Specific Shielding Effectiveness Research Articles

Effect of printing parameters and triply periodic minimal surfaces on electromagnetic shielding efficiency of polyvinylidene fluoride graphene nanocomposites

Electromagnetic interference (EMI) shielding is vital in safeguarding electronic devices from the harmful effects of external electromagnetic signals, a critical factor in ensuring the reliability and functionality of these systems. EMI, originating from a myriad of sources, can range from causing temporary disruptions to catastrophic system failures and potentially harmful consequences. This study delves into the EMI shielding capabilities of 3D printed Polyvinylidene Fluoride (PVDF)-graphene Triply Periodic Minimal Surface (TPMS) structures, fabricated using Material Extrusion (ME) process. The focus on TPMS structures stems from their unique geometrical configurations, offering promising potentials in enhancing EMI shielding effectiveness. Four distinct TPMS topologies—gyroid, Neovius, diamond, and I-WP were explored, with each demonstrating varying degrees of shielding effectiveness. 3D printed solid samples showed an average specific shielding effectiveness (SSE) of 13dB cm3/g, and Neovius triply periodic minimal surface (TPMS) structure exhibited an average SSE of 94dB cm3/g. Absolute shielding effectiveness (SSE/t) for solid samples and Neovius TPMS structure is around 66dB cm2/g and 62.5dB cm2/g respectively. Among the tested samples, those with a Neovius topology emerged as particularly promising, exhibiting high EMI shielding effectiveness suitable for commercial applications. Furthermore, the study investigates the impact of several design and printing parameters, including relative density/infill percentage, print orientation, and the size of unit cells, on total shielding effectiveness (SET). Results revealed SET variations ranging between 25dB and 75dB, suggesting that tuning the SET of these samples is feasible by adjusting these parameters. The study's findings, highlighting a strong correlation between SET and frequency influenced by unique geometrical characteristics and frequency-dependent interactions, underscore the potential of architected PVDF-graphene TPMS structures in EMI shielding applications. This opens new avenues for research and development in this field, paving the way for more advanced and effective EMI shielding solutions.

Multifunctional highly conductive cellulose nanopaper with ordered PEDOT:PSS alignment enabled by external surface area-promoted phase separation

Integrating cellulose, the most abundant biopolymer on Earth, with PEDOT:PSS, the most commercially available conducting polymer, can create multifunctional conductive nanopapers for sustainable electronics. However, conventional PEDOT:PSS/cellulose composites often exhibit limited conductivity, primarily due to the random distribution of PEDOT and the aggregation of PSS within the cellulose matrix. Herein, we introduce a confined phase separation approach that leverages the inherent physical characteristics of the cellulose substrate to enhance the performance of these composites. By systematically investigating the influence of the external surface area of nanocellulose on PEDOT:PSS coverage and composition evolution, we demonstrate that a higher external surface area ensures uniform PEDOT:PSS coating on nanocellulose networks and facilitates effective PSS removal during secondary doping. This process enhances phase separation and promotes ordered alignment of PEDOT chains along nanocellulose, resulting in an electrical conductivity of up to 252 S cm−1. Such highly conductive nanopapers exhibit exceptional performances in supercapacitors and electromagnetic shielding, achieving an ultrahigh specific electromagnetic shielding effectiveness of 33,122 dB cm2 g⁻1 at only 6 μm thickness. Our study highlights the critical role of cellulose substrate selection at the nanoscale and elucidates the interactions within conducting polymers, offering a promising pathway for developing high-performance, sustainable electronics.

