Synthesis of Multifunctional Electrically Tunable Fluorine-Doped Reduced Graphene Oxide at Low Temperatures

Doping with heteroatoms is a well-established method to tune the electronic properties and surface chemistry of graphene. Herein, we demonstrate the synthesis of a fluorine-doped reduced graphene oxide (FrGO) at low temperatures that offers multiple opportunities in applied fields. The as-synthesized FrGO product shows a better electrical conductivity of 750 S m^–1 than that of undoped rGO with an electrical conductivity of 195 S m^–1. To demonstrate the multifunctional applications of the as-synthesized FrGO, it was examined for electromagnetic interference shielding and electrochemical sensing of histamine as an important food biomarker. A laminate of FrGO delivered an EMI shielding effectiveness value of 22 dB in Ku band as compared with 11.2 dB for an rGO laminate with similar thickness. On the other hand, an FrGO modified sensor offered an excellent sensitivity (∼7 nM), wide detection range, and good selectivity in the presence of similar biomarkers. This performance originates from the better catalytic ability of FrGO as compared with rGO, where fluorine atoms play the role of catalytic active sites owing to their high electronegativity. The fluorination reaction also helps to improve the reduction degree of the chemically synthesized graphene, consequently enhancing the electrical conductivity, which is a prime requirement for increasing the electromagnetic and electrochemical properties of graphene

Biomass-Derived Thermally Annealed Interconnected Sulfur-Doped Graphene as a Shield against Electromagnetic Interference

Electrically conductive thin carbon materials have attracted remarkable interest as a shielding material to mitigate the electromagnetic interference (EMI) produced by many telecommunication devices. Herein, we developed a sulfur-doped reduced graphene oxide (SrGO) with high electrical conductivity through using a novel biomass, mushroom-based sulfur compound (lenthionine) via a two-step thermal treatment. The resultant SrGO product exhibited excellent electrical conductivity of 311 S cm^–1, which is 52% larger than 205 S cm^–1 for undoped rGO. SrGO also exhibited an excellent EMI shielding effectiveness of 38.6 dB, which is 61% larger than 24.4 dB measured for undoped rGO. Analytical examinations indicate that a sulfur content of 1.95 atom % acts as n-type dopant, increasing electrical conductivity and, therefore, EMI shielding of doped graphene

Sulfonated Copper Phthalocyanine/Sulfonated Polysulfone Composite Membrane for Ionic Polymer Actuators with High Power Density and Fast Response Time

Ionic polymer composite membranes based on sulfonated poly­(arylene ether sulfone) (SPAES) and copper­(II) phthalocyanine tetrasulfonic acid (CuPCSA) are assembled into bending ionic polymer actuators. CuPCSA is an organic filler with very high sulfonation degree (IEC = 4.5 mmol H⁺/g) that can be homogeneously dispersed on the molecular scale into the SPAES membrane, probably due to its good dispersibility in SPAES-containing solutions. SPAES/CuPCSA actuators exhibit larger ion conductivity (102 mS cm^–1), tensile modulus (208 MPa), strength (101 MPa), and strain (1.21%), exceptionally faster response to electrical stimuli, and larger mechanical power density (3028 W m^–3) than ever reported for ion-conducting polymer actuators. This outstanding actuation performance of SPAES/CuPCSA composite membrane actuators makes them attractive for next-generation transducers with high power density, which are currently developed, e.g., for underwater propulsion and endoscopic surgery

RTA-Treated Carbon Fiber/Copper Core/Shell Hybrid for Thermally Conductive Composites

In this paper, we demonstrate a facile route to produce epoxy/carbon fiber composites providing continuous heat conduction pathway of Cu with a high degree of crystal perfection via electroplating, followed by rapid thermal annealing (RTA) treatment and compression molding. Copper shells on carbon fibers were coated through electroplating method and post-treated via RTA technique to reduce the degree of imperfection in the Cu crystal. The epoxy/Cu-plated carbon fiber composites with Cu shell of 12.0 vol % prepared via simple compression molding, revealed 18 times larger thermal conductivity (47.2 W m^–1 K^–1) in parallel direction and 6 times larger thermal conductivity (3.9 W m^–1 K^–1) in perpendicular direction than epoxy/carbon fiber composite. Our novel composites with RTA-treated carbon fiber/Cu core/shell hybrid showed heat conduction behavior of an excellent polymeric composite thermal conductor with continuous heat conduction pathway, comparable to theoretical values obtained from Hatta and Taya model

Multifunctional Mesoporous Ionic Gels and Scaffolds Derived from Polyhedral Oligomeric Silsesquioxanes

A new methodology for fabrication of inorganic–organic hybrid ionogels and scaffolds is developed through facile cross-linking and solution extraction of a newly developed ionic polyhedral oligomeric silsesquioxane with inorganic core. Through design of various cationic tertiary amines, as well as cross-linkable functional groups on each arm of the inorganic core, high-performance ionogels are fabricated with excellent electrochemical stability and unique ion conduction behavior, giving superior lithium ion battery performance. Moreover, through solvent extraction of the liquid components, hybrid scaffolds with well-defined, interconnected mesopores are utilized as heterogeneous catalysts for the CO₂-catalyzed cycloaddition of epoxides. Excellent catalytic performance, as well as highly efficient recyclability are observed when compared to other previous literature materials

Copper Shell Networks in Polymer Composites for Efficient Thermal Conduction

Thermal management of polymeric composites is a crucial issue to determine the performance and reliability of the devices. Here, we report a straightforward route to prepare polymeric composites with Cu thin film networks. Taking advantage of the fluidity of polymer melt and the ductile properties of Cu films, the polymeric composites were created by the Cu metallization of PS bead and the hot press molding of Cu-plated PS beads. The unique three-dimensional Cu shell-networks in the PS matrix demonstrated isotropic and ideal conductive performance at even extremely low Cu contents. In contrast to the conventional simple melt-mixed Cu beads/PS composites at the same concentration of 23.0 vol %, the PS composites with Cu shell networks indeed revealed 60 times larger thermal conductivity and 8 orders of magnitude larger electrical conductivity. Our strategy offers a straightforward and high-throughput route for the isotropic thermal and electrical conductive composites

High Through-Plane Thermal Conduction of Graphene Nanoflake Filled Polymer Composites Melt-Processed in an L‑Shape Kinked Tube

Design of materials to be heat-conductive in a preferred direction is a crucial issue for efficient heat dissipation in systems using stacked devices. Here, we demonstrate a facile route to fabricate polymer composites with directional thermal conduction. Our method is based on control of the orientation of fillers with anisotropic heat conduction. Melt-compression of solution-cast poly­(vinylidene fluoride) (PVDF) and graphene nanoflake (GNF) films in an L-shape kinked tube yielded a lightweight polymer composite with the surface normal of GNF preferentially aligned perpendicular to the melt-flow direction, giving rise to a directional thermal conductivity of approximately 10 W/mK at 25 vol % with an anisotropic thermal conduction ratio greater than six. The high directional thermal conduction was attributed to the two-dimensional planar shape of GNFs readily adaptable to the molten polymer flow, compared with highly entangled carbon nanotubes and three-dimensional graphite fillers. Furthermore, our composite with its density of approximately 1.5 g/cm³ was mechanically stable, and its thermal performance was successfully preserved above 100 °C even after multiple heating and cooling cycles. The results indicate that the methodology using an L-shape kinked tube is a new way to achieve polymer composites with highly anisotropic thermal conduction