Based on 2D Materials

2D materials have received tremendous scientific and engineering interests due to their remarkable properties and broad-ranging applications such as energy storage and conversion, catalysis, biomedicine, electronics, and so forth. To further enhance their performance and endow them with new functions, 2D materials are proposed to hybridize with other nanostructured building blocks, resulting in hybrid nanostructures with various morphologies and structures. The properties and functions of these hybrid nanostructures depend strongly on the interfacial interactions between 2D materials and other building blocks. Covalent and coordination bonds are two strong interactions that hold high potential in constructing these robust hybrid nanostructures based on 2D materials. However, most 2D materials are chemically inert, posing problems for the covalent assembly with other building blocks. There are usually coordination atoms in most of 2D materials and their derivatives, thus coordination interaction as a strong interfacial interaction has attracted much attention. In this review, recent progress on the coordination-driven hierarchical assembly based on 2D materials is summarized, focusing on the synthesis approaches, various architectures, and structure-property relationship. Furthermore, insights into the present challenges and future research directions are also presented.

Interlocked Graphene Oxide Provides Narrow Channels for Effective Water Desalination through Forward Osmosis

Unique two-dimensional water channels formed by stacked graphene oxide (GO) sheets that are "nonleachable" and nonswellable can show great potential for water remediation. The interlayer spacing controls the solute or ion sieving and plays a crucial role in water transport in GO-based membranes. Herein, the sub-nano-channels adjacent to the sheets are altered by either ionic or covalent cross-linking using magnesium hydroxide (Mg(OH)₂) and graphene oxide quantum dots (GQDs) (named GOM and G-GQD), respectively. In aqueous solution, these cross-linkers prevent the GO sheets from swelling and precisely control the interlayer spacing required for water permeation. In addition, these narrowed GO sheets facilitate significant improvement in salt rejection of a divalent ion by forward osmosis and selective dye rejection and are resistive toward biofouling and bacterial growth. The cross-linked GO membranes are robust enough to withstand strong cross-flow velocity and aided in unimpeded water transport through the nanochannels. Among the membranes, the G-GQD membranes (G-GQD) show better antifouling characteristics, dye separation performance over 95-97% for various dyes, divalent ion rejection by 97%, and no cytotoxicity against HaCaT cells as compared with other GO membranes. Our findings on interlocking the domains of nanoslits of the GO structure by small ecofriendly molecules portray these materials as potential candidates for water separation applications.

Enhanced Dielectric and Mechanical Properties of Ternary Composites via Plasticizer-Induced Dense Interfaces

High overall performance, including high dielectric constant, low loss, high breakdown strength, fine flexibility, and strong tensile properties, is difficult to achieve simultaneously in polymer nanocomposites. In our prior work, we modified the surfaces of alpha-SiC nanoparticles and chemically cross-linked the polymeric matrix to simultaneously promote the dielectric and mechanical properties of composites. In this work, a novel strategy of high-temperature plastification towards a polymeric matrix has been proposed to fabricate ternary nanocomposites with balanced dielectric and mechanical characteristics by the solution cast method in order to reduce costs and simplify steps during large-scale preparation. Poly(vinylidene fluoride-chlorotrifluoroethylene) with inner double bonds as matrix, unfunctionalized alpha-SiC nanoparticles (NPs) as filler, and dibutyl phthalate (DBP) as plasticizer were employed. By introducing DBP and high-temperature treatment, the dispersion of NPs and the degree of compactness of the interface regions were both improved due to the reduced cohesion of the fluoropolymer, resulting in an increase in the dielectric constant (by 30%) and breakdown strength (by 57%) as well as the lowering of loss (by 30%) and conductivity (by 16%) in nanocomposites. Moreover, high-temperature plastification contributed to the promotion of flexible and tensile properties. This work might open the door to large-scale fabrication of nanocomposite dielectrics with high overall properties through the cooperation of the plasticizer and high temperature.

Bio-inspired graphene-derived membranes with strain-controlled interlayer spacing

The precisely controlled size of nanoscale fluidic channels plays a critical role in resolving the permeation-selectivity trade-off in separation and filtration applications, where highly efficient gas separation and water desalination are targeted. Inspired by natural nacre where the spacing between mineral platelets changes upon applying tension as fractured mineral bridges climb over each other, bio-inspired graphene-derived membranes with sheets cross-linked by aligned covalent bonds are proposed in design, to ensure a controlled interlayer spacing ranging from 4 Å to 14 Å while preserving structural and mechanical stabilities by prohibiting swelling. The underlying mechanism is that the tension applied to the membrane is transferred between finite-sized graphene sheets through interlayer shear of the cross-links, which expands the interlayer gallery. First-principles calculations and continuum mechanics based model analysis are combined to explore the feasibility of this protocol, by considering the microstructures of graphene-derived membranes that have recently been demonstrated to offer exceptional performance in selective mass transport. The results show that the critical size range in molecular sieving is covered by this synergetic interface- and strain-engineering approach.

Optimizing Interfacial Cross-Linking in Graphene-Derived Materials, Which Balances Intralayer and Interlayer Load Transfer

Graphene-derived layer-by-layer (LbL) assemblies in the form of films or fibers have recently attracted particular interests owing to their low cost, facile fabrication, and outstanding mechanical properties, which could be further tuned by surface functionalization that cross-links graphene sheets in the assembly. However, this interfacial engineering approach has not yet been finely utilized considering the dual roles of cross-links in modifying the intrinsic properties of graphene sheets and their interlayer interactions. In this work, combining first-principles calculations and continuum-mechanics-based model analysis, we find that the functionalization weakens the intrinsic mechanical resistance of graphene, whereas it enhances interlayer load transfer through interlayer cross-linking. There are optimum cross-linking densities or concentrations of the surface functional groups that maximize the overall tensile stiffness, tensile strength and strain to failure of graphene-derived LbL assemblies, arising from the competition between intralayer and interlayer load-bearing mechanisms, as defined by the type of functionalization and size of graphene sheets. Our work quantifies the ultimate mechanical performance of graphene-derived LbL assemblies, on the condition that their microstructures and functionalization could be adequately controlled in the fabrication process.