Multi‐Functional Ti3C2Tx‐Silver@Silk Nanofiber Composites With Multi‐Dimensional Heterogeneous Structure for Versatile Wearable Electronics

AbstractSilk nanofibers (SNFs) from abundant sources are low‐cost and environmentally friendly. Combined with other functional materials, SNFs can help create bioelectronics with excellent biocompatibility without environmental concerns. However, it is still challenging to construct an SNF‐based composite with high conductivity, flexibility, and mechanical strength for all SNF‐based electronics. Herein, this work reports the design and fabrication of Ti3C2Tx‐silver@silk nanofibers (Ti3C2Tx‐Ag@SNF) composites with multi‐dimensional heterogeneous conductive networks using combined in situ growth and vacuum filtration methods. The ultrahigh electrical conductivity of Ti3C2Tx‐Ag@SNF composites (142959 S m−1) provides the kirigami‐patterned soft heaters with a rapid heating rate of 87 °C s−1. The multi‐dimensional heterogeneous network further allows the creation of electromagnetic interference shielding devices with an exceptionally high specific shielding effectiveness of 10,088 dB cm−1. Besides working as a triboelectric layer to harvest the mechanical energy and recognize the hand gesture, the Ti3C2Tx‐Ag@SNF composites can also be combined with an ionic layer to result in a capacitive pressure sensor with a high sensitivity of 410 kPa−1 in a large range due to electronic‐double layer effect. The applications of the Ti3C2Tx‐Ag@SNF composites in recognizing human gestures and human‐machine interfaces to wirelessly control a trolley demonstrate the future development of all SNF‐based electronics.

Lightweight Fe3O4/Fe/C/rGO multifunctional aerogel for efficient microwave absorption, electromagnetic interference shielding, hydrophobicity and thermal insulation

Effective integration of multiple functions into microwave absorbing materials is a future development direction, but still remains a significant challenge. This work fabricated a lightweight, multifunctional aerogel through electrostatic self-assembly, freeze-drying and in-situ pyrolysis process, achieving an in-situ composite of magnetic/dielectric components. The regulated pyrolysis temperature achieves a good balance between abundant nanopores and heterogeneous interfaces, enriched defects, and conductivity. This balance induced a synergy of dielectric loss, magnetic loss, and conduction loss at low frequencies, improving the impedance matching. The aerogel obtains a minimum reflection loss (RLmin) of −65.17 dB in the low-frequency range and a maximum effective absorption bandwidth (EABmax) of 5.76 GHz. The radar cross section (RCS) simulation confirmed its good stealth performance. In addition, an increase in aerogel loading enhanced its electrical conductivity, resulting in a higher electromagnetic interference (EMI) shielding effectiveness (SE) of 81.83 dB, the specific shielding effectiveness (SSE) up to 359.28 dB·cm3/g and the absolute shielding effectiveness (SSEt) up to 1596.82 dB·cm2/g. Beyond microwave absorption and shielding, this aerogel also exhibited good hydrophobicity and thermal insulation. This study provides a new perspective for the development of materials with microwave absorption properties in low-frequency bands and multifunctional properties for broader applications in military, communication, aerospace, and other fields.

3D-Printed Interfacially Jammed Emulsion Aerogels.

3D printing ultralightweight porous structures using direct ink writing (DIW) while maintaining their mechanical robustness is highly challenging. This difficulty is amplified when low ink concentrations are used to create complex geometries. Herein, this shortfall was addressed by interfacially jammed emulsion gels. The gel emerged from the electrostatic interaction among synergized nanomaterials (graphene oxide (GO) and cellulose nanocrystals (CNCs)) in the aqueous phase and a ligand in the oil phase. This interaction led to the jamming of the nanoparticles and the creation of stable emulsion gels. The formed interfacial assemblies were further treated by post-jamming ionic cross-linking with NaHCO3, which dictated the emulsion gels' rheological characteristics, enhancing the ink's viscoelastic properties for high-resolution 3D printing. The customizable emulsion system allows control over porosity from the macro- to the micro-scale and generates complex geometries with desired compositions. By manipulating post-annealing processes and varying concentrations, it is possible to achieve aerogels that feature a remarkably low density (∼2.63 mg/cm3) and adjustable mechanical robustness (elastic modulus of 0.45 MPa). Additionally, this method allows for producing aerogels with flexible or stiff characteristics as required, alongside the capability to tailor specific electromagnetic shielding effectiveness (ranging from 6791 to 19615 dB cm2/g), showcasing the technique's versatility and engineerability.

