A facile synthesis of graphene nanoribbon-quantum dot hybrids and their application for composite electrolyte membrane in direct methanol fuel cells

Advances in ionogels for proton-exchange membranes

To ensure the long-term performance of proton-exchange membrane fuel cells (PEMFCs), proton-exchange membranes (PEMs) have stringent requirements at high temperatures and humidities, as they may lose proton carriers. This issue poses a serious challenge to maintaining their proton conductivity and mechanical performance throughout their service life. Ionogels are ionic liquids (ILs) hybridized with another component (such as organic, inorganic, or organic-inorganic hybrid skeleton). This design is used to maintain the desirable properties of ILs (negligible vapor pressure, thermal stability, and non-flammability), as well as a high ionic conductivity and wide electrochemical stability window with low outflow. Ionogels have opened new routes for designing solid-electrolyte membranes, especially PEMs. This paper reviews recent research progress of ionogels in proton-exchange membranes, focusing on their electrochemical properties and proton transport mechanisms.

Graphene-derived antibacterial nanocomposites for water disinfection: Current and future perspectives

Antimicrobial nanomaterials provide numerous opportunities for the synthesis of next-generation sustainable water disinfectants. Using the keywords graphene and water disinfection and graphene antibacterial activity, a detailed search of the Scopus database yielded 198 and 1433 studies on using graphene for water disinfection applications and graphene antibacterial activity in the last ten years, respectively. Graphene family nanomaterials (GFNs) have emerged as effective antibacterial agents. The current innovations in graphene-, graphene oxide (GO)-, reduced graphene oxide (rGO)-, and graphene quantum dot (GQD)-based nanocomposites for water disinfection, including their functionalization with semiconductor photocatalysts and metal and metal oxide nanoparticles, have been thoroughly discussed in this review. Furthermore, their novel application in the fabrication of 3D porous hydrogels, thin films, and membranes has been emphasized. The physicochemical and structural properties affecting their antibacterial efficiency, such as sheet size, layer number, shape, edges, smoothness/roughness, arrangement mode, aggregation, dispersibility, and surface functionalization have been highlighted. The various mechanisms involved in GFN antibacterial action have been reviewed, including the mechanisms of membrane stress, ROS-dependent and -independent oxidative stress, cell wrapping/trapping, charge transfer, and interaction with cellular components. For safe applications, the potential biosafety and biocompatibility of GFNs in aquatic environments are emphasized. Finally, the current limitations and future perspectives are discussed. This review may provide ideas for developing efficient and practical solutions using graphene-, GO-, rGO-, and GQD-based nanocomposites in water disinfection by rationally employing their unique properties.

Graphene Synthesis: Method, Exfoliation Mechanism and Large-Scale Production

Graphene is a unique attractive material owing to its characteristic structure and excellent properties. To improve the preparation efficiency of graphene, reduce defects and costs, and meet the growing market demand, it is crucial to explore the improved and innovative production methods and process for graphene. This review summarizes recent advanced graphene synthesis methods including “bottom-up” and “top-down” processes, and their influence on the structure, cost, and preparation efficiency of graphene, as well as its peeling mechanism. The viability and practicality of preparing graphene using polymers peeling flake graphite or graphite filling polymer was discussed. Based on the comparative study, it is potential to mass produce graphene with large size and high quality using the viscoelasticity of polymers and their affinity to the graphite surface.

Acidic Groups Functionalized Carbon Dots Capping Channels of a Proton Conductive Metal-Organic Framework by Coordination Bonds to Improve the Water-Retention Capacity and Boost Proton Conduction

Crystalline porous materials, such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), have been demonstrated to be versatile material platforms for the development of solid proton conductors. However, most crystalline porous proton conductors suffer from decreasing proton conductivity with increasing temperature due to releasing water molecules, and this disadvantage severely restricts their practical application in electrochemical devices. In this work, for the first time, hydrophilic carbon dots (CDs) were utilized to hybridize with high proton conductivity MOF-802, which is a model of MOF proton conductors, aiming to improve its water-retention capacity and thus enhance proton conduction. The resultant CDs@MOF-802 exhibits impregnable proton conduction with increasing temperature, and the proton conductivity reaches 10^-1 S cm^-1, much superior to that of MOF-802, making CDs@MOF-802 one of the most efficient MOF proton conductors reported so far. This study provides a new strategy to improve the water-retention capacity of porous proton conductors and further realize excellent proton conduction.

Synthesis of graphene quantum dots and their applications in drug delivery

This review focuses on the recent advances in the synthesis of graphene quantum dots (GQDs) and their applications in drug delivery. To give a brief understanding about the preparation of GQDs, recent advances in methods of GQDs synthesis are first presented. Afterwards, various drug delivery-release modes of GQDs-based drug delivery systems such as EPR-pH delivery-release mode, ligand-pH delivery-release mode, EPR-Photothermal delivery-Release mode, and Core/Shell-photothermal/magnetic thermal delivery-release mode are reviewed. Finally, the current challenges and the prospective application of GQDs in drug delivery are discussed.

Synthesis and characterization of a novel sulfonated poly (aryl ether ketone sulfone) semi-crosslinked membrane with high proton selectivity through click reaction for direct methanol fuel cells

A novel sulfonated polyvinyl alcohol containing alkynyl groups (SPVA-C≡C) and a new sulfonated poly (aryl ether ketone sulfone) (SPAEKS) are synthesized. Semi-crosslinked membrane (semi-crosslink-SPAEKS-x) was prepared by click reaction of mercapto-alkynes between 1, 5-pentanedithiol and SPVA-C≡C. The chemical structures of SPAEKS, SPVA-C≡C and semi-crosslink-SPAEKS-x are confirmed by 1H-NMR and FTIR spectra. The semi-crosslink-SPAEKS-x membranes show good mechanical properties, excellent dimensional stability and oxidative stability. The proton conductivity of SPAEKS and semi-crosslink-SPAEKS-x membranes is in the range of 25.6–52.5 mS/cm. The methanol permeability of semi-crosslink-SPAEKS-x membranes is in the range of 1.4–1.7 × 10−7 cm−2 s−1, which is much lower than that of Nafion 117 membrane (18.3 × 10−7 cm−2 s−1). Especially, the proton selectivity of semi-crosslink-SPAEKS-15 membrane (24.3 × 104 S s cm−3) is above seven times higher than that of Nafion 117 membrane (3.4 × 104 S s cm−3).

Impact of graphene oxide on epoxy resin characteristics

The incorporation of a small part of graphene oxide (GO) offers an appropriate fire retardant for thermally conductive epoxy (EP) resin composites, which is verified by the upper limiting oxygen index of 24.5% and other standard flame-retardant tests. The smoke production rate, total smoke production (TSP), and the smoke density of EP composites were reduced with additional GO. The increased efficiency of fire resistance and smoke suppression is primarily due to the formation of physical barrier and compactness of the developed GO char layers, serving as an effective barrier layer that increases the fire resistance, and the thermal steadiness of the char layers derives from the effect of GO inclusion. The barrier impact of GO and the limited mobility of polymer chains are crucial factors in increasing thermal stability and reduction of generating dangerous carbon monoxide during burns. The thermal stability increased and the peak heat release rate, total heat release, TSP, and the largest smoke density value reduced to 52.5%, 43.6%, 33.9%, and 44.2%, correspondingly, compared with pure EP. The tensile strength and elongation at break of EP composites were enhanced by 23% and 8.4% compared with pure EP, respectively.