Novel fire-resistant SiBCN fiber paper with efficient electromagnetic interference shielding and Joule-heating performance

Since electromagnetic interference (EMI), icing, and fire incidents greatly threaten aviation safety, multifunctional EMI shielding materials are urgently required in the aviation industry. However, developing highly efficient EMI shielding materials that combine fire resistance and thermal management remains a significant challenge. Here, a novel fire-resistant SiBCN ceramic fiber paper with excellent EMI shielding and Joule heating performance was fabricated via electrospinning followed by cross-linking, pyrolysis, and annealing. Compared with the SiBCN fiber paper prepared at 800 °C with poor EMI shielding performance, the total shielding effectiveness (SET) of the SiBCN fiber paper annealed at 1400 °C significantly increased to 21 dB, with specific shielding effectiveness (SSE/t) as high as 3317 dB•cm2•g−1, due to the precipitation of “island-like” conductive turbostratic C, facilitating the synergistic effects of conduction loss, dipole polarization, and interfacial polarization, resulting in high efficiently attenuation of the electromagnetic waves (EMW). Furthermore, the fiber paper demonstrated excellent fire-resistant and Joule-heating performance, with a rapid electrothermal conversion response and a high saturation temperature of 300 °C at 12 V. Therefore, this work proposes a novel strategy for designing multifunctional ceramic fiber paper with integrated EMI shielding, fire resistance, and Joule heating performance for aircraft safety.

Design of polyimide/carbon nanotube@Ag@polyimide/graphene composite aerogel for infrared stealth and electromagnetic interference protection

CHATGPT artificial intelligence is taking the world by storm, and countless electronic devices will generate massive amounts of electromagnetic interference (EMI). Hence, there is a pressing demand for materials exhibiting high thermal conductivity and superior EMI shielding effectiveness (SE). Thus, we construct a polyimide/carbon nanotube@Ag@polyimide/graphene (PCAPG) composite aerogel with porous, layered, and homogeneous structures in one, which provides a new idea for the multi-interface polarization interaction and special structure of anti-EMI materials. PCAPG has high thermal conductivity of ∼ 0.259 W (mK)-1 at 25 °C, excellent EMI SE of ∼ 90.28 dB and specific shielding effectiveness (SSE) of ∼ 940.42 dB cm3 g−1. The synergistic EMI attenuation mechanism of the PCAPG composite structure is analyzed using an aerogel unit. This composite aerogel provides a viable solution for infrared stealth, promoting heat dissipation from electronic components and reducing electromagnetic interference.

Facile preparation of conductive silicone rubber composite foams with tunable cell morphologies and absorption-dominant characteristics

Flexible silicone rubber (SR) foams with tunable cellular morphologies were fabricated via supercritical CO2 foaming. Conductive carbon black (CB) modified at a low cost and with high complex viscosity was preferentially selected. The effects of the pore size and void fraction on the electrical conductivity and dielectric permittivity of the SR/CB composite foams were carefully investigated. The pore size of the foams affected the specific shielding effectiveness (SSE) and absorption coefficient (A), whereas the variation in the void fraction did not generate evident changes. In comparison with its solid counterpart, a foam with a pore diameter of 59.9 μm showed a 50 % decrease in density, 31.6 % increase in absorptivity, and 95.7 % increase in SSE, demonstrating a considerable electromagnetic interference shielding effectiveness (EMI SE). Decreases in the pore size and void fraction of the foams improved compression modulus and strength. In addition, sample preparation process was simplified, making industrial production easier.

High-Performance Multifunctional Carbon Fibrous Sponges Derived from Pitch.

3D carbon-based porous sponges are recognized for significant potential in oil absorption and electromagnetic interference (EMI). However, their widespread application is hindered by a common compromise between high performance and affordability of mass production. Herein, a novel approach is introduced that involves laser-assisted micro-zone heating melt-blown spinning (LMHMS) to address this challenge by creating pitch-based submicron carbon fibers (PSCFs) sponge with 3D interconnected structures. These structures bestow the resulting sponge exceptional characteristics including low density (≈20mgcm-3), high porosity (≈99%), remarkable compressibility (80% maximum strain), and superior conductivity (≈628 Sm-1). The resultant PSCF sponges realize an oil/organic solvent sorption capacity over 56g/g and possess remarkable regenerated ability. In addition to their effectiveness in cleaning up oil/organic solvent spills, they also demonstrated strong electromagnetic shielding capabilities, with a total shielding effectiveness (SE) exceeding 60dB across the X-band GHz range. In virtue of extreme lightweight of ≈20mgcm-3, the specific SE of the PSCF sponge reaches as high as ≈1466dB cm3g-1, surpassing the performance of numerous carbon-based porous structures. Thus, the unique blend of properties renders these sponges promising for transforming strategies in addressing oil/organic solvent contaminations and providing effective protection against EMI.

Lightweight carbon foam composites embedded with RGO/SrFe12O19 hybrid: Fabrication, structural and electromagnetic shielding performance in 8.2 to 12.4 GHz

Today's growth of wireless technology has increased the demand for composite materials with absorption-based shielding capabilities and the composites of dielectric and magnetic materials are suitable for producing high shielding effectiveness (SE). The present study establishes a facile way to synthesize carbon foam embedded with strontium ferrite (SrFe12O19) nanoparticles decorated within/ on reduced graphene oxide (RGO) sheets. In this work, polyurathene templete slab is dipped in the homogenous slurry prepared from RGO/SrFe12O19 (RS) hybrid and phenolic resin followed by carbonization to produce the CF/RGO/SrFe12O19 (CRS) composite foam. The synthesized CRS3 nanocomposite foam exhibits maximum shielding effectiveness due to an absorption (SEA) value of 26.6 dB i.e., ∼99.7% attenuation, and absolute specific shielding effectiveness (SSEt) value of 250.70 dBcm2g–1. The high SEA value of synthesized composite carbon foam is obtained because of the synergistic effect of porous morphology, dielectric losses and magnetic losses.

Solvent-doped PEDOT:PSS: Structural transformations towards enhanced electrical conductivity and transferable electromagnetic shields

The enhanced electrical conductivity of solvent-doped poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) is attributed to the screening effect between PSS and PEDOT chains. Yet, the precise manner in which this effect influences the crystalline structure and conformation of PEDOT:PSS remains unclear. In this study, we utilize Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and Grazing-incidence wide-angle X-ray scattering (GIWAXS) to examine the conformational changes and two-dimensional (2D) crystalline structure of PEDOT:PSS when doped with a variety of solvents, including dimethyl sulfoxide (DMSO), ethylene glycol (EG), dimethylformamide (DMF), methanol (MeOH), ethanol (EtOH), tetrahydrofuran (THF), and acetone. Our observations unveil that solvent doping improves the electrical conductivity of PEDOT:PSS by modifying its crystalline structure. This alteration leads to reduced inter-lamellar (d200) and π-π stacking (d010) distances, facilitating the formation of densely packed and well-ordered PEDOT crystallites in both face-on and edge-on orientations. Moreover, this doping process enhances the transferability and mechanical properties of drop-casted films, resulting in a flexible and transferable electromagnetic interference (EMI) shield with exceptional total shielding effectiveness (SET) of 35.70 dB and specific shielding effectiveness (SSE/t) of 7105.34 dB cm2.g−1.

In situ reduction of copper nanoparticles in porous carbonized wood for efficiently enhancing electromagnetic interference shielding performance

In this study, porous carbonized wood was used as the substrate, and a multi-layer composite of copper/carbonized wood/copper (Cu/CW/Cu) layer with light weight, flame retardancy, and efficient electromagnetic shielding effectiveness was prepared by electroless copper method. The results showed that the copper particles can be filled in the layered porous structure of the carbonized wood. The metal Cu layer was evenly covered on the surface of the whole carbonized wood, and the average surface roughness was 7.62 µm. The absorption peak at 2340 cm−1 was significantly enhanced, which proved that the increase of the number of electroless Cu on the carbonized wood surface promoted the improvement of Cu autocatalytic ability. After three depositions of Cu, the conductivity of the composite material reached 1154 S/cm, showing good electrical properties. The shielding effectiveness in the X-band from 8.2 to 12.4 GHz was up to 55.97 dB at low density (0.27 g/cm3). Specific shielding effectiveness SSE/t was as high as 581.69 dB cm2 g−1. Through the “absorption–reflection–absorption” path, high absorption and low reflection are achieved, shielding a large number of incident electromagnetic waves.

Popcorn-inspired preparation of carbon aerogel with nano-walls for electromagnetic shielding and thermal insulation

In this study, we devised a green and straightforward approach for fabricating carbon aerogels by heating dextrin, drawing inspiration from the popping mechanism of popcorn. The structure and morphology of the samples were intricately regulated through precise adjustments in the temperature and duration of the heat-treatment process, resulting in the formation of a carbon aerogel comprising nano-walls. Upon carbonisation at 2100 °C, the resultant carbon aerogel exhibited an exceptionally low density of approximately 0.029 g cm−3. Notably, the aerogel demonstrated excellent electromagnetic shielding performance, reaching a shielding effectiveness of approximately 57 dB and an impressive specific shielding effectiveness of 1965 dB cm3 g−1 with a thickness of 5 mm across the entire X band. Additionally, it displayed an ultra-low thermal conductivity of approximately 0.016 W m−1 K−1 and good thermal stability. These characteristics position carbon aerogels as promising materials with vast application potential in electromagnetic shielding and thermal insulation.

PMDI cross-linked rare earth/liquid metal reinforced ANF/MXene membranes for multifunctional electromagnetic interference shielding

With the miniaturization of electronic devices, the creation of efficient and lightweight electromagnetic interference (EMI) shielding materials is of imminent significance. In this context, we reported an electromagnetic shielding membrane with hydrophobic, antioxidative, and high temperature stability. The chemically cross-linked Aramid nanofibers (ANF)/MXene@Ga/Gd2O3 (CAMG) nanocomposite membranes exhibit a considerable tensile strength and possess exceptional flexibility. The CAMG shielding membranes demonstrate multiple heterogeneous interfaces and a magnetic-dielectric synergistic system, thereby effectively enhancing the absorption shielding efficiency, with the specific shielding effectiveness per unit volume (SSE/t) reaching 6788 dB cm2 g−1. Furthermore, the composite membranes demonstrate remarkable electrothermal capabilities, acting as pliable heaters with notable, swiftly replicable, and consistent electrothermal effects at reduced voltages. Additionally, they possess superior heat dissipation efficiency and ensure a uniform heat dispersion. The exceptional electromagnetic shielding performance and multifunctionality of the C-ANF/MXene@Ga/Gd2O3 shielding membranes imply their instructive relevance in next-generation fields such as flexible electronics and aerospace.

Two birds with one stone: High electromagnetic interference shielding effectiveness and high thermal conductivity of ternary polyvinyl alcohol/graphene/ carbonyl iron nanocomposite films

Gaining brilliant flexible, easily-processable, bendable, low-density and high electrical conductivity (σ) materials with an excellent electromagnetic-interference (EMI) shielding performance is urgently needed in the fields of aerospace, aircraft, military, wearable and portable electronic industries. Therefore, the growing desire towards miniaturizing and developing high-frequency electronics is increasing incredibly today and grabbing much attention, however, they cause extreme heat accumulation and EM radiations that affect their performances as well as their hazardous effects on human health. So, polymer nanocomposites with high thermal conductivity (k) and EMI shielding effectiveness (SE) synchronously are urgently required to consume the generated heat and blocks the EM waves. Herein, poly(vinyl alcohol)/graphene nanosheets/carbonyl iron (PVA/GRx/CIR0.1-x) nanocomposite films are introduced as a new alternative candidate for EMI shielding applications with high in-plane k//, high mechanical functions, and EMI SET performance. The synergistic effect of GR and CIR on EMI shielding functions, thermal stability, mechanical properties, electrical features, and surface morphology has been explored. The increase in GR(x) amounts provides continuous GR layers and dense networks for conducting electrons and heats, provides the films with an admirable k// and total SE (SET) synchronously. Particularly, the PVA/GR0.08/CIR0.02 films have shown an σ of 1.72 Sm−1, a large SET of 32.94 dB and a specific SE (SSE/t) of 4365 dBcm2g−1 due to the mutual role (effect) of both high electrical conductive graphene and high magnetic carbonyl iron in cancelling the magnetic and electric fields of the incident EM waves. Moreover, the layered structure of GR endows films with a high k// of 3.62±0.11 W/(m·K), which is 14-fold larger than that of green PVA. The high compatibility and fine dispersion of GR/CIR fillers endow the films with a high Young modulus of 2.16 GPa, which is 7-fold larger than that of green PVA. This work suggests a novel and feasible scheme for producing high EMI shielding and high thermal conductive polymeric films, which will have huge prospects in advanced technology such as electromagnetic (microwave) interference shielding, wearable, biological, smart fabrics, military technologies and electronic equipments.

Guar gum assisted synthesis of high‐quality silver nanoplates and their polyimide matrix nanocomposites for electromagnetic interference shielding applications

AbstractTwo‐dimensional (2D) silver nanoplates are chemically synthesized in the presence of guar gum – a naturally occurring biopolymer. The polymer directs anisotropic growth of silver nuclei into high aspect ratio nanoplates spanning 4500 ± 500 nm lateral length with thickness as small as 40 ± 10 nm. After a thorough investigation of the reaction parameters (temperature, precursor to reductant ratio, and polymer quantity) on the morphology of the product, a scalable synthetic protocol to achieve good yields (95%–98%) of highly pure (~100%) 2D silver nanoplates (AgNPls) in a facile, inexpensive, room temperature, aqueous phase chemical reaction of only about 5 min is devised. The optimized AgNPls induce appreciable conductivity of 5.5 ± 0.38 S/cm in polyimide at only 12 wt% loading. Consequently, the resulting polymer nanocomposite (containing 12 wt% AgNPls), at only 130 ± 15 μm thickness and 0.45 g/cm3 density, effectively blocks electromagnetic radiation in X‐band with a total shield effectiveness of about 10 dB resulting in substantially high specific shielding effectiveness and absolute shielding effectiveness of 22.48 and 1729.23 dB cm3 g−1, respectively. Additionally, the nanocomposites remain thermally stable up to 500°C in oxidative environment and possess an appreciably high storage modulus of 3.113 GPa at 50°C. These low‐density conductive polyimide films, therefore, present great prospects in shielding against electromagnetic interference under extreme conditions.

Hybrid functional membranes through layer-by-layer assembly of Ti3C2Tx MXene and gelatin-stabilized calcium phosphate nanospheres

MXene-based membranes exhibit promising properties for various applications; however, pure MXene membranes lack sufficient environmental stability and mechanical strength. This work demonstrates that incorporating gelatin-stabilized amorphous calcium phosphate (Gel-ACP) nanospheres into MXene membranes via layer-by-layer assembly significantly enhances flexibility and mechanical strength while retaining electrical conductivity. A pressure-assisted stacking technique was introduced to efficiently fabricate membranes with tunable thickness not achievable through single filtration steps. The Gel-ACP nanospheres, synthesized by co-precipitation of calcium phosphate within gelatin solution, provided a ductile and cytocompatible reinforcement that augmented the properties of the MXene matrix. Direct mixing of the components led to particle aggregation and non-uniform dispersion. In contrast, controlled layer-by-layer nanostructuring maintained membrane conductivity around 102 Scm−1 while dramatically improving mechanical integrity. The optimized hybrid membranes exhibited specific electromagnetic shielding effectiveness of ∼21,000 dBcm2g−1 and withstood over 90 kPa vacuum pressure without rupture, six times higher than pure MXene membranes. Cytocompatibility was confirmed by the proliferation of human mesenchymal stem cells on the membranes. Moreover, the layered membrane exhibited excellent adhesion to bone-mimicking structures, indicating potential utility for bone tissue engineering. Overall, this work provides new design principles for engineering hybrid membranes through controlled multicomponent assembly to overcome intrinsic limitations and impart multifunctionality.

3D Graphene Straintronics for Broadband Terahertz Modulation

AbstractThe increasing utilization of terahertz (THz) bandwidth in both industrial and private sectors highlights the significance of efficient terahertz shielding and absorption devices. These devices play a crucial role in safeguarding electronic components from disruptive effects and rendering objects less detectable by radar systems. However, the limited availability of materials and devices hinders progress in this field. In this study, a strain engineering route is presented for the active control of terahertz shielding and absorption properties in 3D graphene through the application of mechanical strain. A straintronic modulator based on 3D graphene is demonstrated, capable of modulating absorption and reflection of THz radiation in real‐time over a wide range of 0.1–3 THz. The modulator can be tuned to exhibit either shielding capability with a specific shielding effectiveness of 0.3 × 105 dB cm2 g−1 or stealth characteristics with an average reflection loss of 25 dB and 99.4% absorption. These findings open new avenues for leveraging 2D materials in their 3D porous form, where strain‐induced changes in interlayer interactions enable control over the properties of these materials. This discovery unveils vast unexplored physical phenomena with immense potential for advanced THz imaging, radar, and electromagnetic applications.

An energy-saving structural optimization strategy for high-performance multifunctional graphene films

Graphene has been widely studied for its excellent properties of outstanding conductivity, strength, and flexibility. However, interlayer defects formed during the macroscopic assembly of graphene nanosheets will severely degrade the performance of graphene films. Herein, a strategy combined with trace carboxyl graphene oxide (GO), mild reduction, and chemical crosslinking is employed to minimize the interlayer defects for enhancing both the conductivity and mechanical strength of graphene films. The trace carboxyl feature of GO allows nanosheets to assemble orderly into highly oriented GO films. Subsequently, the mild chemical reduction preserves the highly oriented and packed microstructure. Coupling with further crosslinking by introducing conjugated molecules with pyrene terminal groups (1-pyrene butyric acid-1,6-hexane diamine, PHD) to provide extra π-π bonds, both the mechanical strength and conductivity of graphene films are improved to 548.4 MPa and 1.7 × 105 S m−1, respectively. In addition, the graphene film with only ∼2 μm in thickness possesses an excellent electromagnetic interference shielding effectiveness (EMI SE) of ∼40 dB and a specific shielding effectiveness of up to 74 278 dB cm2 g−1 in a wide frequency range of 8.2–40.0 GHz. Thus, this study provides an energy-saving fabrication route for mechanically strong, effective thermal management and EMI shielding films.

Conducting polymer hollow nanostructures by surfactant-free Ouzo emulsion for an exceptional EMI shielding performance

Hollow or partially collapsed bowls of conducting polymers, such as poly(3,4-ethylenedioxythiophene) (PEDOT), polypyrrole (Ppy), polyaniline (PANI), and polythiophene (PT), have successfully been synthesized by surfactant-free Ouzo emulsion. The stable Ouzo region has been identified based on three-component phase diagram of FeCl3·6H2O as an oxidant, acetone as solvent, and toluene as anti-solvent, respectively. The solvent/oxidant mixture forms emulsion droplets in anti-solvent medium spontaneously without any surfactant. It is the very first report on the generation of Ouzo state in the chemical oxidative polymerization systems of conducting polymers. Cast thin film of the synthesized conducting polymer hollow nanostructures was infiltrated with commercial PEDOT:PSS solution for the formation of composite structures, where the highly conductive networks of PEDOT:PSS ensures electrical conductivity. In the meanwhile, the embedded hollow nanostructures enable multiple scattering of incident electromagnetic wave. A thin (∼6 μm) composite film shows exceptional electromagnetic interference (EMI) shielding effectiveness of ∼75 dB in X-band (8–12 GHz). Furthermore, thanks to low density of hollow conducting polymer nanostructures, thickness-normalized specific shielding effectiveness (SSE/t) shows the highest value compared to other materials published in literature. The hollow nanostructures of conducting polymers, formed using surfactant-free Ouzo emulsion, may find broader applications thanks to its simple and contaminant-free nature.